What 2 repeating disaccharide units constitute peptidoglycan?

1. N-acetylglucosamine (NAG)
2. N-acetylmuramic acid (NAM)

Peptidoglycan synthesis begins in the bacterial cytoplasm. Which molecule is first made as a sugar-building block?

____-____

UDP-NAM

What is the purpose of attaching NAM to UDP?

To activate _____ for later _____ _____ synthesis

NAM

cell wall

Which lipid carrier helps move peptidoglycan building blocks across the bacterial cytoplasmic membrane?

A. Cholesterol
B. Cardiolipin
C. Bactoprenol
D. Ergosterol

C. Bactoprenol

UDP-NAM attaches to bactoprenol through what type of linkage?

A. Peptide bond
B. Glycosidic bond
C. Disulfide bond
D. Pyrophosphate linkage

D. Pyrophosphate linkage

When UDP-NAM attaches to bactoprenol, which molecule is released?

_____

UMP

After NAM attaches to bactoprenol, what happens next?

The unit is moved across the ____

The unit is moved across the membrane

Which enzyme moves the bactoprenol-linked peptidoglycan precursor to the outside surface of the membrane?

_____

Flippase

Where is the NAG-NAM disaccharide added to the growing peptidoglycan chain?

A. Inside the nucleus
B. In the bacterial cytoplasm
C. Outside the plasma membrane
D. Inside the mitochondria

C. Outside the plasma membrane

Which sequence best summarizes peptidoglycan synthesis?

A. Cross-link peptides → make UDP-NAM → flip bactoprenol → attach NAG-NAM
B. Make UDP-NAM → attach to bactoprenol → flip outside → add to peptidoglycan
C. Attach to ribosome → make protein → export protein → form capsule
D. Make Lipid A → attach O antigen → flip LPS → form outer membrane

B. Make UDP-NAM → attach to bactoprenol → flip outside → add to peptidoglycan

Transpeptidation in peptidoglycan synthesis mainly refers to what process?

A. Sugar activation
B. Peptide cross-linking
C. Bactoprenol flipping
D. NAM synthesis

B. Peptide cross-linking

The transpeptidation reaction forms a bond between peptide side chains attached to which sugar?

_____

NAM

The free amine used in transpeptidation is usually located on which position of the pentapeptide?

_____

3rd

In many Gram-positive bacteria, the 3rd-position amino acid involved in cross-linking is commonly ______.

Lysine

The 3rd-position amino acid cross-links to which residue on a neighboring chain?

A. 1st-position alanine
B. 2nd-position glutamate
C. 4th-position D-alanine
D. 5th-position D-alanine

C. 4th-position D-alanine

What happens to the terminal D-alanine during transpeptidation?

A. It becomes NAG
B. It is released
C. It binds UDP
D. It becomes bactoprenol

B. It is released

Which enzyme performs the transpeptidation reaction?

Transpeptidase

Penicillin-binding proteins are important because they normally function as _____.

Transpeptidases

Beta-lactam antibiotics inhibit bacterial growth mainly by blocking:

A. NAM production
B. NAG transport
C. Peptidoglycan cross-linking
D. Folate synthesis

C. Peptidoglycan cross-linking

Lipoteichoic and teichoic acids are assembled from activated building blocks on the _____ and then translocated to the outer surface

bactoprenol

Which organism is the most likely cause of hemorrhagic colitis?

A. Enterotoxigenic Escherichia coli
B. Escherichia coli O157:H7
C. Shigella sonnei
D. Campylobacter jejuni

B. Escherichia coli O157:H7

Which constituent of the Gram-positive bacterial cell wall is responsible for sequestration of Ca²⁺ ions?

____ ____

Teichoic acid

Unlike most Gram-negative bacteria, Neisseria species contain which endotoxin in their outer membrane?

_______ (____ )

Lipooligosaccharide (LOS)

A light microscope has a resolution of ____ μm

0.2 μm

The diameter of a red blood cell is ____ μm

7

Where does ATP production occur in prokaryotes?

____

cytoplasm

What bacteria cannot be classified by Gram staining?

____

____

Mycobacteria

Mycoplasma

Where are bacterial chromosomes present in the cell?

____

nucleoid

The prokaryotic ribosome consists of _____ and _____ subunits, forming a _____ ribosome

30S, 50S

70S

The eukaryotic ribosome consists of _____ and _____ subunits, forming a _____ ribosome

40S, 60S

80S

What is the difference between cytoplasmic membranes of eukaryotes and prokaryotes?

Eukaryotes- _____ _____
Prokaryotes- _____ _____

Eukaryotes- contain sterols
Prokaryotes- no sterols

Mycoplasma contains no _____

peptidoglycan

Peptidoglycan can be degraded by _____

lysozyme

lysozyme is found in human _____ and _____.

lysozyme cleaves _____ backbone of peptidoglycan

tears and mucus

glycan

Lysozyme is able to cleave the ____-1,4 ____ linkage in peptidoglycan

β-1,4 glycosidic

The presence of peptidoglycan in the cell well protects bacteria from damage against ____ ____.

osmotic pressure

Disruption of the _____ _____ can provide entry of lysozyme to produce _____, which, like protoplasts, are osmotically sensitive.

outer membrane

spheroplasts

Removal of a cell wall produces a _____ that _____ unless it is osmotically stabilized

protoplast

lyses

What is the periplasmic space in gram negative baceteria?

space between the:
1. _____ membrane
2. _____ membrane

1. Cytoplasmic membrane
2. Outer membrane

What is the function of the periplasmic space?

1. Contains components of transport systems for ______ and ______
2. Contains ______ enzymes

1. Contains components of transport systems for iron and sugars
2. Contains hydrolytic enzymes

What genus causes rabbit/deer fever, AKA tularemia?

_____

Francisella

Lipoteichoic acid is only present in gram-______ bacteria. Lipoteichoic acid is anchored in the ______ ______ and extend towards the exterior

gram-positive

cytoplasmic membrane

In bacteria, immediately external to the cytoplasmic membrane is _______.

peptidoglycan

The Shwartzman reaction is the event that occurs in disseminated _____ coagulation when there is a release of a large amount of _____.

intravascular

endotoxin

What protein restricts the entry of large and hydrophobic molecules across the outer membrane?

_____

porin

The outer membrane is connected to the _____ _____ at adhesion sites and is tied to the _____ by _____.

The outer membrane is connected to the cytoplasmic membrane at adhesion sites and is tied to the peptidoglycan by lipoprotein

Disruption of the outer membrane can provide entry of _____ to produce _____

lysozyme

spheroplasts

The capsule and slime layer of the cell are both usually made up of _____

polysaccharides

Bacillus anthracis produces a _____ capsule

polypeptide

_____ _____ will produce a polysaccharide biofilm when sufficient numbers are present. When sufficient numbers are present, this is referred to as a _____.

Pseudomonas aeruginosa will produce a polysaccharide biofilm when sufficient numbers are present. When sufficient numbers are present, this is referred to as a quorum

A _____ is a sticky protective layer that helps bacteria attach to surfaces and resist antibiotics, immune cells, and disinfectants.

biofilm

_____ _____ forms a _____ and _____ biofilm which promotes adhesion to tooth enamel and forms tooth-like plaque

Streptococcus mutans

dextran

levan

What determines if a bacteria swims or tumbles when trying to find a chemoattractant?

____ of ____ spinning

direction of flagellar spinning

What is the role of fimbriae?

promote adherence of _____ to _____ _____

bacteria

cell surface

What are the 3 constituents of LPS?

1. ____ ____ (responsible for ____ activity)
2. ____ ____
3. ____ ____

1. Lipid A (responsible for endotoxin activity)
2. Core polysaccharide
3. O antigen

During cell division, the production of 2 daughter bacteria requires growth and extension of the cell wall components followed by the production of a ____ to divide the 2 cells.

For streptococci, the growth zone is located ____^o from each other and for staphylococci, the growth zone is located ____^o from each other

septum

180

90

The outer coat of a spore contains the protein _____

keratin

How do spores form?

depletion of specific ______ (______) from the ______ medium

depletion of specific nutrients (alanine) from the growth medium

What makes the mycobacterial cell wall unusually waxy and acid-fast?

A. Teichoic acid
B. Mycolic acid
C. Lipooligosaccharide
D. Capsule polysaccharide

B. Mycolic acid

In mycobacteria, peptidoglycan is covalently attached to which polymer?

A. Arabinogalactan
B. Lipid A
C. KDO
D. D-Ala-D-Ala

A. Arabinogalactan

Bacitracin inhibits peptidoglycan synthesis by blocking recycling of:

A. D-Ala-D-Ala
B. Transpeptidase
C. Phosphobactoprenol
D. Arabinogalactan

C. Phosphobactoprenol

Penicillin acts as a structural analog of which peptidoglycan component?

A. NAG-NAM
B. D-Ala-D-Ala
C. KDO
D. Mycolic acid

B. D-Ala-D-Ala

Why does transpeptidase bind penicillin?

A. Penicillin resembles D-Ala-D-Ala
B. Penicillin resembles teichoic acid
C. Penicillin resembles Lipid A
D. Penicillin resembles arabinogalactan

A. Penicillin resembles D-Ala-D-Ala

What happens after transpeptidase binds penicillin?

A. Peptidoglycan cross-linking increases
B. Transpeptidase is inactivated
C. Bactoprenol recycling increases
D. Mycolic acid synthesis increases

B. Transpeptidase is inactivated

The core region of LPS contains which phosphorylated sugar?

A. D-alanine
B. N-acetylglucosamine
C. 2-keto-3-deoxy-octanoate
D. Arabinose

C. 2-keto-3-deoxy-octanoate

Why are Neisseria species more susceptible to host-mediated complement lysis?

They lack the ___-antigen portion of ___

They lack the O-antigen portion of LPS

In Neisseria, lack of O antigen allows LOS aggregates to be shed, which reduces:

A. Ribosomal protection
B. Complement protection
C. DNA replication
D. Spore formation

B. Complement protection

What can stimulate germination of a bacterial spore into the vegetative state?

______ of the outer ______-like protein coat

Disruption of the outer keratin-like protein coat

______ stress or ______ changes can trigger spore germination.

Mechanical

pH

About how long does spore germination take?

A. 5 minutes
B. 30 minutes
C. 90 minutes
D. 24 hours

C. 90 minutes

A bacterium has a structure that can be targeted by both the immune system and antibiotics. Which structure is being described?

____ ____

Cell wall

Gram-positive bacteria have a much thicker cell wall due to increased amounts of what? A. Lipopolysaccharide B. Peptidoglycan C. Sterols D. Mycolic acid

B. Peptidoglycan

Which structure is present in gram-positive bacterial cell walls?

A. Lipopolysaccharide B. Lipoteichoic acid C. Outer membrane D. Sterols

B. Lipoteichoic acid

Which bacterium does not Gram stain because it lacks a cell wall?

A. Mycoplasma

B. Mycobacteria

C. Bacillus

D. Neisseria

A. Mycoplasma

Mycoplasma lacks a cell wall but maintains membrane stability using what?

A. Mycolic acids

B. Lipopolysaccharide

C. Sterols

D. Teichoic acids

C. Sterols

Which bacteria have cell walls containing mycolic acid?

A. Mycobacteria

B. Mycoplasma

C. Neisseria

D. Streptococcus

A. Mycobacteria

Mycobacteria are best visualized using which special stain?

A. Gram stain

B. Capsule stain

C. Ziehl-Neelsen acid-fast stain

D. India ink stain

C. Ziehl-Neelsen acid-fast stain

Why do mycobacteria require an acid-fast stain instead of a standard Gram stain?

A. They lack ribosomes

B. Their cell walls contain mycolic acid

C. They contain endotoxin

D. They have no cell membrane

B. Their cell walls contain mycolic acid

Mycobacteria include organisms that cause which diseases?

A. Syphilis and Lyme disease B. Cholera and plague C. Botulism and tetanus D. Tuberculosis and leprosy

D. Tuberculosis and leprosy

Electron transport and oxidative phosphorylation occur on which bacterial structure?

Cell membrane

Gram-negative bacteria can resist some antibiotics because enzymes are located in which space?

______

Periplasm

β-lactamase in the periplasm of gram-negative bacteria helps resist which type of treatment?

A. Antiviral therapy

B. Antifungal therapy

C. β-lactam antibiotic therapy

D. Antiprotozoal therapy

C. β-lactam antibiotic therapy

Which molecule on the surface of gram-negative bacteria drives a strong immune response?

A. Lipopolysaccharide

B. Sterol

C. Teichoic acid

D. Peptidoglycan

A. Lipopolysaccharide

Lipopolysaccharide is found on which structure?

A. Gram-positive cell wall

B. Mycoplasma membrane

C. Outer membrane of gram-negative bacteria

D. Cytoplasmic membrane of gram-negative bacteria

C. Outer membrane of gram-negative bacteria

Which part of lipopolysaccharide is a major antibody target?

A. O antigen

B. Lipid A

C. Core polysaccharide

D. Peptidoglycan

A. O antigen

IgG antibodies bind bacterial capsules and promote phagocytosis through which receptor interaction?

A. T-cell receptors

B. Fc receptors

C. B-cell receptors

D. Sterol receptors

B. Fc receptors

IgG binding to a bacterial capsule can also promote which immune pathway?

A. Histamine release

B. Complement binding

C. Viral budding

D. Fungal dimorphism

B. Complement binding

Lack of B cells, antibodies, or complement increases susceptibility to which type of bacterial infection?

A. Encapsulated bacterial infections

B. Intracellular viral infections

C. Dimorphic fungal infections

D. Spirochetal infections

A. Encapsulated bacterial infections

Asplenia increases the risk of sepsis from which type of bacteria?

A. Acid-fast bacteria B. Anaerobic bacteria C. Intracellular bacteria D. Encapsulated bacteria

D. Encapsulated bacteria

Why does asplenia increase susceptibility to encapsulated bacteria?

A. Loss of thymic selection

B. Loss of neutrophil oxidative burst

C. Loss of splenic phagocytes

D. Loss of T-cell receptors

C. Loss of splenic phagocytes

Which set contains classic encapsulated organisms remembered by SHiNS?

A. Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Salmonella

B. Staphylococcus aureus, Helicobacter pylori, Neisseria gonorrhoeae, Shigella

C. Streptococcus pyogenes, Histoplasma, Nocardia, Salmonella

D. Shigella, Haemophilus influenzae, Neisseria meningitidis, Staphylococcus epidermidis

A. Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Salmonella

Bacterial capsular polysaccharides are the basis for many what?

A. Gram stains B. Acid-fast stains C. Antibiotic resistance genes D. Vaccines

D. Vaccines

Which organisms are commonly targeted by polysaccharide capsule-based vaccines?

A. Staphylococcus aureus, Helicobacter pylori, Neisseria gonorrhoeae

B. Shigella, Salmonella, Bacillus anthracis

C. Streptococcus pneumoniae, Haemophilus influenzae type b, Neisseria meningitidis

D. Mycoplasma, Mycobacteria, Trichophyton

C. Streptococcus pneumoniae, Haemophilus influenzae type b, Neisseria meningitidis

A bacterium has an irregular, fuzzy outer layer. Which structure is being described?

______

Glycocalyx

A bacterium has a distinct, firmly attached gelatinous layer. Which structure is being described?

______

Capsule

Pili or fimbriae in E. coli help cause which infections?

A. Meningitis and encephalitis

B. Pneumonia and endocarditis

C. Syphilis and Lyme disease

D. UTIs and pyelonephritis

D. UTIs and pyelonephritis

Small DNA elements within bacteria that replicate independently are called _____.

Plasmids

Which bacterial DNA element can carry genes for antibiotic resistance or toxins?

A. Plasmid

B. Flagellum

C. Capsule

D. Lipopolysaccharide

A. Plasmid

Why are plasmids clinically important?

They can transfer _____ _____ between bacteria

They can transfer survival genes between bacteria

Some bacteria can enter a dormant survival state called what?

Spore

What is true of bacteria in spore form?

A. They are metabolically hyperactive

B. They immediately divide

C. They replicate viruses

D. They can survive long periods in extreme conditions

D. They can survive long periods in extreme conditions

Which conditions can bacterial _____ survive?

Lack of nutrients, dehydration, heat, and chemicals

spores

The middle layer, or cortex, of a bacterial spore is made of what?

A. Mycolic acid

B. Lipopolysaccharide

C. Peptidoglycan

D. Sterols

C. Peptidoglycan

The core of a bacterial spore contains _____, _____, and _____ enzymes

DNA, ribosomes, glycolytic

Which genera are known as spore-forming bacteria?

____ and ____

Bacillus and Clostridium

Spore-forming Bacillus and Clostridium are usually classified as what?

gram-____ bacteria

Gram-positive bacteria

What substance is present in the core of a bacterial spore?

_____ bound to dipicolinic acid

Ca2+ bound to dipicolinic acid

Which bacteria have branched filamentous appearances?

A. Neisseria and Streptococcus pneumoniae

B. Bacillus and Clostridium

C. Nocardia and Actinomyces

D. Staphylococcus and E. coli

C. Nocardia and Actinomyces

Which bacteria are classically diplococci?

A. Streptococcus pneumoniae and Neisseria

B. Nocardia and Actinomyces

C. Bacillus and Clostridium

D. E. coli and Salmonella

A. Streptococcus pneumoniae and Neisseria

Which bacterium classically forms chains?

A. Staphylococcus aureus

B. Neisseria meningitidis

C. Bacillus anthracis

D. Streptococcus pyogenes

D. Streptococcus pyogenes

A spherical bacterium is called what?

A. Bacillus B. Coccus C. Spirillum D. Spore

B. Coccus

A rod-shaped bacterium is called what?

A. Coccus B. Spirillum C. Bacillus D. Diplococcus

C. Bacillus

A snakelike bacterium is called what?

A. Spirillum B. Coccus C. Bacillus D. Spore

A. Spirillum

In the gram-negative outer membrane, what makes up the outer leaflet?

_____

Endotoxin

In the gram-negative outer membrane, what makes up the inner leaflet?

_____

Phospholipids

Which ions help hold the gram-negative outer membrane together by linking phosphates on LPS?

______ and ______

Mg2+ and Ca2+

Which interaction helps stabilize the gram-negative outer membrane?

______ interactions between ______ and ______

Hydrophobic interactions between LPS and proteins

During Gram staining, which stain is applied first?

_____ _____

Crystal violet

During Gram staining, crystal violet is precipitated with which substance?

_____

Iodine

During Gram staining, unbound and excess stain is removed using what?

______-based decolorizer and ______

Acetone-based decolorizer and water

Serotyping bacteria involves distinguishing bacteria using antibodies against what?

A. Ribosomal subunits

B. Characteristic antigens

C. Mitochondrial proteins

D. Host cytokines

B. Characteristic antigens

What is the purpose of safranin in Gram staining?

A. To stain decolorized cells red

B. To precipitate crystal violet

C. To dissolve mycolic acid

D. To form spores

A. To stain decolorized cells red

Which process uses antibodies to detect characteristic bacterial antigens?

A. Gram staining

B. Acid-fast staining

C. Serotyping

D. Spore staining

C. Serotyping

Which organisms do not contain a peptidoglycan cell wall?

A. Bacillus and Clostridium

B. Streptococcus and Neisseria

C. Staphylococcus and E. coli

D. Archaea and mycoplasms

D. Archaea and mycoplasms

Teichoic acids in gram-positive bacteria are what type of molecules?

A. Neutral lipid droplets

B. Water-soluble anionic polymers of polyol phosphates

C. Sterol-rich membrane anchors

D. Protein toxins

B. Water-soluble anionic polymers of polyol phosphates

Teichoic acids are covalently linked to which bacterial structure?

_____

Peptidoglycan

Why are teichoic acids important in gram-positive bacteria?

They are essential to _____ viability

They are essential to cell viability

Which gram-positive cell wall component is linked to innate immune activation?

A. O antigen

B. Lipoteichoic acid

C. Sterol

D. Plasmid

B. Lipoteichoic acid

Which bacterial structure is most associated with antibiotic resistance gene transfer?

_____

Plasmid

Which structure allows bacteria to survive extreme conditions with little to no metabolic activity?

_____

Spore

Do gram-negative bacterial cell walls contain teichoic or lipoteichoic acids? A. Yes, both are present B. Only teichoic acid is present C. Only lipoteichoic acid is present D. No, neither is present

D. No, neither is present

What is one major function of the gram-negative outer membrane?

A. Production of ribosomes

B. Formation of spores

C. Storage of plasmids

D. Permeable barrier

D. Permeable barrier

The outer leaflet of the gram-negative outer membrane contains which molecule

A. Teichoic acid

B. Lipopolysaccharide

C. Sterols

D. Mycolic acid

B. Lipopolysaccharide

Lipopolysaccharide in gram-negative bacteria stimulates which host response?

A. Innate immune response

B. Somatic hypermutation

C. T-cell receptor rearrangement

D. Antibody class switching

A. Innate immune response

A gram-negative bacterium triggers a strong innate immune response through LPS. Where is this LPS located?

A. Inner leaflet of cytoplasmic membrane

B. Peptidoglycan cortex

C. Outer leaflet of outer membrane

D. Bacterial chromosome

C. Outer leaflet of outer membrane

Porins in the gram-negative outer membrane allow diffusion of which molecules?

A. Hydrophobic molecules

B. Large proteins only

C. Steroid hormones only

D. Hydrophilic molecules

D. Hydrophilic molecules

A small _____ molecule crosses the gram-_____ outer membrane through porin.

A small hydrophilic molecule crosses the gram-negative outer membrane through porin.

The bacterial flagellum is best described as what?

A. An external structure used for movement

B. A DNA element that carries resistance genes

C. A polysaccharide layer used for immune evasion

D. A membrane pore for hydrophilic molecules

A. An external structure used for movement

A bacterium living in a biofilm becomes harder for antibiotics and immune cells to eliminate. What is the main advantage of the biofilm?

A. Increased oxygen use

B. Increased sporulation

C. Protection

D. Loss of virulence

C. Protection

Which two polysaccharide components make up bacterial peptidoglycan?

A. Glucose and fructose

B. Ribose and deoxyribose

C. N-acetylglucosamine and N-acetylmuramic acid

D. Cellulose and glycogen

C. N-acetylglucosamine and N-acetylmuramic acid

Transpeptidases and carboxypeptidases involved in peptidoglycan synthesis are targets of which antibiotics?

A. Macrolides and a-lactam antibiotics

B. Tetracyclines and a-lactam antibiotics

C. Fluoroquinolones and β-lactam antibiotics

D. Penicillins and β-lactam antibiotics

D. Penicillins and β-lactam antibiotics

Penicillin and β-lactam antibiotics target enzymes involved in which process?

Peptidoglycan ______

Peptidoglycan synthesis

A bacterium forms spores. It is most likely classified as which Gram stain type?

Gram-positive

A bacterial spore contains how many peptidoglycan layers?

Two

Which structure is part of a bacterial spore?

A. Outer membrane with LPS

B. Sterol-rich membrane only

C. Inner membrane

D. Teichoic acid layer

C. Inner membrane

High concentrations of dipicolinic acid in bacterial spores help stabilize contents by binding what?

A. Sodium B. Magnesium C. Potassium D. Calcium

D. Calcium

Which spore component helps stabilize the spore contents by binding calcium?

A. Peptidoglycan

B. Dipicolinic acid

C. Lipopolysaccharide

D. Porin

B. Dipicolinic acid

Which sequence best describes bacterial cell division?

A. Cell wall growth and extension → septum formation → two daughter bacteria

B. Septum formation → loss of cell wall → viral budding

C. Spore coat formation → LPS release → two daughter bacteria

D. Flagellar movement → capsule loss → chromosome deletion

A. Cell wall growth and extension → septum formation → two daughter bacteria

____ is so important that many bacteria secrete special proteins called ____ to concentrate ____ from dilute solutions

Iron

siderophores

iron

What organism causes gas gangrene?

____ ____

Clostridium Perfringes

What are obligate anaerobes?

organisms that ____ grow in the presence of ____ (____ ____)

cannot

O2

Clostridium perfringens

What are obligate aerobes?

organisms that require ____ for metabolism and growth

O2

What are facultative anaerobes?

1. May use ____ as a terminal ____ ____ to generate ____

2. Can also use ____ and other ____ -independent pathways

May use O2 as a terminal electron acceptor to generate ATP

Can also use fermentation and other O2-independent pathways

Aerobic bacteria produce the following 2 enzymes:

1. _____ _____

2. _____

1. Superoxide dismutase

2. Catalase

What are autotrophs?

_____ that can rely solely on _____ chemicals for their energy and source of carbon

bacteria

inorganic

What are heterotrophs?

_____ and _____ cells that require _____ carbon sources

bacteria and animal cells that require organic carbon sources

The _____ species can improve the function of the normal GI flora

Lactobacillus

______: small molecules are assembled into large ones using energy

Anabolism

______: substrate breakdown and conversion into usable energy

Catabolism

______ of the colon can select for and promote the growth of beneficial ______ -producing endogenous bacteria

Acidification

lactate

Electrochemical energy is stored by the _____ of _____ to _____

reduction

NAD

NADH

What enzyme drives the spinning of flagella and drives the conversion of ADP into ATP?

ATP synthase

1. What is the most efficient way in which bacteria can produce energy from glucose?

2. What is the least efficient way in which bacteria can produce energy from glucose?

Aeorobic respiration

Fermentation

Fermentation results in the conversion of _____ into _____ and _____

yeast

ethanol

CO2

Alcoholic fermentation uses the one-step conversion of _____ acid into _____ acid

pyruvic

lactic

What is the theoretical yield from each molecule of pyruvate in the TCA cycle?

____ NADH

____ FADH2

____ CO2

____ GTP

3 NADH

1 FADH2

2 CO2

1 GTP

Acetyl CoA enters the TCA cycle by combining with _____ to form the molecule _____

oxaloacetate

citrate

What is the most efficient mechanism for the generation of ATP?

TCA cycle

Fermentation produces only _____ ATP molecules per glucose.

Aerobic metabolism with ETC and a complete TCA cycle can generate as much as _____ ATP molecules from the same starting material

2

38

Deamination of glutamic acid yields _______ and deamination of aspartic acid yields _______

a-ketoglutarate

oxaloacetate

The ETC resides in the ____ ____ of bacteria.

It uses electrons obtained from ____ and ____ to produce a transmembrane proton electrochemical gradient that drives the ____ ____ and powers transport and flagella

plasma membrane

NADH, FADH2

ATP synthase

What is the function of the pentose phosphate pathway (HMP shunt)?

1. Provides _____ _____ precursors

2. Provides a source of _____

nucleic acid

NADPH

The normal flora of our body process complex carbohydrates and releases _____-_____ _____ _____ as products of _____

short-chain fatty acids

fermentation

The bacterial DNA-dependent RNA Polymerase is inhibited by _____ which is an antibiotic often used in the treatment of _____

rifampin

tuberculosis

How does bacterial protein synthesis begin?

binding of the:

1. ____ ribosomal subunit and the

2. Special initiator ____ for formyl methionine (____) at the ____ start codon to form the initiation complex

30s

tRNA, f-met, AUG

Increased cAMP levels indicate ____ ____ levels

low glucose

The _____ sequence of the tRNA binds to the _____ sequence on the mRNA

anticodon

codon

The trigger for biofilm production by Pseudomonas spp. is triggered by a critical concentration of N-acyl homoserine lactone (_____) produced when sufficient numbers of bacteria are present.

Activation of biofilm, toxin production, and more virulent behavior by Staphylococcus aureus accompanies the increase in concentration of a _____ _____.

AHL

cyclic peptide

What class of drugs are 30s ribosomal subunit inhibitors?

1. _____ (_____ and _____)

2. _____

1. Aminoglycosides (streptomycin and gentamicin)

2. Tetracyclines

What class of drugs are 50s ribosomal subunit inhibitors?

1. _____

2. _____ (_____)

3. _____ (_____)

4. _____

1. Chloramphenicol

2. Lincosamide (clindamycin)

3. Macrolides (erythromycin)

4. Linezolid

_____ peptides are chemotactic and attract neutrophils to the site of infection

fmet

What is the role of a repressor protein?

binds to a specific ____ sequence within the ____, blocking ____ ____ from initiating ____ at the ____ sequence

binds to a specific DNA sequence within the operator, blocking RNA polymerase from initiating transcription at the promoter sequence

In the lac operon, what occurs when there is an absence of lactose?

repressor protein binds to the _____ sequence

operator

In the lac operon, what occurs when there is an absence of glucose?

1. _____ binds to catabolite activator protein (CAP)

2. CAP-cAMP complex enhances binding of _____ _____ to the promoter = _____ _____

1. CAMP binds to catabolite activator protein (CAP)

2. CAP-cAMP complex enhances binding of RNA polymerase to the promoter = increased transcription

When are Salmonella pathogenicity islands turned on?

1. High _____

2. Low _____

These conditions are present in the GI tract/endosomal vesicle within a macrophage

1. High osmolarity

2. Low O2

What can activate expression of hemolysin in E. coli or diphtheria toxin from Corynebacterium diphtheriae?

low ____ levels

iron

for lac operon

No _____→ repressor bound → operon _____
_____ present → repressor removed → operon can turn _____

No allolactose → repressor bound → operon OFF
Allolactose present → repressor removed → operon can turn ON

In DNA synthesis, the _____ strand is synthesized _____ whereas the lagging strand is synthesized as many pieces of DNA using _____ _____ , creating _____ fragments

leading, continously

RNA primers, Okazaki

The lagging strand DNA must be extended in the ____' to ____' direction as its ____ becomes available. Then, DNA pieces are connected via the enzyme ____ ____

5' to 3'

template

DNA ligase

What is the role of DNA topoisomerase?

creates ____ in the ____ to add or remove ____ in the ____

creates breaks in the helix to add or remove supercoils in the DNA

What class of drugs targets topoisomerases in prokaryotes

_____ antibiotics

fluoroquinolone

Depletion of metabolites or a buildup of toxic by-products triggers production of chemical ______

alarmones

When bacteria are added to a new medium, they require time to adapt to the new environment before they begin _____. This phase is known as the _____ _____ of growth.

dividing

lag phase

During the ____ ____ phase, the bacteria will grow and divide with a doubling time

log exponential

1. What occurs in a transition base change?

___ to ___ or ___ to ___

2. What occurs in a transversion base change?

___ to ___ or ___ to ___

purine to purine or pyrimidine to pyrimidine

purine to pyrimidine or pyrimidine to purine

What are the 3 proteins in which the lac operon can be transcribed and translated into?

_____- β galactosidase

_____- permease

_____- acetylase

LacZ

LacY

LacA

An E. coli cell is exposed to a high intracellular concentration of tryptophan. During transcription of the trp operon leader region, the ribosome moves quickly through the leader peptide. Which RNA hairpin forms?

A. Regions 1 and 2
B. Regions 2 and 3
C. Regions 3 and 4
D. Regions 1 and 4

C. Regions 3 and 4

In the trp operon, formation of the 3–4 hairpin loop causes which outcome?

A. Increased translation of tryptophan biosynthetic enzymes
B. Premature termination of transcription
C. Binding of allolactose to the repressor
D. Activation of CAP-cAMP

B. Premature termination of transcription

An E. coli cell has low intracellular tryptophan levels. The ribosome stalls at the tryptophan codons in the leader peptide. Which hairpin forms, allowing transcription to continue?

A. Regions 2 and 3
B. Regions 3 and 4
C. Regions 1 and 4
D. Regions 1 and 3

A. Regions 2 and 3

What occurs in a silent mutation?

a change at the ____ level that codes for the ____ amino acid

DNA

same

What occurs in a missense mutation?

1. Results in a _____ amino acid

2. Called a _____ mutation if _____ amino acid has similar chemical structure

new

conserved, new

What occurs in a nonsense mutation?

results in an _____ _____ _____

early stop codon

A small deletion or insertion that is not in multiples of three produces a _____ mutation.

This results in a change in the reading frame, usually leading to a useless _____ and premature truncation of the _____.

frameshift

peptide, protein

What occurs in a Null mutation?

1. Arise when there is an extensive insertion, deletion, or gross rearrangement of _____ structure

2. Completely destroys _____ function

chromosome

gene

Heat can induce mutations by causing ____ of ____

deamination

nucleotides

DNA-reactive chemicals such as ____ ____ act directly on the DNA to change the chemical structure of the base

nitrous acid

A researcher exposes bacterial DNA to 5-bromouracil (5-BrU). Which property of 5-BrU is primarily responsible for its mutagenic effect?

It can base-pair with ____ instead of ____

guanine

adenine

5-Bromouracil is classified as which type of mutagen?

A. Alkylating agent
B. Intercalating agent
C. Nucleotide-base analog
D. Depurinating agent

C. Nucleotide-base analog

Ethidium bromide causes mutations primarily by which mechanism?

_____ between stacked DNA bases

Inserts

What occurs in base excision repair?

1. Base specific _____ removed altered base and creates AP site
2. AP _____ removes faulty nucleotides and cleaves 5' end
3. AP _____ cleaves 3' end
4. DNA _____ fills the gap and DNA _____ seals it

glycoslyase

endonuclease

Lyase

Polymerase, ligase

What occurs in recombinational/postreplication repair?

replaces a damaged or missing section of DNA with the ____ or ____ sequences that may be present during replication

same or similar

CRISPR/Cas9 is used to protect the bacterial chromosome against integration of ______ and ______ plasmids

bacteriophages

foreign

Borrelia burgdorferi possess _____ genomes and _____ .

causative agent of _____ disease

linear, plasmids

Lyme

What are bacteriophages?

bacterial viruses with a _____ or _____ genome usually protected by a _____ or _____ shell

DNA or RNA

membrane, protein

What are the 2 ways in which bacteriophages infect?

1. _____ infection- replicate in large numbers and cause the cell to lyse

2. _____ state- integrate into host cell without killing

Lytic

Lysogenic

The E. coli bacteriophage ______ remains in a ______ state as long as the repressor protein is synthesized and prevents the phage genome from being excised to replicate and exit the cell

lambda

lysogenic

What are transposons?

a ____ sequence that can change its ____ within a genome

DNA

position

What occurs in transformation?

bacteria take up fragments of naked _____ and _____ them into their own genomes

DNA

incorporate

The hepatitis B surface antigen is produced by ____ ____

Saccharomyces cerevisiae

An F⁺ E. coli cell conjugates with an F⁻ cell. Which structure allows the F⁺ cell to attach to the F⁻ cell?

A. Flagellum
B. Sex pilus
C. Endospore coat
D. Peptidoglycan bridge

B. Sex pilus

In standard F⁺ × F⁻ bacterial conjugation, what is transferred to the recipient cell?

A. The entire donor chromosome
B. Only ribosomal RNA genes
C. A few chromosomal genes near oriC
D. A single strand of F plasmid DNA

D. A single strand of F plasmid DNA

Does standard F⁺ × F⁻ conjugation transfer chromosomal DNA?

A. No, only plasmid DNA is transferred
B. Yes, the entire chromosome is transferred
C. Yes, but only if the recipient already has an F plasmid
D. No DNA is transferred; only proteins are exchanged

A. No, only plasmid DNA is transferred

After successful F⁺ × F⁻ conjugation, what usually happens to the recipient cell?

A. It remains F⁻ because plasmids cannot replicate
B. It becomes HFr because the chromosome is deleted
C. It becomes F⁺ because it receives the F plasmid
D. It loses its ability to undergo conjugation

C. It becomes F⁺ because it receives the F plasmid

The F plasmid contains genes required for which major process?

A. Antibiotic degradation
B. Sex pilus formation and conjugation
C. Endospore formation
D. Capsule synthesis

B. Sex pilus formation and conjugation

A bacterium has its F plasmid integrated into the bacterial chromosome. What is this cell called?

A. F⁻ cell
B. R plasmid cell
C. Competent cell
D. HFr cell

D. HFr cell

In an HFr cell, where is the F factor located?

A. Integrated into the bacterial chromosome
B. Floating separately in the cytoplasm
C. Inside the recipient bacterium only
D. Attached to the outer membrane as a pilus

A. Integrated into the bacterial chromosome

An HFr cell conjugates with an F⁻ cell. Which DNA is most likely transferred first?

A. Random fragments of recipient DNA
B. Only the last portion of the bacterial chromosome
C. The leading portion of the integrated F factor followed by nearby chromosomal genes
D. Only circular double-stranded chromosomal DNA

C. The leading portion of the integrated F factor followed by nearby chromosomal genes

In HFr × F⁻ conjugation, why does the recipient usually remain F⁻?

A. The recipient destroys all incoming chromosomal DNA
B. The entire F factor usually is not completely transferred
C. The F plasmid cannot initiate DNA transfer from oriT
D. The sex pilus prevents transfer of plasmid genes

B. The entire F factor usually is not completely transferred

Which outcome is most characteristic of HFr × F⁻ conjugation?

A. The recipient becomes F⁺ and receives no chromosomal genes
B. The donor becomes F⁻ after losing the entire chromosome
C. The recipient receives only an intact circular F plasmid
D. The recipient may integrate some donor chromosomal genes but usually remains F⁻

D. The recipient may integrate some donor chromosomal genes but usually remains F⁻

What occurs in generalized transduction?

incorporation of ____ sequences into phages are random due to a ____ error

DNA

packaging

What occurs in specialized transduction?

phages transfer _____ genes (not _____)

particular

random

Isolates of S. aureus acquired the _____ resistant gene during a mixed infection with _____ _____

vancomycin

Enterococcus faecalis

_____ _____ recognize a specific palindromic sequence and make a staggered cut that generates sticky ends

Restriction enzymes

A researcher adds a plasmid to competent bacteria so the bacteria will take up and replicate the DNA. Which bacterial genetics process is being used?

A. Transduction

B. Transformation

C. Conjugation

D. Translation

B. Transformation — bacteria take up free/exogenous DNA from the environment.

A virus that infects bacteria is best described as which of the following?

A. Plasmid

B. Transposon

C. Operon

D. Bacteriophage

D. Bacteriophage — also called a phage.

A bacteriophage accidentally carries bacterial DNA from one bacterium to another. What is this process called?

A. Transduction

B. Transformation

C. Conjugation

D. Replication

A. Transduction — DNA transfer between bacteria via a phage.

A newborn’s gut microbiome is shaped by complex carbohydrates in breast milk. Which bacterium is selected for?

A. Staphylococcus aureus

B. Escherichia coli

C. Enterococcus faecalis

D. Bifidobacterium infantis

D. Bifidobacterium infantis — it is selected by breast milk carbohydrates.

Skin bacteria catabolize keratin, oils, and dead cells in which outer skin layer?

A. Stratum corneum

B. Stratum basale

C. Dermis

D. Hypodermis

A. Stratum corneum — the outer layer containing dead keratinized cells.

Which molecules help maintain the structure of the bacterial chromosome?

A. Peptidoglycans

B. Sterols

C. Polyamines

D. Porins

C. Polyamines — examples include spermine and spermidine.

Prokaryotes can couple transcription and translation because they lack which structure?

A. Cell wall

B. Nuclear membrane

C. Ribosome

D. Plasma membrane

B. Nuclear membrane — mRNA can be translated while still being transcribed.

Bacterial chromosomal replication begins at which specific sequence?

oriC — the origin of chromosomal replication.

A bacterium exposed to UV light develops covalent links between adjacent pyrimidines. What caused this mutation?

A. Pyrimidine dimer formation

B. Base deamination

C. Transposon insertion

D. Plasmid loss

A. Pyrimidine dimer formation — UV exposure causes thymine/pyrimidine dimers.

A patient with xeroderma pigmentosum has impaired repair of UV-induced pyrimidine dimers. Which repair pathway is defective?

A. Mismatch repair

B. Homologous recombination

C. Nucleotide excision repair

D. Base insertion repair

C. Nucleotide excision repair — it removes damaged DNA and replaces it.

Which group of bacteria is naturally capable of taking up exogenous DNA?

A. E coli, Salmonella, Shigella

B. S pneumoniae, H influenzae type B, Neisseria

C. Mycoplasma, Chlamydia, Rickettsia

B. Streptococcus pneumoniae, Haemophilus influenzae type B, and Neisseria — these are naturally competent.

The bacterial sex pilus is a specialized form of which secretion system?

A. Type I

B. Type II

C. Type III

D. Type IV

D. Type IV — the sex pilus functions as a type IV secretion device.

Bacteria break down carbohydrates into sugars and short-chain fatty acids. What is this process called?

A. Fermentation

B. Transduction

C. Conjugation

D. Recombination

A. Fermentation — bacteria metabolize carbohydrates into smaller products such as SCFAs.

What is the universal intermediate of cell metabolism?

A. Lactate

B. Acetyl-CoA

C. Pyruvic acid

D. Citrate

C. Pyruvic acid — many metabolic pathways converge on pyruvate.

Fermentation occurs under which condition?

A. Only with oxygen

B. Only in eukaryotes

C. Only during replication

D. Only without oxygen

D. Only without oxygen

Which statement best describes bacterial genetics?

A. Bacteria are haploid and often organize related genes into operons

B. Bacteria are diploid and often organize related genes into operons

C. Bacteria are haploid and lack gene regulation

D. Bacteria are diploid and use introns

A. Bacteria are haploid and often organize related genes into operons.

What is transcription?

A. mRNA to protein

B. Protein to DNA

C. DNA to mRNA

D. DNA to protein

C. DNA to mRNA — RNA polymerase makes an mRNA copy from DNA.

What is translation?

A. DNA to mRNA

B. mRNA to protein

C. Protein to DNA

D. RNA to DNA

B. mRNA to protein — ribosomes synthesize proteins from mRNA.

Promoters and operators are usually located where relative to the gene/operon they regulate?

Beginning

In negative control, genes are expressed unless turned off by what?

A. Repressor protein

B. Ribosome

C. Helicase

D. Primase

A. Repressor protein — negative control blocks transcription unless repression is removed.

Which enzyme unwinds bacterial DNA at the origin during replication?

Helicase

Which enzyme synthesizes primers to start bacterial DNA replication?

Primase

What does semiconservative DNA replication mean?

A. Each daughter DNA has one parental strand and one new strand

B. Both daughter DNAs are completely new

C. One daughter DNA is old and one is new

D. DNA is copied without using a template

A. Each daughter DNA has one parental strand and one new strand.

Bacterial DNA synthesis occurs at growing replication forks and proceeds in which pattern?

A. Unidirectionally from plasmids

B. Only after cell division

C. Bidirectionally from the origin

D. Randomly across the chromosome

C. Bidirectionally from the origin — two forks move away from oriC.

During bacterial growth, chromosome replication is initiated near which bacterial structure?

A. Capsule

B. Membrane

C. Flagellum

D. Ribosome

B. Membrane — membrane growth helps pull daughter chromosomes apart.

Which sequence correctly lists the phases of bacterial growth?

A. Death, lag, stationary, exponential

B. Stationary, death, lag, exponential

C. Exponential, lag, death, stationary

D. Lag, exponential, stationary, death

D. Lag → exponential/log → stationary → death.

A repair system removes a damaged section of DNA and inserts a new DNA strand. Which repair type is this?

A. Direct repair

B. Fermentation

C. Excision repair

D. Conjugation

C. Excision repair — damaged DNA is cut out and replaced.

What does plasmid copy number measure?

A. Ratio of ribosomes to plasmids

B. Ratio of plasmid copies to chromosome copies

C. Ratio of phages to bacteria

D. Ratio of operons to genes

B. Ratio of plasmid copies to chromosome copies.

A mobile genetic element moves DNA from one location to another. What is it called?

A. Bacteriophage

B. Promoter

C. Operator

D. Transposon

D. Transposon — transposons are mobile DNA elements.

Which are the 3 main mechanisms of bacterial horizontal gene transfer?

A. Transformation, conjugation, transduction

B. Transcription, translation, replication

C. Lytic, lysogenic, exponential

D. Fermentation, respiration, oxidation

A. Transformation, conjugation, and transduction.

A donor bacterium transfers DNA directly to a recipient through a sex pilus. Which process is this?

_____

Conjugation

During transduction, two genes are more likely to be cotransduced when they are located how?

A. On different chromosomes

B. Closer together

C. On separate plasmids

D. Farther apart

B. Closer together — nearby genes fit into the same transferred DNA fragment more easily.

Scientists use a DNA carrier to deliver a gene into receptive bacteria. What is this carrier called?

A. Repressor

B. Operator

C. Cloning vector

D. Pyrimidine dimer

C. Cloning vector — it delivers DNA into bacteria for replication or expression.

A patient with gram-negative sepsis has fever, hypotension, and inflammatory cytokine release due to a bacterial membrane component. Which toxin is responsible?

______. ______ is part of the gram-negative bacterial ______ membrane.

Endotoxin — endotoxin is part of the gram-negative bacterial outer membrane.

A secreted bacterial toxin is found to be a protein produced by either gram-positive or gram-negative bacteria. What type of toxin is this?

______

A. Exotoxin — exotoxins are secreted proteins made by gram-positive or gram-negative bacteria.

A researcher isolates a lipopolysaccharide complex from a gram-negative bacterium. Which toxin type is this?

Endotoxin — endotoxin is composed of LPS.

Which part of LPS is mainly responsible for endotoxin toxicity?

____ ____

Lipid A — Lipid A is the toxic portion of LPS.

The terminal portion of LPS varies among bacterial strains and helps distinguish strains. What is this portion called?

____ ____

O antigen — the O antigen is the variable terminal end of LPS.

A toxin has an A component that causes toxicity and a B component that binds the host cell. What type of toxin is this?

_____

Exotoxin — many exotoxins are A-B toxins.

In an A-B exotoxin, which component binds to the host cell surface?

A. A component

B. B component

B. B component — “B” stands for binding.

In an A-B exotoxin, which component performs the toxic activity inside the host cell?

A. A component

B. B component

D. A component — “A” stands for active.

Endotoxin binds CD14 on macrophages. Which mediators are released?

IL-____, IL-____, ____-____, ____ ____

IL-1, IL-6, TNF-alpha, and NO — these drive inflammation and shock.

A gram-negative infection activates complement through LPS. Which complement fragments are released as anaphylatoxins?

____ and ____

C3a and C5a — these promote inflammation and neutrophil chemotaxis.

Why is endotoxin generally a poor target for toxoid-style vaccination?

A. It is only made by viruses

B. It has no toxic activity

C. It generates a weak antibody response

D. It is rapidly secreted from gram-positive cells

C. It generates a weak antibody response — endotoxin does not make a strong protective antibody response.

A bacterial toxin gene is found on a plasmid or bacteriophage rather than the chromosome. What type of toxin is most likely encoded?

_____

Exotoxin — exotoxin genes are often carried on plasmids or bacteriophages.

Which mobile genetic elements commonly encode exotoxin genes?

A. Ribosomes and operons

B. Capsules and fimbriae

C. Endospores and porins

D. Plasmids and bacteriophages

D. Plasmids and bacteriophages — exotoxin genes are often horizontally transferred.

A toxin activates many T cells at once by linking MHC II on an APC to the T-cell receptor. What is this toxin called?

______

Superantigen

Superantigens differ from normal peptide antigens because they are not processed normally and instead bind _____ _____ and _____ directly

Not processed normally and instead bind MHC II and TCR directly

A patient develops shock after massive cytokine release from T-cell activation. Which toxin mechanism is most likely?

A. Botulinum toxin blocking ACh

B. Cytolysin destroying membranes

C. Superantigen causing massive T-cell activation

D. O antigen activating B cells

C. Superantigen causing massive T-cell activation — cytokine release causes vasodilation, hypotension, and shock.

Which two organisms produce superantigens that can cause shock?

______ ______ and ______ ______

Staphylococcus aureus and Streptococcus pyogenes

Most exotoxins are heat labile. What does this mean?

A. They are rapidly destroyed by heat

B. They become stronger after heating

C. They are made only during fever

D. They are identical to LPS

A. They are rapidly destroyed by heat — many exotoxins are inactivated around 60°C.

Which exotoxins are classic exceptions to the “heat-labile exotoxin” rule?

______ ______ and ______ ______ heat-stable toxin

Staphylococcal enterotoxin and E coli heat-stable toxin — these are heat-stable exceptions.

A patient has flaccid paralysis after ingestion of a toxin that prevents acetylcholine release from vesicles. Which toxin is responsible?

A. Endotoxin

B. Superantigen

C. Botulinum toxin

D. Cytolysin

C. Botulinum toxin — it blocks ACh release from presynaptic vesicles.

A burn patient develops a wound infection with a blue-green pigment and fruity odor. Which opportunistic pathogen is classically associated with burns?

_____ _____

Pseudomonas aeruginosa

Patients with cystic fibrosis are especially prone to chronic lung colonization by which organisms?

_____ _____ and _____ _____

Staphylococcus aureus and Pseudomonas aeruginosa — impaired mucociliary clearance promotes colonization.

Why do bacteria not express virulence factors all the time?

A. Virulence genes cannot be regulated

B. They only express them under specific conditions

C. All virulence factors are toxic to bacteria

D. Virulence factors are only found in viruses

B. They only express them under specific conditions — expression is often triggered by the environment.

Large genetic regions on a chromosome or plasmid that contain multiple virulence genes are called:

A. Operons

B. Ribosomes

C. Pathogenicity islands

D. Porins

C. Pathogenicity islands — they encode coordinated sets of virulence factors.

A Salmonella virulence island is activated by acidic pH inside a macrophage phagocytic vesicle. Which pathogenicity island is this?

A. SPI-2

B. O antigen island

C. MSCRAMM island

D. Lipid A island

A. SPI-2 — Salmonella SPI-2 is activated in the acidic phagocytic vesicle.

SPI-2 helps Salmonella survive intracellularly by promoting assembly of which device?

A. Type I secretion pump

B. Type II pili

C. Type IV conjugation pilus

D. Type III secretion device

D. Type III secretion device — it injects bacterial proteins into host cells.

A bacterium injects a pore-forming molecule into a host cell, then injects proteins through that pore. Which structure is being used?

A. Flagellum

B. Type III secretion device

C. Capsule

D. Ribosome

B. Type III secretion device — this syringe-like apparatus delivers bacterial proteins into host cells.

Many proteins injected by a type III secretion system help bacteria enter host cells by promoting what process?

A. Actin polymerization

B. Antibody secretion

C. Complement inhibition

D. Nuclear division

A. Actin polymerization — rearranging actin helps host cells engulf bacteria.

An organism causes disease mainly when host defenses are weakened or tissue barriers are damaged. What is this organism called?

A. Superantigen

B. Endotoxin

C. Opportunistic bacterium

D. Anaphylatoxin

C. Opportunistic bacterium — it takes advantage of preexisting weakness or damage.

Patients with AIDS are especially susceptible to intracellular bacteria such as which group?

_______

Mycobacteria — impaired cell-mediated immunity increases risk.

Systemic symptoms during bacterial infection are often caused by bacterial toxins and which host response?

A. Keratin production

B. Cytokine production

C. Lactose fermentation

D. Flagellar rotation

B. Cytokine production — toxins and host cytokines produce systemic responses.

S aureus and S epidermidis are normal flora of which site and can cause infection after breaks in the barrier?

Skin — they can enter through skin breaks.

Indwelling catheters and IV lines increase risk of infection by skin flora mainly because they:

A. block antibody production

B. damage the spleen

C. reduce stomach acid

D. bypass the skin barrier

D. Bypass the skin barrier — skin flora can enter deeper tissues or blood.

Natural openings such as the mouth, nose, anus, and respiratory/GI/GU tracts are protected by which defenses?

A. Mucus, cilia, lysozyme, and IgA

B. Lipid A, O antigen, and TNF

C. Plasmids, phages, and transposons

D. ATP, NADH, and FADH2

A. Mucus, cilia, lysozyme, and IgA — these protect exposed mucosal surfaces.

E coli remains attached to the urinary or intestinal epithelium instead of being washed away. Which bacterial factor explains this?

A. Endotoxin

B. Capsule

C. Adhesins

D. Botulinum toxin

C. Adhesins — they bind specific receptors on tissue surfaces.

Many bacterial adhesins are located on which surface structures?

A. Fimbriae

B. Ribosomes

C. Nucleoids

D. Inclusion bodies

A. Fimbriae — fimbrial adhesins help bacteria bind host tissues.

Fimbrial adhesins commonly bind tightly to which host molecules?

A. Cytokines

B. Lectins

C. Antibodies

D. Complement proteins

B. Lectins — fimbriae often mediate lectin-like binding to host surfaces.

Which organisms express adhesin proteins that are not located on fimbriae?

_____

_____ _____

_____ _____

Yersinia, Bordetella pertussis, and Mycoplasma pneumoniae — their adhesins are nonfimbrial.

A bacterium moves through the mucous layer toward epithelium. Which structure helps it swim?

_____

Flagella — flagella provide motility through mucus.

Which bacterial enzymes help digest the mucous layer so bacteria can approach epithelial cells?

______

Proteases — they break down mucus proteins.

C perfringens is normal microbiota but can cause gas gangrene under which condition?

____ oxygen

Low oxygen — anaerobic conditions favor C perfringens gas gangrene.

A patient develops rapid vomiting after eating food containing toxin already produced by bacteria. What type of toxin exposure is this?

A. Preformed toxin

B. Endotoxin only

C. Type III secretion

D. Pathogenicity island

A. Preformed toxin — symptoms occur quickly without needing bacterial growth in the host.

Why do preformed toxins cause symptoms quickly?

A. They require bacterial replication first

B. They are already present before ingestion or exposure

C. They only activate complement slowly

D. They must integrate into host DNA

B. They are already present — no time is needed for bacterial growth and toxin production.

Exotoxins can include cytolytic enzymes and receptor-binding proteins. What do these toxins do?

A. Only form bacterial chromosomes

B. Alter cell function or kill cells

C. Become part of gram-negative membranes

D. Prevent all cytokine release

B. Alter cell function or kill cells — exotoxins can disrupt host cell activity or viability.

A toxin directly breaks down host cell membranes. What type of toxin is this?

______ toxin

Cytolytic toxin — cytolytic toxins damage membranes.

A gram-negative bacterium releases LPS during infection, leading to macrophage activation. Which receptor complex is classically involved in recognizing LPS on macrophages?

A. CD14/TLR4

B. CD4/MHC II

C. CD8/MHC I

D. BCR/IgA

A. CD14/TLR4 — LPS binding activates macrophages and cytokine release.

Nitric oxide released after endotoxin stimulation contributes most directly to which shock finding?

A. Bradycardia only

B. Vasodilation and hypotension

C. Increased platelet production

D. Increased gastric acid secretion

B. Vasodilation and hypotension — NO relaxes vascular smooth muscle.

Which toxin type is most likely to be converted into a toxoid vaccine because it is a protein with strong immunogenicity?

Endotoxin or Exotoxin?

Exotoxin

Which factor best explains why Pseudomonas can colonize cystic fibrosis lungs?

Impaired _____ _____ clearance

Impaired ciliary mucous clearance — thick mucus and poor clearance allow colonization.

A device-associated S epidermidis infection persists despite antibiotics. Which bacterial structure most likely contributes?

_____

Biofilm — biofilms protect bacteria on catheters and implanted devices.

Which bacteria produce endotoxin?

A. Gram-positive bacteria only

B. Gram-negative bacteria only

C. Both gram-positive and gram-negative bacteria

D. Anaerobes only

B. Gram-negative bacteria only — endotoxin refers to lipid A in LPS/LOS.

High concentrations of endotoxin can activate which complement pathway?

A. Classical pathway

B. Lectin pathway

C. Alternative pathway

D. Terminal-only pathway

C. Alternative pathway — endotoxin can activate alternative complement.

What is a typical bacterial capsule made of?

_____

Polysaccharide — most bacterial capsules are polysaccharide-based.

A heavily encapsulated bacterium survives despite neutrophil exposure. What is the capsule mainly preventing?

A. Bacterial replication

B. Translation

C. Phagocytosis

D. Fermentation

C. Phagocytosis — capsules help bacteria avoid engulfment.

Which set lists three ways bacteria evade antibody responses?

A. Antigenic variation, antibody inactivation, intracellular growth

B. ATP production, fermentation, replication

C. Capsule loss, ribosome loss, DNA loss

D. Complement fixation, opsonization, phagolysosome fusion

A. Antigenic variation, antibody inactivation, intracellular growth.

A bacterium repeatedly changes its surface antigens so previously made antibodies no longer bind well. Which immune evasion strategy is this?

A. Antigenic variation

B. Complement activation

C. Opsonization

D. Chemotaxis

A. Antigenic variation — changing surface antigens helps evade existing antibodies.

A bacterium produces enzymes that destroy or inactivate host antibodies. Which immune response is it evading?

A. Antibody-mediated immunity

B. Complement-independent killing

C. T-cell receptor rearrangement

D. Macrophage cytokine release

A. Antibody-mediated immunity — antibody inactivation prevents effective humoral defense.

Why does intracellular bacterial growth help evade antibodies?

Antibodies work best _____— intracellular bacteria are _____ from circulating antibodies.

extracellularly

hidden

Which bacterial structure limits complement access in gram-positive bacteria?

A. Thin LPS layer

B. Thick peptidoglycan

C. Long O antigen

D. Outer membrane porins

B. Thick peptidoglycan — it can physically limit complement-mediated killing.

Which gram-negative structure can limit complement access in most gram-negative bacteria?

A. Long O antigen of LPS

B. Teichoic acid

C. Thick peptidoglycan

D. Spore coat

A. Long O antigen of LPS — it can block complement from reaching the membrane.

Why are Neisseria species an important exception when discussing long O antigen protection?

A. They lack peptidoglycan

B. They have LOS rather than full LPS with long O antigen

C. They are gram-positive

D. They cannot activate complement

B. They have LOS rather than full LPS with long O antigen — this gives less protection from complement.

Which strategy helps bacteria evade phagocytic cells by directly damaging those cells?

A. Producing enzymes that lyse phagocytes

B. Activating C3b opsonization

C. Increasing IgA binding

D. Promoting phagolysosome fusion

A. Producing enzymes that lyse phagocytes.

A bacterium avoids being engulfed by macrophages and neutrophils. Which evasion mechanism is this?

A. Inhibition of phagocytic uptake

B. Increased antigen presentation

C. Complement fixation

D. Cytokine neutralization

A. Inhibition of phagocytic uptake — antiphagocytic factors such as capsules can prevent engulfment.

A bacterium is engulfed by a macrophage but survives by preventing phagosome-lysosome fusion. Which evasion strategy is this?

A. Blocking intracellular killing

B. Antibody class switching

C. Alternative complement activation

D. Anaphylatoxin release

A. Blocking intracellular killing — preventing fusion allows survival inside phagocytes.

A gram-negative bacterium releases endotoxin, activates macrophages, and triggers complement. Which final clinical outcome is most concerning at high endotoxin levels?

A. Hypotension and shock

B. Pure flaccid paralysis

C. No inflammatory response

D. Isolated antibody deficiency

A. Hypotension and shock — cytokines, NO, and anaphylatoxins can cause severe vasodilation.

E coli O157:H7 infection is classically associated with which serious complication?

A. Toxic shock syndrome

B. Pseudomembranous colitis

C. Hemolytic uremic syndrome

D. Gas gangrene

C. Hemolytic uremic syndrome — E coli O157:H7 can cause HUS.

The production of type III secretion devices by Shigella flexneri is triggered by which environmental signal?

A. Oxygen tension

B. Acidic pH

C. High temperature

D. Bile salts

A. Oxygen tension — Shigella flexneri type III secretion expression is triggered by oxygen tension.

The production of type III secretion devices by Salmonella typhimurium is triggered mainly by which signal?

A. IgA binding

B. D-mannose binding

C. Fibronectin binding

D. pH

D. pH — Salmonella typhimurium type III secretion expression is triggered by pH.

The SPI-2 pathogenicity island of Salmonella is activated in which location?

Acidic phagocytic vesicle inside a ______

Acidic phagocytic vesicle inside a macrophage — SPI-2 promotes intracellular survival.

A patient develops pseudomembranous colitis after antibiotic use. Which organism is most likely responsible?

____ ____

Clostridium difficile — C difficile causes pseudomembranous colitis.

Which organism is inhaled, grows in the lungs, and is not typically spread person-to-person?

_____

Legionella — it is acquired by inhalation from environmental water sources and does not readily spread between people.

In E coli, type 1 fimbriae bind which receptor molecule?

A. GM1 ganglioside

B. P blood group glycolipid

C. D-mannose

D. Fibronectin

C. D-mannose — E coli type 1 fimbriae bind mannose-containing receptors.

E coli colonization factor antigen fimbriae bind which host receptor?

A. Collagen

B. Laminin

C. D-mannose

D. GM1 ganglioside

D. GM1 ganglioside — colonization factor antigen fimbriae bind GM1.

E coli strains that cause acute pyelonephritis use which adhesin and receptor pair?

A. Type 1 fimbriae; D-mannose

B. P fimbriae; P blood group glycolipid

C. MSCRAMMs; fibronectin

D. Colonization factor antigen; GM1 ganglioside

B. P fimbriae; P blood group glycolipid — P fimbriae help E coli attach to uroepithelial cells.

Streptococci and Staphylococcus aureus bind fibronectin, collagen, or laminin using which adhesin molecules?

A. MSCRAMMs

B. P fimbriae

C. Type 1 fimbriae

D. Colonization factor antigen

A. MSCRAMMs — microbial surface components recognizing adhesive matrix molecules bind extracellular matrix proteins.

_____ and _____ use fimbriae to bind _____ cells before injecting pathogenic proteins.

Salmonella

Yersinia

M cells

Many proteins injected by a type III secretion device promote which host-cell process?

A. Antibody class switching

B. Complement activation

C. Sphingomyelin breakdown

D. Actin polymerization

D. Actin polymerization — this helps invasion or movement within and between cells.

How does Salmonella promote invasion through the GI tract?

_____ tight junctions of _____ cells

Weakens tight junctions of mucoepithelial cells — this helps Salmonella invade across the intestinal barrier.

Rapid food poisoning from a preformed toxin is classically caused by which organisms?

____ ____

____ ____

Staphylococcus aureus and Bacillus cereus — symptoms occur quickly because the toxin is already in the food.

Clostridium perfringens produces alpha-toxin. What is alpha-toxin?

A. IgA protease

B. Superantigen

C. Adenylate cyclase activator

D. Phospholipase C

D. Phospholipase C — C perfringens alpha-toxin damages membranes.

Clostridium perfringens alpha-toxin breaks down which membrane component?

A. Peptidoglycan

B. Hyaluronic acid

C. Sphingomyelin

D. D-mannose

C. Sphingomyelin — alpha-toxin damages cell membranes by cleaving phospholipids such as sphingomyelin.

Cholera toxin increases cAMP by doing which of the following?

Permanently activating _____

Permanently activating Gs

Pertussis toxin increases cAMP by doing which of the following?

inactivating _____

Inactivating Gi — loss of Gi inhibition increases adenylate cyclase activity.

A toxin cross-links the beta region of the T-cell receptor to MHC II on an APC. What type of toxin is this?

A. Endotoxin

B. Cytolysin

C. Superantigen

D. IgA protease

C. Superantigen — it causes massive nonspecific T-cell activation.

Toxic shock syndrome causes shock mainly through overwhelming release of which cytokines?

A. IL-4, IL-5, IL-13, IgE

B. IL-10, TGF-beta, IL-35, IgA

C. C3a, C3b, C5b, C9

D. IL-1, IL-2, IFN-gamma, TNF-alpha

D. IL-1, IL-2, IFN-gamma, TNF-alpha — massive cytokine release causes shock.

Corynebacterium diphtheriae causes disease by inactivating which target?

____ ____ ____

Elongation factor 2

Tetanospasmin from Clostridium tetani causes disease by which mechanism?

Cleaving _____ proteins to block _____ neurotransmitter release

Cleaving SNARE proteins to block inhibitory neurotransmitter release

Which triad best describes the major clinical effects of endotoxin?

A. Flaccid paralysis, diplopia, dry mouth

B. Fever, shock, DIC

C. Pseudomembranes, watery diarrhea, ileus

D. Spastic paralysis, lockjaw, opisthotonos

B. Fever, shock, DIC — endotoxin can trigger systemic inflammation and coagulation.

The Streptococcus pyogenes capsule is made of which substance?

A. Hyaluronic acid

B. Polyribosylribitol phosphate

C. Lipid A

D. Sphingomyelin

A. Hyaluronic acid — it mimics human connective tissue.

Why is the hyaluronic acid capsule of Streptococcus pyogenes useful for immune evasion?

It mimics human _______ tissue — this helps the bacterium _______ from immune recognition.

It mimics human connective tissue — this helps the bacterium hide from immune recognition.

Which organism evades antibodies by antigenic variation and produces an IgA protease?

_____ _____

Neisseria gonorrhoeae — it changes surface antigens and degrades IgA.

Protein A prevents opsonization and phagocytosis by binding which part of IgG?

_____ region

Fc region — Protein A binds Fc so phagocytes cannot recognize IgG normally.

Which organism expresses Protein A?

_____ _____

Staphylococcus aureus

Which Streptococcus pyogenes toxin causes cell membrane lysis?

A. Tetanospasmin

B. Diphtheria toxin

C. Streptolysin O

D. Cholera toxin

C. Streptolysin O — it lyses host cell membranes.

What is the main role of M protein in Streptococcus pyogenes virulence?

A. Prevents phagocytosis

B. Blocks acetylcholine release

C. Activates adenylate cyclase

D. Breaks down sphingomyelin

A. Prevents phagocytosis — M protein is antiphagocytic.

Mycobacterium species survive inside macrophages by blocking which process?

A. IgA secretion

B. Actin polymerization

C. D-mannose binding

D. Phagosome-lysosome fusion

D. Phagosome-lysosome fusion — this prevents exposure to lysosomal killing contents.

Listeria monocytogenes escapes macrophage killing by doing which of the following?

A. Binding Fc region of IgG

B. Lysing the phagosome and escaping into the cytoplasm

C. Producing hyaluronic acid capsule

D. Activating the alternative complement pathway

B. Lysing the phagosome and escaping into the cytoplasm — Listeria avoids phagolysosomal killing.

Which test result best distinguishes Staphylococcus aureus from Staphylococcus epidermidis?

S aureus is _____ _____

S aureus is coagulase positive — S epidermidis is coagulase negative.

What does coagulase do?

Converts _____ into fibrin to form a _____ barrier

Converts fibrinogen into fibrin to form a clotlike barrier — this helps S aureus wall itself off.

Both cholera toxin and pertussis toxin increase cAMP. Which comparison is correct?

A. Cholera inactivates Gi; pertussis activates Gs

B. Cholera blocks adenylate cyclase; pertussis activates EF-2

C. Cholera cleaves SNARE; pertussis lyses membranes

D. Cholera activates Gs; pertussis inactivates Gi

D. Cholera activates Gs; pertussis inactivates Gi — both increase adenylate cyclase activity and cAMP.

A patient has rapid-onset vomiting after eating food left at room temperature. Why do symptoms appear so quickly with S aureus food poisoning?

A. The toxin is preformed in the food

B. The bacteria must invade macrophages first

C. The bacteria must form M protein first

D. The toxin requires phagosome-lysosome fusion

A. The toxin is preformed in the food — bacterial growth inside the host is not required first.

Salmonella and Yersinia bind M cells, inject proteins, and stimulate uptake into the host cell. Which bacterial tool makes this injection possible?

A. Coagulase

B. Type III secretion device

C. Protein A

D. IgA protease

B. Type III secretion device — it injects virulence proteins into host cells.

Listeria and Shigella use actin polymerization mainly for which purpose?

______ within cells and spread to neighboring cells

movement

A clinician is trying to maximize the yield of a blood culture in a patient with suspected bacteremia. What is the most important factor for success?

_____ of blood processed

Volume of blood processed — larger appropriate blood volume improves blood culture yield.

Approximately how much blood should be collected from an adult for each blood culture?

A. 1 mL

B. 5 mL

C. 10 mL

D. 20 mL

D. 20 mL — adult blood cultures require about 20 mL per culture.

How much blood should generally be collected per blood culture in children?

A. 1-5 mL

B. 5-10 mL

C. 20-25 mL

D. 30-35 mL

B. 5-10 mL — children require less blood than adults.

How much blood should generally be collected per blood culture in neonates?

A. 1 mL

B. 5 mL

C. 10 mL

D. 20 mL

A. 1 mL — neonates require only about 1 mL per culture.

A patient with pneumonia has bacteremia that appears only at certain times rather than constantly. What type of septicemia is this?

A. Continuous septicemia

B. Intermittent septicemia

C. Latent septicemia

D. Commensal septicemia

B. Intermittent septicemia — localized infections such as lung, urinary tract, or soft tissue infections can seed blood intermittently.

A patient with infective endocarditis or septic thrombophlebitis has persistent bacteria in the blood. What type of septicemia is most likely?

A. Intermittent septicemia

B. Transient septicemia

C. Continuous septicemia

D. Localized septicemia

C. Continuous septicemia — intravascular infections such as endocarditis or septic thrombophlebitis cause continuous bloodstream infection.

Most clinically significant blood culture isolates are detected within what time frame?

A. 1-2 hours

B. 1-2 days

C. 5-7 days

D. 2-3 weeks

B. 1-2 days

Even though most significant isolates appear early, blood cultures should be incubated for at least how long?

A. 12 hours

B. 24 hours

C. 5-7 days

D. 30 days

C. 5-7 days

When CSF is collected from a suspected patient with ______, the specimen is concentrated by ______ and the sediment is used to inoculate bacteriologic media and prepare a ______ stain

meningitis

centrifugation

Gram

After CSF is centrifuged in suspected meningitis, which part is used to inoculate bacteriologic media and prepare a Gram stain?

A. Supernatant

B. Sediment

C. Serum layer

D. Clot

B. Sediment

For routine bacterial culture of CSF, what specimen volume is usually collected?

A. 0.1 mL

B. 1-5 mL

C. 20 mL

D. 50 mL

B. 1-5 mL

If mycobacterial meningitis is suspected, how much CSF should be collected?

As large a sample as possible — mycobacteria may be _____, so larger volume improves _____.

sparse

detection

Most bacterial infections of the pharynx are caused by which organism?

_____ _____ _____

Group A Streptococcus

Which swab types are appropriate for collecting pharyngeal specimens?

A. Cotton or dacron

B. Wood or dacron

C. Dacron or calcium alginate

D. Metal or calcium alginate

C. Dacron or calcium alginate — these are used for throat specimens.

Why should saliva contamination be avoided when collecting a throat swab for suspected group A strep?

____ bacteria can ____ growth of group A streptococci

Saliva

inhibit

Which specimens should be inoculated onto culture media immediately after collection before transport to the lab?

_____ _____ and _____ _____ — these organisms are fragile and require immediate inoculation.

Bordetella pertussis and Neisseria gonorrhoeae — these organisms are fragile and require immediate inoculation.

Group A streptococci can be detected directly from a clinical specimen using which method?

_____ for _____ -specific antigen

Immunoassay for group-specific antigen

Which set contains the most common bacterial causes of sinusitis?

_____ _____

_____ _____

_____ _____

_____ _____

Haemophilus influenzae

Streptococcus pneumoniae

Moraxella catarrhalis

Staphylococcus aureus

A respiratory specimen has many squamous epithelial cells on microscopy. What does this suggest?

A. Excellent lower respiratory specimen

B. Saliva contamination

C. Mycobacterial infection

D. Bloodstream contamination

B. Saliva contamination — squamous epithelial cells indicate oral contamination.

What procedure is required to make a specific microbiologic diagnosis of a middle ear infection?

A. Nasopharyngeal swab

B. Tympanocentesis

C. Throat culture

D. Blood culture

B. Tympanocentesis — sampling middle ear fluid is needed for a specific diagnosis.

An abscess is drained and cultured. Where within the abscess are organisms most commonly replicating?

A. Surface crust

B. Base of the abscess

C. Surrounding normal skin

D. Necrotic center only

B. Base of the abscess — organisms most actively replicate at the base.

Clostridium difficile — it is a major cause of antibiotic-associated _____ and _____

diarrhea

colitis.

What is the most sensitive and specific test for diagnosing Clostridium difficile infection?

____ ____ ____ ____ (____) detects C difficile toxin genes.

nucleic acid amplification testing (NAAT) detects C difficile toxin genes.

How long does it usually take to isolate and identify enteric pathogens by traditional methods?

A. 1-3 hours

B. 12 hours

C. 3 days

D. 2 weeks

C. 3 days — enteric pathogen isolation and identification usually takes about 3 days.

A lab wants rapid detection of common bacterial, viral, and parasitic enteric pathogens directly from fecal swabs. Which method can detect them in 1-3 hours?

A. High-multiplex NAAT

B. Broth dilution

C. Blood agar hemolysis

D. Acid-fast stain

A. High-multiplex NAAT — it can rapidly detect multiple enteric pathogens directly from fecal swabs.

Which factor is required for aminoglycosides to enter bacterial cells?

A. Carbon dioxide

B. Oxygen

C. Capsule

D. IgA

B. Oxygen — aminoglycoside uptake is oxygen-dependent.

Why are aminoglycosides generally ineffective against anaerobes?

A. Anaerobes destroy all ribosomes

B. Anaerobes lack oxygen-dependent drug uptake

C. Anaerobes always produce beta-lactamase

D. Anaerobes have no cell membrane

B. Anaerobes lack oxygen-dependent drug uptake

What is one advantage of broth dilution antibiotic susceptibility testing?

A. It requires no bacteria

B. Any antibiotic can be tested

C. It only detects viruses

D. It gives results without incubation

B. Any antibiotic can be tested — broth dilution is flexible for different antibiotics.

What is one limitation of broth dilution tests?

The manufacturer determines the _______ range and limited dilutions are _______.

The manufacturer determines the antibiotic range and limited dilutions are available.

Which organisms are alpha-hemolytic?

_____ _____

_____ _____

Streptococcus pneumoniae

Viridans streptococci

Which set contains beta-hemolytic organisms?

_____ _____

_____ _____

_____ _____

_____ _____

Streptococcus pyogenes

Streptococcus agalactiae

Staphylococcus aureus

Listeria monocytogenes

A stool specimen shows gram-negative bacteria arranged in S-shaped pairs. Which organism is most likely?

______

Campylobacter

A blood agar plate shows a large outer zone of alpha-hemolysis with an inner zone of beta-hemolysis. Which organism classically produces this double zone?

_____ _____

Clostridium perfringens

Which specimen should be sampled from an abscess to maximize recovery of actively growing organisms?

_____ base because organisms most commonly _____ there.

Abscess base — organisms most commonly replicate there.

A lab reports the MIC of an antibiotic for a bacterial isolate. What does this value tell the clinician?

The ____ drug concentration that stops ____ growth

The lowest drug concentration that stops visible growth

What is the most common pathogen that causes swimmer's ear?

Pseudomonas aeruginosa

What organism is a gram-negative rod that has bipolar staining?

_____

Enterobacteriaceae

What two classes of organisms are best detected using microscopy?

1. ____-____ rods

2. ____-____ cocci

1. Acid-fast rods

2. Gram-negative cocci

A patient with infective endocarditis has persistently positive blood cultures throughout the day. What septicemia pattern is most likely?

A. Transient septicemia B. Intermittent septicemia C. Continuous septicemia D. Localized septicemia

C. Continuous septicemia — intravascular infections cause continuous bacteremia.

Intermittent septicemia occurs in patients with _____ infections

Continuous septicemia occurs primarily in patients with _____ infections

localized

intravascular

To maximize recovery from an adult blood culture, how should the media bottles be inoculated?

A. One bottle, 20 mL

B. Two bottles, 5 mL each

C. Four bottles, 2 mL each

D. Two bottles, 10 mL each

D. Two bottles, 10 mL each — each culture uses two bottles with 10 mL per bottle.

After blood culture bottles arrive in the laboratory, at what temperature should they be incubated?

A. 25°C

B. 37°C

C. 4°C

D. 60°C

B. 37°C — blood cultures are incubated at body temperature.

A CSF specimen is collected for suspected meningitis. Which handling instruction is most appropriate?

A. Freeze before transport

B. Refrigerate immediately

C. Avoid heat and refrigeration

D. Heat before plating

C. Avoid heat and refrigeration — CSF should not be heated or refrigerated.

Which direct test can detect group A strep?

A. Immunoassay

B. Coagulase test

C. Oxidase test

D. Acid-fast stain

A. Immunoassay — group A strep antigen can be detected directly.

A clinician sends an oropharyngeal and nasopharyngeal culture to diagnose a lower respiratory infection. Why is this specimen inappropriate?

A. It is normally sterile

B. It misses oral flora

C. It is not useful

D. It requires refrigeration

C. It is not useful — nasopharyngeal or oropharyngeal culture should not be used.

A lower respiratory specimen has many squamous epithelial cells on microscopy. What does this indicate?

_____ contamination

Saliva contamination

A wound culture is needed, but the surface is covered with colonizing flora. What is the best collection method?

A. Surface swab only

B. Dried drainage sample

C. Deep aspiration

D. Surrounding skin swab

C. Deep aspiration — collect deep in the wound, preferably by aspiration.

2 most common genital specimens?

_____ _____

_____ _____

Neisseria gonorrhoeae

Chlamydia trachomatis

How should you collect a feces sample?

____ pan not a swab

Clean

Two general forms of antimicrobial susceptibility tests are performed in the clinical laboratory:

_____ _____ tests and _____ _____ tests

broth dilution tests and agar diffusion tests

A broth dilution test is one in which an antibiotic is prepared in a _____ medium and then then _____ with a standardized concentration of bacteria.

nutrient

innoculated

An agar diffusion test has bacteria spread over a surface, then a _____ with _____ is inserted into the surface.

If there is no _____ around the disk it is senstive to the _____ if there are bacteria it is resistant

disk

antibiotics

bacteria

antibiotic

A sputum smear is ordered because the clinician wants direct visualization of organisms often missed by routine Gram stain. Which class is microscopy especially useful for?

A. Anaerobic cocci

B. Viridans streptococci

C. Enteric bacilli

D. Acid-fast rods

D. Acid-fast rods — acid-fast organisms are best detected by microscopy.

A urethral discharge specimen is examined directly because the suspected organism is best detected microscopically. Which organism class fits this?

A. Gram-positive rods

B. Gram-negative cocci

C. Anaerobic bacilli

D. Spore-forming rods

B. Gram-negative cocci — microscopy is useful for gram-negative cocci.

To maximize recovery from an adult blood culture, how should the media bottles be inoculated?

A. One bottle, 20 mL

B. Two bottles, 5 mL each

C. Four bottles, 2 mL each

D. Two bottles, 10 mL each

D. Two bottles, 10 mL each — each culture uses two bottles with 10 mL per bottle.

A clinician wants blood cultures drawn exactly during a fever spike. Which statement is most accurate?

A. Timing is essential

B. Timing prevents contamination

C. Timing detects fungi only

D. Timing is less important

D. Timing is less important — collection timing itself is not very important.

A resident asks for a Gram stain directly on blood from a septic patient. Why is this low yield?

Too _____ organisms — _____ blood usually has very low organism burden.

Too few organisms — septic blood usually has very low organism burden.

A CSF specimen from suspected meningitis is sitting unprocessed. Why is immediate processing important?

A. Some pathogens are labile

B. CSF rapidly clots

C. NAAT requires freezing

D. Anaerobes overgrow quickly

A. Some pathogens are labile — N meningitidis and S pneumoniae are fragile.

Which meningitis pathogens are especially labile in CSF specimens?

A. E coli, B fragilis

B. S aureus, Listeria

C. C difficile, Shigella

D. N meningitidis, S pneumoniae

D. N meningitidis and S pneumoniae — both can degrade quickly.

A CSF specimen is sent to detect bacteria, viruses, and fungi. Which method is commonly used?

A. Coagulase test

B. NAAT

C. Oxidase test

D. Catalase test

B. NAAT — nucleic acid amplification tests detect multiple CSF pathogens.

A sterile abdominal fluid specimen may contain anaerobes. What handling error should be avoided?

A. Oxygen exposure

B. Prompt processing

C. Sterile collection

D. Anaerobic transport

A. Oxygen exposure — oxygen inhibits anaerobe recovery.

Anaerobic culture handling is especially important in which infections?

A. Skin and urinary

B. Bone and joint

C. Intra-abdominal and pulmonary

D. Pharyngeal and sinus

C. Intra-abdominal and pulmonary — these often involve anaerobes.

Most bacterial pharyngitis is caused by which organism?

____ ____ Streptococcus

Group A Streptococcus

A pharyngitis culture is ordered for Bordetella pertussis. What should the lab expect?

A. Routine recovery

B. Special techniques

C. Anaerobic transport

D. Blood culture only

B. Special techniques — B pertussis requires special recovery methods.

When collecting a throat swab for suspected group A strep, what contamination should be avoided?

A. Saliva

B. Exudate

C. Tonsillar tissue

D. Posterior pharynx

A. Saliva — saliva flora can overgrow or inhibit GAS.

Which throat areas should be sampled for suspected bacterial pharyngitis?

A. Tongue and cheeks

B. Teeth and gums

C. Tonsils, posterior pharynx, exudate

D. Lips, palate, uvula

C. Tonsils, posterior pharynx, exudate — include ulcerative areas if present.

A rapid group A strep immunoassay is positive. What is the major strength of immunoassays?

A. High sensitivity

B. Low specificity

C. High specificity

D. Anaerobe detection

C. High specificity — GAS immunoassays are highly specific.

Current NAATs for group A strep are best described as having what major advantage?

A. Low contamination risk

B. High sensitivity

C. No transport needs

D. Detects all anaerobes

B. High sensitivity — current GAS NAATs are highly sensitive.

Which organisms are relatively resistant to drying during throat specimen handling?

A. GAS, C diphtheriae

B. B pertussis, gonorrhoeae

C. S pneumoniae, meningitidis

D. H influenzae, Moraxella

A. Group A strep and C diphtheriae — both resist drying.

A child has suspected epiglottitis. Why should epiglottis culture be avoided?

A. Causes false negatives

B. Requires anaerobic transport

C. May obstruct airway

D. Detects normal flora only

C. May obstruct airway — especially dangerous in children.

A specific microbiologic diagnosis of sinusitis requires direct aspiration, anaerobic transport, and what else?

A. Fever-spike timing

B. Saliva dilution

C. Blood culture

D. Prompt processing

D. Prompt processing — sinus aspirates need rapid lab processing.

A blood culture grows Candida, while another grows E coli. Collectively, these bloodstream infections are called what?

A. Cellulitis B. Empyema C. Septicemia D. Abscess

C. Septicemia — bacteremia and fungemia are collectively septicemia.

A septic patient needs blood cultures before therapy. What collection strategy gives optimal yield?

A. Two to three samples

B. One large syringe

C. One aerobic bottle

D. Fever-spike sampling

A. Two to three samples — collect 2–3 blood samples when possible.

A patient already received antibiotics before blood cultures. Why is this suboptimal?

A. Causes false gram stain

B. Inhibits organism recovery

C. Causes anaerobe overgrowth

D. Dilutes the specimen

B. Inhibits organism recovery — cultures are best collected before antibiotics.

Which organisms should be inoculated onto culture media immediately after collection?

A. GAS, C diphtheriae

B. S aureus, pneumococcus

C. H influenzae, Moraxella

D. B pertussis, N gonorrhoeae

D. B pertussis and N gonorrhoeae — both are fragile.

A cavitary lung infection is suspected to be caused by an organism requiring extended incubation. Which organism fits this concern?

A. Moraxella catarrhalis

B. Streptococcus pneumoniae

C. Mycobacteria

D. Haemophilus influenzae

C. Mycobacteria — mycobacteria need extended incubation.

A branching, weakly acid-fast pulmonary pathogen is suspected. How should the lab handle incubation?

A. Stop at 48 hours

B. Extend incubation

C. Refrigerate only

D. Discard early

B. Extend incubation — Nocardiae require longer incubation than routine pathogens.

A child presents with fever, ear pain, and bulging tympanic membrane. Which set contains the most common otitis media pathogens?

A. Pneumococcus, H influenzae, Moraxella

B. Pseudomonas, S aureus, Candida

C. Gonorrhoeae, Chlamydia, Treponema

D. Mycobacteria, Nocardia, Legionella

A. Pneumococcus, H influenzae, Moraxella — these are classic otitis media pathogens.

Otitis externa culture is needed after treatment failure. What is the best specimen?

A. Middle-ear aspirate

B. Nasal swab

C. Ear-area scraping

D. First-void urine

C. Ear-area scraping — culture uses scraping of the involved ear area.

A patient has suspected bacterial conjunctivitis. How should the initial eye surface specimen be collected?

A. Swab before anesthetic

B. Swab after anesthetic

C. Direct eye aspiration

D. First morning urine

A. Swab before anesthetic — topical anesthetics can interfere with recovery.

A corneal ulcer is suspected after contact lens use. After surface swabbing, what specimen may be needed?

A. Corneal scraping

B. Midstream urine

C. Nasopharyngeal swab

D. Blood culture

A. Corneal scraping — corneal scrapings are used when necessary.

Endophthalmitis is suspected after eye surgery. What is the proper intraocular specimen method?

A. Surface swab

B. Corneal scraping

C. Direct aspiration

D. Eyelid scraping

C. Direct aspiration — intraocular specimens are collected by aspirating the eye.

Why are ocular infection cultures often difficult to interpret?

A. Excessive specimen volume

B. Few organisms present

C. Constant anaerobe overgrowth

D. Routine blood contamination

B. Few organisms present — ocular samples are small with low organism burden.

An ocular specimen may contain Neisseria gonorrhoeae. What special lab need should be considered?

A. Specialized culture media

B. Extended mycobacterial incubation

C. Anaerobic urine preservative

D. Biphasic blood bottles

A. Specialized culture media — N gonorrhoeae requires special media.

An ocular infection is suspected to be caused by Chlamydia trachomatis. Which culture approach is needed?

A. Blood agar only

B. Tissue culture cells

C. Anaerobic broth

D. Routine urine agar

B. Tissue culture cells — Chlamydia requires intracellular culture systems.

A urine culture is collected for suspected cystitis. Why is the first portion of urine discarded?

A. It lacks bladder organisms

B. It contains urethral flora

C. It kills anaerobes

D. It prevents pyuria

B. It contains urethral flora — the urethra is colonized by bacteria.

A urine specimen cannot be plated immediately. What should be done?

A. Leave at room temperature

B. Warm to 37°C

C. Refrigerate or preserve

D. Freeze before transport

C. Refrigerate or preserve — this prevents overgrowth before culture.

Why should urine culture transport not be delayed?

A. Pathogens grow in urine

B. Urine rapidly clots

C. NAATs become nonspecific

D. Pyuria disappears instantly

A. Pathogens grow in urine — delay can falsely increase colony counts.

A urine culture plate is inoculated with a calibrated loop. What volume is typically used?

A. 1–10 µL

B. 0.5–1 mL

C. 5–10 mL

D. 20–30 mL

A. 1–10 µL — measured inoculation allows colony quantification.

Why is a measured urine volume plated for culture?

A. Quantify organism burden

B. Prevent oxygen exposure

C. Detect exotoxin genes

D. Remove urethral cells

A. Quantify organism burden — colony counts help judge significance.

A symptomatic patient has pyuria but only low colony counts. How should this be interpreted?

A. Always contamination

B. Potentially significant

C. Reject automatically

D. Ignore without testing

B. Potentially significant — small numbers matter when pyuria is present.

Most labs evaluating sexually transmitted urethritis focus on which pathogens?

A. Gonorrhoeae and trachomatis

B. Pneumococcus and Moraxella

C. Mycobacteria and Nocardia

D. Pseudomonas and Staph

A. Gonorrhoeae and trachomatis — NAATs commonly target these organisms.

A man has dysuria and urethral discharge. Which urine specimen is preferred for GC/CT NAAT?

A. Midstream urine

B. First-void urine

C. Refrigerated catheter urine

D. Discarded first portion

B. First-void urine — urethritis organisms are captured early.

A woman has suspected cystitis rather than urethritis. Which urine collection best reduces urethral contamination?

A. First-void urine

B. Midstream urine

C. Eye aspirate

D. Corneal scraping

B. Midstream urine — cystitis testing avoids urethral contamination.

A patient has a painless genital chancre, but the suspected organism cannot be cultured. Which diagnostic approach is appropriate?

A. Stool culture

B. Darkfield or serology

C. Blood agar culture

D. Broth dilution

B. Darkfield or serology — Treponema pallidum cannot be cultured routinely.

A spirochete is suspected in a syphilis lesion, but brightfield microscopy is negative. Why can this happen?

A. Too thick

B. Nonmotile organism

C. Intracellular growth

D. Too thin

D. Too thin — Treponema pallidum is too thin for brightfield microscopy.

A clinician collects fluid from a suspected syphilitic chancre for microscopy. When should the exam be performed?

A. After refrigeration

B. After 24 hours

C. At collection

D. After freezing

C. At collection — T pallidum dies rapidly with air and drying.

A stool specimen for enteric culture sits unprocessed for hours. Which change can harm pathogens such as Shigella?

A. Alkaline shift

B. Acidic shift

C. Oxygen depletion

D. Bile dilution

B. Acidic shift — bacterial metabolism acidifies stool and can kill Shigella.

Why should stool specimens be transported promptly for culture?

A. Prevent toxic pH changes

B. Increase bacterial metabolism

C. Preserve urine volume

D. Prevent antibody loss

A. Prevent toxic pH changes — acidic changes can inhibit some enteric pathogens.

A rectal swab is submitted for routine stool culture. Why is this specimen poor?

A. Too anaerobic

B. Too acidic

C. Inadequate pathogen recovery

D. Excessive stool volume

C. Inadequate pathogen recovery — rectal swabs are not ideal for stool culture.

Transport of a stool specimen will be delayed. Which medium is appropriate?

A. Chocolate agar

B. Cary-Blair medium

C. Thioglycolate broth

D. Loeffler medium

B. Cary-Blair medium — delayed fecal specimens need preservative transport medium.

Which preservative can be used for delayed stool transport?

A. Phosphate-glycerol buffer

B. Sheep blood agar

C. Mueller-Hinton agar

D. Sabouraud agar

A. Phosphate-glycerol buffer — phosphate buffer with glycerol helps preserve feces.

A patient has rapid vomiting after reheated rice. Stool culture is negative for the causative organism. Why?

A. Intracellular infection

B. Preformed toxin disease

C. Slow anaerobic growth

D. Acid-fast organism

B. Preformed toxin disease — B cereus illness is toxin-mediated before ingestion.

Which organisms are not expected in stool because illness is caused by preformed food toxin?

A. Shigella, Salmonella

B. Vibrio, Campylobacter

C. S aureus, B cereus

D. Giardia, Cryptosporidium

C. S aureus, B cereus — disease comes from toxin already in food.

A clinician strongly suspects a specific unusual enteric pathogen. What should be done for optimal testing?

A. Notify the laboratory

B. Delay specimen transport

C. Request rectal swab

D. Avoid preservatives

A. Notify the laboratory — special media or tests may be required.

Why can culture-based enteric pathogen identification take several days?

A. Feces lacks bacteria

B. Feces has mixed flora

C. Culture is always anaerobic

D. NAAT blocks growth

B. Feces has mixed flora — many normal and pathogenic bacteria are present.

Which method is becoming preferred for broad enteric pathogen detection?

A. High multiplex NAAT

B. Gram stain only

C. Blood culture

D. Broth dilution

A. High multiplex NAAT — it is rapid and more sensitive than culture.

High multiplex NAAT can detect common enteric pathogens directly from fecal swabs in what time?

A. 24–48 hours

B. 1–3 hours

C. 3–5 days

D. 2–4 weeks

B. 1–3 hours — multiplex NAAT gives results in hours.

High multiplex NAAT is especially useful for pathogenic E coli because it can distinguish it from what?

A. Normal enteric E coli

B. C difficile toxin

C. Acid-fast rods

D. Anaerobic lung flora

A. Normal enteric E coli — pathogenic strains may resemble normal flora by culture.

In a broth dilution test, antibiotics are prepared how?

A. On paper disks

B. In dilution series

C. On corneal scrapings

D. Inside blood bottles

B. In dilution series — serial antibiotic dilutions are inoculated with bacteria.

Broth dilution testing is used to determine which value?

A. O antigen

B. Toxin titer

C. MIC

D. Capsule thickness

C. MIC