Microbiology Test 1- Lecture

Helpfulness: 0
Set Details Share
created 7 months ago by gissromero
book cover
No Chapter
Microbiome (Ch 14&1) Principles of Disease and Epidemiology (Ch 14) Functional Anatomy of Prokaryotic Cells (Ch 4) Microbial Mechanisms of Pathogenicity (Ch 15)
updated 7 months ago by gissromero
show moreless
Page to share:
Embed this setcancel
code changes based on your size selection

Define Microbiota

The group of microbes that normally inhabit the surfaces of the body without causing disease

ex: Staphylococcus is part of the normal microbiota on the surface of the skin and sweat ducts.


Define Opportunistic Pathogens

Microorganisms that cause disease when the immune system is suppressed, when microbial antagonism is reduced, or when introduced into an abnormal area of the body.

ex: E.Coli can be an opportunistic pathogen even though it is part of the intestinal microbiota. Should E.Coli move into the urethra a UTI could result.


Define Microbial Antagonism

Normal condition in which established microbiota use up available nutrients and space, reducing the ability of arriving pathogens to colonize.

ex: microbial antagonism is also called microbial competition


Define Acne

Skin disorder characterized by the presence of white heads, black heads, and in severe cases, cysts; typically caused by infection with Propionibacterium acnes.

ex: Acne can be formed by biota living on the skin


Discuss the pros and cons of using long term antibiotics to treat acne

Pros: With treatment, acne can be reduced

Cons: Treatment with Doxycyclin or Benzol Peroxide can help diminish & exfoliate the dead skin cells


Define Normal Biota

Also termed normal flora and indigenous microbiota

*Organisms that colonize the body's surface without normally causing disease


Will died of E.Coli infection after an intestinal puncture. Explain why this microbe, which normally lives in the colon, could kill this patient.

E.Coli is part of the microbiota of the GI tract and has a mutualistic relationship where we need them for nutrient absorption. Normally, the mucous in the epithelial tissue and the tightly packaged cells blocks the invasion of E.Coli from moving to and infecting other parts of the body. But if the intestines are punctured, the tissue below becomes exposed and E.Coli is able to enter the body and produce growth where the defenses against this bacterium are poor


What role do normal microbiota play in protecting the GI tract from colonization by pathogens?

The normal microbiota serve to protect the body by outcompeting pathogens. The metabolism of intestinal microorganisms also produces vitamins.


Why does treatment of strep throat with an antibacterial drug increase the chances of vaginal candidiasis?

The antibiotics kill the bacteria in the throat, but they also kill the bacteria in the vagina, which allows the room for bacterium that cause yeast infection (vaginal candidiasis).


Define Mutualism

A symbiotic relationship in which both members benefit from their interaction

ex: the normal biota in your colon. they help you absorb nutrients and you provide them with a warm moist place to live.


Define Reservoir of Infection

Living or nonliving continuous source of infectious disease

ex: animals can act as reservoirs of infections and during zoonoses those diseases can be spread from the animals to humans.


Define Signs

Objective changes in a patient that can be observed and measured

ex: Blood pressure and temperature are signs of a disease as they can be measured or see by an observer


Define Symptoms

A changes in body function that are subjective and are not apparent to an observer.

ex: pain and other feelings a patient has are symptoms that can not be measured or seen by an observer


Define Nosocomial Infections

An infection acquired in a health care facility

ex: Health care workers that see many immune compromised patients create the ideal conditions for nosocomial infections to occur.


Define Epidemiology

Study of the occurrence, distribution and spread of disease in humans

ex: epidemiology helps us understand where diseases start and how they spread through a population


Define and list Koch's Postulates

A procedure to establish the specific cause of disease


1) The agent must be found

2)Pure culture must reproduce the same disease in animals

3)The agent must again be present in the experimental animal

4)A pure culture must be obtained


Define Latent Disease

A disease in which the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease

ex: shingles- latent disease as it is caused by the reactivation of Varicellovirus (chicken pox)


How are Koch's postulates used in etiology?

The microorganism isolated must be present in all organisms suffering from the same disease. If the same microorganism is isolated from the patients then there is the possible cause for their disease.


Define Commensalism

One organism benefits and one is unaffected


Define Mutualism

Both organisms benefit


Define Parasitism

One organism benefits at the expense of others


Distinguish the types of symbiosis from most beneficial to most harmful for the host

Mutualism, Commensalism, Parasitism


Categorize diseases according to frequency of occurence



Direct/Indirect Contact Transmission

Direct Contact: Requires close association between the infected & susceptible host

ex: sexually transmitted infections

Indirect Contact: Spreads to a host by a nonliving object called a fomite ex: pinpads


Vehicle Transmission

Could be through air, water and food


Vector Transmission

Anthropods: ticks, mosquitos and especially fleas


Vector Transmission- Mechanical

Anthropods carry pathogen on its feet


Vector Transmission- Biological

Pathogen reproduces in the vector transmitted via bite or feces`


The three modes of disease transmission

Direct Contact: person to person, placental, fecal-oral

Indirect Contact: Fomites

Droplet Transmission: Transmission via airborne droplet < than 1 meter away


Give one example of a microbe that has: a human reservoir, an animal reservoir, and a nonliving reservoir



Describe the difference between an acute infection and a chronic infection. What are the signs and symptoms of acute Lyme disease and chronic Lyme disease?

Acute infection- an infection in which symptoms develop rapidly but last for only a short amt of time

Chronic infection- an illness that develops slowly and is likely to continue or recur for long periods


Define Gram Positive

A bacterial wall whose cell wall consists chiefly of peptidoglycan; it lacks the user membrane of gram negative cells

ex: gram positive bacteria have only 2 membrane structures, having a thick cell wall


Define Chemotaxis

Directed movement of an organism toward (positive chemotaxis) or away (negative chemotaxis) a chemical gradient

ex: chemotaxis determines where bacteria will move


Define Morphology

The shape of a cell

ex: coccus, rod, spirillum


Define Flagellum

A long, thin cellular appendage capable of rotation and responsible for swimming motility in prokaryotic cells

ex: the flagellum is powered by a proton motive force and causes movement of Many different types of bacteria


Define Endospore

A highly heat resistant, thick walled, differentiated structure produced by certain gram-positive bacteria

ex: endospore can survive for hundreds of years helping to ensure bacteria growth


Define Diffusion

the dispersal of molecules, ions, or microscopic particles propelled down a concentration gradient by spontaneous random motion to achieve a uniform distribution

ex: osmosis is the diffusion of water across a biological membrane


Define Active Transport

Nutrient transport method that requires carrier proteins in the membranes in the living cells and expenditure of energy

ex: active transport moves molecules against their concentration gradient and this is why it uses energy


Define Group Translocation

Active process, occurring in some prokaryotes, by which a substance being actively transported across a cell membrane is chemically changed during transport

ex: glucose is a phosphorylated while being transported to maintain the glucose gradient


Describe basic bacterial morphology

Coccus: spherical or ovoid bacterium

Bacillus: any rod shaped bacterium

Spirillum: helical or corkscrew shaped bacterium


Describe the process of endospore formation

1) spore septum begins to isolate newly replicated DNA and a small portion of cytoplasm

2) plasma membrane starts to surround DNA cytoplasm and membrane isolated in step 1

3) Spore septum surrounds isolated portion forming forespore

4)Peptidoglycan layer forms between membranes

5) Spore coat forms

6)Endospore is free from cell


How does flagellum aid in bacterial cell movement

Flagella allow bacteria to move toward (positive chemotaxis) or away (negative chemotaxis) from stimuli


How does Osmosis play a role in the pathogenies of cholera

Osmosis- the tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, equalizing the concentration of materials on either side of the membrane.

IN CHOLERA- increased concentration of cyclic AMP pumps Cl- and Na+ (electrolytes) out f cells into the lumen, increasing ions in the lumen and lowering water potential. Osmosis tries to mediate hydration in lumen but dehydrates cells


Define Toxins

Any poisonous substance produced by a microorganism

ex: toxins are often the factor produced by pathogens that induces the structural change in a patient that causes disease


Define Superantigens

An antigen that activates many different T cells, thereby eliciting a large immune response

ex: superantigens induce such a strong immune response that shock may occur


Define Virulence Factor

Enzymes, toxins, and other factors that affect the relative ability of a pathogen to infect and cause disease

ex: Virulence Factors are anything that helps the microbe cause disease


Define Endotoxins

Potentially fatal toxin released from the cell wall of dead and dying Gram negative bacteria

ex: endotoxin is the lipid A part of the LPS that is found on the outer membrane of Gram negative bacteria. Rapid release of endotoxin can induce shock in some patients.


Define Hemolysis

An enzyme that lyses red blood cells

ex: there are different types of hemolysis that work in different conditions, such as streptlysin O works in anaerobic environments


Define Shock

Any life-threatening loss of blood pressure

ex: septic shock is shock induced by a bacterial infection of the blood


Identify principal portals of entry

Mucous membranes, skin, direct deposition beneath the skin or membranes (parenteral route)


List types of adhesion factors and the roles they play in infection

Adhesion- process by which microorganisms attach themselves to host cells.

Adhesins (ligands) on the pathogen bind to receptors on the host cell



Microbes form biofilm ( communities that share nutrients)


Describe Biofilm Formation


2) irreversible attachment

3) growth and division

4)mature microcolony formation



Explain how biofilms can prevent antibiotic treatment

The higher resistance is due to lower metabolisms in biofilm

Slow penetration of antimirobial

Resistant phenotype due to HGT and close proximity

Altered microenvironment doesn't work due to nutrient availability


Why is attachment of a microbe considered a virulence factor?

The way they attach can cause damage to the host cell. After that the intruder bacterium could secrete toxins into the cells.


Describe the steps a pathogen has to do in order to cause a communicable disease in an individual

1) enter a host through a portal of entry

2)attach itself to a vulnerable host cell

3)avoid immune system then replicate

4)find a portal of exit through the body

5) infect another persons


Explain how microbial extracellular enzymes affect virulence

Many pathogens secrete enzymes that enable them to dissolve structural chemicals in the body and thereby maintain an infection, invade further and avoid body defenses


Explain how microbial toxins affect virulence

Chemicals harm tissues or trigger host immune responses that cause damage. They enter the blood stream and are carried to other parts of the body

Exotoxins- secrete central to their pathogenicity in that they destroy host cells or interfere with host metabolism

Endotoxins- are also called lipid A and are the lipid portion of the bacteria membranes lipopolysaccharide. They can be released when gram negative bacteria divide.


Explain how microbial antiphagocytic factors affect virulence

The body phagocytic cells are called macrophages and they engulf and remove invading pathogens

Some bacteria produce chemicals that prevent the fusion of lysosomes with phagocytic vesicles and allows the bacteria to survive on phagocytes