Microbiology Test 1- Lecture
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
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).
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.
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
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.
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.
One organism benefits and one is unaffected
Both organisms benefit
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
Could be through air, water and food
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
Directed movement of an organism toward (positive chemotaxis) or away (negative chemotaxis) a chemical gradient
ex: chemotaxis determines where bacteria will move
The shape of a cell
ex: coccus, rod, spirillum
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
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
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
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
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
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.
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
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