chapter 15: microbial mechanisms of pathogenicity

Question 1

portals of entry

Answer 1

how microorganisms enter a host; affect whether infection occurs; affect the course of the disease
-ex) mucous membranes; skin; parenteral route (deposited directly into tissues when barriers are penetrated)

Question 2

ID50

Answer 2

infectious dose for 50% of the population; measures virulence of a microbe

Question 3

LD50

Answer 3

lethal dose for 50% of the population

Question 4

how bacteria beat host defenses [examples]

Answer 4

• slippery capsules
• waxy mycolic acid cell wall of mycobacterium resists digestion
• production of enzymes (IgA proteases) which break down IgA antibodies
• bacterial biofilms keep WBCs & antibiotics out

Question 5

endotoxin

Answer 5

toxin that is present in a bacterial cell & is released when cell disintegrates
- ex) lipopolysaccharide (LPS) = portion of outer membrane of gram-negative cells

Question 6

exotoxin

Answer 6

a toxin released by a living bacterial cell into its surroundings; most prominent poisons known; made of protein & can be denatured by heating

Question 7

cytopathic effect (CPE)

Answer 7

detectable changes (damage) in host cells caused by viral infections; depends on the point in the viral infection cycle the cell is in; can be used to identify the virus by looking at infected cells

Question 8

microbiome

Answer 8

all of the microbes that live on or inside of the human body; competitively exclude pathogens by taking food & space; compromised immune system can cause disease
- microbes commonly found in the human
microbiome = normal flora