22 Pathogenic interactions

Question 1

ability of microbe to cause disease

Answer 1

pathogenicity

Question 2

quantitative measure of degree of pathogenicity, as indicated by mortality rate, disease severity, etc.

Answer 2

virulence

Question 3

any microbial comp. that is required for/contributes to pathogenicity

Answer 3

virulence factor

Question 4

how to quantitate virulence?

Answer 4

infect susceptible host with ^ higher doses of org, monitor progession of disease over time, determine LD50 (# orgs that will cause disease in 50% animals over specified time)

Question 5

how determine whether particular microbe comp. is virulence factor?

Answer 5

create microbe deficient in particular comp and test ability cause disease

Question 6

end in -emia mean?

Answer 6

microbe in bloodstream

Question 7

steps that must be completed to successfully infect and cause disease?

Answer 7

1) be transmitted to, and enter into, a suitable host 2) avoid being removed after entry 3) migrate to a site within the host able to support growth 4) overcome host defenses and multiply at the preferred site 5) exit host and transfer to a new host to repeat cycle

Question 8

most common portals of entry:

Answer 8

body tracts (resp, intestinal, uro-genital), conjunctival mes

Question 9

orgs required to start infection

Answer 9

infectious dose

Question 10

resp requires ____ infectious dose, ingestion requires ____ dose

Answer 10

lower; higher

Question 11

strategies avoid removal after entry?

Answer 11

pili, cell surface proteins, capsular polysacc

Question 12

strategies for migrate to other body sites?

Answer 12

bacterial tissue-degrading enzymes (hyaluronidase, collagenase)

Question 13

to grow and survive in host, bacteria must:

Answer 13

obtain nutrients from host (hemolysins) and evade host immune sys (bacteria capsule, bacterial toxins)

Question 14

strategies exit host?

Answer 14

mucus/saliva, feces, semen/vag discharge, pus/blood/urine–>exit much larger numbers than enter

Question 15

how do pathogens damage host?

Answer 15

1) host immune response 2) direct result of pathogen actions (tissue degrading enzymes, bacterial toxins)

Question 16

two types bacterial toxins?

Answer 16

endo and exo

Question 17

lipid A portion of LPS (gram neg only) is ____

Answer 17

endotoxin

Question 18

LPS cause:

Answer 18

immune sys ^ cytokine production, activation of blood coagulation pathway–>toxic shock

Question 19

current limit in IV fluids and drugs is:

Answer 19

0.25 units/mL for IV

Question 20

bio detection of endotoxin?

Answer 20

limulus amoebocyte lysate assay (WBC of horseshoe crab will clot when exposed to LPS)

Question 21

LPS destroyed at ___ degrees for __ minutes

Answer 21

250; 30

Question 22

immobilized resins that bind LPS

Answer 22

affinity matrixes

Question 23

toxic proteins secreted by bacteria as grow; highly potent in very small amounts, act on eucaryotic cells to kill or alter metabolism

Answer 23

exotoxins

Question 24

three general types of exotoxins?

Answer 24

cytotoxins (block protein synth), enterotoxin (cause hypersecretion of water from intestinal cells), neurotoxin (interfere neurotrans)

Question 25

therapeutic use of botulinum toxin to treat involuntary muscle contraction (Meige Syndrome)

Answer 25

Botox

Question 26

exotoxins are ___ and can be carried by ___ to act at site far removed from origin site

Answer 26

soluble; bloodstream

Question 27

___ can be chemically inactivated

Answer 27

exotoxins

Question 28

exotoxin + formaldehyde =

Answer 28

toxoid (inactive)

Question 29

exotoxin mostly in gram ___ and part of growth and metabolism

Answer 29

positive

Question 30

exotoxin or endotoxin stim. antitoxin?

Answer 30

exo only

Question 31

method for diagnosis that is fast and easy, not very sensitive, good for specimens that should be sterile in healthy people

Answer 31

gram stain+microscopy

Question 32

gram stain + microscopy limits:

Answer 32

doesn’t ID species, not useful if lots of normal flora present

Question 33

limits of ELISA (serological tests)

Answer 33

doesn’t distinguish between current and past infection

Question 34

non-growth methods require you know :

Answer 34

exactly what bacterial species to look for

Question 35

pros and cones of PCR ?

Answer 35

fast and sensitive but technically complex and expensive

Question 36

good reason to culture bacteria?

Answer 36

> 1 pathogen present or if symptoms so non-specific that you can’t guess what it might be

Question 37

cons of culturing bacteria?

Answer 37

labor intensive, slow, only work if bacteria can be grown on lab media

Question 38

most often used diagnostic method in micro labs?

Answer 38

bacterial culture

Question 39

other types of tests to perform?

Answer 39

antibiotic susceptibility testing, bacterial enumeration(UTI), genetic analysis/comparison of diff strains or isolates (public health labs)