Lecture 6: Commensalism Vs Pathogenicity

Question 1

How many organisms benefit in mutualism/symbiosis? How many are harmed?

Answer 1

2 benefit

none harmed

Question 2

How many organisms benefit in commensalism? How many are harmed?

Answer 2

1 benefits
none harmed
2nd neutral

Question 3

How many organisms benefit in parasitism/pathogenesis? How many are harmed?

Answer 3

1 benefits

1 is harmed

Question 4

Where is S. epidermatis commensal?

Answer 4

Skin

Question 5

Where is C. albicans commensal?

Answer 5

Skin

Question 6

Where are staph and strep commensal?

Answer 6

Throat

Question 7

Where are coliforms commensal?

Answer 7

Gut

Question 8

What is a symbiotic bacterium in the vagina?

Answer 8

Lactobacillus

Question 9

What type of bacteria are symbiotic in the gut?

Answer 9

Nutrient-generating

Question 10

Commensals participate in what kind of resistance?

Answer 10

Colonization resistance

Question 11

Colonization resistance is an important element of what type of immunity?

Answer 11

innate immunity

Question 12

A nonpathogen has a ____ LD50 and a _____ ID50

Answer 12

high
high
need lots to infect/kill

Question 13

An opportunistic pathogen has a _____ LD50 and a _____ ID50

Answer 13

high LD50 - need lots to be lethal

mid-low ID50 - need less to infect

Question 14

An opportunistic pathogen is unlikely to cause disease, unless host is ________.

Answer 14

Debilitated

Question 15

A pathogen has _______ pathogenicity, ______ LD50, and ______ ID50

Answer 15

high pathogenicity
mid-low LD50
low ID50

Question 16

What are defined as genes found experimentally necessary for pathogens to produce disease?

Answer 16

Virulence factors

Question 17

What are the 5 specific categories of virulence factors (6 is other)?

Answer 17

Survive Extreme Environments
Adhesion
Immune evasion
Host cell takeover
Poisoning host

Question 18

Where are virulence factors usually found within the bacterial genome?

Answer 18

Plasmids (accessory DNA)

Question 19

How are virulence factors usually regulated?

Answer 19

Pathogenicity Island

Question 20

What are the two common methods for transferring virulence factors?

Answer 20

horizontal transfer (plasmids)
phage infection

Question 21

What are defined as polypeptides secreted form pathogen or injected into host cell by TSS3, as they relate to virulence factors?

Answer 21

Exotoxins

Question 22

What are three specific sources of profound toxicity from virulence factors?

Answer 22

Superantigenicity
interference with signal transduction
depolymerization of actin

Question 23

A toxin which is inactivated chemically or with heat is called what? What can it be used for?

Answer 23

Toxoid

Used for vaccines

Question 24

In an exotoxin with A-B subunit structure, what does each subunit do?

Answer 24

A has toxic activity

B delivers a to target site

Question 25

What are endotoxins?

Answer 25

intrinsic to surface of bacteria

cause immunogenic symptoms

Question 26

Is either previous exposure or vaccination protective against endotoxins?

Answer 26

No - neither is protective

Question 27

What are Kock’s postulates?

Answer 27

Observe disease
Culture pathogen
Infect new host from culture
Observe same disease
Culture same pathogen