5. Microbial and Host Interactions

Question 1

What are Koch’s postulates used for?

Answer 1

Evidence to prove a specific microorganism to be the cause of a given disease.

Question 2

What is normal flora and transient normal flora?

Answer 2

Normal flora - bacteria normally found on the outer surfaces and mucous membranes of the body

Transient normal flora - bacteria different from usual flora and present for a short time eg. From antibiotic use or hospitalization

Question 3

What does contamination refer to?

Answer 3

The presence of bacteria in or on a body site that is not a part of the usual flora
Bacteria are present but not growing

Question 4

What is colonization?

Answer 4

Differs from contamination in that the bacteria are growing or have colonized the site

Question 5

What does infection refer to?

Answer 5

Bacteria growing in or on a body site and causing a host reaction

Question 6

What is pathogenicity? Virulence?

Answer 6

Ability of a microorganism to cause disease

Virulence is the degree of pathogenicity

Question 7

What is a pathogen and a non pathogen?

Answer 7

A Pathogen is a microorganism capable of causing disease

A Nonpathogen is when the microorganism is not capable of causing disease, very few are classified as this

Question 8

Name the 6 bacterial virulence factors.

Answer 8

1. Capsules
2. Hyaluronidase
3. Collagenase
4. Hemolysins
5. Leukocidins
6. Kinases

Cause damage in the host in the immediate area

Question 9

Name Koch’s postulates.

Answer 9

1. Microorganism must be found in every case of the disease to be called the causative agent
2. Microorganism must be isolated from the diseased host and grown in pure culture
3. Disease must be reproduced when a pure culture of the microorganism is injected into a healthy susceptible host
4. Microorganism must be recoverable once again from the experimentally injected host

Question 10

What is the function of capsules?

Answer 10

Prevent attachment of phagocyte to bacteria

Question 11

What is the function(s) of hyalurondiase?

Answer 11

Is an extra cellular enzyme produced by Gram + bacteria

Dissolves hyaluronic acid a compound found in tissue, this allows the bacteria to spread throughout the hosts tissue

Question 12

What is collagenase?

Answer 12

Brakes down collagen of connective tissue, allowing bacteria to spread faster through connective tissue

Question 13

What is the function of hemolysins?

Answer 13

Lyse red blood cells which decreases the hosts immunity

Question 14

What is the function of leukocidins?

Answer 14

Kills phagocytic cells creating pus

Question 15

What are the functions of kinases?

Answer 15

Break down fibrin clot that’s formed by the body to isolate infection
Bacteria can then break through the clot and spread

Question 16

Define toxins.

Answer 16

Substances that cause damage to sites far removed from the site of invasion.

Question 17

What are endotoxins and exotoxins?

Answer 17

Exotoxins - Gram + bacteria, excreted from living cells, protein molecules, causes immune response, can me converted to toxoids for immunization, have a specific site of action in host

Endotoxins - Gram - bacteria, part of the cell wall, released when cell walls are lysed from antibiotic action, do not form toxoids, nonspecific sites of action, cause aches, fever, shock

Question 18

What are some signs of bacterial infection?

Answer 18

Fever, lymph node swelling, inflammation, exudate (accumulation of fluid), granulomatous infection (granuloma forms), cellulitis (purulent ((pus)) inflammation involving loose connective tissue)

Question 19

What are the different types of Exudate?

Answer 19

Purulent exudate - many white blood cells, may be called polymorphonuclear neutrophils (PMNs), pus

Serous exudate - watery fluid, few PMNs, less protein

Transudate - noncellular fluid caused by passive leakage from blood or lymph vessels

Question 20

What is an epidemic?

Answer 20

Many people in a given area having a disease over a shirt period of time

Question 21

What is an Endemic?

Answer 21

Constantly present in a small percentage of the population

Question 22

What is a Pandemic?

Answer 22

An epidemic that occurs worldwide

Question 23

What is Epidemiology?

Answer 23

The study of when and where diseases occur and how they are spread

Question 24

What is an Endogenous infection?

Answer 24

Infecting bacteria come from the hosts own body

Question 25

What is an Exogenous infection?

Answer 25

Infecting bacteria come from outside the hosts body

Question 26

What is a Nonsocomial infection?

Answer 26

Infection is a result of being in a hospital, a hospital acquired infection, or an infection that’s a result of treatment

Question 27

What is a Carrier?

Answer 27

Potential pathogen carried by the host without any signs of infection

Question 28

What is a Primary infection?

Answer 28

The initial infection caused by a microorganism

Question 29

What is a Secondary infection?

Answer 29

Infection following a primary infection caused by a different microorganism

Question 30

What is a Nonspecific infection?

Answer 30

Microbial cause not identified

Question 31

What is an Opportunistic infection?

Answer 31

Caused by a low grade pathogen usually in a patient with lowered defences

Question 32

What is an Acute infection? Chronic infection?

Answer 32

Acute, short lasting

Low grade infection lasting a long time

Question 33

What is a Localized infection vs. a Disseminated infection?

Answer 33

Localized is restricted to a small area

Disseminated is spread to most parts of the body