Module 5: Microbial & Host Interactions

Question 1

What are Koch’s Postulates (four other them)?

Answer 1

1. Microorganism must be found in every case of disease .
2. Microorganism must be isolated from the diseased host and growth in pure culture.
3. The specific disease must be reproduced, when injected into the healthy host.
4. Microorganism must be recovered from injected host.

Question 2

What is norma flora?

Answer 2

normal bacteria that is found on the outside surfaces and mucous membranes of the body. Eg. skin, hair, mucous membrane openings.

Question 3

Transient Normal Flora

Answer 3

bacteria that is different from usual flora and present for a short time. Eg. due to antibiotics or hospitalization

Question 4

What is contamination of bacteria?

Answer 4

presence of a bacteria in or on a body site. it is just present not growing. Eg. decal matter on our hands.

Question 5

What is colonization of bacteria?

Answer 5

when the bacteria are growing or have colonized a site, no host reaction.

Question 6

What is infection of bacteria?

Answer 6

bacteria growing in or on a body site and causing host reaction. Eg. fever, inflammation

Question 7

Pathogenicity

Answer 7

ability to cause disease

Question 8

Virulence

Answer 8

degree of pathogenicity

Question 9

Non-pathogen

Answer 9

not capable of causing disease

Question 10

Describe Bacterial Virulence Factor: Capsules

Answer 10

prevent phagocytosis

Question 11

Describe Bacterial Virulence Factor: Hyaluronidase

Answer 11

• extra cellular enzyme produced by gram positive bacteria

- dissolves hyaluronic acid in connective tissue and allows bacteria to spread through tissue.

Question 12

Describe Bacterial Virulence Factor: Collagenase

Answer 12

-breaks down collagen of connective tissue causing bacteria to spread faster in the connective tissue

Question 13

Describe Bacterial Virulence Factor: Hemolysins

Answer 13

-lyse RBC’s & this decreases the host’s immunity

Question 14

Describe Bacterial Virulence Factor: Leukocidins

Answer 14

-kills phagocytic cells (white blood cells) creating pus

Question 15

Describe Bacterial Virulence Factor: Kinases

Answer 15

-breaks down fibrin clot (breaks through) formed by the body to isolate infected bacteria, bacteria spread into tissue.
Eg. Can be used as “clot busters” to break down fibrin in patients with “thick blood”, stroke victims with clots

Question 16

Describe exotoxins (gram +) and give an example.

Answer 16

• they are mainly produced in gram positive bacteria
  -they are excreted from living bacterial cells
  -mostly are protein molecules
  -antigenic, causes an immune response
  -can be converted to toxoids for immunization
  -have specific site of action in host
  EG. Botox and tetanus

Question 17

Describe endotoxins (gram -) and give an example.

Answer 17

• produced by gram negative bacteria
  -they are past of the cell wall: lipopolysaccharide (outer part), they are released when the walls are lysed from antibiotics
  -NOT antigenic- don’t form toxoids
  -non-specific site in hosts
  -effects: aches, malaise, fever, decreased blood pressure, shock.
  EG. salmonella endotoxin

Question 18

Give the 6 signs of a bacterial infection.

Answer 18

1. Fever
2. Lymph node swelling
3. Inflammation
4. Exudate (accumulation of fluid at the site or infection)
5. Granulomatous
6. Cellulitis (diffuse pus inflammation)

Question 19

Describe inflammation.

Answer 19

• Histamine released at site of infection
• Dilation of blood vessels
• Swelling, Redness, pain, heat

Question 20

Describe the 3 different types of exudate.

Answer 20

1. Purulent exudate- many WBC’s or PMN’s (polymorphonuclear neutrophils) at the site of infection causes pus.
2. Serous exudate- water fluid with few PMN’s (neutrophils)
3. Transudate- non-cellular fluid caused by passive leak from blood & lymph vessels.

Question 21

Describe granulomatous infection.

Answer 21

• Granuloma at site of infection contains large macrophages

- Epithelioid cells: giant cells caused by macrophages fusing together, wall off infection in body site.

Question 22

Describe cellulitis.

Answer 22

• subcutaneous loose connective tissue, fluid spreads between layers causing redness and swelling.

Question 23

Epidemic

Answer 23

outbreak of a disease in a short amount of time.

Question 24

Endemic

Answer 24

present in small % of population

Question 25

Pandemic

Answer 25

epidemic that occurs world wide

Question 26

Endogenous infection

Answer 26

infecting bacteria come from outside hosts body. Eg. UTI

Question 27

Exogenous infection

Answer 27

infecting bacteria come from outside hosts body. E. Strept throat.

Question 28

Nosocomial

Answer 28

infection acquired from a hospital environment.

Question 29

Describe the types of infections by bacteria (primary, secondary, nonspecific, opportunistic).

Answer 29

Primary: initial infection

Secondary infection: an infection following a primary infection and usually caused by a different bacterium

Nonspecific infection: bacterial cause of infection is not identified

Opportunistic: low grade pathogen causes infection in immunosuppressed or chronically ill patients. (takes advantage) Eg. Yeast infection in Chemotherapy patient

Question 30

Describe acute and chronic infections.

Answer 30

Acute= drastic and short lasting
Chronis= low grade and long lasting

Question 31

Describe localized and disseminated infections.

Answer 31

Localized= restricted to small area
Disseminated= spread to most part of body