Chapter 15: How Microbes Cause Disease

Question 1

pathogenicity

Answer 1

pathogen’s ability to cause disease by overriding body’s defenses

Question 2

virulence

Answer 2

degree of pathogenicity

Question 3

virulence factors

Answer 3

assist the pathogen to enter a host, evade the host’s defenses, and damage the host cells, and exit the host

Question 4

portals of entry

Answer 4

1) mucous membranes- respiratory tract, GI tract (food and water ingested), genitorurinary tract, conjunctiva
2) skin- can be infected by hair follicles
3) parenteral route- depost m/os underneath the skin mucous membranes ex. HIV

Question 5

penetration or evasion of host defences

Answer 5

1) capsule: impair phagocytosis
2) cell wall components: chemical substances
3) enzymes: coagulase, kinase, hyalonidase, IGA proteases
4) antigenic variation ex influenza
5) invasions (rearrange actin filamints in cytoskeleton of host cell- cause ruffling ex salmonella
6) intracellular growth

Question 6

coagulase

Answer 6

clots fibronitrogen so it can’t heal ex streptococcus

Question 7

kinase

Answer 7

digest fibrin clots

Question 8

hyalonidase

Answer 8

hydrolyzes hyaluronic acid (holds all cells together, CT)

Question 9

IGA proteases

Answer 9

destroys antibodies

Question 10

damage to host cell

Answer 10

1) slidophores
2) direct damage
3) toxins- endotoxin and exotoxin
4) lysogenic conversion
5) cytopathic effect

Question 11

slidophores

Answer 11

take iron from host cells/ proteins (transferrin)

Question 12

exotoxin

Answer 12

proteins produced inside pathogenic bacteria and then are secretes into the surrounding medium
1) A-B toxins (active binding components
2) membrane disrupting (lyse cells)
3) superantigens (intense immune response

Question 13

endotoxin

Answer 13

portions of LPS part of outer membrane of cell wall and then break apart when cell wall lyses/ breaks apart

Question 14

portals of exit

Answer 14

same as portals of entry
- mucous membranes- respiratory, GI tract, genitourinary tract, conjunctiva, -skin
- parenteral route

Question 15

How do pathogens penetrate host’s defenses?

Answer 15

Adhesins or Invasins (glycoproteins or lipoproteins) use to attach to host cell:
- Capsules & cell wall components
- Glycocalyx of Streptococcus mutans: surface of teeth
- Fimbriae in Escherichia coli & Neisseria gonorrhoeae: cells in genitourinary tract
- Tapered end as a hook: Treponema pallidum
- Invasins rearrange nearby host cell cytoskeleton and induce ruffling

Question 16

How do pathogens evade host’s immunity?

Answer 16

Virulence of some bacteria is aided by:
- Capsule: Impair phagocytosis (S. pneumoniae)
- Waxy layer: resist digestion by phagocytes (M. tuberculosis)
- Coagulase: Coagulate the fibrinogen in blood (S. aureus)
- Kinase: Digest fibrin clots (S. pyogenes, S. aureus)
- Hyaluronidase: Hydrolyses hyaluronic acid that holds together some cells in body (i.e. connective tissue) - Streptococcus spp, Clostridium spp
- Collaginase: Hydrolyzes collagen: Clostridium spp
- IgA proteases: Destroy IgA antibodies (N. gonorrhoeae)
- Antigenic Variation (Influenza virus, N. gonorrhaeae)

Question 17

toxins are produced and secreted by actively growing cells

Answer 17

exotoxin

Question 18

host responds by producing antibodies called antitoxin

Answer 18

exotoxin

Question 19

these toxins may be found in foods but are usually inactiviated by cooking

Answer 19

exotoxin

Question 20

these toxins may be toxic in very tiny (nanogram amounts)

Answer 20

exotoxin

Question 21

these toxins may be produced by gram negative or gram positive bacteria

Answer 21

exotoxin

Question 22

these toxins are often released upon phagocytosis of or death of bacterial cells

Answer 22

endotoxin

Question 23

these toxins are produced exclusively by gram negative bacteria

Answer 23

endotoxin

Question 24

These toxins are produced by bacteria but not viruses

Answer 24

exotoxins and endotoxins