Chapter 25: Infection/Pathogenesis

Question 1

Normal microflora

Answer 1

non-transient, established
- do not cause disease

Question 2

infection

Answer 2

microorganism is established and growing in a host
- not necessarily harming the host

Question 3

pathogen

Answer 3

microbial parasites with the ability to cause disease and/or damage tissue

Question 4

Opportunistic pathogen

Answer 4

cause disease only when the opportunity arises

Question 5

true pathogens

Answer 5

cause disease in virtually any host

Question 6

obligate pathogens

Answer 6

infection is part of the life cycle (require host)

Question 7

facultative pathogens

Answer 7

can cause disease or can live apart from host

Question 8

pathogenicity

Answer 8

ability of a pathogen to inflict damage to the host

Question 9

Stages of Pathogenesis

Answer 9

Exposure : Adherence : Invasion : Colonization & Growth : Toxicity OR Invasiveness : Tissue damage/disease

Question 10

Toxicity

Answer 10

toxin effects are local or systemic
- inhibit host cell function or kills host cells

Question 11

Invasiveness

Answer 11

further growth at original site and distant sites

Question 12

Adherence

Answer 12

ability of microbes to attach to host tissues (mucosa/skin), necessary to start disease

Question 13

Adhesions

Answer 13

glycoproteins/lipoproteins found on the pathogens surface to enable them to bind to host cells
- many different receptors

Question 14

Adherence factors

Answer 14

capsule/slime layer, Adherence proteins, lipoteichoic acid, fimbriae

Question 15

Colonization

Answer 15

growth of microbes after they’ve gained access to host cells (process begins at birth)
- starts with mucous membrane, or epithelial cells coated with mucus -> then a secretion of glycoproteins

Question 16

Virulence

Answer 16

the relative ability of a pathogen to cause disease (measured in LD 50)

Question 17

LD 50

Answer 17

lethal dose 50 - amount of an agent required to kill 50% of the population

Question 18

Virulence factors

Answer 18

toxic/destructive substances
enhances invasivity (directly or indirectly)
- proteases, nucleases, lipases
- coagulase, kinases, hyaluronidase, collagenase, IgA proteases
- Adhesions, LPS, capsule (attachment to host cells)

Question 19

Attenuation

Answer 19

decrease/loss of virulence
- mutations occur
- in a lab, nonvirulent/weakly virulent cells grow faster because virulence is not selectively advantageous
- used for viral vaccines

Question 20

Endotoxins

Answer 20

lipopolysaccharides found in the cell walls of gram-negative bacteria
- generally less toxin than exotoxins

Question 21

Exotoxins

Answer 21

proteins released from the pathogen cell as it grows
- some are enterotoxins (found in the gut)
- cytolytic toxins, AB toxins, Superantigen toxins

Question 22

AB-Toxins

Answer 22

Active (A) Domain and Binding (B) Domain
- A catalyzes the blocking of elongation of translation

Question 23

Diphtheria Toxins

Answer 23

block protein synthesis

Question 24

Neurological toxins

Answer 24

Botulinum and Tetanus Toxins
- AB Exotoxin
- Clostridium tetani and Clostridium botulinum produce exotoxins targeting nervous tissue
- 1 nanogram = fatal to guinea pig
- paralysis, spastic

Question 25

Cytolytic exotoxins

Answer 25

degrade cytoplasmic membranes integrity, causing cell lysis and death
- hemolysins = lyse red blood cells

Question 26

Superantigen exotoxins

Answer 26

overstimulate immune system, local infections w systemic effects
- autoimmune disease

Question 27

Biosafety levels (culturing pathogens)

Answer 27

1. don’t cause human disease (most lab stains)
2. can cause disease, transmission potential is limited (salmonella)
3. May be easily transmitted and cause serious infections (tuberculosis)
4. high risk of life-threatening disease, may be transmitted by aerosol route, no vaccine or therapy (Ebola)