ID patho

Question 1

Pathogenicity
Microbial Pathogenesis
Pathogen
Virulence Factors

Answer 1

Virulence Factors: traits that render microorganisms pathogenic

Pathogen: something that causes disease

Microbial Pathogenesis: mechanisms by which microbes cause disease

Pathogenicity: the ability of microorganisms to cause disease

Question 2

Division of Virulence Factors:
(2)

first (4)

second (4)

Answer 2

1. microbial invasion
   a) portal of entry
   b) surface colonization
   c) surviving host defences
   d) portal of exit/transmission
2. host damage
   a) host responses
   b) toxins
   c) apoptosis
   d) mechanical causes

Question 3

Division of Virulence Factors:
(2)

first (4)

second (4)

Answer 3

1. microbial invasion
   a) portal of entry (trauma/bite, mucosal membranes, transplantation)

b) surface colonization
- adhesins
- -> fimbriae (type 1 pili, on gram-negative organisms)
- -> surface proteins
- specific binding proteins on host surfaces (used by host for other reasons)

c) surviving host defences

non-specific host defences:

i) adhesins (stick there)
ii) capsule (protect antigens from being seen from non-specific host defence)
iii) biofilm (excrete substance, hides bacteria, not seen by non-specific host defences)
iv) intracellular survival (supposed to by lysed; can evade this - exocytosed alive and well)

specific host defenses:

i) superantigens (interact w every single t-cell and b-cell, make a mess - activate everything)
ii) antigenic variation (influenza - continue to change antigens)
iii) proteolysis of antibodies
iv) protein A binds to the wrong end of antibodies
v) viral latency

d) portal of exit/transmission
i) exaggerate host defence: coughing, sneezing, diarrhea
ii) increase environmental survival:
- -> spores (c. diff). can exist in very bad conditions
- -> cysts (protozoa)

2. host damage

a) host responses
- specific and non-specific host responses are rarely so finely tuned that only infection is controlled
- -> inflammation secondary to prostate infection response = urinary obstruction
- -> overwhelming activation of immune response = septic shock
- -> autoimmune response to streptococcus pyogenes (group A strep) = rheumatic fever

b) toxins
- exotoxins: secreted by bacteria into surrounding environment (help bacteria spread in tissues, lyse cells, block nerves (c. tetanus tensed, c. botulinum floppy)
- endotoxins: part of outer membrane of all gram-negative bacteria (LPS - lipopolysaccharide). Low level = fever, vasodilation. High level = alarming immune response leading to septic shock.

c) apoptosis
- programmed cell death; healthy cells maintained
- some organisms block apoptosis, immortalizing host cells (HPV)
- some organisms stimulate cells to undergo premature apoptosis (HIV, herpesvirus)

d) mechanical causes
- infectious agents can cause obstruction (block intestinal lumen)
- e.g. large roundworms

Question 4

opportunists vs. “true pathogens”

Answer 4

• true pathogens have more virulence factors
• opportunists (normal microbiota) - organisms with very few virulence factors, but if host defence is down, they can take advantage
• its a spectrum

Question 5

Skin Microbiota (3)

Answer 5

Bacillus spp.
Corynebacterium spp.
Staphylococcus spp.

Question 6

Oropharynx Microbiota (5)

Answer 6

Neisseria spp. 
Haemophilus spp.
Viridans group streptococci
Candida
Peptostreptococcus spp.

Question 7

Intestinal Microbiota (5)
--> and phyla

Answer 7

Enterobacteriaceae (escherichia coli, klebsiella)
Bacterioides spp.
Candida spp.
Enterococcus spp. 
Clostridium spp.

Firmicutes: enterococci, clostridium
Bacterioidetes: bacterioides
Actinobacteria
Proteobacteria: e. coli, enterobacteriaceae

Question 8

Vaginal Microbiota (4)

Answer 8

Candida spp.
Viridans group strep
Lactobacillus spp.
Peptostreptococcus spp.

Question 9

QUIZ (T/F)

• All microorganisms can cause disease equally well
• Our normal microbiota has no beneficial function
• Opportunistic infections typically arise from our normal microbiota

Answer 9

F
F
T