Enteric Infections

Question 1

What are some host factors that influence infection?

Answer 1

Gastric acidity, intestinal motility, micro flora, GALT, personal hygiene.

Question 2

What are some microbial factors that influence infection?

Answer 2

Neurotoxins (pre-formed causing vomiting), enterotoxins (fluid secretion), cytotoxins (mucosal destruction), adhesins, invasiveness (propel through cytoplasm.

Question 3

What are the main cholera serotypes in pandemic cholera?

Answer 3

O and O139 (all strains have the H antigen-flagella) however there is no difference in presentation between these.

Question 4

Compare the minimum infectious dose of cholera and shigella.

Answer 4

Cholera: 10 to the power of 3- 10 to the power of 6 in water and in food it is 10 to the power of 2 and 10 to the power of 4
For shigella it is 10-100 microbes.

Question 5

Why is the cholera vaccine (oral vaccine-killed or live attenuated) not an effective prevention strategy?

Answer 5

It requires two doses two weeks apart and immunity achieved a week later with poor efficacy and decreasing efficacy over time.

Question 6

What are he four strains of shigella?

Answer 6

Listed in decreasing virulence:
Shigella dysenteriae
Shigella flexenari (40% of cases)
Shigella boydi
Shigella sonnei (lease virulent) (50% of cases)