Cholera

Question 1

Describe the gram status, shape, and motility of cholera

Answer 1

Gram negative, polar flagellum, comma shape

Question 2

What media does cholera grow on?

Answer 2

TCBS medium

Question 3

Which antigens does cholera have?

Answer 3

O, H antigens, endotoxin, and cholera exotoxin

Question 4

What is the major colonization factor for cholera?

Answer 4

toxin coregulated pilus

Question 5

What are the 2 O1 types for cholera?

Answer 5

classical and El Tor (hemolytic). El tor has been responsible for most recent epidemic choleras

Question 6

Describe the pathogenesis cycle of cholera

Answer 6

1. gastric acid inactivates ingested organisms
2. Organisms enter small bowel and bind to epithelium
3. Using TCP, cholera form microcolonies
4. Cholera toxin binds to GM1 gangliosides
5. neuraminidase converts other gangliosides to GM1, increasing sites for toxin binding
6. Cholera stimulates adenylate cyclase and cAMP causing massive fluid loss

Question 7

What is the significance of GM1 in cholera virulence?

Answer 7

Binds to cholera toxin

Question 8

What does cholera’s nueraminidase do?

Answer 8

Converts other gangliosides to GM1

Question 9

How does stimulation of adenylate cyclase and cAMP production result in intestinal fluid loss?

Answer 9

1. Decreases NaCl absorption from gut in villus cells

2. Secretory cells increase Cl and HCO3 secretion into the gut. H2O follows.

Question 10

How is cholera treated?

Answer 10

Mostly through fluid and electrolyte replacement

Question 11

What does the infectious dose of cholera depend on?

Answer 11

Source. Varies from 10^2 to 10^9

Question 12

Are there any vaccines for cholera?

Answer 12

Yes–current inactivated vaccine 70% effective

Also, live attenuated vaccine

Question 13

How is campylobacter spread?

Answer 13

Through uncooked food. Usually chicken or milk

Question 14

What is the gram status and morphology of campylobacter species?

Answer 14

Gram negative rods

Question 15

Does campylobacter need air to survive?

Answer 15

Yes-microaerophile

Question 16

Can campylobacter cause bacteremia?

Answer 16

Rarely

Question 17

What is the most common aetiologic cause of diarrhea?

Answer 17

campylobacter

Question 18

What is the infectious dose?

Answer 18

500 organisms

Question 19

What are the clinical features of a campylobacter infection?

Answer 19

headache, fever, abdominal pain, diarrhea. Occasionally leads to guillain-barre.

Question 20

How can you treat campylobacter?

Answer 20

Supportive therapy, some may need erythromycin or ciprofloxacin

Question 21

Describe the gram status and morphology of H pylori

Answer 21

spiral gram negative bacteria

Question 22

What does H pylori secrete?

Answer 22

urease. Allows for a less acidic environment in the stomach.

Question 23

What are the virulence factors of H pylori?

Answer 23

BabA binds to lewis b antigen on stomach epithelium
CagA disrupts the cytoskeleton and cell polarity of stomach cells
VacA further damages the epithelial lining

Question 24

Aside from virulence factors, what else aids the pathogenesis of H pylori?

Answer 24

Death of WBCs which release superoxide radicals that further destroy stomach cells

Question 25

What is the infectious dose for H Pylori?

Answer 25

10000

Question 26

How can you diagnose H pylori?

Answer 26

1. urea C14 test. If urease is present, C14 will be released
2. Stool culture.
3. Seroconversion-look for blood antigens
4. PCR
5. Endoscopy

Question 27

How can you distinguish between campylobacter and helicobacter in feces?

Answer 27

Use a urease test. Urease is only present in the urine for campylobacter not helicobacter