export_gi bacteria iii

Question 1

Vibrio features

Answer 1

Gram-negative, facultative anaerobes, curved
Broad temperature and pH range for growth, but susceptible to stomach acid, free living in water

Requires NaCl to grow

Question 2

Vibrio cholerae range of disease

Answer 2

Asymptomatic to severe watery diarrhea

Question 3

Vibrio cholerae incubation

Answer 3

2-3 days

Question 4

Vibrio cholerae immunity

Answer 4

Appears to be O Ag specific

If the O Ag on the LPS on the Vibrio cholerae strain mutates, you lose immunity to that strain

Question 5

Vibrio cholerae pathogenesis

Answer 5

Toxin co-regulated pilus (TCP)

Cholera toxin

Question 6

TCP

Answer 6

Adherence of Vibrio cholerae to intestinal epithelial cells

Question 7

Cholera toxin

Answer 7

AB toxin
Increase cAMP, mass efflux of water

Encoded on CTX-phi (prophage)

Question 8

Vibrio cholerae diagnosis and treatment

Answer 8

Culture (differential media)

Rehydration therapy

Question 9

Vibrio parahaemolyticus disease

Answer 9

Explosive watery diarrhea, nausea, vomiting, abdominal cramps

Question 10

Vibrio parahaemolyticus epidemiology, treatment, and prevention

Answer 10

Raw shellfish
Self-limiting disease

Properly cook shellfish

Question 11

Yersinia enterocolitica features and symptoms

Answer 11

Gram-negative coccobaccilli

Fever, abdominal cramps, water to bloody diarrhea, can last 1-2 weeks

Question 12

Yersinia enterocolitica pathogenesis

Answer 12

Poorly understood
Binds to M-cells

Involves T3SS

Produces heat-stable enterotoxin

Question 13

Clostridium difficile features

Answer 13

Gram-positive aerobe
Non-invasive
Spore forming
nosocomial infection
(people may get it from long stretches of taking broad-spectrum antibiotics)

Question 14

Clostridium difficile disease

Answer 14

Wide range, asymptomatic to diarrhea to colitis to toxic megacolon

Question 15

What is CDAD?

Answer 15

C. difficile-associated diarrhea

Question 16

What is pseudomembrane colitis?

Answer 16

Raised, adherent yellow plaques in the colon

Can progress to fulminant colitis

Question 17

C. diff. pathogenesis

Answer 17

Toxin A and toxin B
Damages the mucosa

Disrupt host cell cytoskeleton = diarrhea

Question 18

C. diff. diagnosis, treatment, and prevention

Answer 18

Toxin detection in stool
Vancomycin or metronidazole
Culture NOT helpful (can be part of normal microbiota)

Fecal transplant

Question 19

Enterohemorrhagic E. coli (EHEC) features

Answer 19

Gram-negative, facultative anaerobe, lots of animal reservoirs, generally non-invasive

Question 20

EHEC disease

Answer 20

Hemorrhagic colitis = bloody diarrhea

Sequelae (hemolytic uremic syndrome)

Question 21

EHEC pathogenesis

Answer 21

Attaching and effacing lesion (like EPEC)

Produces Shiga-like toxin (verotoxin)

Question 22

Verotoxin

Answer 22

Cleaves part of the 60S subunit of the ribosome, resulting in cell death

Question 23

EHEC and the kidneys

Answer 23

Glomeruli are rich in Gb3 (toxin glycolipid receptor) which will bind the verotoxin, resulting in kidney failure

Question 24

EHEC diagnosis

Answer 24

Bloody diarrhea WITHOUT fever (presumption)
Culture

NAAT (stx genes that encode verotoxin)

Question 25

EHEC treatment

Answer 25

Supportive therapy | NOT antibiotics - results in increased toxin production, which increases HUS rate

Question 26

Shigella features

Answer 26

Gram-negative rods, facultative anaerobes, intracellular pathogens Incredibly acid tolerant (few organisms needed for infection) humans are only reservoir

Question 27

Shigella transmission

Answer 27

Fecal-oral route

Question 28

Shigella incubation period

Answer 28

1-3 days | Disease is self-limiting, resolving within 3-5 days

Question 29

Shigella soneii disease

Answer 29

Developing countries | Fever, malaise, watery diarrhea

Question 30

Shigella flexneri disease

Answer 30

Developing countries | Dysentery, fever, malaise, watery diarrhea, abdominal cramps, tenesmus, bloody/purulent excretions

Question 31

Shigella dysenteriae disease

Answer 31

Underdeveloped countries Dysentery, fever, malaise, watery diarrhea, abdominal cramps, tenesmus, bloody/purulent excretions Potential for HUS

Question 32

Shigella pathogenesis

Answer 32

Adhere to M-cells T3SS Escape from phagosome Macrophage apoptosis Actin polymerization - spread to neighboring cells -ulcers form in infected areas severe inflammation = diarrhea Shiga toxin (binds Gb3 = kidney damage= hemolytic uermic syndrome

Question 33

Shiga toxin

Answer 33

Binds to Gb3 Inhibits translation HUS

Question 34

Shigella diagnosis and treatment

Answer 34

Culturing and serology | Rehydration and antibiotic therapy

Question 35

Shigella prevention

Answer 35

No vaccine | Infection does NOT confer immunity

Question 36

Enteroinvasive E. coli features

Answer 36

Same as Shigella except NO Shiga-toxin | May have obtained pathogenicity island from Shigella via horizontal gene transfer