GI bacteria III

Question 1

What are the characteristics of vibrio spp.?

Answer 1

1. Gram negative 2. Facultative anaerobe 3. Comma shaped 4. Broad temperature and pH range 5. Require sodium for growth

Question 2

Which cholera serotype is toxin-producing?

Answer 2

O1

Question 3

What are the properties of the current cholera pandemic serotype (El Tor)?

Answer 3

1. Less severe disease (1 symptomatic to 30-100 asymptomatic) 2. Duration of carriage longer than classic strain 3. Survives better in environment

Question 4

What is the pathogenesis of vibrio cholerae?

Answer 4

1. Toxin co-regulated pilus (TCP) mediates adherence to intestinal epithelial cells 2. Cholera toxin

Question 5

What are the properties of the cholera toxin?

Answer 5

1. AB toxin 2. Activates adenylate cyclase - increases cAMP production 3. No significant cell damage 4. Similar to ETEC LT toxin in structure and function 5. Encoded on a prophage

Question 6

What are the symptoms of vibro parahaemolyticus?

Answer 6

Explosive watery diarrhea, nausea, vomiting, abdominal cramps, low grade fever

Question 7

What is the virulence for vibrio parahaemolyticus?

Answer 7

Kanagawa hemolysin - induces chloride secretion thus watery diarrhea

Question 8

Vibrio parahaemolyticus is associated with what food?

Answer 8

Raw shellfish

Question 9

Yersinia enterocolitica is what kind of bacterium?

Answer 9

Gram negative coccobacilli

Question 10

What is the pathogenesis of yersinia enterocolitica?

Answer 10

1. Binds to and invades M cells in terminal ileum 2. T3SS and injection of Yops 3. Produces heat stable enterotoxin

Question 11

What are the characteristics of clostridium difficile?

Answer 11

1. Gram positive anaerobe 2. Spore forming (important part of life cycle) 3. Non-invasive 4. Inflammatory 5. Associated with CDAD, pseudomembrane colitis, and fulminant colitis with toxic megacolon

Question 12

What is the pathogenesis of clostridium difficile?

Answer 12

AB toxin causes damage to mucosa and host cell cytoskeleton

Question 13

What is the treatment for clostridium difficile?

Answer 13

Vancomycin or metronidazole

Question 14

What should be considered in a patient who has diarrhea and is on short or long term BSAs?

Answer 14

Clostridium difficile

Question 15

What are the characteristics of enterohemorrhagic E. coli (EHEC)?

Answer 15

1. Gram negative 2. Facultative anaerobe 3. Animal reservoirs - cattle, ruminants 4. Generally non-invasive

Question 16

What is the disease progression for enterohemorrhagic E. coli (EHEC)?

Answer 16

1. Hemorrhagic colitis - bloody diarrhea 2. No fever 3. Abdominal tenderness 4. Hemolytic uremic syndrome (HUS) - anemia and kidney failure 5. Similar to EPEC

Question 17

What is the pathogenesis of enterohemorrhagic E. coli (EHEC)?

Answer 17

1. Attaching and effacing lesion like EPEC 2. Shiga-like toxin (verotoxin) blocks translation by cleaving part of 60S ribosomal subunit

Question 18

How is hemolytic uremic syndrome (HUS) caused by the EHEC shiga-like toxin?

Answer 18

1. Shiga-like toxin binds kidney receptor, is internalized 2. Kidney cell death and ischemic damage from thrombi lead to kidney failure

Question 19

What is the diagnosis for enterohemorrhagic E. coli (EHEC)?

Answer 19

1. Bloody diarrhea WITHOUT fever 2. Culture 3. PCR for stx gene that encodes toxin

Question 20

Why is antibiotic therapy not indicated for enterohemorrhagic E. coli (EHEC)?

Answer 20

1. Shiga toxin is coded on a lysogenic phage 2. When phage detects damage, replicates its genome

Question 21

What are the characteristics of shigella spp.?

Answer 21

1. Gram negative rods 2. Facultative anaerobes 3. Intracellular pathogens 4. Very acid tolerant 5. Inflammatory 6. Dysentery

Question 22

What is the epidemiology of shigella spp.?

Answer 22

1. Humans are only reservoir 2. Fecal-oral 3. Extremely low infectious dose (

Question 23

What are the clinical manifestations of shigellosis?

Answer 23

1. 1-3 days post infection 2. Usually self limiting 2-5 days post infection 3. Generally strain specific

Question 24

What is the pathogenesis of shigella spp.?

Answer 24

1. Acid resistant 2. Adhere selectively to and pass through M cells - T3SS 3. Phagocytosis by macrophages 4. Rapid escape from phagosome 5. Rapid induction of macrophage apoptosis

Question 25

How are shigella spp. taken up by the intestinal cell?

Answer 25

1. T3SS 2. Injection of Ipa proteins 3. Cytoskeletal rearrangement

Question 26

How do shigella spp. spread to neighboring cells?

Answer 26

1. Hijack host actin 2. Evasion of host defense

Question 27

How does the shiga toxin cause damage?

Answer 27

1. Binds to host Gb3 receptor 2. Inhibits translation - cell damage - tissue damage 3. Glomerular endothelial cells are rich in Gb3 receptors

Question 28

What causes the diarrhea seen in shigella infection?

Answer 28

Severe inflammation

Question 29

Does shigella infection confer immunity?

Answer 29

No

Question 30

What are the properties of enteroinvasive E. coli?

Answer 30

1. Same as shigella but NO shiga toxin 2. Can move around intracellularly but since there is not shiga toxin there is no chance of HUS 3. Appears to have acquired a pathogenicity island from shigella via horizontal gene transfer