GI bacteria III Flashcards Preview

Year 1 Microbiology > GI bacteria III > Flashcards

Flashcards in GI bacteria III Deck (30):

What are the characteristics of vibrio spp.?

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


Which cholera serotype is toxin-producing?



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

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


What is the pathogenesis of vibrio cholerae?

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


What are the properties of the cholera toxin?

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


What are the symptoms of vibro parahaemolyticus?

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


What is the virulence for vibrio parahaemolyticus?

Kanagawa hemolysin - induces chloride secretion thus watery diarrhea


Vibrio parahaemolyticus is associated with what food?

Raw shellfish


Yersinia enterocolitica is what kind of bacterium?

Gram negative coccobacilli


What is the pathogenesis of yersinia enterocolitica?

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


What are the characteristics of clostridium difficile?

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


What is the pathogenesis of clostridium difficile?

AB toxin causes damage to mucosa and host cell cytoskeleton


What is the treatment for clostridium difficile?

Vancomycin or metronidazole


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

Clostridium difficile


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

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


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

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


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

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


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

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


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

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


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

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


What are the characteristics of shigella spp.?

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


What is the epidemiology of shigella spp.?

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


What are the clinical manifestations of shigellosis?

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


What is the pathogenesis of shigella spp.?

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


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

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


How do shigella spp. spread to neighboring cells?

1. Hijack host actin 2. Evasion of host defense


How does the shiga toxin cause damage?

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


What causes the diarrhea seen in shigella infection?

Severe inflammation


Does shigella infection confer immunity?



What are the properties of enteroinvasive E. coli?

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