Other GI Bacteria Flashcards by Jerrica Park

Name the other bacteria (aside from E coli, Shigella, Salmonella, and Yersina) that we discussed:

Vibrio spp
Campylobacter jejuni
H pylori
S. aureus
B cereus
Listeria monocytogenes
Clostridium spp.:
   - C perfringens
   - C. botulinum
   - C. difficile

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What metabolic characteristic differentiates Vibrio spp. from Enterobactericae?

Vibrio are oxidase positive, unlike enterobactericae

Campylobacter jejuni is also oxidase-positive

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Which genus is found in salt water?

Vibrio

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Describe the morphology and motility of Vibrio spp.

Comma-shaped; darting motility

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Sodium deoxycholate is added to bacteria. When touched with an inoculation loop, a mucoid string stretches from the plate. What is this called, and what is the bacteria?

String test: sodium deoxycholate dissolves DNA of Vibrio, causing mucoid string

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Buzzword: agent O/129

Bacteriostatic to Vibrio spp.

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In what environments are Vibrio found?

Water: fresh, salt, brackish

More common in warmer months due to association with water

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Buzzword: Shellfish

Vibrio

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Buzzword: Ice cream

Vibrio

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What is the causative agent of cholera?

Vibrio cholerae

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What is a likely agent of septicemia following ingestion of seafood?

Vibrio vulnificus

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Aside from ingestion, what is another mode of transmission of Vibrio vulnificus?

Inoculation of open wounds

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How does cholera toxin cause symptoms?

It stimulates a hyperactivation of adenylate cyclase (the A subunit of the AB toxin catalyzes ADP ribosylation of the Gs protein, locking it in active state).

This causes an accumulation of cAMP

This causes hypersecretion of electrolytes/water

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Buzzword: rice water stool

Cholera

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What is one method of increasing chances of recovery/isolation of Vibrio cholerae from a stool sample?

Enrichment in alkaline media

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What is the treatment for Vibrio infection?

Fluid/electrolyte replacement (oral and/or IV)

Antimicrobial such as azithromycin

Buzzword: “Seagull” appearance on microscopy

Campylobacter jejuni

What is a unique metabolic characteristic shared by Campylobacter jejuni and H. pylori?

Both are microaerophilic: unable to grow in atmospheric concentrations of oxygen, but also unable to grow in anaerobic environments.

What is the most common bacterial cause of diarrhea worldwide?

Campylobacter jejuni

What are some of the virulence factors of Campylobacter jejuni?

Flagellum: aids motility, adherence, and invasion
Some strains produce heat-labile cholera-like enterotoxin
CDT: Cytolethal-distending toxin, an A-B toxin

What does cytolethal-distending toxin do, and what organism is it associated with?

Associated with Campylobacter jejuni

Causes cell-cycle arrest, and the destruction of enterocytes, immune cells, and fibroblasts

What is the reservoir for Campylobacter jejuni?

Warm-blooded animals (cattle, poultry, dogs, etc)

How is Campylobacter transmitted?

Fecal-oral transmission - low infectious dose
Direct contact with warm-blooded animals, humans, ingestion of under-cooked poultry or meat, unpasteurized milk, or contaminated water

Buzzword: Guillain-Barre Syndrome

Campylobacter jejuni

Which organism causes disease most similar to a mild form of cholera?

Campylobacter jejuni: watery, dysenteric diarrhea with blood and pus, as well as abdominal pain and fever

Which organism is associated with formation of abscesses in the intestinal crypts?

Campylobacter jejuni

What medium is used to culture Campylobacter jejuni?

Skirrow medium, in microaerophilic conditions

What is the treatment for disease caused by Campylobacter jejuni?

Typically, the disease is self-limited and does not require treatment. For severe/prolonged (>1 week) disease, consider azithromycin.

Metabolically, what is a major difference between H pylori and C. jejuni?

H pylori is urease-positive. Campylobacter is not. Both are microaerophilic.

What are some diseases associated with H pylori?

Gastritis, peptic ulcers, gastric carcinomas, and MALT lymphomas

What is the reservoir for H pylori?

Humans only; present in ~50% of the population worldwide

How is H pylori diagnosed?

Breath-urease test** (best, non-invasive) Biopsy, isolation on Campylobacter media Serology Stool antigen detection

How is H pylori treated?

2 options: Bismuth Quadruple: bismuth, metornidazole, teracycline, and a PPI Clarithromycin Triple: Clarithomycin, a PPI, and EITHER amoxicillin or metronidazole

How are S aureus GI infections acquired? What causes symptoms?

Ingestion of contaminated food: food might be contaminated by someone with nasal colonization or an infected skin lesion. Symptoms are caused by enterotoxins produced by S aureus; they are NOT caused just by bacterial replication.

What kind of foods are more often contaminated by S aureus?

Rich foods: those made with creams, mayonnaise, dairy, meats, etc. Toxin is heat stable!! Cooking does not deactivate.

How soon after ingestion food contaminated by S aureus do symptoms occur?

2-8 hours

How do S aureus symptoms differ if the toxin is ingested vs inhaled?

Ingestion S/S: diarrhea, vomiting, abdominal pain. (no fever, blood, or pus) Inhalation S/S: fever, nauseau, vomiting, and difficulty breathing

What virulence factors are associated with H pylori?

Urease: allows bacterial to break urea down into ammonia and CO2. The ammonia neutralizes stomach acid and create a more neutral microenvironment. VacA: Vaculating cytoxin. Forms vacuoles in the mucosa. CagA: alters the host's actin cytoskeleton and stimulates cytokine production. Introduced to the host cell via a Type IV secretion system.