Other GI Bacteria Flashcards
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
What metabolic characteristic differentiates Vibrio spp. from Enterobactericae?
Vibrio are oxidase positive, unlike enterobactericae
Campylobacter jejuni is also oxidase-positive
Which genus is found in salt water?
Vibrio
Describe the morphology and motility of Vibrio spp.
Comma-shaped; darting motility
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
Buzzword: agent O/129
Bacteriostatic to Vibrio spp.
In what environments are Vibrio found?
Water: fresh, salt, brackish
More common in warmer months due to association with water
Buzzword: Shellfish
Vibrio
Buzzword: Ice cream
Vibrio
What is the causative agent of cholera?
Vibrio cholerae
What is a likely agent of septicemia following ingestion of seafood?
Vibrio vulnificus
Aside from ingestion, what is another mode of transmission of Vibrio vulnificus?
Inoculation of open wounds
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
Buzzword: rice water stool
Cholera
What is one method of increasing chances of recovery/isolation of Vibrio cholerae from a stool sample?
Enrichment in alkaline media
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.
