Vibrio Cholera Flashcards
Cholera general properties
Motile gram negative fermenter, comma shape, polar flagellum
Yellow opaque colonies on special TCBS medium (usual media for enteric pathogens such as EMB may inhibit growth)
Produces O, H antigens, endotoxin and potent enterotoxin
All epidemic cholera is O1 (with 0139 in mid-90s)
Two 01 biotypes
classical and El Tor (hemolytic)
toxin coregulated pilus
Cholera pathogenesis
Gastric acid inactivates ingested organisms but some survive
enter small bowel and bind to epithelium
TCP is expressed and bacteria form microcolonies in intestinal crypts
Cholera toxin expressed and secreted expressed and secreted, binding to GM1 gangliosides of cell membrane
Neuraminidase coverts other gangliosides to GM1 and increases toxicity
toxin enters cells by endocytosis and stimulates adenylate cyclase and cAMP production, results in massive intestinal fluid loss via 2 mechanisms
1. villus cells:decreased NaCl absportion from gut
2. Secretory cells: increased Cl and increased HC03 secretion into gut, along with H20 (secretory diarrhea)
Cholera clinical features
Painless, odorless profuse watery diarrhea (rice water stool)
Isotonic volume loss (10-15 liters a day) and dehydration, low blood pressure (shock), potential death
Cholera treatment
Replace fluid using same concentrations of electrolyte
Oral or IV rehydration solutions both acceptable
Cholera cot facilitates measurement of stool volume to be replaced
Antibiotics reduce duration of diarrhea from 5-10 to 1-3 days
Doxycycline for adults or azithromycin for children and pregnant women
Cholera epidemiology
accounts of cholera since BC
limited to humans and associated with poverty and inadequate sanitation
Cholera prevention
Water precautions
food precautions
cholera vaccine
1. current inactivated vaccine: two oral doses of crude bacterial suspension, 70% effective
2. live attenuated vaccine: effective in N. American clinical trials but unproven in field studies
