Vibrio cholera Flashcards
General features and habitat of Vibrio cholera
Gram – Comma shape (curved rod)
Primarily found in water- endemic to developing countries (Southeast Asia)
Polar flagella and fimbriae (pili)
Biochemical Properties of Vibrio cholera
Oxidase + (differentiate from Enterobacteriaceae)
Acid labile- sensitive to acid (grows well in alkaline pH with the range of 6.5 to 9)
Halophile- can survive high salt concentration (can survive in salted water)
Facultative anaerobe
Pathogenesis of Vibrio cholera
Transmitted by fecal-oral from contaminated food or water (by feces)
The bacteria attach to mucosal wall of intestine by fimbriae (pili), multiply there (never enter the cell) and release enterotoxins- Cholera toxin (AB type toxin):
A = Continuously activating adenylate cyclase (GS) thus increase cAMP ()
B = Binds to the receptor, facilitates the entry of toxin A into cell
Increase in cAMP leads to inhibition of Na-pump, and hypersecretion of ions, that will also cause water hypersecretion and therefore diarrhea
Clinical Features Cholera
Watery diarrhea (“rice-water”)- 10-20L/day Complications: dehydration, acidosis and shock
Diagnosis of Vibrio cholera
Microscopy:
Gram staining
Dark-field microscope from stool
TCBS selective media (Thiosulfate, Citrate, Bile, Sucrose + Bromthimol blue indicator)- at pH near 9 (alkaline), in 37C for 18 hours.
Colonies appear smooth, round and yellow colored
Serology- slide agglutination with specific anti-‘O’ test serum (against O1 and O139) O1 has three serotypes: Inaba, Ogawa and Hikojima
Treatment of Vibrio cholera
Oral Rehydration Therapy (ORT)- water + electrolytes (or IV)
Tetracycline, Ciprofloxacin
Prevention of Vibrio cholera
Inactivate (killed) vaccine or per os vaccine with live attenuated bacteria- stimulation of IgA (only work for several months and 50% protection) and keeping good hygiene
