Vibrio cholerae

General: Numerous serogroups (O1-O140), with O1 and O139 causing cholera epidemics; these are further split into serotypes and biotypes. The three serotypes are Inaba, Ogawa, and Hikojima; strains may switch serotypes between Inaba and Ogawa, with Hikojima a transitional serotype with antigens of each. The O1 biotypes are classical and el tor; the only named O139 biotype is Bengal.

Clinical: Symptoms range from asymptomatic to severe, rapidly fatal diarrhea, and develop 2~3 days following exposure with abrupt onset of watery diarrhea and vomiting. The diarrhea progresses from fecally streaked to colorless, odorless, protein free, and mucous speckled (rice water). This may cause profound dehydration (hypovolemic shock), metabolic acidosis due to bicarbonate loss, and hypokalemia, with subsequent dysrhythmias and renal failure. Mortality is ~60% untreated, but only ~1% treated. May resolve spontaneously within days of symptomatic onset.

Resistance:

Morphology: Curved Gram- rod with a single polar flagellum.

Growth characteristics: Facultative anaerobe, lactose fermenter, oxidase+.

Common/important pathogens:

• O1 el tor (1961 pandemic, spread through 1991)
• O139 Bengal (1992 pandemic)