Cholerae

Cholerae refers to the bacterium Vibrio cholerae, a Gram-negative, curved, motile rod that colonizes aquatic environments. The clinically important serogroups are O1 and O139; non-O1/non-O139 strains can cause milder gastroenteritis. V. cholerae is adapted to estuarine habitats and often associates with plankton and shellfish. Humans typically become infected by ingesting contaminated water or seafood, with transmission strongly linked to poor sanitation and water treatment.

Pathogenesis: infection causes acute secretory diarrhea due to cholera toxin (ctxAB) encoded by the CTXφ phage, which raises cAMP in enterocytes and drives fluid loss. The organism uses toxin-coregulated pilus for colonization, with expression governed by the ToxR–ToxS regulatory system.

Diagnosis and treatment: diagnosis is clinical in outbreaks; stool culture on TCBS agar yields oxidase-positive curved rods; rapid tests exist but vary in accuracy. Management centers on rapid rehydration with oral rehydration solution or intravenous fluids, electrolyte replacement, and zinc in children. Antibiotics (such as doxycycline or azithromycin) can shorten illness and reduce fecal shedding, though antimicrobial resistance is a concern.

Prevention and epidemiology: prevention relies on safe water, sanitation, and hygiene. Vaccines are available, including oral killed vaccines used in outbreaks or high-risk settings. Cholera has caused multiple pandemics since the 19th century, driven mainly by O1 and O139, with control emphasizing water, sanitation, surveillance, and rapid public health responses.