Vibrio cholerae Antigenic Structure

Study Notes

Limited knowledge on antigenic structure of Vibrio, except for V. cholerae, V. parahaemolyticus, V. fluvialis, and V. vulnificus
V. cholerae has three major subgroups: V. cholerae O1, V. cholerae O139, and V. cholerae non-O1, sharing a common flagellar (H) antigen and somatic (O) antigen
V. cholerae O1 divided into serotypes based on O antigen composition: Ogawa (A, B), Inaba (A, C), and Hikojima (A, B, C)
V. parahaemolyticus serotyped using O and K (capsule) antigens, mainly during epidemiologic studies in reference laboratories

V. cholerae O1 causes cholera, a disease of major public health significance, endemic in developing countries, particularly in the Bengal region of India and Bangladesh
Seventh and current pandemic originated in Indonesia in 1961, spreading throughout Asia and Africa, and later to South America and Central America
Cases of cholera rare in the United States, mostly reported as imported cases

Cholera is an acute diarrheal disease, mainly spread through contaminated water, and sometimes through improperly handled foods
Symptoms include severe gastroenteritis, vomiting, and diarrhea, with characteristic "rice water stools" and frequent bowel movements (10-30 per day)
If untreated, cholera can lead to rapid fluid and electrolyte loss, dehydration, hypovolemic shock, metabolic acidosis, and death within hours
Caused by the powerful enterotoxin choleragen, produced by V. cholerae in the small intestine, which leads to hypersecretion of electrolytes and water into the intestine

Choleragen consists of two toxic A subunits and five binding B subunits
B subunits bind to GM1 ganglioside receptor on the cell membrane, allowing A2 subunit to facilitate entrance of A1 subunit into the cell
Active A1 subunit stimulates production of adenylate cyclase, leading to accumulation of cyclic adenosine monophosphate (cAMP) and hypersecretion of electrolytes and water into the intestine

Treatment involves administration of large amounts of intravenous or oral fluids to replace lost fluids
Antimicrobial agents like doxycycline can shorten duration of diarrhea, but resistance has been reported, and additional antimicrobials like azithromycin and ciprofloxacin may be used