VIBRIO-CHOLERAE O139 BENGAL POSSESSES A CAPSULAR POLYSACCHARIDE WHICH MAY CONFER INCREASED VIRULENCE

A newly described Vibrio cholerae serogroup—O139 Bengal, the causative agent of the recent large epidemics of cholera-like disease in the Indian subcontinent and neighbouring countries — possesses a high molecular weight capsular polysaccharide (CPS) that can be visualized by electron microscopy and in composition differs from the lipopolysaccharide (LPS). The CPS and LPS can be separated from each other by a two-step extraction procedure a phenol-water extraction in order to extract all polysaccharides from the bacterial suspension followed by a phenol-chloroform-petroleum ether (PCP) extraction. The CPS is mainly composed of 3,6-dideoxyhexose (abequose or colitose), quinovosamine and glucosamine. The LPS of the O139 Bengal strain appears to possess a short polysaccharide which contains glucose, galactose, glucosamine and heptose. Both the LPS and CPS are immunogenic. They react in an enzyme immunoassay with rabbit antibodies generated against whole heat-killed bacteria. By analogy with other capsulated bacteria, the possession of a capsule may confer increased virulence of O139 Bengal. © 1994 Academic Press.