True about V. Cholerae is -

Ans. is 'd' i.e., Pathogenecity of 0-139 vibrio is due to 0 antigen I know this answer is going to raise many eyebrows but have patience and lets see each option one by one OptionA . This is very easily ruled out as an attack of Vcholera can give immunity lasting for only 6-12 months. Option B . In non-epidemic region cholera is mainly seen in the children. . During epidemics, it affects adults and children with equal propensity. . Harrison states . "Cholera is predominantly a pediatric disease in endemic areas, but it affects the adults and children equal when newly introduced into a population (as during epidemics)." Option C . Though chronic carrier states are seen is V.cholera, but its a rare phenomenon. . These infrequent chronic carriers are not able to maintain the organism in between epidemics. . The organism is maintained is between epidemics by its natural habitat in coastal salt water and brackish estuaries. . Harrison writes " The natural habitat of V. Cholerae is coastal salt water and brackish estuaries, where the organism lives in close relation to plankton. Humans become infected incidentally but, once infected, can act as vehicles for spread." Option D . This is going to be most controversial of all but read these lines from Harrison " V. Cholerae 0 139 Bengal strain is in fact viually identical to V. Cholerae 01 EL Tor strain except for two impoant differences, . Production of the new 0 139 LPS and . of an immunologically related 0-antigen polysaccharide capsule. . Both of these molecules are putative virulence factors, independently enhancing colonization in a murine infection model." . These lines very clearly state that the 0139 LPS (0 139 LPS and 0 antigen mean the same thing) is responsible for the virulence of this paicular 0 139 strain of V. Cholera.