All of the bacterial isolates were screened for oxidase reaction
followed by standard biochemical tests for presumptive identification
of V. cholerae (Nair et al., 1987; Tamrakar et al., 2006). Isolates
were serotyped with polyvalent antiserum against V. cholerae O1
(Ogawa and Inaba) and O139 (Difco, USA). Voges Proskauer (VP)
test, sheep erythrocyte haemolysis and polymyxin B susceptibility
tests were performed for determination of biotype of isolates.