Expanding multiple antibiotic resistance among clinical strains of Vibrio cholerae isolated from 1992-7 in Calcutta, India

Antimicrobial susceptibilities of Vibrio cholerae strains isolated from cho lera patients admitted to the Infectious Diseases Hospital, Calcutta, India for 6 years were analysed to determine the changing trends; 840 V. cholera e strains isolated in 1992-1997 were included in this study. Among V. chole rae serogoup O1 and O139, ampicillin resistance increased from 1992 (35 and 70 %, respectively) to 1997 (both serogroups 100%). Resistance to furazoli done and streptomycin was constantly high among V. cholerae O1 strains with gradual increase in resistance to other drugs such as ciprofloxacin, co-tr imoxazole, neomycin and nalidixic acid, V. cholerae O139 strains exhibited susceptibilities to furazolidone and streptomycin comparable with those of O1 strains. However, after initial increase in resistance to chloramphenico l and co-trimoxazole, all the V. cholerae O139 strains became susceptible t o these two drugs from 1995 onwards. Both V. cholerae O1 and O139 remained largely susceptible to gentamicin and tetracycline. V. cholerae non-O1, non -O139 strains, in contrast, exhibited high levels of resistance to virtuall y every class of antimicrobial agents tested in this study especially from 1995. Kruskal-Wallis one-way analysis showed that V. cholerae O1 Ogawa sero group exhibited significant yearly increase in resistance to nine antibioti cs followed by non-Ol non-O139 and O139 strains to six antibiotics and two antibiotics respectively. Interesting observation encountered in this study was the dissipation of some of the resistant patterns commonly found among V. cholerae non-O1 non-O139 or O1 serogroups to the O139 serogroup and vic e versa during the succeeding years.