Cluster-analysis & patterns of dissemination of multidrug resistance amongclinical strains of Vibrio cholerae in Calcutta, India

Background & objectives: Antimicrobial resistance among Vibrio cholerae has been monitored for several years in Calcutta. To investigate the changing trends in multidrug resistance (MDR) among different serogroups of V. chole rae and to perform software assisted cluster analysis the current study was undertaken. Methods: Strains isolated from patients with cholera and "cholera-like" dia rrhoea admitted in the Infectious Diseases Hospital, Calcutta were analysed . Eight hundred and forty V. cholerac strains isolated from 1992 through 19 97 were tested for susceptibility to 11 antibiotics. Cluster analysis was d one using SPSS software. Results: Most of the strains exhibited MDR with fluctuating trends as the r esistance profile diverged each year. A total of 119 different resistance p rofiles exhibited by V. cholerae O1, O139 and non-O1, non-O139 serogroups w ere analysed by cluster combination method. During 1993 and 1994, 53 per ce nt of V. cholera O139 and 82 per cent of V. cholerae O1 serogroups, respect ively, exhibited maximal number of new resistance patterns. The frequency o f new resistance patterns among V. cholerae non-O1, non-O139 was constantly high (33-47%) during 1995 to 1997. Interpretation & conclusions : With a few exceptions, preponderance of the resistance profiles was generally not confined to any serogroup. The cluste r analysis depicted dissemination of some of the resistance patterns common ly found among V. cholerae non-O1, non-O139 belonging to different serogrou ps to the O139 serogroup in the succeeding years. In this study we have sho wn that the V. cholerae strains are resistant to several antibiotics with c onstant change in the MDR profiles. It is imperative to define the suscepti bility pattern of the strains to determine the effective drug of choice for the treatment of cholera.