Plasmid profile and phage type of Salmonella typhimurium strains encountered in different regions of India

A total of 190 Salmonella typhimurium strains encountered in different parts of India were characterized on the basis of plasmid profile, phage type and antimicrobial resistance pattern. Recent trends in the epidemiology of R-plasmids were also studied. The majority of S. typhimurium strains (90.5%) were untypable by phage typing. Only 18 strains (9.5%) were phage typable. The phage untypable strains isolated from northern (57) central (65), and southern (50) regions of India could be subgrouped into 24, 12 and 16 different plasmid profiles respectively. Heterogeneity was the prominent feature although most of the plasmid profiles were related among strains isolated from particular place. A great diversity among small plasmids (2.7-8.3 kb) made subgrouping of majority strains (71%) with R-pattern ApCmKmSmSuTcTp possible. Conjugation studies and plasmid profile analysis of transconjugants revealed all the strains to harbour non conjugative non-auto transmissible plasmids with the exception of 7.2 and 2.7 kb plasmids which were not mobilizable.