Effect of Drug Resistance on the Pathogenicity and Virulence of Salmonella Typhimurium

Various strains of E. coli. and Salmonella typhimurium were studied in vitro for the presence of plasmids controlling haemolysin, drug resistance, serum resistance and colonization factor etc. They were also tested in mice to determine the probable role of the plasmids on the host pathogenicity. To determine the effect of associated R-factor on the pathogenicity and virulence of S. typhimurium, antibiotic sensitive and resistant strains were tested for virulence in mice. The experiments showed that drug resistance plasmids enhance the lethality of their host. This causes a serious problem in effective treatment of patient suffering with Salmonella and E. coli infections.