Molecular characterization of Salmonella Typhimurium and Salmonella Enteritidis by plasmid analysis and pulsed-field gel electrophoresis

Forty-one paediatric isolates of Salmonella spp. from Cerrahpasa Faculty of Medicine, Istanbul, Turkey, between 2001 and 2004 were examined for susceptibility to various antibiotics and presence of antibiotic resistance genes. Pulsed-field gel electrophoresis and plasmid profiling were used to determine possible genetic relationships among Salmonellaenterica subsp. enterica clinical isolates. Plasmids from resistant strains were not transferred by conjugation to recipient Escherichia coli cells. Pulsed-field gel electrophoresis and restriction enzyme digestion analysis of DNA revealed that multidrug-resistant isolates belonged to the same clonal group, characterized by ACSSuT resistotype. Isolates of R-type ACSSuT were positive for the intI gene and possessed a single plasmid of 60 MDa.