SALMONELLA-TYPHIMURIUM DT-193 - DIFFERENTIATION OF AN EPIDEMIC PHAGE TYPE BY ANTIBIOGRAM, PLASMID PROFILE, PLASMID FINGERPRINT AND SALMONELLA PLASMID VIRULENCE (SPV) GENE PROBE

Of over 2000 isolates of Salmonella typhimurium DT 193 from humans exa mined in the 2 year period 1991-92, 93% were antibiotic-resistant with the most common R-types being ASSuT (38%) and T (29%). Fourteen plasm id profiles were identified in DT 193 R-type ASSuT with the majority o f isolates being characterized by a single plasmid of 80 MDa (pDEP 34) which in addition to coding for ASSuT, also hybridized with a spy gen e probe prepared from the 50 MDa Salm. dublin serovar-specific plasmid . On the basis of restriction fragment length polymorphisms, two varia nt lines of pDEP 34-like plasmids were identified and a third line whi ch had lost the genes coding for resistance to ampicillin, streptomyci n and sulphonamides, was recognized. Although 18 plasmid profile types were identified in DT 193 R-type T, all isolates carried a high mol. wt plasmid which coded for tetracycline resistance only. Further discr imination was achieved on the basis of hybridization of tetracycline r esistance plasmids with the spy gene probe and restriction enzyme fing erprinting. These results demonstrate that Salm. typhimurium DT 193 ca n be rapidly subdivided by antibiogram and that further subdivision ca n be achieved on the basis of plasmid profile, plasmid fingerprint and hybridization with a spy gene probe.