ABSTRACT
Tetracyclines have been among the most widely used antibiotics worldwide. Plasmid-mediated tetracycline resistance among hospital strains of bacteria has increased through the many years of usage. The major concern has been the transfer of resistance to pathogenic organisms. Bacteraemia due to S. typhimurium has been a major cause of morbidity at Kenyatta National Hospital (KNH); hence the need to study drug resistance patten of this organism and to characterize the tetracycline resistance genes using oligonucleotide probes. 97 S. typhimurium strains isolated from patients at KNH were used. Agar dilution method was used todetermine minimum inhibitory concentration (MIC). Plasmids were isolated from each strain and the different plasmid profiles were grouped by their molecular weights into 6 plasmid profile groups. Tetracycline resistance genes were characterized using oligonucleotide probes. 87 out of 97 (88) strains were resistant. MIC ranged from 1 ug/ml to 128 ug/ml. Genes encoding for tetracycline resistance were located on plasmids of molecular weights 65 MDa; 5.2 or both. Salmonellosis is a public health problem in Kenya especially bacteraemia due to S. typhimurium. Plasmid-encoded natimicrobial resistance is likely to spread to other pathogenic organisms; reduce our ability to treat the infection and increase cost and duration of treatment