Tetracycline resistance genes in Kenyan hospital isolates of Salmonella typhimurium

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Abstract
All 97 strains of Salmonella typhimurium isolated from patients at a hospital in Nairobi, Kenya, during 1988-90 were resistant to tetracycline. The minimum inhibitory concentration (MIC) showed a large distribution range from 1 μg/ml to 128 μg/ml. The strains were heterogeneous with respect to plasmid content, but initially all strains possessed, in addition to other plasmids, a large 60-, 63-or 65-MDa plasmid. The tetracycline resistance genes were characterized using oligonucleotide probes, and 20% of the resistant strains possessed tetracycline type A (tetrA), 6%tetr B, and 4%tetrC genes. Three strains possessed both type A and B tetracycline resistance determinants, which were shown to be located on the large 65-MDa plasmid. There was no correlation between strains isolated from stools, blood, cerebrospinal or epidural fluids, pus, or urine, with respect to the tetracycline genotypes, MIC values or plasmid content.