Trimethoprim resistance amongst urinary pathogens in south India

Two hundred and eighty four strains of Enterobacteriaceae, responsible for significant bacteriuria, were isolated, over a three month period, in Vellore, India. Sixty-four per cent of these strains were resistant to 10 mg/l of trimethoprim. Moreover, this population was dominated by high level resistance (minimum inhibitory concentration greater than 1000 mg/l) and these accounted for 57.3% of all strains studied. Over half of the resistant strains were able to transfer trimethoprim resistance to standard Escherichia coli strains. However, the high incidence of transferable resistance did not result from the spread of one plasmid type as 58 different plasmid types were identified. These results are in marked contrast to recent findings in Europe where the incidence of high level transferable trimethoprim resistance is falling.