Trimethoprim/sulphainethoxazole resistance in Escherichia coli and Klebsiella spp. urinary isolates

Abstract

The susceptibility of 40 Escherichia coli and 35 Klebsiella spp. urinary isolates to trimethoprim/ sulfamethoxazole (cotrimoxazole) was determined. The determination was based on the activity of the standard multodiscs-cotrinioxazole (25 jig). (Oxoid); sulphafurazole (5(K) ng). (Mastring-S); and the minimum inhibitory concentration of trimethoprim and sulphamethoxazole singly against the isolates. Thirty-two (S()%) of 40 isolates of Escherichia coli. and 26 (74%) of 35 isolates of Klebsiella spp. were resistant to cotrimoxazole. All the isolates were resistant to more than 500 ing/l sulphamethoxazole. Twenty of the 32 (62%) cotrimoxazole-resistant E. coli strains and IS of the 26 (69%) cotrimoxazole-resistant Klebsiella strains were resistant to more than 2000 mg/l trimethoprim. These high level trimcthoprimresistant strains invariably carried transferable resistance to at least the sulphonamidcs. atnpicillin and tetracycline, which could be transferred en bloc to known sensitive recipients by the process of conjugation. The high incidence of the R-plasmid-mediated resistance to high levels of trimethoprim suggests the presence of a selective pressure from the increased, and probably the uncontrolled, use of trimethoprim/sulphonamide proprietary formulations in the society.