Trimethorprim-sulfamethoxazole resistance mediated by r-plasmid inthe clinical isolates of shigella in Bangladesh

Abstract

The differential resistance of most prevalent ShigeUa serotypes, S. flexneri fn = 2940) and S. dv.ienterioe type. I (n = 16l8) to the drug trimethoprim itself and to trimethoprim-sulfamethoxazole are reposed. The predominant resistance pattern (R-type) in S, dysenteriae type 1 was CSTTmp Smx and in S, flexneri was ST. Minimum inhibitory concentration (MIC) values to trimethoprim and Tmp-Smx in 75% and 84% isolates of S. dysenteriae type Ifn-250) were >400 ug/ml and >2000 ug/ml respectively whereas the degree of sensitivity was completely reversed in S. flexneri (n=250) where 96%-91% strains showed MIC equal to or less than 1.6 ug/ml and 2 ug/ml with trimethoprim and Tmp-Smx. respectively 5. dysenteriae type 1 strain with R-type C.S.T. Tmp-Smx, harboured 4 plasmids of molecular weights 140,6,4, and 1.94 megadaltons. The 4 Md plasmid was cured with acridine orange treatment. The possible role of 4 megadalton plasmid in conferring resistance to TMP-SMX in S. dysenteriae type 1 has also been investigated. All the strains were isolated from patients attending the International Center for Diarrhoeal Disease Research, Bangladesh, Hospital at Dhaka during the period 1981-1984.