Transferable resistance to trimethoprim in enteric pathogens isolated in Kuwait

Trimethoprim resistance was seen in 14.8% of 500 strains of salmonella, 43.1% of 153 strains of shigella and 59% of 27 strains of Escherichia coli isolated from stools of patients with diarrhoea. Strains with a high level of trimethoprim resistance (MIC of much greater than 512 micrograms) were subjected to conjugal transfer. Trimethoprim resistance was plasmid-mediated in all of 42 strains of shigella and 12 strains of E. coli examined. However, 2 of the 47 strains of salmonella could not transfer their trimethoprim resistance either directly or by mobilization with the transfer factors X and delta both at 37 and 25 degrees C overnight incubation.