Trimethoprim Resistance Conferred by W Plasmids in Enterobacteriaceae

Abstract

SUMMARY High-level resistance to trimethoprim (minimum inhibitory concentration > 1000 μg/ml) was conferred by R factors of the W compatibility group in Escherichia coliand Klebsiellaspp. isolated from patients in three London hospitals. We suggest that we are observing the early stages in the spread of a new R factor.