Plasmid determined drug resistance in clinically isolated Escherichia coli.

The results of a survey for the presence of R plasmids in 100 clinically isolated strains of Escherichia coli are presented. Sixty-nine per cent of the strains were resistant to at least one of the antimicrobial agents tested and 63.7% of the resistant strains transferred all or part of their resistance genes to Escherichia coli k 12.