Mercury resistance and R plasmids in Escherichia coli isolated from clinical lesions in Japan.

The mercury and antibiotic resistance of 338 strains of Escherichia coli isolated from hospital patients was determined. Resistance to mercury was found in 58.6% of the isolates. The frequencies of resistance to streptomycin (Sm), tetracycline (Tc), chloramphenicol (Cm), kanamycin (Kan), cephaloridine (Cer), and gentamicin (Gm) were 66.3, 60.3, 56.5, 42.9, 32.1, and 1.5%, respectively. Among the above, 198 mercury- and antibiotic-resistant isolates were selected and tested for their ability to transfer the resistance to susceptible strains of E. coli K-12 and Klebsiella pneumoniae JK5. R plasmids carrying mercury resistance were demonstrated in 89.9% of the mercury-resistant strains of E. coli. Furthermore, R(Hg,Sm,Tc,Cm) plasmids were demonstrated most frequently, followed by R(Hg,Sm,Tc,Cm,Kan), R(Hg,Cm,Kan), and R(Hg,Sm,Tc,Cm,Kan,Cer) plasmids.