Dissemination of a plasmid determining multiple antibiotic resistance between two Veterans Administration Medical Centers.

The endemic R-plasmids mediating resistance to gentamicin and multiple other antibiotics among many species of Enterobacteriaceae from the Minneapolis and Cleveland Veterans Administration Medical Centers were compared by restriction endonuclease digestion profiling and by phenotype expressed in sensitive E. coli recipients. Southern hybridizations were also performed. Our data indicate that these plasmids demonstrate some microheterogeneity, but are very closely related. Both are self-transferable and mediate resistance to ampicillin, carbenicillin, chloramphenicol, gentamicin, tobramycin, neomycin and kanamycin. These results suggest the dissemination of a conjugal R-plasmid or of Enterobacteriaceae bearing the plasmid between two midwestern Veterans Administration Medical Centers. The most likely mechanism of transmission may be the frequent transfer of patients between midwestern Veterans Administration Medical Centers.