Characterization of an hospital disseminated plasmid encoding resistance to gentamicin and other antimicrobial agents.

A preliminary report has shown the existence of an endemic R plasmid in the University Hospital of Zaragoza. The results presented in this paper demonstrate the dissemination of a new 73 kilobases plasmid into multiple strains and species of gram-negative bacilli. This transferable plasmid belongs to Incompatibility group P and mediates resistance to ampicillin, tetracycline, gentamicin, kanamycin, streptomycin, chloramphenicol and sulfamethoxazole, synthesizing the aminoglycoside-modifying enzymes 3-acetyltransferase, 3'phosphotransferase, and 3"nucleotidyltransferase, and a TEM-1 beta-lactamase. These results and the previous findings show that a family of gentamicin-resistance plasmids exists among the gram-negative bacteria in the University Hospital. Resistance to gentamicin in all these plasmids is associated with the formation of 3-N-acetyltransferases.