URINARY ISOLATES OF APRAMYCIN-RESISTANT ESCHERICHIA-COLI AND KLEBSIELLA-PNEUMONIAE FROM DUBLIN

Twenty-two gentamicin-resistant urinary isolates of Escherichia coli a nd five gentamicin-resistant urinary isolates of Klebsiella pneumoniae from a Dublin hospital were examined for resistance to the veterinary aminoglycoside antibiotic apramycin. Five isolates off. coli and one isolate of K. pneumoniae were found to be resistant. The apramycin-res istant isolates, which were also resistant to the veterinary anthelmin tic agent hygromycin B, hybridized with a DNA probe for the gene encod ing the enzyme 3-N-aminoglycoside acetyltransferase type IV (AAC(3)IV) . Resistance to apramycin and hygromycin B was co-transferable in four of the five isolates of E. coli and the isolate of K. pneumoniae. In one isolate of E. coli apramycin resistance was not transferable. On t he basis of their restriction enzyme digestion profiles and the antimi crobial resistance traits encoded, the transferable plasmids encoding resistance to apramycin and hygromycin B comprised three distinct type s. Genetic linkage between the gene encoding ABC(3)IV and genes encodi ng resistance to ampicillin and either tetracycline or trimethoprim, m eans that the relatively widespread use of these antimicrobial agents provides a selective pressure for the persistence of resistance to apr amycin and gentamicin even in the absence of bacterial exposure to ami noglycosides.