3-N enzymatic acetylation of gentamicin, tobramycin, and kanamycin by Escherichia coli carrying an R factor.

A new R factor-mediated gentamicin acetyltransferase obtained from a clinical isolate of gentamicin-, tobramycin-, and kanamycin-resistant Klebsiella was characterized. R factor R 176 was transferred to Escherichia coli K-12 LA 290 from a Klebsiella. Resistance transfer, minimal inhibitory concentrations of various aminoglycoside antibiotics, enzymatic inactivation, and the isoelectric point of the enzyme obtained were determined. We found that R factor R 176 could govern the enzymatic 3-N acetylation of gentamicin, tobramycin, and kanamycin, and isoelectric point determinations suggested that the enzymes governed by R 176 and R 135 are different. The genes responsible for resistance to gentamicin, tobramycin, and kanamycin govern the synthesis of an isoenzyme of AAC(3)I, which we propose to call AAC(3)II.