Gentamicin resistance in clinical strains of Enterobacteriaceae associated with reduced gentamicin uptake.

Seven strains of Enterobacteriaceae resistant to gentamicin obtained as representatives of the predominant resistance profiles in the clinical laboratories of Rafeidia and Al-Watani Hospitals in Nablus (Palestine) were included. Five strains showed a broad aminoglycoside resistance profile but contained no evidence of gentamicin acetylation, adenylation, or phosphorylation. Gentamicin uptake in two tested strains was significantly reduced, compared to that of gentamicin-sensitive E. coli (MIC, 0.5 microgram/mL). These strains are likely resistant due to a relative reduction of the amount of gentamicin and other aminoglycosides entering the bacterial cell. Two strains showed evidence of adenyltransferase ANT(2")-I activity.