Netilmicin: in-vitro activity compared with that of other aminoglycosides against Serratia marcescens

The activity of netilmicin, a semisynthetic aminoglycoside, was compared with that of gentamicin, tobramycin, and amikacin against 100 clinical isolates of Serratia marcescens. Minimum inhibitory concentrations (MIC) were determined by an agar dilution procedure. Defining amikacin resistance as an MIC of greater than 16 mg/l, and netilmicin, gentamicin and tobramycin resistance as an MIC greater than 4 mg/l, 1% were resistant to amikacin, 3% to netilmicin, 8% to tobramycin, and 43% to gentamicin. The majority of isolates that were resistant to both gentamicin and tobramycin were sensitive to netilmicin. These results indicate that the activity of netilmicin against Ser. marcescens is closely comparable to that of amikacin.