In Vitro Studies with Netilmicin Compared with Amikacin, Gentamicin, and Tobramycin

Abstract

Netilmicin, a new semisynthetic aminoglycoside derived by ethylation of the 1- N position of the deoxystreptamine ring of sisomicin, was tested in vitro with 4,070 strains of gram-negative bacilli isolated at the UCLA Medical Center during 1975 to 1976, using the agar dilution technique and an inoculum of approximately 10 ⁴ organisms. Results were compared with those simultaneously obtained for amikacin, gentamicin, and tobramycin. Using Mueller-Hinton medium, inhibitory concentrations in broth correlated with those obtained by the agar dilution method except for Pseudomonas aeruginosa , where a 2- to 16-fold difference in susceptibility was noted. For most clinically significant Enterobacteriaceae and P. aeruginosa , the activity of netilmicin in vitro was comparable or superior to that of gentamicin, tobramycin, and amikacin with respect to potency by weight and achievable blood levels. Against gentamicin-resistant strains (MIC > 16 μg/ml), the activity of netilmicin paralleled that of amikacin with the exception of Providencia stuartii , which was inhibited by amikacin but not by netilmicin.