A laboratory assessment of the activities of four aminoglycosides.

An in vitro comparison of the activities of gentamicin, tobramycin, amikacin and netilmicin against selected clinical isolates showed differences in the susceptibility of individual strains to the four drugs, as well as substantial differences in sensitivity patterns between genera. Sensitive strains of Klebsiella and Enterobacter were most susceptible to netilmicin, but amikacin was more active against resistant strains. Tobramycin was most active against sensitive strains of Pseudomonas aeruginosa, but resistant strains were more susceptible to amikacin. In serious infections caused by these Gram-negative bacilli knowledge of the organism's identity and susceptibility may help in the selection of the most suitable aminoglycoside.