Suceptibility of aminoglycoside-resistant gram-negative bacilli to amikacin: delineation of individual resistance patterns.

Gram-negative bacilli isolated from clinical specimens submitted for culture in two Paris hospitals during 1974 were studied for susceptibility to six currently used aminoglycosides: kanamycin, neomycin, paromomycin, lividomycin, gentamicin, and tobramycin. Resistance patterns of strains of various species including those of Enterobacteriaceae, Pseudomonas, and Moraxella were determined, and the strains were grouped into eight resistance "phenotypes." In comparative studies of 807 strains belonging to different phenotypes, amikacin was markedly more active than any of the six other antibiotics; at concentrations of less than or equal to 4 mug/ml, it inhibited about 88% of the strains, including those resistant to gentamicin and tobramycin. Some amikacin-resistant strains were found among different species. The mechanism of resistance to amikacin of strains of Serratia and Moraxella group II was related to an N-acetylating enzyme. Amikacin can be expected to be useful as an alternative treatment of infections due to gram-negative bacilli sensitive to aminoglycosides and also, more particularly, for the treatment of patients infected with multiresistant strains.