Susceptibility of "enterobacteria" to aminoglycoside antibiotics: comparisons with tetracyclines, polymyxins, chloramphenicol, and spectinomycin.

Strains of enterobacteria, including common, aerobic, pathogenic gram-negative bacilli, and enterococci were tested for susceptibility to 11 aminoglycoside antibiotics by a twofold agar-dilution method with an inocula replicator. For comparison, similar tests were done with seven tetracycline analogues, two polymyxins, chloramphenicol, and spectinomycin. Tobramycin compared favorably with the more active aminoglycosides, with some exceptions related to individual strains of species. The tetracyclines and chloramphenicol were generally less active than the more active aminoglycosides. The polymyxins were as active or more active against most species of gram-negative rods but were essentially inactive against Proteus, Providencia, and many strains of Enterobacter.