[Combined action of cephamycin and aminoglycoside antibiotics]

The combined actions of cefoxitin (CFX) with amikacin (AMK), gentamicin (GM) and dibekacin (DKB) were studied against Gram-positive and Gram-negative bacteria. The following results were obtained. The synergistic actions of CFX with AMK, GM and DKB were observed on S. aureus, S. epidermidis, E. coli, S. marcescens, K. pneumoniae, Proteus spp. and Acinetobacter by checker board titration method. The combination of CFX with AMK was most effective. In case of the combination of CFX with AMK, the simultaneous administration showed the highest bactericidal effect, followed by the case of addition of AMK after adding CFX. The phase-contrast microscopic observation on S. marcescens revealed that the bacterial cell prolonged with CFX showed a filament-like form and with AMK almost a normal form. In the combination, lysed cells were observed. The therapeutic experiment of S. marcescens infection in mice demonstrated that the combination of CFX with AMK showed superior effect than that of each drug alone.