[Studies on the combination action of sisomicin, gentamicin and cefmenoxime, ceftizoxime, cefoperazone, cefotetan against Serratia marcescens and Pseudomonas aeruginosa].

The combined actions of sisomicin (SISO), gentamicin (GM) and cefmenoxime (CMX), ceftizoxime (CZX), cefoperazone (CPZ), cefotetan (CTT) against S. marcescens IFO-3735 and P. aeruginosa IFO-12689 were investigated. The results were summarized as follows. The synergistic effect of the combinations of SISO-CMX, SISO-CZX, SISO-CPZ, SISO-CTT, GM-CMX, GM-CZX, GM-CPZ and GM-CTT using the checker board dilution method on S. marcescens IFO-3735 and P. aeruginosa IFO-12689 were found. Especially the minimum FIC index value of combination of SISO-CTT and GM-CTT were rather low as 0.14 and 0.13, respectively and these synergistic effect was remarkably strong on S. marcescens IFO-3735. With the killing kinetic method, all combinations tested showed the synergistic effect in both bacteria.