[In vitro study on the combined effect of mezlocillin and sisomicin on clinically pathogenic P. aeruginosa and E. coli].

Clinically pathogenic Pseudomonas aeruginosa and Escherichia coli were subjected to test in vitro combination effect of mezlocillin (MZPC) and sisomicin (SISO). The chequer board titration method, using brain heart infusion broth (BHIB, Difco), demonstrated the combination effect of MZPC and SISO on the both isolates. The bactericidal combination effects (MBCs) were clearly higher than the bacteriostatic combination effects (MICs). The bactericidal activities of combination with MZPC and SISO were tested on both P. aeruginosa and E. coli. The MZPC plus SISO of low concentrations showed the synergistic effects on both isolates.