[Effects of ampicillin and cefazolin combined with mecillinam (author's transl)]

Combination effects of mecillinam + ampicillin and mecillinam + cefazolin were investigated by the cross diffusion test and by the kinetics of bactericidal action. Synergism was found by cross diffusion in about 50% of strains of E. coli, Klebsiella and Proteus. Sensitivity against ampicillin was correlated with synergism. In mecillinam-resistant strains, synergism is usually absent. The combination of ampicillin or cefazolin with mecillinam leads to bactericidal acceleration; the effects are comparable to those of the combination with gentamycin. Mecillinam seems to be a clinically promising agent for combination chemotherapy. A simple test for synergism is desirable.