[Studies on the combination action of ampicillin and dicloxacillin (author's transl]

The combination action of ampicillin and dicloxacillin was studied in vitro. The following conclusions were obtained. 1) When both ampicillin and dicloxacillin were employed, an increase in antibacterial activity was observed against beta-lactamase producing E. coli No. 106 (clinical isolated strain). 2) A synergistic action of ampicillin and dicloxacillin was proved by chequer board dilution method for E. coli No. 106. 3) A same synergistic action of ampicillin and dicloxacillin was also proved by the growth curve for E. coli No. 106. 4) Dicloxacillin showed an inhibition in degradation of ampicillin brought about by beta-lactamase extracted from E. coli No. 106. 5) When the organisms of E. coli No. 106 were exposed to the combination of ampicillin and dicloxacillin, spheroplast-like structure and lysis were observed by scanning electron microscope.