Abstract
The protective effect of dicloxacillin on an inactivation of Ampicillin caused by β-lactamase was studied in vitro.
The following conclusions were obtained.
1) When both Ampicillin and Dicloxacillin were employed, an increase in antibacterial activity was observed for Klebsiella pneumoniae, Shigella boydii, Shigella flexneri, Proteus vulgaris OX-19 and Proteus morganii Kono.
2) No increase in antibacterial activity of these drugs was demonstrated for ampicillin-resistant strains of Staph. aureus isolated clinically.
3) A synergistic effect of these drugs was proved by the tube dilution method for the strains for which the same effect was shown by agar streak method.
4) Same synergistic effect of these drugs was proved by growth curve for both Proteus vulgaris OX-19 and Proteus morganii Kono.
5) Dicloxacillin showed a competitive inhibition in degradation of ampicillin brought about by cell-bound penicillinase extracted from Proteus morganii Kono.
