[Comparative activity of new semisynthetic penicillins and their combinations with gentamycin against gram-negative bacteria].

Comparative antibacterial activity of two novel ureidopenicillins (azlocillin and piperacillin), carbenicillin and ampicillin against 170 clinical strains of Enterobacteriaceae and 43 strains of Pseudomonadaceae was studied. Higher antibacterial activity of azlocillin and piperacillin evident from lower frequency of resistant strains and lower MICs for the majority of the isolates was shown. Impact of the inoculum size on the MIC values was observed with respect to all the penicillins. The study on the kinetics of Pseudomonadaceae death under the effect of azlocillin and carbenicillin revealed an increase in the bacteria growth after 6- to 8-hour contact with therapeutic concentrations of azlocillin and 4-hour contact with carbenicillin. Nor renewal of the culture growth was observed within 10-hour contact with combinations of the penicillins and 2 micrograms/ml of gentamicin.