[In vitro examination on antibacterial activity of ciclacillin (ACPC) against clinically isolated strains (author's transl)]

(1) The antibacterial acivity of ciclacillin (ACPC) with inoculum size of 10(6) cells/ml was four times less potent than that of ampicillin (ABPC) and 4 approximately 8 times less potent than that of AMPC, but was 4 approximately 8 times more potent than that of CEX against Streptococcus pyogenes. For Streptococcus pneumoniae, ACPC was 2 approximately 4 times less active than ABPC and AMPC, but 16 approximately 32 times more active than CEX. Staphylococcus aureus was 4 approximately 8 times less susceptible to ACPC than to ABPC and AMPC, but 1 approximately 2 times more susceptible than to CEX. Against E. coli, ACPC was as active as CEX, 2 approximately 4 times less active than ABPC, and 4 approximately 8 times less active than AMPC. (2) It was suposed that ACPC was more resistant to penicillinase and more antibacterial with inoculum size of 10(6) cells/ml cells/ml than with 10(6) cells/ml. ACPC was 4 approximately 8 times less active than ABPC, and AMPC against Staphylococcus aureus with 10(8) cells/ml, while with 10(6) cells/ml, it was 2 times less active than ABPC and AMPC. (3) ACPC-resistant strains (greater than or equal to 3.13 microng/ml) of Streptococcus pyogenes and Streptococcus pneumoniae were not found. (4) A difference was noted in MIC of three semi-synthetic penicillins, ACPC, ABPC and AMPC, against Staphylococcus aureus, and E. coli between the sources from which their strains were isolated. (5) There were many strains resistant to erythromycin (EM) and josamycin (JM) (greater than 60%, respectively to both antibiotics) in Stretpococcus pyogenes and pus-isolated Staphylococcus aureus. No strains of Streptococcus pyogenes, were found resistant to EM and JM.