[Antibacterial action of cefoperazone and piperacillin against Escherichia coli].

A study of the antibacterial action of cefoperazone (CPZ) and piperacillin (PIPC) against E. coli demonstrated clear differences between these 2 drugs. CPZ showed higher bactericidal and lytic activity which was dose dependent and not greatly influenced by inoculum size. In contrast, the activity of PIPC was strongly influenced by inoculum size and showed high bactericidal activity only against a low inoculum size. The activity of CPZ was not related to the pH of the culture medium, whereas PIPC showed increased activity in an acid medium. In a study of the drug sensitive phase of a synchronous culture, CPZ was highly effective during the period of cell division showing strong bactericidal activity at that time. The bactericidal action of CPZ was inhibited by the addition of chloramphenicol. In contrast, PIPC which by itself demonstrated only weak bactericidal activity was not effective during the period of cell division. Although CPZ and PIPC both activate autolysin activity, CPZ was more active in this regard.