[Bacteriostatic activity of apalcillin on Gram-negative bacilli and strict anaerobic bacteria. Multicenter study].

This work reports a multicenter study of the bacteriostatic activity of apalcillin, a new N-acyl-penicillin, against 1 827 clinical isolates of Gram-negative bacilli and obligate anaerobes. The modal minimal inhibitory concentrations (MICs) for susceptible strains are (mg/l) : Salmonella-Shigella : 1 ; E. coli : 0.5-2 ; Klebsiella : 4 ; Citrobacter : 1-2 ; Enterobacter : 2 ; Serratia : 8 ; Proteus-Providencia : 1 ; Acinetobacter : 1-4 ; P. aeruginosa : 2 ; H. influenzae : 0.06 ; C. perfringens : 0.03-01 ; Peptococcus : 0.2 ; B. fragilis : 16. Against Enterobacteriaceae and Acinetobacter, apalcillin is as active as mezlocillin and piperacillin, and much more than carbenicillin. Against P. aeruginosa, apalcillin is the most active penicillin : 2 to 16 fold more active than azlocillin and piperacillin, and 2 to 128 fold more active than ticarcillin. Against H. influenzae, C. perfringens and Peptococcus, apalcillin has MICs similar to those of other N-acyl penicillins, and inferior to those of carboxypenicillins . Apalcillin, as other penicillins, is poorly active against B. fragilis.