[Comparative antibacterial activity of piperacillin against Pseudomonas aeruginosa, Escherichia coli and Streptococcus faecalis in cultures and human serum].

The in vitro activity of piperacillin at 1/4, 1 and 4 X MHK against 5 strains each of Pseudomonas aeruginosa, Escherichia coli and Streptococcus faecalis was compared in Mueller-Hinton-bouillon and human serum. Serum without piperacillin was bacteriostatic against P. aeruginosa for 8 hrs., against E. coli for 24 hrs. Subinhibitory piperacillin concentrations were bacteriostatic against E. coli, but had no effect against P. aeruginosa and S. faecalis. Bactericidal activity against E. coli was achieved at 1 X MHK against P. aeruginosa and S. faecalis at 4 X MHK. Except for P. aeruginosa in concentrations of 1/4 and 1 X MHK the piperacillin activity in bouillon and serum was almost identical.