[In vitro bacteriostatic activity of piperacillin sodium against Pseudomonas]

One hundred and twenty-two strains of Pseudomonas isolated from diverse pathological processes were typified. In vitro activity of Piperacillin (antibiogram and MIC) was studied and compared with another two semisynthetic penicillins, Carbenicillin and Mezlocillin, and two aminoglycosides, Amikacin and Gentamicin. The strains isolated corresponded to: Pseudomonas aeruginosa (116), Pseudomonas cepacia (3), Pseudomonas fluorescens (1) and Pseudomonas putida (1). It was found that 110 Pseudomonas aeruginosa, one Pseudomonas cepacia and one Pseudomonas fluorescens were susceptible to Piperacillin. The susceptibility to this drug was quite higher than to the other penicillins tested. The MIC50 and MIC90 of Piperacillin were lower than those of semisynthetic penicillins and the minimum susceptibility value. In comparison with aminoglycosides it was found that, although Amikacin and Gentamicin did not reach the minimum value, Piperacillin exhibited higher MICs.