title: Comparative in-vitro activity of piperacillin and piperacillin plus tazobactam towards beta-lactamase producing clinical isolates.
abstract: The authors evaluated the in-vitro antibacterial activity of piperacillin alone and of piperacillin combined with tazobactam, a new beta-lactamase inhibitor, on 398 clinical isolates, both Gram-positive and Gram-negative. The piperacillin/tazobactam combination was evaluated in the fixed ratio 8:1. The vast majority of the microorganisms tested had reduced susceptibility to piperacillin (minimum inhibitory concentration (MIC) range 0.12- greater than 256 mg/l) due to beta-lactamase production. The following results were obtained: against Haemophilus influenzae, tazobactam was effective in reducing the MICs of piperacillin by 512 fold. The activity of piperacillin/tazobactam was lower against Pseudomonas sp., while some activity was demonstrated against some strains of Klebsiella. Good activity was seen not only against methicillin-susceptible (MS) staphylococci but also against some methicillin-resistant (MR) strains. In the latter, the combination of piperacillin/tazobactam was active only if the strains showed beta-lactamase production. These findings are interesting above all in regard to the synergistic effect demonstrated against MR beta-lactamase producing staphylococci and the Klebsiella-Enterobacter-Serratia (KES) group.
authors.affiliation: Institute of Microbiology, University of Catania, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Stefani
authors.forename: P
authors.initials: P
authors.lastname: Castiglia
authors.forename: A
authors.initials: A
authors.lastname: Maida
authors.forename: E
authors.initials: E
authors.lastname: Muresu
authors.forename: M L
authors.initials: ML
authors.lastname: Mezzatesta
authors.forename: G
authors.initials: G
authors.lastname: Nicoletti
mesh_terms: D004357:Drug Synergism; D004359:Drug Therapy, Combination / Q000494:pharmacology; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000201:enzymology; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000201:enzymology; D008826:Microbial Sensitivity Tests; D010397:Penicillanic Acid / Q000494:pharmacology*; D010878:Piperacillin / Q000494:pharmacology*; D000078142:Tazobactam; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D065093:beta-Lactamase Inhibitors; D010397:Penicillanic Acid; D001618:beta-Lactamases; D000078142:Tazobactam; D010878:Piperacillin