title: In vitro activity of piperacillin/tazobactam against 615 Pseudomonas aeruginosa strains isolated in intensive care units.
abstract: From May 1996 to September 1997, 615 Pseudomonas aeruginosa strains isolated from patients in intensive care units collected from different Italian laboratories were studied. The susceptibility of piperacillin/tazobactam, in comparison with other antipseudomonal antibiotics, to their NCCLS breakpoints was evaluated: amikacin 79. 6%, carbenicillin 67.0%, ceftazidime 73.4%, ciprofloxacin 55.8%, imipenem 64.1%, piperacillin 88.1%, piperacillin/tazobactam 92.4% and ticarcillin/clavulanic acid 69.0%. Seventy-three strains were selected because of their resistance to piperacillin and the mechanisms underlying such a resistance were investigated. Isoelectric focusing and hydrolysis assays revealed the presence of 15 plasmid-mediated beta-lactamases. Chromosomal beta-lactamase derepression was demonstrated in 34 isolates. The remaining 24 piperacillin-resistant strains did not produce beta-lactamases and an 'intrinsic mechanism' of resistance was inferred. The piperacillin/tazobactam combination restored resistance in 25 piperacillin strains. Nine of these were derepressed for chromosomal beta-lactamase, 8 showed impermeability and 8 showed plasmid enzymes.
authors.affiliation: Istituto di Microbiologia, Università di Catania, Italia.
authors.forename: G
authors.initials: G
authors.lastname: Bonfiglio
authors.forename: Y
authors.initials: Y
authors.lastname: Laksai
authors.forename: N
authors.initials: N
authors.lastname: Franceschini
authors.forename: M
authors.initials: M
authors.lastname: Perilli
authors.forename: B
authors.initials: B
authors.lastname: Segatore
authors.forename: C
authors.initials: C
authors.lastname: Bianchi
authors.forename: S
authors.initials: S
authors.lastname: Stefani
authors.forename: G
authors.initials: G
authors.lastname: Amicosante
authors.forename: G
authors.initials: G
authors.lastname: Nicoletti
mesh_terms: D004359:Drug Therapy, Combination / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007362:Intensive Care Units; D008826:Microbial Sensitivity Tests; D010397:Penicillanic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D010403:Penicillin Resistance; D010406:Penicillins / Q000494:pharmacology*; D010878:Piperacillin / Q000494:pharmacology*; D010957:Plasmids / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification; D000078142:Tazobactam; D001618:beta-Lactamases / Q000096:biosynthesis / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D010406:Penicillins; D010397:Penicillanic Acid; D001618:beta-Lactamases; D000078142:Tazobactam; D010878:Piperacillin