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Properties of multidrug-resistant, ESBL-producing Proteus mirabilis isolates and possible role of β-lactam/β-lactamase inhibitor combinations

2001; Elsevier BV; Volume: 17; Issue: 2 Linguagem: Inglês

10.1016/s0924-8579(00)00325-3

1872-7913

Francesco Luzzaro, Mariagrazia Perilli, Gianfranco Amicosante, Gianluigi Lombardi, R. Belloni, Alessanro Zollo, Ciro Bianchi, Antonio Toniolo,

Infections and bacterial resistance

At our institution, isolation rates of clinical strains of ESBL-producing Proteus mirabilis increased to 8.8% of all P. mirabilis isolates during the period 1997–1999. To evaluate the susceptibility of ESBL-producing P. mirabilis strains against commonly used drugs, we studied 50 non-duplicated isolates selected on the basis of synergy between clavulanate and β-lactams (ceftazidime, aztreonam, cefotaxime, and ceftriaxone). The presence of ESBL-coding genes was confirmed by colony hybridization with blaTEM-1 and blaSHV-1 probes. Minimum inhibitory concentrations of several antimicrobial agents for each isolate were obtained using the Etest method. All strains were encoding for TEM-derived enzymes. Gene sequencing showed that at least three different genes (TEM-15, TEM-20, and TEM-52) were present. These enzymes have not been previously reported in P. mirabilis. Isolates were characterized by: (a) reduced susceptibility or resistance to third- and fourth-generation cephalosporins (MIC≥2 mg/l), (b) resistance to piperacillin that was abolished by tazobactam (MIC≥256 vs. ≤2 mg/l, respectively), (c) multiple antibiotic resistance that included gentamicin, fluoroquinolones and co-trimoxazole. Therapeutic failure and lack of eradication of ESBL-positive P. mirabilis by third-generation cephalosporins has been repeatedly observed both at our Institution and elsewhere. Piperacillin-tazobactam, as well as amikacin and meropenem appear to be important therapeutic options for infections due to multidrug-resistant, ESBL-producing P. mirabilis isolates.