Widespread detection of PER-1-type extended-spectrum beta-lactamases among nosocomial Acinetobacter and Pseudomonas aeruginosa isolates in Turkey: a nationwide multicenter study

Abstract

We studied the prevalence and molecular epidemiology of PER-1-type beta-lactamases among Acinetobacter, Klebsiella, and Pseudomonas aeruginosa strains isolated over a 3-month period in eight university hospitals from distinct regions of Turkey. A total of 72, 92, and 367 Acinetobacter, Klebsiella, and P. aeruginosa isolates were studied, respectively. The presence of blaPER was determined by the colony hybridization method and later confirmed by isoelectric focusing. We detected PER-1-type beta-lactamases in 46% (33/72) of Acinetobacter strains and in 11% (40/367) of P. aeruginosa strains but not in Klebsiella strains. PER-1-type enzyme producers were highly resistant to ceftazidime and gentamicin, intermediately resistant to amikacin, and susceptible or moderately susceptible to imipenem and meropenem. Among PER-1-type-beta-lactamase-positive isolates, five Acinetobacter isolates and six P. aeruginosa isolates from different hospitals were selected for ribosomal DNA fingerprinting with EcoRI and SalI. The EcoRI-digested DNAs were later hybridized with a digoxigenin-labelled PER-1 probe. The ribotypes and the lengths of blaPER-carrying fragments were identical in four Acinetobacter strains. A single isolate (Ac3) harbored a PER gene on a different fragment (approximately 4.2 kbp) than the others (approximately 3.4 kbp) and showed a clearly distinguishable ribotype. Ribotypes of P. aeruginosa strains obtained with EcoRI showed three patterns. Similarly, in Pseudomonas strains two different EcoRI fragments harbored blaPER (approximately 4.2 kbp in five isolates and 3.4 kbp in one isolate). PER-1-type beta-lactamases appear to be restricted to Turkey. However, their clonal diversity and high prevalence indicate a high spreading potential.