Widespread Detection of VEB-1-Type Extended-Spectrum Beta-Lactamases Among Nosocomial Ceftazidime-Resistant Pseudomonas aeruginosa Isolates in Sofia, Bulgaria

Abstract

A total of 132 ceftazidime-resistant clinical isolates of Pseudomonas aeruginosa were collected during 2001-2005 from 5 university hospitals in Sofia, Bulgaria to assess the current levels of antimicrobial susceptibility and to evaluate resistance mechanisms to β-lactams. Antimicrobial susceptibilities were detected by a disk diffusion method and E-test. Polymerase chain reaction amplification and sequencing of bla _VEB-1 and bla _PER-1 were performed. The antibiotic resistance rates were: to piperacillin 90.2%, piperacillin/tazobactam 52.3%, ceftazidime 94.7%, cefepime 88.6%, cefpirome 98.5%, aztreonam 85.6%, imipenem 66.6%, meropenem 63.6%, amikacin 81.1%, gentamicin 84.8%, tobramycin 89.4%, netilmicin 57.6%, ciprofloxacin 83.4%. Structural genes for VEB-1 extended-spectrum β-lactamases (ESBLs) were found in 75 (56.8%) of the isolates. PER-1 ESBLs were not detected. The VEB-1-producing strains were more resistant than VEB-1 non-producers to amikacin, gentamicin, tobramycin and ciprofloxacin (P<0.001). VEB-1 appears to have a significant presence among ceftazidime-resistant P. aeruginosa isolates from Sofia.

Keywords:

• Pseudomonas aeruginosa
• resistance mechanisms
• β-lactams
• extended-spectrum β-lactamases
• VEB-1