Pseudomonas aeruginosa is the most common pathogen causing nosocomial infections. The objective of this study was to investigate the extended-spectrum-beta-lactamase (ESBLs) producing and multidrug resistance of hospital isolates of P. aeruginosa and to determine the presence of several resistance genes. A total of 86 isolates of P. aeruginosa were collected from teaching hospital in Kashan, Iran. Susceptibility to eight antimicrobial agents was performed by disk diffusion method. ESBL-phenotypic detection was carried out by double-disk synergy test; and the presence of the genes encoding of bla(TEM), bla(SHV), bla(CTX-M), bla(OXA) and bla(GES)-like genes was studied by polymerase chain reaction. The prevalence of ESBLs was 8.1%. The presence of genes encoding ESBLs was confirmed in seven isolates, comprising seven bla (GES-2), one bla(SHV-1), one bla(SHV-5) and one bla(CTX-M-1) genes. P. aeruginosa demonstrated the highest resistance rate to piperacillin (38.4%), 67.5% of isolates were sensitive to imipenem whereas 32.5% were MDR (resistant to three or more classes of antibiotics). A multidrug-resistant (MDR) phenotype occurred frequently in P. aeruginosa. bla (GES-2), which compromises the efficacy of imipenem detected in all of seven ESBLproducing P. aeruginosa strains. Proper infection control practices and barriers are essential to prevent spreading and outbreaks of ESBL-producing and MDR P. aeruginosa in our teaching hospital.

Background: Guiana Extended-Spectrum (GES-2) as one of the Extended-spectrum β-lactamases (ESBLs), produced by Pseudomonas aeruginosa, is able to compromise the effectiveness of imipenem and tends to be geographically limited. Objectives: The aim of this study was to detect the spread of GES-2 β-lactamase gene among ESBL-producing P. aeruginosa isolates in a teaching hospital in Kashan, Iran. Materials and Methods: Detection of β-lactamase gene blaGES-2 in eight ESBL producing isolates of P. aeruginosa collected from 100 clinical and environmental specimens was performed by PCR method. The susceptibility of the isolates to eight antibacterial agents was determined by disk diffusion method. ESBL production of the isolates was detected by double disk synergy test. DNA sequencing and aligning with the reference sequence were performed using BLAST and CLUSTAL W for selected PCR products of the blaGES-2 gene. Results: A total of 100 environmental and clinical isolates of P. aeruginosa were collected. Eight of the isolates were found to be ESBL positive. The highest resistance rate was detected for piperacillin (75%), while the lowest resistance rate was for ciprofloxacin (12.5%). Fifty percent of the isolates (four out of eight) were imipenem-susceptible and MDR. The blaGES-2 gene was detected in all ESBL-producing isolates. Sequencing of both forward and reverse strands of the blaGES-2 gene were identified by BLASTn search as the ATP-binding cassette (ABC) transporter permease, partial cds, clone G-1 P. aeruginosa (Accession no. AB591379.1). Conclusions:According to the present data, this is the first report on the presence of blaGES-2 gene of ESBL-producing P. aeruginosa from teaching hospitals of Iran. Fifty percent of the blaGES-2 positive P. aeruginosa isolates were multi-drug resistance (MDR).