Evaluation of Antibiotic Resistance and Detection of CTX-M Type Extended Spectrum Beta-lactamase in Clinical Isolates of Pseudomonas aeruginosa in Mashhad

Extended-spectrum beta-lactamases (ESBLs) make some bacteria resistance to broad spectrum beta-lactam antibiotics. The aim of the present study was to evaluate the antibiotic resistance of clinical isolates of Pseudomonas aeruginosa in Mashhad and to detect CTX-M type extended-spectrum beta-lactamase among them. Clinical isolates of P. aeruginosa were collected from different samples (wound, urine, ear, lung, peritoneal fluid and other body fluids) of hospitalized patients in Mashhad in 2013. The antibiotic susceptibility was examined by disc diffusion method and Kirby-Bauer standards. The frequency of ESBL producing strains was determined via the combined disk method. After DNA extraction, the existence of blaCTX-M gene was detected by polymerase chain reaction (PCR) using specific primers. All isolates were resistance to ceftizoxime, cefoxitin and oxacillin. Resistance to ciprofloxacin, gentamicin, imipenem, piperacillin and co- trimoxazole was 45.31%, 48.44%, 45.31%, 43.75 and 98.44%, respectively. A large percentage of ESBL-producing isolates compared with ESBL-non producers were resistant to co-trimoxazole, gentamicin, and piperacillin and the difference for gentamicin was significant. Out of 64 clinical isolated bacteria, 8 (12.5%) isolates were beta- lactamase producers and none of them were positive for blaCTX-M type ESBL. Discussion and Results of this study showed that however resistance of clinical isolates of P. aeruginosa to beta-lactam antibiotics was high in our community, but this resistance was not related to prevalence of blaCTX-M gene among isolated strains. Antibiotic resistance among these isolates could be associated with other types of beta-lactamases.