Characterization of the Extended-Spectrum beta-Lactamase Producers among Non- Fermenting Gram-Negative Bacteria Isolatedfrom Burnt Patients

Background & Aims of the Study: Extended-spectrum beta-Lactamases (ESBLs) representa major group of beta-lactamases which are responsible for resistance to oxyiminocephalosporinsand aztreonam and currently being identified in large numbers throughoutthe world. The objective of this study was to characterize ESBL producers among nonfermentergram-negative bacteria isolated from burnt patients.Materials & Methods: During April to July 2012, 75 non-fermenter gram-negative bacilliwere isolated from 240 bacterial cultures collected from wounds of burnt patients admittedto the Burn Unit at Shahid Motahari Hospital (Tehran, Iran). Bacterial isolation andidentification was done using standard methods. Antimicrobial susceptibility testing wasperformed by disk diffusion method for all strains against selected antibiotics and minimuminhibitory concentration was determined by microdilution test. The ability to produce ESBLwas detected through double disk synergy test among candidate strains.Results: Of 75 non-fermenter isolates, 47 Pseudomonas aeruginosa and 28 Acinetobacterbaumannii were identified. The resistance of P. aeruginosa isolates to tested antibiotics inantibiogram test were 100% to cefpodoxime, 82.98% to ceftriaxone, 78.73% to imipenem,75% to meropenem, 72.72% to gentamicin, 69.23% to ciprofloxacin and aztreonam,67.57% to cefepime, 65.95% to ceftazidime, and 61.53% to piperacillin. The results forAcinetobacter baumannii were 100% to ceftazidime, cefepime, ciprofloxacin, imipenem,meropenem, cefpodoxime, and cefotaxim, 96.85% to gentamicin, 89.65% to ceftriaxone,65.51% to aztreonam, and 40% to piperacillin. Double disk synergy test showed that 21(28%) of non-fermenter isolates were ESBL producer.Conclusions: None of the third or fourth generation of cephalosporins is suitable fortreatment of Pseudomonas aeruginosa and Acinetobacter baumannii isolated from burntpatients.

کلیدواژه ها:

Acinetobacter baumannibeta-LactamasesDrug ResistanceIranPatients ، BurntPseudomonas aeruginosa