distribution of ambler class a β-lactamase genes and evaluation of resistance patterns in multi-drug and extensively-drug resistant p. aeruginosa clinical isolates

Background and objectives: emergence and spread of multidrugresistant (mdr) and extensivelydrug resistant (xdr) pseudomonas aeruginosa strains could complicate antipseudomonal chemotherapy. dissemination of resistance genes, such as beta;lactamases encoding genes by horizontal gene transfer can lead to development of multidrug resistance in p. aeruginosa. the purpose of this study was to investigate the latest resistance patterns in mdr and xdr strains and evaluate ambler class a beta;lactamase gene distribution in p. aeruginosa clinical isolates. methods: one hundred molecularly and biochemically identified p. aeruginosa strains isolated from different clinical specimens were tested for sensitivity to 17 antibiotics using the kirbybauer disk diffusion method. pcr was performed to detect bla tem1, bla shv1, bla rep1 and bla veb1 genes. results were analyzed using spss and ntsyspc softwares. results: based on the results of antibiogram, the highest rate of resistance was observed against amikacin (100%), aztreonam (83%), ceftazidime (55%), cefepime (55%) and netilmicin (48%). in addition, the frequency of mdr and xdr isolates was 95% and 5%, respectively. the blashv1, bla tem1, bla per1 and bla veb1 genes were detected in 31%, 24%, 13% and 10% of the isolates, respectively. conclusion: antibiotic resistance to beta;lactam antibiotics and frequency of beta;lactamase genes were relatively high in the study area. we also found that a significant proportion of xdr strains with different antibiotic resistance profile is isolated from tracheal specimens. keywords: pseudomonas aeruginosa, betalactamase, multidrug resistant, extensively drug resistant.