Detection of blaCTX, blaTEM beta-lactamase genes in clinical isolates of Acinetobacter spp. from selected Tehran hospitals

Due to importance and prevalence of ESBL producing isolates in nosocomial infections, this study was undertaken with the aims to determine antibiotic susceptibility patterns,identification of ESBL producing isolates and detection of blaCTX, blaTEM of Acinetobacter spp in clinical isolates from selected Tehran hospitals. Ninety five isolates of Acinetobacter were collected from Tehran’s hospitals.Susceptibility patterns of various antibiotics and MIC for ceftazidime were determined by disk diffusion and microbroth dilution methods respectively based on CLSI protocols. The ESBL producers were screened by phenotypic confirmatory test. PCR was used for detection of blaCTX and blaTEM genes. The lowest and highest resistance rates to investigated antibiotics were seen against colistin (4.2%) and cefexime (100%) respectively. By using PCT, 18.9% of the isolates were ESBL positive. About 83.1 % of Acinetobacter isolates showed MIC ≥ 64 μg/ml to ceftazidime, however only 18.9% of isolates were ESBL producer. Based on the results from PCR technique,1.2% and 12.8% of the isolates were TEM and CTX positive respectively. The rate of MIC to ceftazidime and presence of blaTEM and blaCTX among ceftazidime resistant isolates was very noteworthy in present study. Since less than one fifth of the isolates in present study were ESBL producer, it seems that apart from beta-lactamases, other resistance mechanisms such as efflux pumps and impermeability of the cell membrane may be responsible for this situation.As resistance factors are located on mobile elements, identification and detection of strains producing these enzymes is important in preventing of the expansion of these isolates