Background and Objective: Extended-Spectrum Beta Lactamase enzymes (ESBLs) are the most important factor for antimicrobial resistance in Enterobacteriaceae The resistance to beta-lactam antibiotics is the main problem in the bacterial infections therapy. This study was done to determine the prevalence of Extended-Spectrum Beta Lactamase enzymes in clinical isolates of Enterobacteriaceae family.

Methods: In this descriptive study, 240 isolates of Enterobacteriaceae family were collected from clinical specimens obtained in Shohada, Rahimi and Madani hospitals in Khorramabad city, Iran. Antibiotic susceptibility of isolates was performed by disk diffusion method. ESBLs production in all isolates was determined using the combination disk method.

Results: Bacteria strains isolated in this study were Escherichia coli (76%), Klebsiella pneumonia (16.2%), Citrobacter (5.4%), Enterobacter spp. (0.83%) and Proteus (1.6%). The results of antimicrobial susceptibility of isolates showed that the highest rate of antibiotic resistance was toward Ampicillin (88%) and Cefotaxime (43%) and the lowest rate was observed to Amikacin (2.5%). According to the results of the phenotypic tests, 141(59%) isolates out of 240 Enterobacteriaceae were beta-lactamase producers.

Conclusion: ESBL producer isolates and antibiotic resistant due to of Enterobacteriaceae isolated from clinical samples from hospitals are high prevalence in Khorramabad city, Iran.