Introduction: Frequency of extended-spectrum beta-lactamases (ESBLs) and its variants may vary in different geographical areas, as reports indicate their spread in some certain communities. The aim of this study was to determine the frequency of ESBLs in strains of Klebsiella and E. coli, isolated from patients hospitalized in teaching hospitals of Yazd.

Methods: This cross-sectional study was carried out on samples including E. coli and Klebsiella strains collected from laboratories of Shahid Sadoughi and Shahid Rahnemoun hospitals in Yazd, Iran in the period of 2011-2012. The colonies which were positive in lactose Eosin methylene-blue (EMB) medium were identified by biochemical methods, and 270 strains of Klebsiella and E. coli were isolated. Collected data and information were analyzed using Fisher's exact test and descriptive statistics such as mean in SPSS software, version 15, at a significant level of 0.05.

Results: In this study, 270 samples were examined, including 152 samples of E. coli (56.3%) and 118 samples of Klebsiella pneumonia (43.7%). Among the 152 samples of E. coli, 45 strains (30%) were producers of ESBLs. In addition, among the 118 samples of Klebsiella pneumonia, 44 strains (37.3%) were producers of ESBLs. E. coli strains showed the most resistance to Cefotaxime (100%), Ceftazidime (97.7%), and Cefepime (75.5%) respectively and Klebsiella strains showed the most resistance to Cefotaxime (100%), Ceftazidime (100%) and Cefepime (79.5%), respectively. 

Conclusion: Frequency of ESBLs in Klebsiella strains was higher than E. coli strains. No significant relationship was found between frequency of ESBLs and age or gender. In addition, E. coli strains showed the highest sensitivity to Imipenem, Amoxicillin/clavulanate, and Ciprofloxacin, while the highest antibiotic sensitivity of Klebsiella strains was shown to be to Piperacillin, Imipenem, and Amoxicillin/clavulanate.


Keywords: ESBLs, Klebsiella, E. coli, Resistance
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