Prevalence of ESBL phenotype, blaCTX-M-1, blaSHV and blaTEM genes among uropathogenic Escherichia coli isolates from 3 military hospitals of Tehran, Iran

Abstract

Objective: To determine the extended-spectrum beta-lactamase (ESBL) production and prevalence of blaCTX-M-1, blaSHV and blaTEM genes among uropathogenic Escherichia coli (UPEC) isolates from 3 military hospitals of Tehran during 2015-2016. Methods: One-hundred and eleven isolates were adopted. The antibiotic susceptibility testing was conducted according to Clinical and Laboratory Standards Institute guidelines. The combine disk was used for phenotypic ESBL production. The ceftazidime MIC was conducted with the micro-broth dilution test. The PCR assay was used to detect the blaCTX-M-1, blaSHV and blaTEM genes. Results: In the broth microdilution method, 103 (92.7%) isolates showed minimal inhibitory concentration (MIC) ≥ 1 µg/mL, and also in the combined disk method, 89 (80.1% of all) were ESBL positive. On the other hand, among 91 ceftazidime resistant isolates, 86 (77.4% of all) were ESBL positive. The difference between the two methods for ESBL confirmation was not significant. The result of MIC was similar to the disk diffusion method in the detection of phenotypic ESBL production. Among ESBL producer isolates, the prevalence of blaCTX-M-1, blaSHV and blaTEM was 77.4% (n = 86), 47.4% (n = 53) and 2.4% (n = 2), respectively. These genes were amplified in a wide range MIC of ceftazidime. Conclusions: The prevalence of multi-drug resistant UPEC and ESBL positive isolates was high in military hospitals. The majority of UPEC isolates amplified blaCTX-M-I and blaSHV type β-lactamase genes. One-third of isolates were positive in presence of both these genes. There was no relation between ceftazidime MIC and presence of beta-lactamase genes.