Evaluation of the Prevalence of blaSHV, blaTEM, and blaCTX Genes in Escherichia coli Isolated From Urinary Tract Infections

Beta-lactamases are the most important factors in the resistance to beta-lactam antibiotics among gram-negative bacteria, especially Escherichia coli. Today, the prevalence of infections caused by extendedspectrum β-lactamases (ESBLs)-producing E. coli is increasing, as one of the emerging health problems worldwide. This study aimed to investigate the prevalence of blaSHV (sulfhydryl variable β-lactamase), blaTEM (temoneira β-lactamase), and blaCTX (cefotaximase β-lactamase) genes in E. coli isolated from urinary tract infections (UTIs).

In this study, 3192 midstream urine samples collected from Babol and Qaemshahr counties, Mazandaran province (Iran) were cultured on eosin methylene blue and blood agars. An antibiotic susceptibility test was performed to determine ESBL-producing E. coli isolates using the combined disk method. Finally, the ESBLs were evaluated for the presence of blaSHV, blaTEM, and blaCTX genes by the polymerase chain reaction (PCR) technique.

Of the 3192 cultured urine samples, 192 isolates were identified as E. coli by the IMViC and biochemical tests. In addition, the ESBL producers were detected in 45 (28/12 %) out of 192 E. coli isolates by the doubleblind synergism test. The PCR of the 45 ESBL-producing E. coli isolates demonstrated that the blaTEM was the most abundant gene (89%), followed by blaCTX-M (27%) and blaSHV (20%). Eventually, the co-existence of blaSHV, blaCTX-M, and blaTEM was detected in 3 (7%) isolates.

Due to the high prevalence of ESBL-producing uropathogenic E. coli (UPEC) in the studied region, future studies are recommended to perform phenotypic or genotypic tests to detect ESBL-producing isolates in laboratories to select appropriate antibiotics for treating UTIs.