Phenotypic and Genotypic Detection of AmpC and ESBL Beta-Lactamase Resistance in Escherichia Coli Strains Isolated from Patients with Urinary Tract Infections

Escherichia coli (E. coli) is one of the major pathogens causing urinary tract infection (UTI). The Spread of Extended-Spectrum β-Lactamases (ESBL)/AmpC enzymes has become a major issue, particularly due to the antibiotic therapeutic failures that result in less favorable patient outcomes, including higher mortality. This study aimed to investigate the prevalence of phenotypic and genotypic beta-lactamase resistance in E. coli strains isolated from the urine sample.

A total of 231 E. coli isolates were collected from urine samples of patients from Tehran Children's medical center hospital between 2012 to 2015. The antibiotic resistance pattern of clinical isolates was determined by using the disk diffusion method. AmpC β-lactamases and ESBLs, alone and in combination, could reliably be detected using a disc diffusion method. Genes encoding beta-lactamases were detected by PCR method using β-lactamase gene-specific primers.

All isolates of the present study were resistant to ampicillin and cefazoline. The resistance rate to other antibiotics was as follows: trimethoprim-sulfamethoxazole 85.7%, gentamicin 37.6%, levofloxacin 35.9%, and cefoxitin 24.6%. A high sensitivity rate was observed against meropenem and nitrofurantoin. Among collected isolates, 81.5% were ESBLsproducers. The prevalence of ESBLs production in CTX-M, SHV, and TEM was 100%, 35%, and 46.7%, respectively. Among 68 presumptive AmpC producers, CIT was the most prevalent detected gene, while FOX was the least seen.

Regarding the production of ESBL by some E. coli isolates, phenotypic detection for determining the antibiotic profile and resistance genes is recommended to formulate an effective antibiotic therapy.