Antimicrobial Resistance Pattern in Escherichia coli Causing Urinary Tract Infection in Humans

Abstract

Extraintestinal infections caused by Escherichia coli cause serious illness and death. Every year 130-175 million cases occur globally; >80% are associated with E. coli. To investigate the prevalence of E. coli causing urinary tract infections in humans, a cross sectional study was conducted by taking 100 urine samples from 100 suspected patients visited to a local hospital at Chattogram during the period of December 2021 to April 2022. A mid-stream urine sample was collected from each of the suspected patient following standard procedures and tested for the presence of E. coli using conventional bacteriological procedures. Culture-positive E. coli isolates were confirmed by detecting a housekeeping gene adk by polymerase chain reaction (PCR). The E. coli isolates obtained were subsequently investigated to determine their susceptibility against a panel of 14 antimicrobials by disc diffusion method and by assessing the minimum inhibitory concentration (MIC) of colistin using broth microdilution method. A subset of strains displaying resistance to colistin, fluoroquinolones and third generation cephalosporins were characterized by PCR to determine the genetic determinants of resistance. The results of the study revealed that the prevalence of E. coli in UTI patients was 37% (95% Confidence Interval 28.2% - 46.8%). In vitro antimicrobial susceptibility of E. coli isolates revealed that 75.7% isolates displayed resistance to Azithromycin and 54.1% to Ampicillin while 37.8% and 29.7% to Tetracycline and Trimethoprim-sulfamethoxazole, respectively. More than 25% isolates displayed resistance to Cefotaxime, Cefoxitin, Ceftriaxone, Ciprofloxacin and Nalidixic Acid. About 52% of the total isolates showed resistance to ≥3 antimicrobials. The minimum inhibitory concentration of colistin in E. coli isolates ranged from ≤1 to ≥128 µg/mL, and 1 out of 2 colistin-resistant E. coli isolates harbored mcr-1 gene. All fluoroquinolone-resistant isolates contained gyrB gene while 9 isolates harbored gyrA gene. None of the isolates examined harbored parC gene. Third-generation cephalosirin-resistant isolates harbored extended-spectrum beta-lactamases (ESBLs)- encoding genes, namely blaTEM (37.5%) while 41.7% and 8.3% isolates harbored blaCTX-M, blaSHV genes, respectively. This study highlights the circulation of MDR E. coli in UTI patients in Chattogram region.