Antimicrobial resistance in Escherichia coli strains from urinary tract infections

Background: An increase in resistance against many different drugs among urinary tract infection (UTI) E coli isolates has been observed in the last 2 decades. This study determined the trends of antimicrobial resistance in E coli to commonly used antibiotics. Methods: The study was conducted in lle-lfe, southwest Nigeria. Patients with features suggestive of UTI were investigated for presence of significant bacteriuria. Urine isolates were identified. Antimicrobial susceptibility was evaluated in accordance with standard bacteriological methods. Results: Of 442 urine specimens, 158 (35.8%) yielded significant growth, including 41 (25.6%) with E coli. Among the E coli isolates, antimicrobial susceptibility varied in prevalence by agent in descending order as follows: nitrofurantoin (80%), ofloxacin (24%), ciprofloxacin (15%), nalidixic acid (10%), cotrimoxazole (5%), and amoxicillin/clavulanic acid (2%). No isolate was susceptible to amoxicillin, gentamicin, or tetracycline. All were also found to be resistant to at least 3 commonly used drugs. All 25 isolates tested for extended-spectrum β-lactamase (ESBC) production were found to be presumptive ESBCs producers. Conclusion: The results demonstrate the continued susceptibility of E coli to nitrofurantoin and their widespread and increasing resistance to amoxicillin, gentamicin, cotrimoxazole, ciprofloxacin, ofloxacin, and tetracycline. Nitrofurantoin is a - and, in this locale, perhaps the only - rational drug for empiric treatment of uncomplicated UTI. There is a need for a comprehensive study of the involvement of ESBC-producing E coli in UTI in this environment.