Occurrence of gyrA Gene Mutations and their Association with Ciprofloxacin MIC Levels among Uropathogenic Escherichia coli Isolates

Open Access

Abstract

Introduction: Uropathogenic Escherichia coli is the leading cause of urinary tract infection, while increasing ciprofloxacin resistance has reduced the effectiveness of empirical therapy. Mutations in the gyrA gene, especially at Ser83 and Asp87, are important mechanisms of fluoroquinolone resistance and may increase ciprofloxacin minimum inhibitory concentration (MIC). Methods & Materials & Materials: This cross-sectional analytical study aimed to determine the prevalence of gyrA mutations among uropathogenic E. coli isolates and assess their association with ciprofloxacin MICs. The study was conducted at the Department of Microbiology, Sir Salimullah Medical College, Dhaka, from January to December 2020. A total of 229 urine samples from clinically suspected UTI patients were cultured, and 113 uropathogenic E. coli isolates were analyzed. Antimicrobial susceptibility was tested by Kirby-Bauer disc diffusion, ciprofloxacin MIC was determined by agar dilution following CLSI 2019 breakpoints, and gyrA mutations at Ser83 and Asp87 were detected by PCR-RFLP. Result: Among culture-positive isolates, E. coli was predominant (113, 81.88%). Ciprofloxacin MICs ranged from 0.007 to 16 µg/mL; 52 (46.02%) isolates were sensitive, 4 (3.54%) intermediate, and 57 (50.44%) resistant. The gyrA gene was detected in all isolates, with mutations in 63 (55.75%). A single Ser83 mutation was found in 21 (18.58%), while double Ser83 and Asp87 mutations were found in 42 (37.17%). Conclusion: The gyrA gene mutations were common among uropathogenic E. coli and were significantly associated with ciprofloxacin resistance and elevated MIC levels. Double mutations at Ser83 and Asp87 were strongly associated with high MIC values, indicating the need for culture-guided, cautious use of ciprofloxacin in UTI treatment.