Detection of Virulence Determinants of Uropathogenic Escherichia coli

Background Escherichia coli is the major causative agent of urinary tract infections (UTIs). Emergence and spread of multidrug-resistant strains of E. coli have raised considerable interest in understanding their diversity and epidemiology of infections in humans. Knowledge of virulence factors of E. coli responsible for pathogenesis of UTIs and their antibiotic susceptibility pattern will help in better understanding of the treatment of UTI. This study was undertaken to characterize virulence determinants of uropathogenic E. coli (UPEC) by genotypic methods and to determine their susceptibility to various classes of antibiotics. Materials and methods A total of 150 clinically significant, non-repetitive, consecutive E. coli isolated from urine were included in this study. Polymerase chain reaction (PCR) was done to detect the presence of virulence genes namely fim H, iut A, hly A, pap C, cnf 1, and sat. Antibiotic susceptibility testing was done by the disc diffusion technique according to Clinical and Laboratory Standards Institute (CLSI). The antibiotics tested were amikacin, gentamicin, fosfomycin, ampicillin, cefotaxime, ciprofloxacin, cotrimoxazole, nitrofurantoin, piperacillin-tazobactam and imipenem. Results Of the 150 Escherichia coli, 112 carried one or more of the virulence genes included in the study protocol. The genes fim H (77%), iut A (57%), and sat (45%) were the most common. The other genes include cnf 1(26%) and hly A (2%). Pap C gene was not detected in any of the isolates. Among the 150 study isolates, the antimicrobial resistant pattern was 12.6% (19/150) for amikacin, 18.6% for gentamicin, 2% for fosfomycin, 88% for ampicillin, 67% for cefotaxime, 85% for ciprofloxacin, 62% for cotrimoxazole, 7.3% for nitrofurantoin and piperacillin-tazobactam, and 12% for imipenem. The frequency of sat gene was significantly higher in isolates resistant to gentamicin, ampicillin, cefotaxime, and cotrimoxazole. The occurrence of iut A was higher among isolates resistant to ampicillin, ciprofloxacin, cotrimoxazole, and piperacillin-tazobactam.  Conclusion fim H is the most common virulence determinant among UPEC. Pap gene was not anchored in the study isolates. A combination of two or more virulence in single isolates was frequently encountered. Among the 150 study isolates, 68% were extended spectrum beta-lactamase producers and 12 % were carbapenem-resistant Escherichia coli. There was no significant association between the virulence gene and the antimicrobial resistance profile.