Distribution of Virulence and Antimicrobial Resistance Genes in Phylogenetic Groups of Escherichia coli Strains Isolated from Mexican Patients with Urinary Infection

Background: The causative primary agent of urinary tract infections (UTI) is uropathogenic Escherichia coli (UPEC); however, commensal Escherichia coli (CEC) has been also implicated in the development of UTI. Due to the recent emergence of virulent and resistant strains, it is necessary to have evidence to demonstrate that UPEC and CEC are isolated from patients with UTI and subsequently they have the genes to be considered pathogenic. Objectives: To determine the distribution of resistance and virulence genes in UPEC and CEC strains isolated from the patients with UTI (hospitalized and ambulatory). Methods: One hundred seven E. coli strains were genotyped according to Clermont protocol and were subjected to PCR assays in order to detect resistance and virulence genes. In addition, the antimicrobial test in solid media was performed to determinate the correlation “pheno/genotype”. Results: Genotyping analysis showed that group B2 (42.05%) was the most predominant, strains followed by A (27.1%), D (24.29%), and finally, B1 (6.54%). β-lactams, carbapenems, aminoglycosides, and nitrofurans showed the best activity. The virulence gene frequencies were: fimH (92/85.98%), iutA (68/63.55%), traT (66/61.68%), papC (36/33.64%), and cnf1 (15/14.02%) while resistance genes were: blaCTX-M(41/38.32%), blaOXA (49/45.79%), and blaSHV (2/1.87%). The associations fimH/blaCTX, fimH/blaOXA, traT/blaCTX, traT/blaOXA, iutA/blaCTX, and iutA/blaOXA showed higher incidence while the associations with cnf1 and papC genes were low. Conclusions: Uropathogenic E. coli has the necessary genetic elements (virulence and resistance) to be considered the main pathogen causing UTI in the Mexican population. Additionally, to our knowledge, there are no studies in our country demonstrating that the CEC isolated from the patients with UTI contains genetic elements of virulence and resistance that allow them to be potentially pathogenic.