The Molecular Characterization and Risk Factors of ST131 and Non-ST131 Escherichia coli in Healthy Fecal Carriers in Tehran, Iran

Commensal extended-spectrum β-lactamase (ESBL) producing Escherichia coli isolates in the gut can be the reservoir of virulence factors and resistance genes.

We investigated the molecular feature, risk factors, and quinolone/fluoroquinolone (Q/FQ) resistance in sequence type 131 (ST131) and non-ST131: ESBL-producing E. coli (EPE) isolates in healthy fecal carriers.

A total of 540 fecal samples and its demographic data were collected from healthy adults in Tehran in 2018. ST131 isolates were identified by multilocus sequence typing (MLST) analysis, and the characteristics of the virulence factor, phylogenic assay, and Q/FQ resistance genes in ST131 and non-ST131 were determined by polymerase chain reaction (PCR).

The EPE isolates mainly belonged to the commensal phylogenetic groups A (54.9%) and D (18.1%). The type 1 fimbriae (fimH; 89.6%) gene was the predominant virulence factor, and there was a significant correlation between ferric yersiniabactin uptake (fyuA; 52.9%), aerobactin receptor (iutA; 17.6%), and group II capsule synthesis (kpsMII; 35.3%) with ST131. In Q/FQ-resistant isolates, qnrS (19%) was the predominant gene, and mutations mostly occurred at codon S83 in GyrA The number of mutations in gyrA and parC genes was significantly higher in ST131 isolates than in non-ST131 isolates. There was a significant positive correlation between diabetes, male gender, and living in the south of the city with EPE carriage (P < 0.05).

Accumulation of multiple virulence factors and high- level resistance to Q/FQ in some phylogroups (B2 and D), particularly ST131 isolates, require to be considered in detecting resistant isolates in healthy carriers. According to the risk factor for spreading of EPE isolates (diabetes, living in low-income parts of the city, and male gender), the necessary strategies are required to be developed to control the dissemination of antimicrobial-resistant isolates in the community.