Virulence genotypes and phylogenetic distribution of the community-onset Escherichia coli

Abstract

Background: The concept that not all E. coli are equally able to cause UTI, and that the uropathogenic E. coli (UPEC) strains possess distinctive traits that confer enhanced virulence potential compared to other source E. coli, is supported by abundant epidemiologic and experimental evidence. Virulence factors (VFs) are the specific genes encoding a diverse array of specialized properties that are postulated to contribute to virulence. The aim of this study was to find the prevalence difference of virulence genes and phylogenetic lineages between E. coli from community-onset urinary tract infection (CO-UPEC) and hepatobiliary infection (CO-HBEC) compared to rectal commensal E. coli (RCEC) in a healthy population. Methods and materials: We conducted a case-control study of patients with positive UPEC & HBEC between 2006 and 2008 at a teaching hospital in South Korea. Community-onset (CO) was the isolated from the patients from whom the specimen was obtained within 2 calendar days of hospitalization or at outpatient department. We also collected the rectal commensal E. coli (RCEC) of healthy people. All isolates underwent PCR-based microarray for phylotyping and detection of 11 VFs, including adhesins (prf, sfa, drb, prsGj96, papGad), toxins (hly, cnf1), siderophores (iroN, aer), capsule (kpsMT), and other (ompT). The virulence score was defined as the number of virulence genes identified. Results: A total of 548 CO-UPEC and 140 HBEC with 486 CREC isolates were collected. Compared with CREC, CO-UPEC showed higher VFs (3.92 ± 2.22 vs. 2.28 ± 1.90, p < 0.001) and CO-HBEC averaged fewer VFs (1.56 ± 1.64 vs. 2.28 ± 1.90, p < 0.001). Overall distribution of phylogenic group were B2(52.5%) and D(33%) in CO-UPEC, A(37.9%) and D(31.4%) in CO-HBEC and A(38.3%) and B2(29%) in RCEC. Conclusion: In conclusion, we observed the differences of VFs between clones from community- onset UPECs and HBECs compared to RCEC, and this result explain that UPECs would be more virulent than HBECs which could be less virulent than RCECs considering only VFs distribution. In phylogenetic analysis, each group of E. coli showed different phylogenic distribution, which imply group B E. coli might be more specifically associated with uropathogenecity.