Virulence genotypes and phylogenetic distribution between upper and lower community-onset urinary tract infections caused by Escherichia coli

Abstract

Background: The aim of this study was to find the prevalence difference of virulence genes between upper urinary tract infection (UUTI) uropathogenic E. coli (UPEC) and lower urinary tract infection (LUTI) UPEC among community-onset UPEC (CO-UPEC). Methods: We conducted a case-control study of patients with positive UPEC between 2006 and 2007 at a teaching hospital in South Korea. CO-UPEC was the isolated from the patients from whom the specimen was obtained within 2 calendar days of hospitalization or at outpatient department. We divided CO-UPEC into UUTI- and LUTI-UPEC. All isolates underwent PCR-based microarray for phylotyping and detection of 11 virulence factors (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. We also collected the rectal commensal E. coli (RCEC) of healthy people. Results: A total of 548 CO-UPEC (UUTI-UPEC, n = 324; LUTI-UPEC, n = 224) and 183 RCEC isolates were collected. Compared with LUTI-UPEC, UUTI-UPEC showed higher virulence scores (4.38 ± 1.94 vs. 3.23 ± 2.41, p < 0.001) and more frequent traits in some VFs (prf, Odd ratio = 2.47 [95% confidence interval = 1.98 - 3.08]; aer, 1.31 [1.07 – 1.60]; kspMT, 1.76 [1.46 - 2.13]; ompT, 1.75 [1.45 - 2.12]; papGad, 3.11 [2.40 – 4.03]) but less frequent traits in some VFs(drb, 0.73 [0.56 -0.97]; prsGj96, 0.63 [0.48 – 0.83]). RCEC had less VFs than UUTI- and LUTI-UPEC. Phylogenic group B2 was more prevalent in UUTI-UPEC than LUTI-UPEC (58.3% vs. 44.2%, p < 0.001), however LUTI-UPEC belonged to phylogenic group A and B1 more frequently (13.8% vs. 4.0% and 9.8% vs. 4.0%, respectively, p < 0.001). Conclusion: Even though UTI-UPECs previously considered as same entity, UUTI-UPEC was more virulent than LUTI-UPEC.