Molecular Characteristics and Risk Factors of Bloodstream Infection Caused by Escherichia coli ST131 in Southeast China

Background: E. coli ST131 is the predominant lineage among extraintestinal pathogenic E. coli isolates worldwide and is an important pathogen associated with all kinds of human infections. The aim of this study was to investi-gate the prevalence and molecular characteristics of E. coli ST131 and non-ST131 isolates that cause bloodstream infections and evaluate the risk factors for E. coli ST131. Methods: A total of 103 E. coli isolates associated with bloodstream infection were collected between August 2014 and August 2015 at a Chinese university hospital. The isolates were classified into ST131 and non-ST131 E. coli groups by multilocus sequence typing. Phylogenetic analysis, susceptibility testing, virulence genotyping, PCR-based O typing, and pulsed-field gel electrophoresis (PFGE) were performed, and the clinical features of patients in both groups were compared. Results: Overall, 12 isolates (11.7%) were identified as ST131 isolates, including 10 O25b-ST131 (83.3%) and 2 O16-ST131 (16.7%) clones. All 103 E. coli isolates were divided into four phylogenetic groups: B2 was the pre-dominant phylogenetic group (n = 39, 37.9%), and it was followed in descending order by D (n = 33, 32.0%), A (n = 20, 19.4%), and B1 (n = 11, 10.7%). Compared with the non-ST131 isolates, the E. coli ST131 isolates har-bored more virulence factors and were associated with a significantly higher incidence of urinary tract infection (p = 0.040) and a significantly greater length of hospital stay (p = 0.045). According to PFGE analysis, the molecu-lar features of the E. coli ST131 isolates were highly diverse, and there was no dominant clone. Conclusions: The ST131 isolates collected from Southeast China in this study exhibited strong virulence and multiple drug resistance, and the main serotype was O25b-ST131. Therefore, future studies should focus on O16-ST131 subclones in order to better understand the prognosis of patients with bloodstream infection caused by E. coli ST131.

Automated summary

The study investigated the prevalence and molecular characteristics of E. coli ST131 and non-ST131 isolates that cause bloodstream infections, with ST131 isolates showing higher virulence factors, incidence of urinary tract infections, and hospital stay time. The dominant serotype was O25b-ST131.