Characteristics of Escherichia coli Urine Isolates and Risk Factors for Secondary Bloodstream Infections in Patients with Urinary Tract Infections

Escherichia coli is responsible for more than 80% of all incidences of urinary tract infections (UTIs). We assessed a total of 636 cases of patients with E. coli UTIs occurring in June 2019 in eight tertiary hospitals in South Korea for the traits of patients with E. coli UTIs, UTI-causative E. coli isolates, and risk factors associated with bloodstream infections (BSIs) secondary to UTIs. Antimicrobial susceptibility testing was conducted using the disc diffusion method, and the genes for extended-spectrum beta-lactamases (ESBLs) and plasmid-mediated ampC genes were screened by using PCR and sequencing. Multilocus sequence typing and virulence pheno-/genotyping were carried out. A total of 49 cases developed BSIs. The E. coli urine isolates primarily comprised sequence type 131 (ST131) (30.0%), followed by ST1193, ST95, ST73, and ST69. Three-quarters of the ST131 H30Rx isolates possessed the bla(CTX-M-15)-like gene, whereas 66% of H30R and 50% of H41 isolates possessed the bla(CTX-M-14)-like gene. All the ST1193 isolates showed biofilm formation ability, and three-quarters of the ST73 isolates exhibited hemolytic activity with high proportions of papC, focG, and cnf1 positivity. The prevalence of the ST131 H41 sublineage and its abundant CTX-M possession among the E. coli urine isolates were noteworthy; however, no specific STs were associated with bloodstream invasion. For BSIs secondary to UTIs, the papC gene was likely identified as a UTI-causative E. coli-related risk factor and urogenital cancer (odds ratio [OR], 12.328), indwelling catheter (OR, 3.218), and costovertebral angle tenderness (OR, 2.779) were patient-related risk factors. IMPORTANCE Approximately half of the BSIs caused by E. coli are secondary to E. coli UTIs. Since the uropathogenic E. coli causing most of the UTIs is genetically diverse, understanding the risk factors in the E. coli urine isolates causing the BSI is important for pathophysiology. Although the UTIs are some of the most common bacterial infectious diseases, and the BSIs secondary to the UTIs are commonly caused by E. coli, the assessments to find the risk factors are mostly focused on the condition of patients, not on the bacterial pathogens. Molecular epidemiology of the UTI-causative E. coli pathogens, together with the characterization of the E. coli urine isolates associated with the BSI secondary to UTI, was carried out, suggesting treatment options for the prevalent antimicrobial-resistant organisms.