Role of the K1 Capsule, PapG II, and Afa Adhesins in Escherichia coli Infections Arising from the Urinary Tract

BACKGROUND: Escherichia coli is the major pathogen in many extraintestinal Gram-negative bacillus infections. Both E. coli virulence characteristics and host factors contribute to the development of E. coli bacteremia in urinary tract infection (UTI). The aim of this study was to examine the bacterial virulence characteristics in E. coli infections arising from the urinary tract. METHODS: A total of 186 consecutive E. coli isolates from the urine or bloodstream of patients with urinary tract-related colonization/ infection were collected. They were grouped as asymptomatic bacteriuria (ABU), UTI, and urosepsis. Phylogenetic groups, K1 capsule and 14 virulence factor genes, and antimicrobial susceptibility of E. coli isolates were determined. RESULTS: There were 55 ABU and 67 UTI strains derived from urine, and 64 urosepsis strains derived from the bloodstream. There were more bacterial virulence characteristics of E. coli isolates derived from urosepsis patients. In the overall analysis of 186 E. coli isolates arising from the urinary tract, multivariate logistic regression analysis demonstrated neuA (OR 3.37, 95% CI 1.18-9.64), papG II (OR 12.34, 95% CI 4.47-34.06) and afa (OR 13.20, 95% CI 5.81-29.99) were independently associated with the development of E. coli urosepsis. The prevalence of antimicrobial resistance of E. coli isolates was similar between the immunocompromised and immunocompetent groups, and among the ABU, UTI, and urosepsis subgroups in immunocompromised patients. CONCLUSION: Regarding the bacterial virulence characteristics, this study demonstrated the K1 capsule, PapG II, and Afa adhesins play important roles in the development of E. coli urosepsis. (Acta Nephrologica 2011; 25: 125-131)