Roles of host and bacterial virulence factors in the development of upper urinary tract infection caused by Escherichia coli

Aims of this study are to identify host and Escherichia coli virulence factors associated with upper urinary tract infection (UTI) by comparing them with those for lower UTI and determining the association between major predisposing host factors for upper UTI and urovirulence genes for E coli. Host factors and urovirulence genes of E coli associated with bacteremia in patients with upper UTI and their interactions also were studied. One hundred thirty-nine adult patients who fulfilled clinical diagnostic criteria for upper (n = 81) or lower UTI (n = 58) caused by E coli between January 1997 and December 1999 were retrospectively enrolled into this study. Old age (or =60 years), male sex, diabetes with poor blood glucose control (ie, glycosylated hemoglobin A1Cor = 8.1%), immunosuppression, and urinary tract obstruction were more frequently associated host factors for patients with upper UTI than for those with lower UTI. Using polymerase chain reaction, the papG class II allele was detected more frequently for E coli strains isolated from patients with upper UTI than for those from patients with lower UTI (85% versus 52%; P0.0001). Multivariate analysis showed that diabetes with poor blood glucose control, immunosuppression, urinary tract obstruction, and papG class II allele were independently associated with upper UTI. For patients without these three predisposing host factors, the prevalence of papG class II allele was significantly greater in those with upper UTI than those with lower UTI. However, the papG class II allele was less prevalent in strains isolated from patients with upper UTI with urinary tract obstruction or with two of the three predisposing host factors. In addition, both univariate and multivariate analyses showed that old age and papG class II allele were risk factors for the development of E coli bacteremia in patients with upper UTI. In conclusion, both host and E coli virulence factors contribute to the development of upper UTI, and less virulent strains can cause upper UTI in hosts with predisposing factors.