The presence of the virulence island containing the USP gene in uropathogenic Escherichia coli is associated with urinary tract infection in an experimental mouse model

Purpose: A putative virulence island commonly noted in the genome of uropat hogenic Escherichia coli strains has recently been reported. We have observ ed that the island includes a gene consisting of a protein designated uropa thogenic specific protein (usp) and 3 small open reading frames (orfU1-3). In our current study we assessed the importance of the genes located in the putative virulence island in the pathogenesis of urinary tract infection u sing a mouse pyelonephritis model. Materials and Methods: A total of 427 E. coli strains isolated from the uri ne of 194, 76 and 107 subjects suffering from cystitis, pyelonephritis and prostatitis, respectively, and 50 isolates from the feces of healthy indivi duals were examined for genotypes and serotypes. In addition, several recom binant E. coli strains possessing usp and/or orfU1 to 3 were constructed fo r evaluating the significance of these genes using an experimental pyelonep hritis mouse model. Results: The usp was significantly more often associated with uropathogenic E. coli strains (79.4% from cystitis, 93.4% from pyelonephritis and 88.8% from prostatitis) than with fecal E, coli strains from healthy individuals (24%). Furthermore, usp was frequently associated with all common serotypes of uropathogenic E. coli (71.7% to 100%). In challenge experiments using t he mouse urinary tract infection model the vector possessing usp significan tly enhanced the infectibility of the E. coli host cell, whereas the 3 smal l proteins at the downstream of usp failed to show the effect. Conclusion: Our results indicate that usp may contribute to the causation o f urinary tract infection and may be considered a major virulence determina nt of uropathogenic E. coli.