Background: Uropathogenic Escherichia coli (UPEC) are the most common bacteria causing urinary tract infection (UTI). The putative pathogenicity island (PAI) which contains the gene encoding uropathogenic specific protein (usp) and three small open reading frames (orfU1, orfU2 and orfU3) encoding OrfU1, OrfU2 and OrfU3 proteins respectively is widely distributed in UPEC strains. This pathogenicity island was designated as PAIusp.
Objective: To provide an overview of previous studies on uropathogenic specific protein (Usp) and to recommend future studies on Usp.
Methods: We performed the detailed review of the previous reports on Usp with special emphasis on structural diversity and molecular epidemiology of PAIusp, role of Usp in urovirulence and molecular activity of Usp.
Results: As usp gene is frequently detected in E. coli strains isolated from UTI and enhances the infectivity of non-pathogenic host E. coli strains in mouse pyelonephritis model, Usp is thought to be an important virulence factor. In addition, Usp is thought to have bacteriocin activity because Usp shares homology with nuclease-type bacteriocins. PAIusp can be divided into four subtypes based on its sequence and structural diversity. A recent study has demonstrated that Usp is a non-specific DNase belonging to H-N-H nuclease superfamily.
Conclusion: Although there are many questions regarding Usp, it has been revealed that usp gene is widely distributed in UPEC strains and PAIusp subtyping is a useful method to characterize usp-positive UPEC strains epidemiologically. Moreover, Usp has non-specific DNase activity. Future studies should investigate the expression of Usp in UPEC during UTI.