Characterization of four novel genomic regions of uropathogenic Escherichia coli highly associated with the extraintestinal virulent phenotype: a jigsaw puzzle of genetic modules.

Extraintestinal pathogenic Escherichia coli (ExPEC) are a major cause of urinary tract infections, sepsis, and neonatal meningitis. A variety of virulence factors in these strains is encoded by mobile genetic elements, such as transposons or pathogenicity islands (PAIs). Using subtractive cloning of ExPEC genomes, we recently detected short DNA fragments, which were significantly associated with the extraintestinal virulent phenotype. In this study, we identified four novel genomic DNA regions of the highly virulent uropathogenic E. coli strain JS299 carrying these previously identified DNA fragments. Characterization of the partial sequences of the genomic DNA regions revealed complex DNA arrangements with variable genetic compositions regarding the G+C contents and codon usage patterns. The prevalence of 15 previously uncharacterized genes was determined in a collection of clinical ExPECs and commensal E. coli strains by means of DNA microarray analyses. From this, 13 novel DNA sequences were demonstrated to be significantly associated with extraintestinal virulent strains, and thus may represent new virulence traits. Beside genes predicted to play a role in metabolic functions, such as sucrose utilization (scr), we identified DNA sequences shared by both ExPEC and enteropathogenic E. coli (EPEC). These sequences were significantly more prevalent among ExPECs when compared to commensal E. coli isolates. Our results support the idea of a considerable genetic variability among ExPEC strains and suggest that the novel genomic determinants described in this study may contribute to the ExPEC virulence.