The Pathogenicity Island-Associated K15 Capsule Determinant Exhibits a Novel Genetic Structure and Correlates with Virulence in Uropathogenic Escherichia coli Strain 536

Abstract

The K15 capsule determinant of uropathogenic Escherichia coli strain 536 (O6:K15:H31) is part of a novel 79.6-kb pathogenicity island (PAI) designated PAI V 536 that is absent from the genome of nonpathogenic E. coli K-12 strain MG1655. PAI V 536 shows typical characteristics of a composite PAI that is associated with the pheV tRNA gene and contains the pix fimbriae determinant as well as genes coding for a putative phosphoglycerate transport system, an autotransporter protein, and hypothetical open reading frames. A gene cluster coding for a putative general secretion pathway system, together with a kps K15 determinant, is localized downstream of a truncated pheV gene (pheV) also present in this chromosomal region. The distribution of genes present on PAI V 536 was studied by PCR in different pathogenic and nonpathogenic E. coli isolates of various sources. Analysis of the 20-kb kps locus revealed a so far unknown genetic organization. Generally, the kps K15 gene cluster resembles that of group 2 and 3 capsules, where two conserved regions (regions 1 and 3) are located up-or downstream of a highly variable serotype-specific region (region 2). Interestingly, recombination of a group 2 and 3 determinant may have been involved in the evolution of the K15 capsule-encoding gene cluster. Expression of the K15 capsule is important for virulence in a murine model of ascending urinary tract infection but not for serum resistance of E. coli strain 536.

Characterization of the Structure and Biological Functions of a Capsular Polysaccharide Produced by Staphylococcus saprophyticus

“…Nonetheless, there is a precedent for CP enhancing the virulence of uropathogenic bacteria. Intact K2 and K15 capsule loci of E. coli have been shown to be critical for virulence in a murine model of ascending UTI (3,54). Likewise, Bahrani-Mougeot et al (1) used signature-tagged mutagenesis to identify genes that are essential for the survival of uropathogenic E. coli within the murine urinary tract.…”

Molecular Epidemiology and Phylogenetic Distribution of the Escherichia coli pks Genomic Island

“…Primers for two internal loci within the pks island, i.e., clbA (phosphopantetheinyl transferase) and clbQ (thioesterase), were IHAPJPN42 (clbAr) (5Ј-CAG ATA CAC AGA TAC CAT TCA-3Ј), IHAPJPN46 (clbAf) (5Ј-CTA GAT TAT CCG TGG CGA TTC3Ј), IHAPJPN55 (clbQr) (5Ј-TTA TCC TGT TAG CTT TCG TTC-3Ј), and IHAPJPN56 (clbQf) (5Ј-CTT GTA TAG TTA CAC AAC TAT TTC-3Ј). Primers for the K15 kpsM variant and tsh, as designed based on published sequence data (15,23), were k15f (5Ј-ACG GAT TCA CGA CAA AGC TC-3Ј), k15r (5Ј-GGC AAA TAT CGC TTG GGT TA-3Ј), tshf (5Ј-GGC GCA TAT CTG GAT AAG GA-3Ј), and tshr (5Ј-GCA GGT TAT CGC CCT TAA CA-3Ј). Testing was done in duplicate using separately prepared boiled lysates as template DNA, with appropriate positive and negative controls, and published amplification conditions (7,10,11).…”

How to become a uropathogen: Comparative genomic analysis of extraintestinal pathogenic Escherichia coli strains

“…The two O6 strains 536 (pyelonephritis isolate) and CFT073 (urosepsis isolate) became generally accepted UPEC model organisms, and several PAIs of them have been described in detail (10)(11)(12)(13)(14)(15)(16). The complete CFT073 genome sequence shows a mosaic structure in terms of the distribution of backbone genes conserved in E. coli, and ''foreign'' genes, which presumably have been acquired horizontally (17).…”