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Prevalence of Pathogenicity Island IICFT073 Genes among Extraintestinal Clinical Isolates of Escherichia coli

Abstract : Uropathogenic Escherichia coli is the most common cause of urinary tract infection (UTI). Cystitis in women is by far the most common UTI; pyelonephritis in both sexes and prostatitis in men are more severe but are less frequent complaints. The ability of E. coli to cause UTI is associated with specific virulence determinants, some of which are encoded on pathogenicity islands (PAI). One such PAI (PAI II CFT073), of the prototypical uropathogenic E. coli strain CFT073, contains 116 open reading frames, including iron-regulated genes, carbohydrate biosynthetic genes, the serine protease autotransporter picU, a two-partner secretion system, a type I secretion system, mobility genes, and a large number of hypothetical genes. To determine the association of PAI II CFT073 with UTI, PCR was used to examine the prevalence of the five virulence-associated loci among the ECOR collection and a collection of E. coli isolated from patients with cystitis, pyelonephritis, prostatitis, or septicemia. All PAI II CFT073 loci were found to be more prevalent among the B2 phylogenetic group than any other group within the ECOR collection and among invasive prostatitis strains than were cystitis or pyelone-phritis strains. These data support the theory that clinical isolates causing prostatitis are more virulent than those producing cystitis or pyelonephritis in women. Urinary tract infections (UTIs) continue to be among the most common extraintestinal diseases. In the United States, UTIs account for 8.7 million annual physician and 2.3 million hospital visits (49). Cystitis in women is by far the most common UTI; pyelonephritis in both sexes and prostatitis in men are more severe but less frequent complaints. Several bacterial species may cause UTIs, but Escherichia coli is by far the most common cause (14), accounting for 50% of all nosocomial UTIs and 90% of infections among ambulatory patients. It is believed that uropathogenic E. coli (UPEC) are adapted to colonizing the urinary tract. The liberation of specific viru-lence factors may aid attachment to host mucosal tissue, allow evasion of immune defenses, and promote invasion of the normally sterile urinary tract and tissues (14, 15). Among these factors, adhesins, capsule, aerobactin, toxins, and proteases have been described (1, 15, 36, 46). Analysis of the prevalence of virulence factors among commensal E. coli and those causing different UTIs has indicated a greater virulence potential of the disease-causing strains (18, 33, 46). Moreover, virulence determinants appear to be more prevalent among strains causing invasive disease (46). Interestingly, half of all UPEC isolates possess none, or only one, of the virulence factors characterized thus far. As such, it is reasonable to assume other, as-yet-uncharacterized, bacterial factors may be important in the pathogenesis of UTI (33). The genome sequence of the UPEC strain CFT073 has been determined, and this has allowed the identification of potential virulence genes (54). Several of the genes associated with the acquisition and development of UTIs are encoded on pathogenicity islands (PAIs), e.g., hemolysin and P fimbriae (3). By definition, PAIs contain genes that are associated with virulence and are absent from avirulent or less virulent strains of the same species. Multiple PAIs varying in size and gene complement have been described in UPEC isolates (2, 13, 34). Recently, we described the existence within uropathogenic E. coli strains of the serine pro-tease autotransporter PicU (40). In silico analysis of the genomic context of the gene encoding PicU revealed that, like other virulence factors, it was located on a PAI. The 100-kb PAI contains 116 open reading frames (ORFs) which, in addition to PicU, encode a type I protein secretion system, a member of the two-partner protein secretion system (TPSS), iron-sequestering proteins, proteins involved in carbohydrate metabolism, insertion elements, and ORFs of unknown function. The PAI encoding PicU demonstrates homology with PAI II CFT073 , a 71.6-kb PAI previously characterized in E. coli CFT073 (43). In silico investigations of the previously described PAI II CFT073 revealed that it was incorrectly assembled from three distinct regions of the E. coli CFT073 complete genome sequence. Here we describe the correct genetic organization of PAI II CFT073 and investigate the prevalence of these genes among populations of E. coli including pathogenic E. coli causing cystitis and py-elonephritis in women, prostatitis in men, and septicemia in both sexes.
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Nick Parham, Samantha Pollard, Roy Chaudhuri, Scott Beatson, Mickael Desvaux, et al.. Prevalence of Pathogenicity Island IICFT073 Genes among Extraintestinal Clinical Isolates of Escherichia coli. Journal of Clinical Microbiology, American Society for Microbiology, 2005, 43 (5), pp.2425-2434. ⟨10.1128/JCM.43.5.2425-2434.2005⟩. ⟨hal-02910754⟩



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