Characterizing the APEC pathotype

Abstract

-The purpose of this study was to compare avian pathogenic Escherichia coli (APEC) isolates to fecal isolates of apparently healthy poultry (avian fecal E. coli or AFEC) by their possession of various traits in order to ascertain whether APEC and AFEC are distinct and if the APEC strains constitute a distinct pathotype. Four hundred and fifty-one APEC and one hundred and four AFEC isolates were examined for possession of traits associated with the virulence of human extraintestinal pathogenic E. coli (ExPEC) as well as APEC. Several of the genes occurred in the majority of APEC and only infrequently in AFEC, including cvaC, iroN, iss, iutA, sitA, tsh, fyuA, irp2, and ompT. Of these genes, several have been found on large plasmids in APEC. Other genes occurred in significantly more APEC than AFEC but did not occur in the majority of APEC. Isolates were also evaluated by serogroup, lactose utilization, and hemolytic reaction. Twenty-nine and a half percent of the APEC and forty-two and three tenths percent of the AFEC were not serogrouped because they were not typeable with standard antisera, typed to multiple serogroups, were rough, autoagglutinated, or were not done. Around 65% of the typeable APEC (205 isolates) and AFEC (41 isolates) were classified into shared serogroups, and about a third of both fell into APEC-(113 isolates) or AFEC-(19 isolates) unique serogroups. Most were able to use lactose. No isolate was hemolytic. Overall, the majority of the APEC isolates surveyed shared a common set of putative virulence genes, many of which have been localized to an APEC plasmid known as pTJ100. This common set of genes may prove useful in defining an APEC pathotype. avian pathogenic Escherichia coli (APEC) / pathotype / virulence plasmid / ExPEC / pTJ100

Differential effects of short-chain fatty acids and iron on expression of iha in Shiga-toxigenic Escherichia coli

“…1b). The observation that Iha is better expressed in DMEM than LB medium has been reported previously for O157:H7 STEC, non-O157:H7 STEC and UPEC strains (Johnson et al, 2005;Rashid et al, 2006b;Schmidt et al, 2001). …”

“…Iha is a potentially important accessory virulence factor for several pathotypes of E. coli, including STEC, UPEC and avian-pathogenic strains (Ewers et al, 2007;Johnson et al, 2000;Ons et al, 2007;Rodriguez-Siek et al, 2005;Touati, 2000), functioning as an adhesin and, at least for UPEC, as a catecholate siderophore receptor (Leveille et al, 2006). This latter function is consistent with the fact that iha is induced under iron-limiting conditions and is subject to Fur-mediated repression in iron-replete environments in both UPEC and O157:H7 STEC strains (Leveille et al, 2006;Rashid et al, 2006b), as well as in the hyper-virulent LEE-negative STEC strain 98NK2, as shown in this study.…”

“…The high prevalence (91 %) of iha in STEC belonging to different seropathotypes and the presence of multiple iha copies in some strains point to the potential importance of this novel adhesin Toma et al, 2004). In the UPEC strain CFT073, iha functions as a urovirulence factor, by contributing to colonization in a mouse urinary tract infection model (Johnson et al, 2005). Furthermore, Iha from UPEC strain UCB34 functions as a catecholate siderophore receptor in E. coli K-12.…”

Colibacillosis in poultry: unravelling the molecular basis of virulence of avian pathogenicEscherichia coliin their natural hosts

“…These predominant serogroups can also be recovered from faeces of apparently healthy birds (Blanco et al, 1998), reinforcing the notion that the intestinal tract may be an important natural reservoir for APEC and that predisposing factors may be required to produce disease. Significantly, several studies have reported shared characteristics including serogroups between commensal E. coli and APEC (Heller & Drabkin, 1977;Blanco et al, 1998;McPeake et al, 2005;Rodriguez-Siek et al, 2005a), implying that APEC could arise from commensal E. coli following acquisition of pathogenic traits. Indeed, widespread variation in phenotypic and virulence characteristics within a single APEC serotype has been reported.…”

“…Plasmidmediated horizontal gene transfer results in extensive diversity within the APEC. The APEC plasmids carry several putative virulence factors, although some of these have been encountered in E. coli isolates from apparently healthy birds (McPeake et al, 2005;Rodriguez-Siek et al, 2005a;Kawano et al, 2006). A high degree of variability in the number, size and virulence traits carried on large plasmids exists in both APEC and isolates from apparently healthy birds (Doetkott et al, 1996).…”