Association of iss and iucA , but Not tsh , with Plasmid-Mediated Virulence of Avian Pathogenic Escherichia coli

Abstract

Avian pathogenic Escherichia coli (APEC) is an economically important respiratory pathogen of chickens worldwide. Factors previously associated with the virulence of APEC include adhesins, iron-scavenging mechanisms, the production of colicin V (ColV), serum resistance, and temperature-sensitive hemagglutination, but virulence has generally been assessed by parenteral inoculation, which does not replicate the normal respiratory route of infection. A large plasmid, pVM01, is essential for virulence in APEC strain E3 in chickens after aerosol exposure. Here we establish the size of pVM01 to be approximately 160 kb and show that the putative virulence genes iss (increased serum survival) and tsh (temperature-sensitive hemagglutinin) and the aerobactin operon are on the plasmid. These genes were not clustered on pVM01 but, rather, were each located in quite distinct regions. Examination of APEC strains with defined levels of respiratory pathogenicity after aerosol exposure showed that both the aerobactin operon and iss were associated with high levels of virulence in APEC but that the possession of either gene was sufficient for intermediate levels of virulence. In constrast, the presence of tsh was not necessary for high levels of virulence. Thus, both the aerobactin operon and iss are associated with virulence in APEC after exposure by the natural route of infection. The similarities between APEC and extraintestinal E. coli infection in other species suggests that they may be useful models for definition of the role of these virulence genes and of other novel virulence genes that may be located on their virulence plasmids.

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

“…TraT and Iss are believed to prevent deposition of the membrane attack complex of complement by an unknown mechanism. TraT is thought to antagonize C3 deposition (Agü ero et al, 1984) and to inhibit formation of the C5b6 complex (Pramoonjago et al, 1992) (Mellata et al, 2003a) but it is required for full virulence (Tivendale et al, 2004). It has already been suggested that there could a compelling but imperfect relationship between complement resistance, virulence and the presence of iss (Nolan et al, 1992a), and that high resistance to complement may be necessary but not sufficient for virulence (Chaffer et al, 1999).…”

“…Notably, a 94 kb region of a 180 kb ColV plasmid carries genes encoding for iron acquisition and transport systems, and these are more prevalent in APEC than avian faecal Escherichia coli (AFEC) . Importantly, a link between APEC virulence and possession of ColV plasmids has been revealed by several studies (Ginns et al, 2000;Johnson et al, 2002;Gibbs et al, 2003;Tivendale et al, 2004). Transformation of an avirulent wild-type E. coli strain with a recombinant plasmid (pHK11) encoding for colicin V led to increased colonization of the chicken trachea (Wooley et al, 1998).…”

Genotypic Analyses of Escherichia coli Isolated from Chickens with Colibacillosis and Apparently Healthy Chickens in Japan

“…It has been reported elsewhere (14,16,19) that APEC expresses many virulence-associated traits such as adhesion to the host cells, resistance to host anti-bactericidal activity, iron uptake systems, and the production of hemolysins and other toxins. Some of these traits are encoded chromosomally (11,15): fimC and papC responsible for adhesion factors F1 and P fimbriae, respectively, irp2 and fyuA for iron uptake systems, astA and vat for heat-stable toxin and vacuolating autotransporter toxin, respectively (7).…”

Similaridade genética entre APEC e cepas de Escherichia coli isoladas de Guaruba guarouba em um estudo com psitacídeos hígidos de cativeiro

“…While the genes were found in higher frequency in symptomatic birds, some virulence genes were also present in asymptomatic individuals. has been correlated with highly pathogenic strains 23 .…”

“…These genes encode proteins that facilitate the air sac colonization, iron uptake and serum survival in extraintestinal infections 16,17,21,23 .…”