Characterisation of avian pathogenic Escherichia coli (APEC) associated with colisepticaemia compared to faecal isolates from healthy birds

Queen's University Belfast, Béal Feirste, Northern Ireland, United Kingdom
Veterinary Microbiology (Impact Factor: 2.73). 11/2005; 110(3-4):245-53. DOI: 10.1016/j.vetmic.2005.08.001
Source: PubMed

ABSTRACT A total of 114 avian pathogenic Escherichia coli (APEC) isolates were collected from cases of colisepticaemia occurring in broilers (77) and layers (37) within Ireland. In addition 45 strains isolated from faeces of healthy birds were included for comparison. All isolates were serogrouped, and examined for known virulence factors, mostly by PCR. The O78 serogroup represented 55 and 27% of broiler and layer colisepticaemic isolates respectively. All isolates were positive for curli fimbriae (crl, csg) and negative for afimbrial adhesin (afa). S-fimbrial (sfa) sequences were present in 8.8% of septicaemic isolates and 8.9% of healthy bird isolates. The majority of E. coli from cases of colisepticaemia (97.4%) and healthy bird (95.6%) isolates were positive for aerobactin (aer), and temperature sensitive haemagglutinin (tsh) was similarly detected in high numbers in 93.9 and 93.3%, respectively. In comparison to E. coli isolates from the faeces of healthy birds, a significantly higher percentage of isolates from septicaemic cases possessed Type 1 fimbriae (fimC) and increased serum survival (iss) gene sequences. Forty-seven (41.2%) isolates from septicaemic birds possessed P-fimbriae (pap) gene sequences, compared with only 15.6% from E. coli isolated from healthy birds. Haemolysin (hlyE) sequences were detected in 46.7% of isolates from healthy birds in comparison with 6.1% of septicaemic isolates. Sequences encoding colicin V (cvaC) were detected in 99.1% of septicaemic isolates and 82.2% of isolates from healthy birds. The K1 capsule was only present in two septicaemic isolates, both taken from layers. Motility was detected in 36.8% of E. coli isolated from cases of septicaemia, compared with 93.3% of isolates from healthy birds. These results demonstrate the presence of 11 virulence genes in E. coli isolated from cases of colisepticaemia within Ireland, and indicate the prevalence of iss and fimC.

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    ABSTRACT: Avian Pathogenic Escherichia coli (APEC) strains are extra-intestinal E. coli that infect poultry and cause diseases. Nitrite is a central branch-point in bacterial nitrogen metabolism and is used as a cytotoxin by macrophages. Unlike nitric oxide (NO), nitrite cannot diffuse across bacterial membrane cells. The NirC protein acts as a specific channel to facilitate the transport of nitrite into Salmonella and E. coli cells for nitrogen metabolism and cytoplasmic detoxification. NirC is also required for the pathogenicity of Salmonella by downregulating the production of NO by the host macrophages. Based on an in vitro microarray that revealed the overexpression of the nirC gene in APEC strain SCI-07, we constructed a nirC-deficient SCI-07 strain (ΔnirC) and evaluated its virulence potential using in vivo and in vitro assays. The final cumulative mortalities caused by mutant and wild-type (WT) were similar; while the ΔnirC caused a gradual increase in the mortality rate during the seven days recorded, the WT caused mortality up to 24h post-infection (hpi). Counts of the ΔnirC cells in the spleen, lung and liver were higher than those of the WT after 48hpi but similar at 24hpi. Although similar number of ΔnirC and WT cells was observed in macrophages at 3hpi, there was higher number of ΔnirC cells at 16hpi. The cell adhesion ability of the ΔnirC strain was about half the WT level in the presence and absence of alpha-d-mannopyranoside. These results indicate that the nirC gene influences the pathogenicity of SCI-07 strain. Copyright © 2014 Elsevier B.V. All rights reserved.
    Veterinary Microbiology 11/2014; 175(1). DOI:10.1016/j.vetmic.2014.11.015 · 2.73 Impact Factor
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    ABSTRACT: Research has been performed on a total of 121 E. coli strains isolated from broilers corpses of different ages with lesions of colisepticaemia. Classification of strains in APEC pathotype was realized by identifying genes OmpA, iss and fimH by the multiplex PCR technique. The binding of Congo Red was tested on TSA agar. The epidemiological marker followed, respectively the binding of Congo Red, was present in 112 strains, respectively 92.56% of the strains tested. Multiplex PCR technique has allowed detection of the genes OmpA, iss and fimH, which generates the synthesis of some virulence factors specific to APEC strains, in 118 of the strains tested, respectively 97.52%. APEC pathotype (Avian Pathogenic Escherichia coli) includes pathogenic strains for birds, causing extraintestinal infections of septicemic type, starting from the respiratory mucosa. Overwhelming majority of the strains classified in this pathotype is serogroup O78 and binding of Congo Red is an epidemiological marker that can be used for discrimination of pathogenic strains from the commensal ones, especially in the serogroup O78 (1, 2).