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Gedruckt mit Genehmigung des Fachbereichs Veterinärmedizin der Freien Universität Berlin

Virulence characteristics of 50 strains of Escherichia coli isolated from chickens with swollen head syndrome were examined. The results were the following: in the absence of D‐mannose, 74% of strains agglutinated guinea pig erythrocytes, but in the presence of D‐mannose 32% agglutinated guinea‐pig erythrocytes and 62% agglutinated human erythrocytes. When slide agglutination assays were carried out with antisera to adhesin of bovine and swine origin (K88, K99, F41, F42 987P and 2134P), only 14% of strains agglutinated with antiserum to F41. Colicin V was produced by 78% of the E. coli strains and 80% produced aerobactin. In the serum resistance test, 36 (72%) of strains showed resistance to normal chicken serum. Only seven (14%) strains expressed K1 capsular antigen, while motility was found in 62% of the strains.

https://www.tandfonline.com/doi/pdf/10.1080/03079459808419316

Virulence factors of avian Escherichia coli associated with swollen head syndrome.

Colibacillosis in battery-caged layer hens: clinical and bacteriological characteristics, and risk factor analysis

The aim of this work was to isolate, clone and characterize the iron uptake gene iutA from avian pathogenic E. coli (APEC). The iutA gene was isolated from the strain APEC 9, serotype O2:H9, which was cloned in the expression vector pET101/D-TOPO. The gene of 2.2 Kb was sequenced (AY602767, which showed high similarity to the iutA gene from three plasmids, two from APEC, pAPEC-02-ColV (AY545598.4) and pTJ100 (AY553855.1), and one from a human invasive E. coli strain, the pColV K30. The recombinant protein IutA was over expressed in E. coli BL21(DE-3) and was solubilized with urea and purified by Ni-NTA column. This method produced a relatively high yield of r-IutA of approximately 74kDa, which was used to produce the antibody anti-IutA. This anti-IutA reacted with the protein r-IutA and native IutA of APEC 9, as demonstrated by Western blot, showing that the r-IutA conserved epitopes and its antigenicity was preserved. The anti-IutA IgY was able to inhibit the IutA biological activity, inhibiting the sensitivity to cloacin DF13 of APEC9. However, it did not inhibit the growth of APEC9 in M9 and did not protect the chickens inoculated with the APEC, suggesting that the APEC possessed another iron acquisition mechanism distinct of aerobactin.

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Cloning and characterization of the iron uptake gene iutA from avian Escherichia coli

The iron uptake mechanisms of enteroinvasive Escherichia coli

1. We cloned the aerobactin region and its receptor from pMV14, a large nonconjugative plasmid isolated from the virulent strain UEL14, to assess the importance of the aerobactin iron uptake system as a virulence determinant in septicemic avian Escherichia coli. 2. The physical map of the region of the recombinant plasmid (pGMV1) containing the genes for synthesis of aerobactin and its receptor was very similar to the corresponding region in pABN1 containing the genetic determinants for the aerobactin system of pColV-K30. 3. The 74-kDa outer-membrane protein encoded by pGMV1 cross-reacted immunologically with the 74-kDa aerobactin receptor protein encoded by pABN1. 4. Various avirulent E. coli strains carrying the recombinant plasmid, which contains only the aerobactin system, were assayed for virulence and were found to be avirulent for chickens. Only the wild-type aerobactin-producing strain was virulent in a pathogenicity test for chickens. 5. These results show that the aerobactin system by itself does not confer virulence, and that other factors are necessary for virulence of avian strains of E. coli.

L. C. J. Gaziri

Papers

Cloned genes of the aerobactin system of virulent avian Escherichia coli do not confer virulence to recombinant strains.