BACKGROUND: The mechanism of pathogenesis and the role of virulence factors of avian pathogenic E. coli is still ill-defined. The ostrich industry is expanding, resulting in the interaction between poultry and ostrich. It is reported that the investigation of iss and bor virulence genes together, due to their structural and functional similarities, is valuable. Objectives: The investigation and comparison of presence of two genes involved in serum resistance, iss and bor, in E. coli isolated from apparently healthy ostriches and poultry with colibacillosis. Methods: As a cross-sectional study, E. coli was recovered from fecal samples of apparently healthy ostriches and poultry with colibacillosis, and iss and bor genes were screened and compared via PCR in E. coli isolates. Results: iss frequencies, with no statistical difference, were 50% and 64.4% in E. coli isolated from apparently healthy ostriches and poultry with colibacillosis, respectively (P>0.05). 31.8% and 15.6% of E. coli isolated from apparently healthy ostriches and poultry with colibacillosis were positive for bor, respectively, with no statistical difference (P>0.05). 11.1% of isolates from colibacillosis and 18.2% of isolates from apparently healthy ostriches feces, with no statistical difference, were positive for both genes (P>0.05). Conclusions: Equal statistical distribution of both genes, bor and iss, between apparently healthy ostriches and poultry with colibacillosis and the health level of studied ostriches indicated that E. coli isolated from ostrich, probably employs other virulence factors instead of bor and iss to establish a disease. This hypothesis needs to examine more virulence genes in ostrich-origin E. coli. In addition, the ostrich feces could be introduced as a source of iss and bor genes.

BACKGROUND: Extensive effort is focused on identifying genomic conserved antigens in development of effective vaccine against Enterotoxigenic Escherichia coli. Antigen 43 is one of the members of a large secreted protein family named autotransporters in the E.coli and other gram negative bacteria. Autotransporter proteins have a similar conserved structure. Some of them are recognized during both experimental and naturally occurring ETEC infections. Antigen 43 is represented as a potential target in vaccine development because of its virulence functions such as cell aggregation, biofilm formation and its presence in convalescent sera from human patients with ETEC diarrhea. OBJECTIVES: In this study, we carefully investigate antigenic structure and immunogenicity of the Antigen 43 protein of strain 510 E.coli isolated from calves by experimental methods and immunoinformatics tools. METHODS: Amino acid sequence, physico-chemical parameters, stability, secondary and tertiary protein structure, the ability of induction the B and T cell immune responses by having the effective epitopes and also the allergenicity assessment were analyzed. RESULTS: In this study, we identified 15 peptide sequences that can potentially induce B and T cell immune responses and finally, 9 of them were introduced as antigens. CONCLUSIONS: The results of in-silico analysis on this protein suggested that it can be used in bovine colibacillosis vaccine development.