A funded research project at the University of Georgia in Athens, Ga. was completed, in which researchers revealed a method to improve Escherichia coli vaccines. The research was made possible in part by an endowing Foundation gift from Koch Foods and is part of the Association’s comprehensive research program encompassing all phases of poultry and egg production and processing.
Project #698: Production of Cross-Protective Autogenous Bacterin Vaccine Strains for controlling Escherichia Coli Infections in Poultry ––(Dr. John Maurer, University of Georgia, Athens, Ga.)
Dr. John Maurer and colleagues at the University of Georgia recently completed a research project in which they developed a new method to create killed vaccines for E. coli. This technique involves growing the bacteria in such a way that it can provide broad immunity against many E. coli types when incorporated into a killed vaccine. The new production method has the potential to provide enhanced protection to layers and breeders against a broader array of E. coli types and help minimize losses due to E. coli infection.
Escherichia coli (E. coli) is an important opportunist bacterial pathogen of poultry, causing significant economic loss from carcass condemnations, airsacculitis, septicemia, yolk peritonitis and cellulitis. Because the isolates are frequently multidrug-resistant, there is often no effective antibiotic therapy. Vaccination has been a moving target for this pathogen because avian pathogenic E. coli exhibits significant O-antigen serogroup diversity, and protective immunity is serogroup specific. This is the reason that killed E. coli killed vaccines (bacterins) provide protection only against the type of E. coli in the vaccine. The O-antigen is the terminal part of the lipopolysaccharide (LPS) surface molecule of the organism. Despite O-antigen serogroup diversity, avian E. coli does possess cross-reactive antigens within the LPS core structure. The LPS core structure is not diverse, and only two types are found among pathogenic E. coli. The central hypothesis was that cross-reactive antigens within the E. coli core LPS can elicit cross-protective antibodies in the absence of the O-antigen portion of the molecule. Therefore, developing an easy method to remove the O-antigen from avian E. coli field isolates offers the industry the ability to produce cross-protective bacterins from autogenous strains. A culture method that inhibits O-antigen production was developed. This method takes just a couple of weeks to generate the candidate strain for autogenous bacterin production. An avian E. coli, devoid of O-antigen, was produced using a culture-based approach. This strain was used to formulate a water-oil-water emulsion bacterin to vaccinate pullet chickens. Chickens were vaccinated with this bacterin, or a Salmonella water-oil emulsion bacterin; or Pasteurella multocida (P. multocida) water-oil-water emulsion bacterin. Vaccinated chickens were evaluated for tissue reaction at the site of injection and the immunological response to various avian E. coli, O-antigen serogroups and strain types, and to Salmonella. The E. coli killed vaccine produced mild reactivity, comparable to the P. multocida bacterin. Chickens immunized with the E. coli bacterin produced broadly cross-reactive, strongly-agglutinating antibodies to several E. coli O-antigen serogroups and strain types. Sera from pre- and post-vaccinated chickens were used to develop an enzyme-linked immunosorbent assay (ELISA) for measuring antibody responses to the E. coli bacterin. The best titer and antigen concentration was identified for optimizing the ELISA. The E. coli bacterin is currently being evaluated in the field for its ability to reduce disease in breeder hens. A cross-protective E. coli vaccine is expected to significantly reduce disease in the field and reduce the economic impact that E. coli infection has on breeder hen health and productivity. This culture-based method can easily identify candidate E. coli strains for bacterin production and may also be applied to Salmonella and the production of a single bacterin for immunizing poultry against several Salmonella serogroups.
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