Location: Poultry Research
2022 Annual Report
Objectives
1. Use proteomics, genomics, and systems biology approaches to identify molecular determinants of pathogenesis, strain variation, and tissue tropism of different E. coli strains.
2. Identify immunological targets that will confer cross-protection against prevalent E. coli strains in poultry production and develop vaccine platforms that are effective in very young birds, provide cross- protection, and can be easily administered.
2.a. Identify genetic determinants for antigenicity and pathogenicity of E. coli through comparative genomics and analyses.
2.b. Identification of immunological targets will provide a cross protection against different strains of Avian Pathogenic Escherichia coli (APEC).
2.c. Assess in ovo vaccination technology for delivery of live attenuated APEC vaccines.
3. Develop systems-level capabilities to evaluate the effects of commercial-scale, poultry management practices on animal health and production; microbial ecology, development of antimicrobial resistance and bacterial pathogen transmission to develop mitigation strategies.
3.a.1. Evaluate performance of three bio-aerosol samplers for collecting airborne E. coli attached to dust particles from poultry production environments.
3.a.2. Quantify concentration and size distribution of airborne E. coli in representative US broiler and layer houses.
3.a.3. Evaluate electrostatic particle ionization (EPI) and ultraviolet (UV) radiation to reduce airborne E. coli.
3.b.1. Evaluate effects of litter amendment application rate on E. coli populations in broiler litter.
3.b.2. Assess E. coli populations and antibiotic growth promoter (AGP) residue concentrations in biochar-treated and untreated litter (live study).
3.b.3. Evaluate effects of litter management [top-dressed (TD) vs non-top-dressed] and bedding type (pine vs switchgrass) on litter E. coli populations over successive flocks.
Approach
Proteomic, genomic, and systems biology approaches will be applied to identify molecular determinants of pathogenesis, strain variation, and tissue tropism of different E. coli strains. The E. coli strains analyzed will be isolated from varying diseased poultry flocks and strain genomic & proteomic characteristics and isolate epidemiological factors will be applied model development for greater understanding of pathogenic E. coli and associated disease. To further protect against pathogenic E. coli, immunological targets will be identified that will confer cross-protection against prevalent E. coli strains in poultry production. The genomic and plasmid sequences of various E. coli strains will be aligned, and antigenic factors will be determined. Immunological targets will be identified and assessed via challenge models that provide cross-protection against pathogenic E. coli. In addition, vaccination platforms that are effective in very young birds, provide cross-protection, and can be easily administered will be developed. In ovo technologies will be assessed for delivery of protective vaccines and associated protocols developed. To increase the understanding of environmental E. coli and evaluate risks to poultry and associated antimicrobial resistance, studies will evaluate airborne E. coli associated with dust particles and E. coli linked to poultry litter. Further, mitigation means will be assessed for their impact on environmental E. coli populations.
Progress Report
A total of 189 Avian Pathogenic E. Coli (APEC) strains have been sequenced, assembled, and annotated and ten of those were selected for comparison. Additional strains are currently being assembled, annotated, and compared. Cooperator has hired a new post-doc to complete this portion of the research. Two trials were conducted by stakeholder request to evaluate the potential application of modified-live Salmonella typhimurium vaccine via an in ovo route. This experiment was conducted to scale the correct dosage of the vaccine for use in ovo and subsequent effects on a 3-week rearing period. Initial results indicate that lower dosages of the modified-live Salmonella typhimurium vaccine are more appropriate for use in ovo. Aerosol sampler evaluations have been completed. Three aerosol sampling technologies (media plates, liquid capture, and filter-based) were evaluated for E. coli sampling performance. The filter-based system showed significantly reduced capture (28% reduction) and airborne concentration (50% reduction) when compared to media plates or liquid capture. Settled airborne E. coli survivability was evaluated and the mean half-life time was 74.3 hours, indicating that post-aerosolization survivability was significantly less than when directly deposited (28 days). Research to determine the concentration and size distributions of airborne E. coli in U.S broiler and layer houses has not been initiated due to travel restrictions and access limitations at commercial farms. UV and EPI mitigation research is proceeding and on-schedule.
Accomplishments
1. In-ovo delivery of APEC vaccines. Protocols were developed to apply in ovo-based technologies for delivery of live attenuated APEC vaccines. The vaccines were successfully delivered to broiler embryos and impacts on hatchability were demonstrated to be dose dependent. This research will allow for more efficient and effective delivery of available APEC vaccines as compared to traditional spray application.
2. APEC lethality model. Based on the mortality and the status of egg, isolates were characterized on the basis of pathogenicity to implement into the chick disease model. Development of the embryo lethality test allows for the identification of important virulence factors and characterization of APEC disease.
