Incidence and pathogenesis of enterococcus associated chicken embryo and neonatal mortality
Date
2020-01-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0003-4091-3034
Type
Thesis
Degree Level
Doctoral
Abstract
Chicken embryo mortality and yolk sac infections (YSI) of neonatal chickens cause a significant economic loss to the poultry industry. In recent years, an emergence of Enterococcus associated YSI in neonatal broiler chickens was reported in many countries around the world including Canada, but reasons associated with the emergence of enterococcal infections in poultry were not understood. Although Escherichia coli was predominantly isolated from dead embryos and YSI in neonatal chickens in the past, enterococci emerged as the main bacterial species from these incidents in the western Canadian poultry industry. Hence, our main objectives were to identify the incidence of enterococci in commercial hatcheries in western Canada associated with embryonic death and to study the pathogenesis of embryonic and neonatal death related with enterococci.
Chicken embryo death could result from many reasons, but as described in Chapter 2, 65.82% of yolk materials from non-viable chicken embryos were positive for at least one bacterial species. Enterococci was predominantly isolated from non-viable chicken embryos followed by E. coli. E. faecalis was the predominant enterococcal isolate followed by E. faecium. While polymicrobial growths were common, 56% of the embryos were co-infected with E. faecalis and E. coli. We have demonstrated that matrix-assisted laser desorption/ionization time-of-flight mass spectrometry can distinguish enterococci into the species level with 97.18% accuracy, and can be applied for use in routine poultry pathogen identification.
In the third chapter, we have demonstrated that the majority of isolated enterococci and E. coli are multidrug resistant and highlighted the urgency of antimicrobial resistance surveillance in this reservoir of non-viable chicken embryos to understand antimicrobial resistance dissemination and its control.
In the fourth chapter, we have utilized an egg infection model to understand the pathogenesis of enterococci and E. coli. We were able to demonstrate that E. faecalis was able to penetrate the eggshell, and colonize internal organs of chicken embryos without causing inflammation or death. However, once E. faecalis co-infected with E. coli, it led to high chick mortality due to septicemia and associated increased proinflammatory cytokines prior to hatch. Overall, our research findings highlight the importance of maintaining proper hygienic and biosecurity measures in commercial hatcheries and poultry production facilities in order to minimize bacterial contamination of hatching eggs to control neonatal chicken mortality.
Description
Keywords
Enterococci, E. coli, Chicken embryo death, Neonatal Chick Mortality, Yolk sac infections, Multidrug resistant enterococci, Pathogenesis
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Veterinary Pathology
Program
Veterinary Pathology