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Enterococci and Escherichia coli are opportunistic pathogens of poultry and are associated with embryo and neonatal chick mortality. We have recently demonstrated that 56% of dead broiler chicken embryos in commercial hatcheries in western Canada were due to the coinfection of Enterococcus species and E. coli. The objective of this study was to investigate the host-pathogen interactions of Enterococcus faecalis and E. coli in developing chicken embryos. Embryonating eggs at 12 d of incubation were dipped in a solution of E. faecalis and/or E. coli for 30 s to expose the eggshell to study the migration and colonization of E. faecalis and E. coli in the internal organs of chicken embryos and subsequent neonatal chicken mortality following hatch. A multidrug-resistant E. faecalis isolate from a dead chicken embryo and an E. faecalis isolate from a case of yolk sac infection were able to colonize the internal organs of chicken embryos rapidly compared to an E. faecalis isolate from a healthy chicken without affecting viability or hatchability of embryos. Although E. faecalis colonized internal organs of chicken embryos, no evidence of inflammation of these organs nor the expression of virulence genes of E. faecalis was observed. Although E. faecalis and E. coli alone did not affect the viability of embryos, a significantly high neonatal chicken mortality (27%) was observed following exposure of embryos to both E. faecalis and E. coli. Upregulation of IL-1 and CXCR4 was evident 48 h before peak mortality of neonatal chickens; this could suggest a possible link of cytokine dysregulation to increased mortality in coinfected neonatal chickens. However, further studies are warranted to investigate this issue vis-à-vis coinfection with E. faecalis and E. coli in chicken embryos and neonatal chickens., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Synthetic DNA containing CpG motifs (CpG-ODN) are potent innate immune stimulators in neonatal and adult broiler chickens against bacterial septicemia. We have recently demonstrated that intrapulmonary (IPL) delivery of CpG-ODN as microdroplets under laboratory conditions can protect neonatal chickens against lethal Escherichia coli septicemia. The objectives of this study were to develop a commercial-scale poultry nebulizer (CSPN) that can deliver CpG-ODN as microdroplets in neonatal broiler chicks in the hatcheries and study the efficacy of CSPN in inducing immune-protective effects under different environmental conditions in 2 geographical locations in Canada. Three field experiments were conducted in commercial poultry hatcheries during different seasons of the year in Saskatchewan and British Columbia, Canada. Neonatal broiler chicks (n = 8,000/experiment) received CpG-ODN by the IPL route in the CSPN chamber for 30 min, and control chicks received distilled water (DW) for 30 min. Broiler chicks (CpG-ODN-240 chicks/experiment and DW-40 chicks/experiment) were randomly sampled from all locations of the CSPN after nebulization and challenged with a lethal dose of E. coli to examine the CpG-ODN nebulization induced protection. We found a significant level (P < 0.05) of protection in broiler chicks against E. coli challenge, suggesting that the newly built CSPN successfully delivered CpG-ODN via the IPL route. We found that when the CSPN was maintained at humidex 28°C or below and relative humidity (RH) between 40 and 60%, neonatal birds were significantly (P < 0.05) protected against E. coli septicemia after IPL delivery of CpG-ODN. By contrast, protection in chicks was adversely affected when the CSPN was maintained at the humidex of 29°C or higher and RH of 70%. Overall, the present study successfully built a CSPN for CpG-ODN delivery in chicks at the hatchery and revealed that the temperature, humidity, and humidex were critical parameters in CSPN for efficient delivery of CpG-ODN., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)