Characterizing the impact of Enterococcus cecorum infection during late embryogenesis on disease progression, cecal microbiome composition, and early performance in broiler chickens

Marcela Arango; Aaron Forga; Jing Liu; Guolong Zhang; Latasha Gray; Randy Moore; Makenly Coles; Abdiel Atencio; Carolina Trujillo; Juan David Latorre; Guillermo Tellez-Isaias; Billy Hargis; Danielle Graham

doi:10.1016/j.psj.2023.103059

Characterizing the impact of Enterococcus cecorum infection during late embryogenesis on disease progression, cecal microbiome composition, and early performance in broiler chickens

Poult Sci. 2023 Nov;102(11):103059. doi: 10.1016/j.psj.2023.103059. Epub 2023 Aug 24.

Affiliations

¹ Division of Agriculture, Department of Poultry Science, University of Arkansas, Fayetteville AR 72701, USA.
² Department of Animal Science, Oklahoma State University, Stillwater, OK 74078, USA.
³ UADA-Veterinary Diagnostic Laboratory, University of Arkansas, Fayetteville AR 72701, USA.
⁴ Division of Agriculture, Department of Poultry Science, University of Arkansas, Fayetteville AR 72701, USA. Electronic address: bmahaffe@uark.edu.

Abstract

Enterococcus cecorum (EC) has been associated with septicemia and early mortality in broiler chickens. There is limited research investigating the pathogenicity of EC field strains obtained from affected birds. The purpose of this study was to evaluate the effect of in-ovo administration into the amnion with different EC field isolates at d 18 of embryogenesis (DOE18). In Exp 1, 7 EC field isolates alone or in combination (EC1-EC3, EC4-EC5, EC6, and EC7) were selected based on phenotypic characteristics and evaluated at different concentrations (1 × 10², 1 × 10⁴, and 1 × 10⁶ CFU/200 µL/embryo) to assess the impact on early performance and macroscopic lesions. Three isolates (n = 3; EC2, EC5, EC7) were selected for additional evaluation based on the significant (P < 0.05) BWG reduction (d 0-21) compared to the negative control (NC) and the presence of macroscopic lesions observed during posting sessions at d 14 and d 21. An additional isolate associated with enterococcal spondylitis was included in Exp 2 (EC11B). Treatment groups for Exp 2 include: 1) NC, 2) EC2, 3) EC5, 4) EC7, and 5) EC11B (n = 90-120/embryos/group). Groups 2 to 5 were challenged at 1 × 10² CFU/200 µL/embryo by in-ovo injection into the amnion at DOE18. Chicks were placed in battery cages for the duration of the study (21 d), and pen weights were recorded at d 0, d 7, d 14, and d 21 to calculate average BW and BWG. At d 14 and d 21 posthatch, liver, spleen, free thoracic vertebrae (FTV), and femoral head (FH) were aseptically collected to enumerate Enterococcus spp. using Chromagar Orientation as the selective media. Cecal contents were collected at d 21 to evaluate the effect of EC challenge on the cecal microbiome composition. There was a significant (P < 0.05) reduction in BW at d 21, and BWG from d 14 to 21 and d 0 to 21, for EC7 and EC11B. Enterococcus cecorum was recovered from the FTV of all challenged groups at d 14 and d 21. The most representative lesions were pericarditis, hydropericardium, focal heart necrosis, and FH osteomyelitis. However, lesions were not uniform across challenged groups or ages (d 14 and d 21). Alpha diversity of the cecal contents was markedly lower in EC5 and EC11B compared to all treatment groups suggesting that EC exposure during late embryogenesis affect the cecal microbiome up to 21 d posthatch. Additionally, these results highlight the differences in pathogenicity of EC strains isolated from field cases and suggest that hatchery exposure to EC during late embryogenesis is a potential route of introduction into a flock.

Keywords: Enterococcus cecorum; bacterial infection; broiler; enterococci.