Genetic and Genome Analyses of Bacteria Cultured from Lame Broilers with Osteomyelitis

Lameness is a significant problem resulting in millions of dollars in lost revenue annually. In commercial broilers, the most common cause of lameness is bacterial chondronecrosis with osteomyelitis (BCO). We are using a wire flooring model to induce lameness attributable to BCO. We used 16S ribosomal DNA sequencing to determine that Staphylococcus spp. were the main species associated with BCO. Staphylococcus agnetis, which previously had not been isolated from poultry, was the principal species isolated from the majority of the bone lesion samples. Staphylococcus spp. also were isolated from the blood of apparently healthy broilers. Administering S. agnetis in the drinking water to broilers reared on wire flooring increased the incidence of BCO three-fold when compared with broilers drinking tap water (P = 0.001), conclusively demonstrating bacterial translocation across the gut. We found that the minimum effective dose of Staphylococcus agnetis to induce BCO in broilers grown on wire flooring experiment is 10⁵ cfu/ml.

More severe lesions were found in the proximal femoral and tibial heads in the lame birds that received S. agnetis in the water compared to the control group. We sequenced and assembled a draft of the S. agnetis genome for further investigation of genetic diversity, toxins, and pathogenicity determinants, for this poorly characterized species. Isolating pathogenic bacterial species, defining their likely route of transmission to broilers, and genomic analyses will contribute substantially to the development of measures for mitigating BCO losses in poultry.