Observations on Arthritis in Broiler Breeder Chickens Experimentally Infected with Staphylococcus aureus

Staphylococcus aureus is the most common cause of bacterial arthritis in broiler breeder chickens. In this study, we established a model of broiler breeder chicken arthritis inoculated with Staph. aureus isolated from a spontaneously occurring bacterial arthritis in chickens. We evaluated the model by bacteriology, serology, pathology, and immunology. The results showed that 2.5 × 10^9 cfu Staph. aureus injected into the right joint cavity can successfully induce a chicken arthritis model. The majority of the infected chickens suffered lameness and joint swelling at 3 days post-inoculation (DPI). The death peak time was on 7 DPI and the mortality rate was 51.1%. Staph. aureus can be continuously isolated from the blood and left joint synovial fluid of the infected chickens. Lesions found on the infected chickens consisted of swollen joints full of caseous exudates, cartilage injury, and synovial membrane thickening with infiltration of inflammatory cells. The center of the lesion contained many round bacterial cocci. With joint injury aggravation, intraarticular hyaluronic acid gradually decreased, and serum interleukin-6 became significantly higher compared with the control (P 0.01) from 3 DPI. The results indicated that the chicken models of Staph. aureus-mediated arthritis were successful, and can be used to gain a better understanding of the host-bacterium relationship.