Addition of corticosteroids to antibiotic treatment ameliorates the course of experimental Staphylococcus aureus arthritis

Objective. To evaluate the combined effect of systemic corticosteroid and antibiotic therapy on the course of septic arthritis. Methods. The murine model of hematogenously acquired Staphylococcus aureus arthritis was used. Mice were treated with corticosteroids and antibiotics, and were followed up individually. Arthritis was evaluated clinically and histopathologically. Serum samples and bacterial isolates were also analyzed. Results. The prevalence of arthritis 14 days after the onset of the disease was 22% in the corticosteroid and antibiotic-treated group, as compared with 81% in the control (nontreated) group and 48% in the antibiotic-treated group. The severity of arthritis also decreased in the corticosteroid and antibiotic-treated group, as did the mortality rate. Immunohistochemical analysis revealed a dramatic decrease in T cells and macrophages in the synovium of mice that took the combined therapy. The mechanisms leading to this outcome include the inhibitory effect of corticosteroids on T cell and B cell proliferation and differentiation, such as suppression of interferon-gamma (IFN gamma) production. Serum levels of IFN gamma were decreased 4-fold in the antibiotic-treated group compared with the controls; a 15-fold decrease was observed in the corticosteroid and antibiotic-treated animals. In addition, serum NO3- was significantly decreased in mice treated with antibiotics (P less than or equal to 0.05), as well as in mice treated with corticosteroids and antibiotics (P less than or equal to 0.001). Conclusion. Systemic corticosteroid administration along with antibiotic therapy had beneficial effects on the course and outcome of S aureus arthritis.