Azithromycin in combination with riboflavin decreases the severity of Staphylococcus aureus infection induced septic arthritis by modulating the production of free radicals and endogenous cytokines.

Objective And Design: To determine alternate therapeutic measures to combat Staphylococcus aureus induced arthritis. Thus, azithromycin was combined with riboflavin, which may combat the ROS production and inflammation.

Methods: An in vivo model of S. aureus infection-induced arthritis was set up by infecting mice with 5 × 10⁶ bacterial cell/mouse. S. aureus was administered intravenously. Azithromycin and riboflavin was injected intraperitoneally at a single dose of 100 and 20 mg/kg body, respectively. The mice were sacrificed at 3, 9, 15 days post infection (dpi). TNF-α, IFN-γ, IL-6 and IL-10 from serum and SOD, catalase and reduced glutathione concentration were observed in hepatic, cardiac, renal and splenic tissue.

Results: CFU was found very prominent in spleen and joints and reduced in blood at 3 and 9 dpi. However, treatment with azithromycin and riboflavin completely eradicated the bacteria from blood and spleen. TNF-α, IFN-γ, IL-6, and MCP-1 were induced due to infection which were downregulated by treatment with azithromycin and riboflavin. Infected mice were also found to have altered antioxidant status, measured in terms of reduced glutathione and anti-oxidant enzymes such as SOD and catalase.

Conclusion: These changes were found to be ameliorated when the animals were co-treated with azithromycin and riboflavin.