Therapeutic efficacy of compound organic acids administration on methicillin-resistant Staphylococcus aureus-induced arthritis in broilers

Avian arthritis is a common disease in the poultry industry, and the etiology is complex. Bacterial arthritis is usually caused by Staphylococcus aureus (S. aureus) infection. This study explored the minimum inhibitory concentration (MIC) of different organic acids against S. aureus MRSA85 and found that vanillic acid, suberic acid, itaconic acid, salicylic acid, and other organic acids had significant inhibitory effects on this strain, especially cinnamic acid, which exhibited the best inhibitory effect. The Fractional Inhibitory Concentration Index (FICI) test further revealed the synergistic effect among some compound organic acids, which can significantly enhance the antibacterial efficiency against MRSA85 while reducing the risk of bacterial resistance. Under the low concentrations (1/2 or 1/4 MIC) conditions, the MIC of the compound organic acids against S. aureus remains unchanged, and it can even enhance the sensitivity of antibiotic-resistant S. aureus to Oxacillin. Furthermore, the compound organic acids could effectively promote the recovery of S. aureus-induced arthritis in broiler models, reduce inflammatory responses, and lower down bacterial loads and inflammatory cytokine levels in joints, which indicated that the effects of the Compound 2 is comparable to that of the trimethoprim-sulfamethoxazole group. These results support the potential and application value of organic acids and their compounds, including Compound 1 to 3, as novel antibacterial agents in the treatment of S. aureus infections.