Efficacy of Quinupristin-Dalfopristin against Methicillin-Resistant Staphylococcus aureus and Vancomycin-Insensitive S. aureus in a Model of Hematogenous Pulmonary Infection

Background: Quinupristin-dalfopristin (Q-D) is a mixture of quinupristin and dalfopristin, which are semisynthetic antibiotics of streptogramin groups B and A, respectively. Methods: We compared the effect of Q-D to that of vancomycin (VCM) in murine models of hematogenous pulmonary infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and VCM-insensitive S. aureus (VISA). Results: Treatment with Q-D resulted in a significant decrease in the number of viable bacteria in the lungs of mice in an MRSA infection model [Q-D 100 mg/kg, Q-D 10 mg/kg, VCM and control (mean ± SEM): 2.99 ± 0.44, 6.38 ± 0.32, 5.75 ± 0.43 and 8.40 ± 0.14 log10 CFU/lung, respectively]. Compared with VCM, high-dose Q-D significantly reduced the number of bacteria detected in the VISA hematogenous infection model [Q-D 100 mg/kg, Q-D 10 mg/kg, VCM and control (mean ± SEM): 5.17 ± 0.52, 7.03 ± 0.11, 7.10 ± 0.49 and 7.18 ± 0.36 log10 CFU/lung, respectively]. Histopathological examination confirmed the effect of Q-D. Conclusion: Our results suggest that Q-D is potent and effective in the treatment of MRSA and VISA hematogenous pulmonary infections.