Objective: The increasing resistance against methicillin and macrolide in Staphylococcus aureus strains is an important problem in many countries. Quinupristin/dalfopristin (Q/D) which is a ribosomal protein synthase inhibitor, is a member of streptogramin group of antibiotics effective against staphylococci and other gram positive bacteria. In this study, we aimed to investigate the MLSB phenotypes and in vitro activity of Q/D among methicillin-resistant (MRSA) and methicillin-sensitive S. aureus (MSSA) strains isolated from clinical samples of patients between May 2015 and April 2016 in Hacettepe University hospitals.

Material and Methods: A total of 151 S. aureus strains were included in the study. The isolates were identified by using conventional methods and VITEK MS (bioMérieux, France). The resistance of the isolates to methicillin, has been determined with sefoxitin (30 μg) disc diffusion MLSB resistance was investigated by D-test method using erythromycin (15 μg) and clindamycin (2 μg) disks. Susceptibilities of isolates to methicillin, erythromycin, clindamycin and Q/D were determined by D-test method using erythromycin (15 μg)and clindamycin (2 μg) disks.

Results: Of the 151 S. aureus isolates, 44 were MRSA and 107 were MSSA. Of the 48 MLS_B resistant S. aureus isolates, 50% (24/48) revealed inducible type, 14.6% (7/48) constitutive type and 35.4% (17/48) MS_B type MLS resistance. All S. aureus strains were found to be susceptible to Q/D.

Conclusion: The results of the present study demonstrated that Q/D exhibited in-vitro inhibitory activity against both MRSA and MSSA isolates with or without MLS_B resistance