IN VITRO EFFECTIVENESS OF CEFTOBIPROLE ALONE AND IN COMBINATION AGAINST METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS ISOLATED FROM CLINICAL SPECIMENS

<strong>Objective:</strong> Methicillin-resistant <em>Staphylococcus aureus</em> (MRSA) in fections cause reduced treatment options, longer hospital stays, increased healthcare costs and pose a global threat to public health. Decreased susceptibility to vancomycin (VAN) and the emergence of daptomycin (DAP) resistance in MRSA isolates have necessitated new treatment options. The in vitro activity of ceftobprole (BPR) alone and in combination against 100 MRSA isolates was investigated in this study. <strong>Material and Methods: </strong>The susceptibility tests for routinely used antibiotics were performed using the disk diffusion method. The minimum inhibitory concentration (MIC) values for BPR, DAP, and VAN were determined by the broth microdilution method. The presence of heteroresistant-VAN-intermediate <em>S. aureus</em> (hVISA) was investigated using the macrogradient test method. The effec tiveness of the BPR-DAP and BPR-VAN combinations in BPR-resis tant isolates was investigated using the checkerboard method. <strong>Results:</strong> The categorical agreement between the disk diffusion and broth microdilution methods used to determine the BPR sensi tivity was 100%. Four isolates were found to be resistant to BPR (4%; MIC: &gt;2 µg/ml) and another four isolates were found to be resistant to DAP (4.12%; MIC: &gt;1 µg/ml) by the broth microdilution method. The presence of VAN-resistant <em>S. aureus</em> (VRSA), VAN in termediate <em>S. aureus</em> (VISA), and hVISA was not detected. BPR-DAP and BPR-VAN combinations in BPR-resistant isolates exhibited an indifference effect. <strong>Conclusion: </strong>Although the resistance rate to BPR was relatively low, the MIC₉₀ value for BPR was 2 mg/L, raising concerns that resis tance to BPR would increase over time. Future studies on different antibiotic combinations can treat serious infections caused by BPR-resistant isolates.