Evaluation of in vitro activity of delafloxacin against Staphylococcus aureus MSSA and MRSA isolated from a Brazilian tertiary hospital

Abstract

Proper treatment for infections caused by Staphylococcus aureus, particularly methicillin-resistant strains (MRSA), remains a constant challenge in hospital settings. In this context, the search for new antimicrobials, such as delafloxacin, has become necessary. Delafloxacin is a novel quinolone with a broad spectrum of activity against both gram-positive and gram-negative bacteria, offering a new therapeutic option for the treatment of infections caused by multidrug-resistant bacteria. 117 S. aureus isolates were included in this study: 48 S. aureus methicillin-susceptible (MSSA) and 69 S. aureus methicillin-resistant (MRSA). Isolates were recovered from skin and soft tissue sites, respiratory tract, and blood cultures. Delafloxacin susceptibility was assessed using the gradient diffusion strip (Liofilchem®), and the results were interpreted according to the BrCAST guidelines. To assess the clonal profile of S. aureus, Fourier-transform infrared (FTIR) spectroscopy was employed using the IR Biotyper system. Susceptibility to delafloxacin varied from 97.8% to 54.7% for isolates from skin/soft tissue and from respiratory tract, respectively. Blood culture isolates exhibited a Minimum Inhibitory Concentration (MIC) ≤ 0.5 mg/L. FTIR analysis using the IR Biotyper indicated a diverse distribution among the isolates. Due to the high sensitivity rates found in this study, delafloxacin may be considered as a good therapeutic option for the treatment of S. aureus infections, including MRSA, particularly in skin and soft tissue infections. The IR Biotyper analysis revealed considerable clonal variation among the isolates, enhancing the robustness of the study.