Tedizolid versus linezolid activity against Staphylococcus aureus clinical isolates

Background: In recent years, emergence of linezolid-resistant strains has gained a considerable clinical concern. Tedizolid, a relatively new antibiotic, showed strong effectiveness against S. aureus; however, few data are available from Egypt in this regard. Objectives: This study aimed to assess the in vitro susceptibility of S. aureus clinical isolates from Mansoura University Hospitals (MUHs), Egypt to linezolid and tedizolid, and to unveil the underlying molecular mechanisms for resistance. Methodology: In vitro susceptibility of 113 S. aureus isolates from various clinical samples was determined by disc diffusion method. The broth microdilution method was used to determine the MICs of linezolid and tedizolid. Detection of mecA and cfr genes among MRSA and linezolid-resistant isolates, respectively was performed using polymerase chain reaction (PCR). Results: In this study, 16.8% of S. aureus isolates were methicillin-resistant. On the other hand, resistance to vancomycin and linezolid was identified in 15%, and 9.7 % of the isolates, respectively. All the isolates were susceptible to tedizolid. In comparison between methicillin-sensitive S. aureus (MSSA) and MRSA as regards tedizolid and linezolid susceptibility, tedizolid retained low MIC 50 , and MIC 90 (0.25, and 0.5 µg/L) for all S. aureus isolates. On the other hand, the MICs of linezolid were 0.5–2 µg/L for MSSA, and 0.5–>4 µg/L for MRSA isolates. All MRSA isolates (n= 19) were found to harbor the mecA gene. The cfr gene was identified in 57.9% of linezolid-resistant MRSA isolates. Conclusion: Tedizolid is highly effective against S. aureus clinical isolates, including linezolid-resistant strains.