Rev Esp Quimioter 2016, 29(5):255-258

Activity of linezolid and tedizolid against clinical isolates of methicillin-resistant and methicillin and linezolid resistant Staphylococcus aureus: an in vitro comparison                     

MARINA PEÑUELAS, FRANCISCO JAVIER CANDEL, CLARA LEJARRAGA,  LAURA LÓPEZ-GONZÁLEZ, JOSE MANUEL VIÑUELA-PRIETO, DIEGO LÓPEZ DE MENDOZA          

Introduction. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in Spain is approximately 20-30%. However, resistance to linezolid is rare, and the main reports are from nosocomial outbreaks. The objective of the present study was to compare the in vitro susceptibility of linezolid with that of tedizolid against MRSA isolates and methicillin-and linezolid-resistant isolates (MLRSA) mediated by the cfr gene.
Material and methods. The in vitro susceptibility of linezolid and tedizolid was determined using the E-test with 18 MRSA strains and 18 cfr-mediated MLRSA strains obtained from clinical isolates in the microbiology service of a tertiary university hospital.
Results. All MRSA strains were susceptible to both antibiotics. Analysis of the MRSA isolates revealed that the MIC₅₀ and MIC₉₀ of linezolid were 1.5 and 2 mg/L, respectively; those of tedizolid were 0.25 and 0.4 mg/L. The MIC₅₀ and MIC₉₀ of tedizolid remained at 0.75 and 1 mg/L against the MLRSA strains (MIC₉₀ ≥ 8 mg/L).
Conclusions. Both for MRSA and for MLRSA, the MICs obtained for tedizolid were at least 2 dilutions lower than those of linezolid, thus demonstrating between 2 and 4 times greater activity in vitro than linezolid.

Rev Esp Quimioter 2016; 29(5):255-258 [pdf]