title: Activity of linezolid and tedizolid against clinical isolates of methicillin-resistant and methicillin and linezolid resistant Staphylococcus aureus: an in vitro comparison.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.forename: M
authors.initials: M
authors.lastname: Peñuelas
authors.affiliation: Francisco Javier Candel, Servicio de Microbiología Clínica, Hospital Clínico San Carlos. Universidad Complutense Avda Dr Martín Lagos s/n 28040 Madrid, Spain. fj.candel@gmail.com.
authors.forename: F J
authors.initials: FJ
authors.lastname: Candel
authors.forename: C
authors.initials: C
authors.lastname: Lejarraga
authors.forename: L
authors.initials: L
authors.lastname: López-González
authors.forename: J M
authors.initials: JM
authors.lastname: Viñuela-Prieto
authors.forename: D
authors.initials: D
authors.lastname: López de Mendoza
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial; D000069349:Linezolid / Q000494:pharmacology*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology*; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics; D013777:Tetrazoles / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C539943:CFR protein, Staphylococcus aureus; D023303:Oxazolidinones; D013777:Tetrazoles; C546016:tedizolid; D000069349:Linezolid