title: [Linezolid resistant coagulase-negative Staphylococcus: phenotypical and genotypical characteristics and sensitivity to antibiotic combinations].
abstract: OBJECTIVE
  We recovered 22 coagulase-negative staphylococci isolates in our hospital to study their identity, susceptibility, epidemiological profile, linezolid resistance mechanisms, and the possibilities of different antibiotic combinations.
  
  
  METHODS
  Isolate identification was performed using mass spectrometry (Vitek-MS, bioMérieux). Susceptibility testing was carried out with the Vitek-2 system and the broth microdilution method according to CLSI guidelines. Pulsed-field gel electrophoresis (PFGE) was performed to analyze the genetic relationship between isolates. Linezolid resistance mechanisms were evaluated by PCR/sequencing: presence of cfr gene, point mutations in domain V of 23S ribosomal RNA and additional ribosomal mutations (in the rplC, rplD and rplV genes). The in vitro activity of linezolid was investigated alone and in combination with another three antibiotics acting on different cellular targets, using E-test strips.
  
  
  RESULTS
  Twenty isolates were identified as Staphylococcus epidermidis, and 2 as Staphylococcus hominis. PFGE showed that isolates belonged to diverse clones, 21 of them presented mutations in the domain V region of 23S rRNA and the cfr gene was found in 54.5%. Prior administration of linezolid was documented in most of cases. Linezolid in combination with gentamicin showed a synergistic activity in 45.5% of isolates.
  
  
  CONCLUSIONS
  Staphylococcus epidermidis was the most prevalent linezolid-resistant coagulase-negative staphylococci. All isolates showed increased MIC values compared to other anti-staphylococcal drugs and several linezolid resistance mechanisms. Our data suggest that linezolid plus gentamicin could be a synergistic combination against linezolid-resistant coagulase-negative staphylococci.
authors.affiliation: Servicio de Microbiología, Hospital Universitario de Móstoles, Madrid, España. flopezf@salud.madrid.org
authors.forename: Fátima
authors.initials: F
authors.lastname: López-Fabal
authors.forename: Federico
authors.initials: F
authors.lastname: Román Alonso
authors.forename: María
authors.initials: M
authors.lastname: Almagro Moltó
authors.forename: Nuria
authors.initials: N
authors.lastname: Sanz Rodríguez
authors.forename: José Luis
authors.initials: JL
authors.lastname: Gómez-Garcés
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology*; D003030:Coagulase; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005838:Genotype; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology*; D010641:Phenotype; D013210:Staphylococcus / Q000187:drug effects* / Q000235:genetics*
chemical_list: D000081:Acetamides; D000890:Anti-Infective Agents; D003030:Coagulase; D023303:Oxazolidinones; D000069349:Linezolid