title: [Characterization of methicillin- and linezolid-resistant Staphylococcus epidermidis and S. haemolyticus strains in a Spanish hospital].
abstract: BACKGROUND
  Linezolid resistance is mainly due to mutations in the 23S rRNA target. The aim of this study was to characterize linezolid and methicillin resistant Staphylococcus epidermidis (SE-LM(R)) and S. haemolyticus (SH-LM(R)) strains detected in a Spanish hospital.
  
  
  METHODS
  SE-LM(R) and SH-LM(R) strains obtained in the period June 2009-August 2011 in a second level hospital were recorded along with the epidemiological characteristics of the patients. These strains were typed, and their resistance, phenotype, genotype and the factors determining their virulence were analysed.
  
  
  RESULTS
  Linezolid resistance was explained by the presence of G2603T mutation (23S rRNA) and aminoacid changes in L3 and L4 ribosomal proteins. The 25 SE-LM(R) strains belonged to sequence type ST2, presented SCCmec typeIII, and two different PFGE patterns. The two SH-LM(R) strains showed non-typeable SCCmec. SE-LM(R) strains harboured the resistance genes aac(6')-aph(2"), and dfrS1. SH-LM(R) strains contained these genes and the gene erm(C). No lincomycin resistance mechanism was identified in SE-LM(R) strains regardless of showing lincomycin resistance and diminished susceptibility to clindamycin.
  
  
  CONCLUSIONS
  Linezolid resistance is of concern in hospitals, and requires continued vigilance. Several linezolid resistance mechanisms (mutation in 23S RNAr and amino acid changes in L3 and L4) were identified in this study.
authors.affiliation: Área Bioquímica y Biología Molecular, Universidad de La Rioja, Logroño, España.
authors.forename: Carmen
authors.initials: C
authors.lastname: Lozano
authors.forename: Carmen
authors.initials: C
authors.lastname: Aspiroz
authors.forename: Elena
authors.initials: E
authors.lastname: Gómez-Sanz
authors.forename: Gabriel
authors.initials: G
authors.lastname: Tirado
authors.forename: Blanca
authors.initials: B
authors.lastname: Fortuño
authors.forename: Myriam
authors.initials: M
authors.lastname: Zarazaga
authors.forename: Carmen
authors.initials: C
authors.lastname: Torres
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D000890:Anti-Infective Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D006761:Hospitals; D006801:Humans; D000069349:Linezolid; D008297:Male; D016106:Methicillin Resistance; D008875:Middle Aged; D023303:Oxazolidinones / Q000494:pharmacology*; D013030:Spain; D013212:Staphylococcus epidermidis / Q000187:drug effects*; D041162:Staphylococcus haemolyticus / Q000187:drug effects*
chemical_list: D000081:Acetamides; D000890:Anti-Infective Agents; D023303:Oxazolidinones; D000069349:Linezolid