Detection of New Mutations Conferring Resistance to Linezolid in Glycopeptide-Intermediate Susceptibility Staphylococcus Hominis Subspecies Hominis Circulating in an Intensive Care Unit

Eur J Clin Microbiol Infect Dis. 2010 Jan;29(1):73-80. doi: 10.1007/s10096-009-0823-4. Epub 2009 Oct 30.

Abstract

Glycopeptides and linezolid are the most widely used antibiotics to treat infections by methicillin-resistant Staphylococcus spp. We report the presence of various isolates of methicillin-resistant S. hominis subsp. hominis with resistance to linezolid and reduced susceptibility to glycopeptides. We studied ten blood culture isolates of S. hominis subsp. hominis from nine patients admitted to our hospital. Etest was used to study susceptibility to antibiotics commonly prescribed against staphylococci. Domain V region of the 23S rRNA gene was amplified and sequenced to detect possible mutations that confer resistance to linezolid. Pulsed-field gel electrophoresis (PFGE) was used for the clonality study of isolates. All isolates were resistant to oxacillin, gentamicin, levofloxacin, cotrimoxazole, and linezolid, and susceptible to tigecycline and daptomycin. Nine of the isolates were resistant to erythromycin and clindamycin, and showed heterogeneous resistance to glycopeptides. C2190T, G2603T, and G2474T mutations were detected in domain V of the 23S rRNA gene. PFGE showed the presence of two different clones. This report alerts to the possible appearance of clinical strains of methicillin-resistant staphylococci with intermediate resistance to glycopeptides, resistance to linezolid, and multiple resistance to other second-line antibiotics.

MeSH terms

  • Acetamides / pharmacology*
  • Anti-Bacterial Agents / pharmacology*
  • Bacteremia / microbiology
  • Bacterial Typing Techniques
  • Blood / microbiology
  • Cross Infection / microbiology
  • DNA Mutational Analysis
  • Drug Resistance, Bacterial*
  • Electrophoresis, Gel, Pulsed-Field
  • Genotype
  • Glycopeptides / pharmacology*
  • Humans
  • Intensive Care Units
  • Linezolid
  • Microbial Sensitivity Tests
  • Mutation, Missense*
  • Oxazolidinones / pharmacology*
  • RNA, Bacterial / genetics
  • RNA, Ribosomal, 23S / genetics
  • Sequence Analysis, DNA
  • Staphylococcal Infections / microbiology
  • Staphylococcus hominis / classification
  • Staphylococcus hominis / drug effects*
  • Staphylococcus hominis / genetics*
  • Staphylococcus hominis / isolation & purification

Substances

  • Acetamides
  • Anti-Bacterial Agents
  • Glycopeptides
  • Oxazolidinones
  • RNA, Bacterial
  • RNA, Ribosomal, 23S
  • Linezolid