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Nasal carriage of methicillin resistant staphylococci

Nuno A Faria1, Teresa Conceição, Maria Miragaia

  • 11 Laboratorie of Molecular Genetics, Instituto de Tecnologia Química e Biológica (ITQB) , Oeiras, Portugal .

Microbial Drug Resistance (Larchmont, N.Y.)
|February 26, 2014
PubMed

Insights

Coagulase-negative staphylococci (CoNS) may transfer staphylococcal chromosome cassette mec (SCCmec) to Staphylococcus aureus. This study found common nasal colonization by S. epidermidis and S. aureus, with SCCmec type IV prevalent, but no direct evidence of SCCmec transfer.

Area of Science:

  • Microbiology
  • Genetics
  • Epidemiology

Background:

  • Coagulase-negative staphylococci (CoNS) are potential reservoirs for staphylococcal chromosome cassette mec (SCCmec) elements.
  • The frequency, partners, and factors influencing SCCmec transfer from CoNS to Staphylococcus aureus remain largely unknown.
  • The nasal mucosa is a likely site for such in vivo genetic exchange, hosting both CoNS and S. aureus.

Purpose of the Study:

  • To characterize Staphylococcus aureus and CoNS strains colonizing the anterior nares of patients.
  • To investigate the prevalence of methicillin resistance and SCCmec types within these nasal staphylococcal populations.
  • To explore potential interspecific genetic transfer events, particularly SCCmec acquisition by S. aureus.

Main Methods:

  • Collection of nasal swabs from 67 patients in Denmark.
  • Identification of staphylococcal species using internal transcribed spacer PCR (ITS-PCR) and 16S rRNA sequencing.
  • Characterization of methicillin resistance, S. aureus genetic background (spa typing), CoNS genetic background (pulsed-field gel electrophoresis), and SCCmec typing.

Main Results:

  • Staphylococcal colonization was high (80%), with S. epidermidis (58%) and S. aureus (39%) being most prevalent.
  • Methicillin resistance was common across multiple species, including S. aureus (53%) and S. epidermidis (53%).
  • SCCmec type IV (2B) was the most frequent type (65%), but strains from patients carrying multiple species, including S. aureus and S. epidermidis, harbored different SCCmec types.

Conclusions:

  • Nasal carriage of diverse staphylococcal species, including methicillin-resistant strains, is common.
  • While CoNS and S. aureus frequently co-colonize the nares, this study did not find direct evidence of SCCmec transfer between them.
  • Further research in similar settings is needed to elucidate interspecific genetic events involving SCCmec acquisition by S. aureus.

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