Detection and characterisation of SCCmec remnants in multiresistant methicillin-susceptible Staphylococcus aureus causing a clonal outbreak in a Swedish county

Eur J Clin Microbiol Infect Dis. 2012 Feb;31(2):141-7. doi: 10.1007/s10096-011-1286-y. Epub 2011 May 18.


The purpose of this study was to investigate if multiresistant methicillin-susceptible Staphylococcus aureus (MR-MSSA) causing a clonal outbreak in Östergötland County, Sweden, were derived from methicillin-resistant S. aureus (MRSA) by carrying remnants of SCCmec, and, if so, to characterise this element. A total of 54 MSSA isolates with concomitant resistance to erythromycin, clindamycin and tobramycin from 49 patients (91% clonally related, spa type t002) were investigated with the BD GeneOhm MRSA assay and real-time polymerase chain reaction (PCR) targeting the SCCmec integration site/SCCmec right extremity junction. DNA sequencing of one isolate representing the MR-MSSA outbreak clone was performed by massive parallel 454 pyrosequencing. All isolates that were part of the clonal outbreak carried SCCmec remnants. The DNA sequencing revealed the carriage of a pseudo-SCC element 12 kb in size, with a genomic organisation identical to an SCCmec type ΙΙ element, except for a 41-kb gap. This study demonstrates the presence of a pseudo-SCC element resembling SCCmec type II among MR-MSSA, suggesting possible derivation from MRSA. The presence of SCCmec remnants should always be considered when SCCmec typing is used for MRSA detection, and may not be suitable in locations with a high prevalence of MR-MSSA, since this might give a high number of false-positive results.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Typing Techniques
  • DNA Transposable Elements / genetics
  • Disease Outbreaks
  • Drug Resistance, Multiple, Bacterial*
  • Humans
  • Methicillin / pharmacology*
  • Methicillin Resistance / genetics*
  • Methicillin-Resistant Staphylococcus aureus / genetics
  • Microbial Sensitivity Tests
  • Polymerase Chain Reaction
  • Sequence Analysis, DNA
  • Staphylococcal Infections / epidemiology*
  • Staphylococcal Infections / microbiology
  • Staphylococcus aureus / classification
  • Staphylococcus aureus / drug effects*
  • Staphylococcus aureus / genetics
  • Sweden / epidemiology


  • Anti-Bacterial Agents
  • DNA Transposable Elements
  • Methicillin