Archaic strains of methicillin-resistant Staphylococcus aureus: molecular and microbiological properties of isolates from the 1960s in Denmark

Microb Drug Resist. Spring 2000;6(1):1-10. doi: 10.1089/mdr.2000.6.1.


Methicillin-resistant Staphylococcus aureus (MRSA) isolated in the 1960s in Denmark are among the historically earliest samples of these bacteria. We determined microbiological and molecular properties of 46 such isolates. They showed remarkably uniform properties, which included: (i) low methicillin MIC value (6-25 microg/ml); (ii) heterogeneous expression of resistance; (iii) the presence of a single, common, mecA polymorph II; (iv) lack of the regulatory gene mecI; (v) frequent lack of Tn554; and (vi) a common pulsed-field gel electrophoresis (PFGE) type. These properties, together with the chronological dates of isolation, and recovery of the strains from 18 hospitals scattered over Denmark, suggest that they represent a lineage close in time to the evolutionary origin of European strains of MRSA.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • DNA Transposable Elements
  • Denmark
  • Electrophoresis, Gel, Pulsed-Field
  • Genes, Bacterial*
  • Methicillin Resistance / genetics*
  • Microbial Sensitivity Tests
  • Polymorphism, Genetic
  • Species Specificity
  • Staphylococcus aureus / classification
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / genetics
  • Staphylococcus aureus / isolation & purification*


  • Anti-Bacterial Agents
  • DNA Transposable Elements