The decline of methicillin resistance among Danish Staphylococcus aureus strains

Infect Control Hosp Epidemiol. 1991 Feb;12(2):83-8. doi: 10.1086/646291.


Objective: To describe the occurrence and decline of methicillin-resistant Staphylococcus aureus in Denmark from 1966 to 1986, and to illustrate why it has been possible to retain a frequency of only 0.2% MRSA since 1984.

Design: A study of antibiotic susceptibility and phage-type of 522,978 S aureus strains isolated from hospitalized patients in Denmark during the years 1960 to 1988 combined with clinical information on patients with methicillin-resistant strains during the years 1986 through 1988.

Setting: All strains and information were collected at the centralized, national laboratory for S aureus phage-typing.

Patients: Hospitalized patients with S aureus isolates, and especially patients with methicillin-resistant strains.

Intervention: Antibiotic treatment.

Results: The frequency of MRSA rose to 15% in the years 1967 through 1971 but decreased to 0.2% in 1984, and has remained so ever since. The increase was due mainly to the spread of a single or a few clones of the phage-type complex 83A. Occurrence of strains of these phage-types declined from 18% in 1969 to 0.6% in 1989. In 1986 through 1988, at least 48% of the MRSA strains were imported by patients from abroad. Cross-infection occurred only in two cases. High awareness and special precautions were taken when MRSA was detected.

Conclusions: MRSA of a single or a few clones spread in Danish hospitals in the years 1967 through 1971. Since 1984, only 0.2% of the Danish S aureus population has been MRSA, and imported MRSA strains have been prevented from spreading.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Bacteriophage Typing
  • Child
  • Child, Preschool
  • Cross Infection / microbiology
  • Cross Infection / transmission
  • Denmark
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Methicillin Resistance*
  • Middle Aged
  • Species Specificity
  • Staphylococcus aureus / classification*