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The emergence of Staphylococcus aureus with reduced susceptibility to vancomycin in Japan

K Hiramatsu1

  • 1Department of Bacteriology, Juntendo University, Tokyo, Japan.

The American Journal of Medicine
|July 31, 1998
PubMed

Insights

Methicillin-resistant Staphylococcus aureus (MRSA) strains with reduced vancomycin susceptibility are emerging globally. Early detection and control measures are crucial to prevent the spread of these dangerous infections.

Area of Science:

  • Infectious Diseases
  • Microbiology
  • Antimicrobial Resistance

Background:

  • Emergence of methicillin-resistant Staphylococcus aureus (MRSA) strains with reduced vancomycin susceptibility reported in Japan and the US.
  • These strains pose a significant public health threat due to potential treatment challenges.
  • Identification of specific MRSA strains (Mu3 and Mu50) with reduced vancomycin susceptibility at Juntendo Hospital in 1996.

Purpose of the Study:

  • To initiate a screening program to identify MRSA strains exhibiting reduced susceptibility to vancomycin.
  • To assess the prevalence of vancomycin-resistant subpopulations within MRSA strains in Japan.
  • To understand the characteristics of vancomycin resistance in these MRSA isolates.

Main Methods:

  • Screening of 970 MRSA strains from 195 non-university hospitals in Japan.
  • Testing of 129 MRSA strains from 7 university hospitals in Japan.
  • Determination of vancomycin Minimum Inhibitory Concentration (MIC) and assessment for heterogeneous resistance.

Main Results:

  • 13 out of 970 (1.3%) MRSA strains from non-university hospitals showed subpopulations with reduced vancomycin susceptibility (heterogeneous resistance).
  • 12 out of 129 (9.3%) MRSA strains from university hospitals demonstrated heterogeneity for vancomycin resistance.
  • One strain from a university hospital had a vancomycin MIC of 7 microg/mL; resistance was not due to vanA or vanB genes.

Conclusions:

  • MRSA strains with heterogeneous vancomycin resistance are present in Japanese hospitals.
  • The clonal spread of MRSA with vancomycin-resistant subpopulations is a concern.
  • Recommendations include intensified vancomycin resistance testing and implementation of control measures to prevent spread.

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