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Published on: May 8, 2013

Lack of increase in vancomycin resistance of pediatric methicillin-resistant Staphylococcus aureus Isolates from 2000

Xiaotian Zheng1, Chao Qi, Mollyn Arrieta

  • 1Department of Pathology and Laboratory Medicine, Children's Memorial Hospital, Chicago, IL, USA. x-zheng@northwestern.edu

The Pediatric Infectious Disease Journal
|May 11, 2010
PubMed

Insights

Methicillin-resistant Staphylococcus aureus (MRSA) vancomycin MICs in children did not increase. Inducible clindamycin resistance declined, but USA300 strain prevalence rose. Laboratory methods varied in vancomycin MIC results.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Clinical Laboratory Science

Background:

  • Pediatric methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health challenge.
  • Monitoring antimicrobial resistance trends, particularly to vancomycin, is crucial for effective treatment strategies.
  • Previous studies have indicated potential shifts in MRSA characteristics over time.

Purpose of the Study:

  • To investigate changes in vancomycin minimum inhibitory concentration (MIC) of pediatric MRSA isolates over an eight-year period.
  • To assess trends in inducible clindamycin resistance and the prevalence of the USA300 strain.
  • To compare the performance of different laboratory methodologies in determining vancomycin MICs.

Main Methods:

  • Retrospective analysis of 306 pediatric MRSA isolates collected between 2000 and 2007.
  • Determination of vancomycin MICs using Etest, agar dilution, and broth microdilution (MicroScan).
  • Evaluation of inducible clindamycin resistance and identification of MRSA strain types (e.g., USA300).

Main Results:

  • No significant increase in vancomycin MICs was observed over the study period.
  • A dramatic decline in inducible clindamycin resistance was noted, from 53% to 0% (P < 0.001).
  • Significant variations in the proportion of isolates with vancomycin MIC = 2 microg/mL were detected across different laboratory methods.
  • The prevalence of the USA300 MRSA strain increased substantially during this timeframe.

Conclusions:

  • Vancomycin susceptibility in pediatric MRSA isolates remained stable during 2000-2007.
  • The decline in inducible clindamycin resistance suggests a potential shift in resistance mechanisms or strain characteristics.
  • Discrepancies in vancomycin MIC results among laboratory methods highlight the need for careful interpretation and standardization.
  • The rise of the USA300 strain warrants continued surveillance due to its association with community-acquired infections.

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