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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
14:04

Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

Published on: May 8, 2013

Vancomycin MICs for Staphylococcus aureus vary by detection method and have subtly increased in a pediatric

Edward O Mason1, Linda B Lamberth, Wendy A Hammerman

  • 1Section of Infectious Diseases, Department of Pediatrics, Baylor College of Medicine, and Infectious Disease Research Laboratory, Texas Children's Hospital, Houston, Texas 77030, USA. emason@bcm.edu

Journal of Clinical Microbiology
|May 1, 2009
PubMed

Insights

Vancomycin minimum inhibitory concentrations (MICs) for pediatric Staphylococcus aureus isolates show a slight increase since 2005. Therapeutic decisions require careful consideration of the testing methodology used for MIC determination.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Clinical Pharmacy

Background:

  • Staphylococcus aureus infections are common in pediatric settings.
  • Vancomycin is a critical antibiotic for treating resistant strains like methicillin-resistant S. aureus (MRSA).
  • Monitoring vancomycin MIC trends is essential for effective treatment strategies.

Purpose of the Study:

  • To investigate the trend of vancomycin minimum inhibitory concentrations (MICs) in pediatric Staphylococcus aureus isolates over a 7-year period.
  • To compare MICs determined by broth microdilution and Etest methods.
  • To assess the impact of infection source and duration of bacteremia on vancomycin MICs.

Main Methods:

  • Analysis of 165 Staphylococcus aureus isolates from pediatric patients over 7 years.
  • Comparison of vancomycin MICs using broth microdilution and Etest.
  • Categorization of isolates by resistance (MRSA/MSSA), acquisition (nosocomial, community-acquired, healthcare-associated), and bacteremia duration.

Main Results:

  • Broth microdilution showed most isolates had MICs < 1.0 µg/ml, while Etest indicated 96% had MICs ≥ 1 µg/ml.
  • Etest detected a significant increase in vancomycin MICs after study year 4 (2004-2005), but broth microdilution did not.
  • No significant difference in MICs was observed based on isolate origin or duration of bacteremia.

Conclusions:

  • Vancomycin MICs in pediatric S. aureus isolates have slightly increased since 2005.
  • Discrepancies between broth microdilution and Etest highlight the importance of methodology in interpreting MIC values.
  • Clinical decisions regarding vancomycin therapy must account for the specific MIC testing method employed.

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