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14:04
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Comparison of detection methods for heteroresistant vancomycin-intermediate Staphylococcus aureus, with the
Sarah W Satola1, Monica M Farley, Karen F Anderson
1Emory University School of Medicine, Atlanta, Georgia, USA. ssatola@emory.edu
Journal of Clinical Microbiology
|November 5, 2010
Summary
Detecting heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) is crucial for treatment success. A brain heart infusion (BHI) screen agar method demonstrated high sensitivity and specificity for identifying hVISA in MRSA blood isolates.
Area of Science:
- Clinical microbiology
- Infectious diseases
- Antimicrobial resistance
Background:
- Heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) is associated with vancomycin treatment failure.
- The standard population analysis profile (PAP) method for hVISA detection is time-consuming and labor-intensive.
Purpose of the Study:
- To evaluate alternative methods for detecting hVISA in methicillin-resistant Staphylococcus aureus (MRSA) blood isolates.
- To identify a sensitive, specific, and practical method for clinical hVISA detection.
Main Methods:
- Compared Etest macromethod, Etest glycopeptide resistance detection (GRD), and brain heart infusion (BHI) screen agar against the PAP-AUC reference method.
- Tested 140 MRSA blood isolates with vancomycin MICs of 2 μg/ml.
- Evaluated different inocula (0.5 and 2.0 McFarland) and incubation times (48 hours).
Main Results:
- BHI screen agar with a 0.5 McFarland inoculum showed the best performance: 90% sensitivity and 95% specificity.
- With a 2.0 McFarland inoculum, BHI screen agar achieved 100% sensitivity but lower specificity (68%).
- Etest methods demonstrated lower sensitivity (57%) but high specificity (96-97%).
Conclusions:
- BHI screen agar with 4 μg/ml vancomycin, casein, and a 0.5 McFarland inoculum offers a sensitive, specific, and easy-to-perform method for hVISA detection.
- This method may be valuable for routine clinical laboratories to guide vancomycin therapy.
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