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Updated: Jun 3, 2026
14:04
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Predicting high vancomycin minimum inhibitory concentration in methicillin-resistant Staphylococcus aureus
Andrew S Lubin1, David R Snydman, Robin Ruthazer
1Division of Geographic Medicine and Infectious Diseases, Department of Medicine, Tufts Medical Center, Boston, Massachusetts 02111, USA.
Summary
A clinical rule can predict high vancomycin minimum inhibitory concentration (MIC) in patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. This tool aids clinicians in identifying patients likely to have MRSA isolates with elevated vancomycin MIC.
Area of Science:
- Infectious Diseases
- Clinical Microbiology
- Pharmacology
Background:
- Elevated vancomycin minimum inhibitory concentration (MIC) in methicillin-resistant Staphylococcus aureus (MRSA) bacteremia correlates with increased mortality and treatment failure.
- Standard automated susceptibility testing may fail to accurately identify MRSA isolates with high vancomycin MIC (> 1 μg/mL).
- Accurate and timely identification of MRSA with high vancomycin MIC is crucial for effective patient management.
Purpose of the Study:
- To develop and validate a simple clinical prediction rule for identifying MRSA bacteremia with a vancomycin MIC of 2 μg/mL.
- To improve the early detection of MRSA isolates that may be less susceptible to vancomycin therapy.
Main Methods:
- A prospective cohort study was conducted at a tertiary care hospital and an acute rehabilitation facility.
- Consecutive patients with MRSA bacteremia (2001-2007) were analyzed for associations between patient characteristics and high vancomycin MIC.
- A multivariable logistic regression model was used to create a predictive rule based on identified risk factors.
Main Results:
- Of 296 MRSA bacteremic episodes, 19% exhibited isolates with a vancomycin MIC of 2 μg/mL.
- Predictive factors for high vancomycin MIC included older age, prior vancomycin or daptomycin exposure, central venous catheter, prosthetic heart valve, prior MRSA bacteremia, sepsis, and shock.
- A predictive rule incorporating age > 50, prior vancomycin, history of MRSA bacteremia, chronic liver disease, and central venous catheter achieved 75% sensitivity and 59% specificity.
Conclusions:
- Several clinical factors reliably predict the likelihood of MRSA isolates having a high vancomycin MIC.
- A straightforward predictive tool has been developed to assist clinicians in identifying patients at risk for MRSA with elevated vancomycin MIC.
- This tool can guide vancomycin dosing and selection of alternative antimicrobial agents for patients with MRSA bacteremia.
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