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A 1.5 Hour Procedure for Identification of Enterococcus Species Directly from Blood Cultures
Published on: February 10, 2011
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Disk diffusion-based method aids in the detection of vanM-positive Enterococcus faecium with low vancomycin minimum
Jue Wang1,2, Pei Li1,2, Lin Xin1,2
1Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.
Clinical and Experimental Pharmacology & Physiology
|March 20, 2023
Summary
A modified disk diffusion test identified vancomycin resistance in 10 Enterococcus faecium strains previously classified as sensitive. This method helps detect vanM-positive strains with low vancomycin minimum inhibitory concentrations, preventing misdiagnosis of vancomycin-resistant enterococci.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Clinical Diagnostics
Background:
- Vancomycin resistance in enterococci (VRE) is a significant healthcare concern.
- The vanM gene is a predominant cause of VRE in Shanghai, China.
- Standard diagnostic systems may misclassify certain vancomycin-sensitive strains.
Purpose of the Study:
- To evaluate a modified disk diffusion method for detecting vancomycin resistance in Enterococcus faecium.
- To identify vanM-positive Enterococcus faecium isolates with low vancomycin minimum inhibitory concentrations.
- To improve the detection of vancomycin sensitivity-variable enterococci.
Main Methods:
- Collection and VITEK 2 system susceptibility testing of 1292 Enterococcus faecium and Enterococcus faecalis isolates.
- Modified macromethod-based disk diffusion testing for vancomycin susceptibility.
- Pulse-field gel electrophoresis for clonal analysis.
- vanM gene detection using molecular methods.
Main Results:
- 1290 out of 1292 isolates were vancomycin-sensitive by VITEK 2.
- 10 Enterococcus faecium isolates showed growth within the vancomycin disk zone, indicating potential resistance.
- All 10 isolates were confirmed vanM-positive.
- Pulse-field gel electrophoresis confirmed isolates with zone growth were the same clone as the original strain.
Conclusions:
- A modified disk diffusion test can detect vanM-positive Enterococcus faecium with low vancomycin MICs that may be missed by automated systems.
- This method enhances the identification of vancomycin sensitivity-variable enterococci.
- Improved diagnostic approaches are crucial for managing antimicrobial resistance.
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