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Clinical-use-associated decrease in susceptibility of vancomycin-resistant Enterococcus faecium to linezolid: a
Issam I Raad1, Hend A Hanna, Ray Y Hachem
1Department of Infectious Diseases, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA. iraad@mdanderson.org
Antimicrobial Agents and Chemotherapy
|August 26, 2004
Summary
Vancomycin-resistant Enterococcus faecium isolates showed high susceptibility to linezolid initially. After 6 months of clinical use, linezolid susceptibility decreased, linked to a specific gene mutation.
Area of Science:
- Antimicrobial resistance
- Molecular biology
- Infectious diseases
Background:
- Vancomycin-resistant Enterococcus faecium (VRE) poses a significant treatment challenge.
- Linezolid and quinupristin-dalfopristin are crucial agents for VRE infections.
Purpose of the Study:
- To assess the susceptibility of VRE isolates to linezolid and quinupristin-dalfopristin.
- To monitor changes in susceptibility following the introduction of these antibiotics into clinical practice.
Main Methods:
- Determination of antimicrobial susceptibility for 135 VRE bacteremic isolates.
- Phenotypic susceptibility testing before and after 6 months of clinical drug use.
- Genotypic analysis to identify potential resistance mechanisms, including mutations in the 23S rRNA gene.
Main Results:
- Initially, 100% of isolates were susceptible to linezolid and 88% to quinupristin-dalfopristin.
- After 6 months, linezolid susceptibility decreased to 83%.
- A G2576U mutation in the 23S rRNA gene was identified as a contributing factor to reduced linezolid susceptibility.
Conclusions:
- Linezolid remains highly effective against VRE, but a slight decrease in susceptibility was observed.
- Emergence of linezolid resistance in VRE is associated with specific ribosomal RNA gene mutations.
- Continued surveillance of antimicrobial susceptibility is essential for effective VRE treatment strategies.