Detection of vanA genes in vancomycin-susceptible Enterococcus faecium isolates: implications for additional testing

Area of Science:

• Microbiology
• Molecular Biology
• Clinical Diagnostics

Background:

• Enterococcus faecium is a common cause of hospital-acquired infections.
• Vancomycin resistance in Enterococcus faecium is a significant public health concern.
• Silent vancomycin resistance genes can lead to undetected resistance.

Purpose of the Study:

• To determine the prevalence of silent vancomycin resistance genes (vanA and vanB) in phenotypically susceptible Enterococcus faecium isolates.
• To evaluate the utility of genotypic testing for identifying silent resistance.
• To highlight the challenges faced by clinical laboratories in detecting such resistance.

Main Methods:

• Phenotypic susceptibility testing of Enterococcus faecium isolates.
• Genotypic testing using Cepheid's Xpert vanA/vanB PCR assay for vanA and vanB genes.
• Analysis of isolate data to identify silent resistance.

Main Results:

• 6% of phenotypically susceptible Enterococcus faecium isolates harbored silent vanA genes.
• The study identified the presence of vanA genes in isolates that did not exhibit vancomycin resistance phenotypically.
• No vanB genes were reported in the abstract.

Conclusions:

• Silent vancomycin resistance genes are present in a subset of Enterococcus faecium isolates.
• The clinical relevance of these silent genes requires further investigation.
• The lack of rapid, random-access genotypic methods presents a challenge for accurate and timely laboratory detection of vancomycin resistance.