Evaluation of the Xpert vanA/vanB Assay Using Enriched Inoculated Broths for Direct Detection of vanB Vancomycin-Resistant Enterococci

摘要

Rapid and accurate detection of VRE (vancomycin-resistant enterococci) is required for adequate antimicrobial treatment and infection prevention measures. Previous studies using PCR for the detection of VRE, including Cepheid's Xpert vanA/vanB assay, reported accurate detection of vanA VRE; however, many false-positive results were found for vanB VRE. This is mainly due to nonenterococcal vanB genes, which can be found in the gut flora. Our goal was to optimize the rapid and accurate detection of vanB VRE and to improve the positive predictive value (PPV) by limiting false-positive results. We evaluated the use of the Xpert vanA/vanB assay on rectal swabs and on enriched inoculated broths for the detection of vanB VRE. By adjusting the cycle threshold (C-T) cutoff value to 30 appeared to be true negative. In conclusion, this study shows that the Cepheid's Xpert vanA/vanB assay performed on enriched inoculated broths with an adjusted cutoff C-T value is a useful and rapid tool for the detection of vanB VRE.