Diagnostic accuracy of the Cepheid GeneXpert vanA/vanB assay ver. 1.0 to detect the vanA and vanB vancomycin resistance genes in Enterococcus from perianal specimens.

Rapid detection of vancomycin-resistant enterococci (VRE) carriers could be useful to health care facilities to minimize transmission. To that end, we compared the performance of the Cepheid GeneXpert vanA/vanB assay with that of direct and broth-enriched culture methods for detection of VRE from perianal swabs. Enterococci were cultivated on Enterococcosel™ agar with 8 μg/mL vancomycin, Bile Esculin Azide Agar with 6 μg/mL vancomycin, and Bile Esculin Azide Enterococcosel Broth. Compared to the reference standard (combination of direct agar plating, broth-enriched culture, and clinical chart review), the sensitivity, specificity, positive predictive value, and negative predictive value of the vanA/vanB assay were 96.4%, 93.0%, 92.0%, and 96.9%, respectively (n=184). The 95% limit of detection was 100 colony-forming units (CFU)/mL for vanA and 114 CFU/mL for vanB. In summary, the GeneXpert vanA/vanB assay is a rapid and accurate method to identify vanA/vanB-colonized patients for VRE screening programs that use perianal swab specimens.