Affiliation:
1. Department of Pathology and Immunology, Washington University School of Medicine
2. Barnes-Jewish Hospital, St. Louis, Missouri
3. Microbiology Research and Development, bioMérieux, La-Balme-les-Grottes, France
Abstract
ABSTRACT
The development of reliable and rapid methods for the identification of patients colonized with vancomycin-resistant enterococci (VRE) is central to the containment of this agent within a hospital environment. To this end, we evaluated a prototype chromogenic agar medium (VRE-BMX; bioMérieux, Marcy l'Etoile, France) used to recover VRE from clinical specimens. This medium can also identify isolated colonies as either vancomycin-resistant
Enterococcus faecium
or
Enterococcus faecalis
, based on distinct colony colors. We compared the performance of VRE-BMX with bile esculin azide agar supplemented with vancomycin (BEAV). For this study, 147 stool samples were plated on each test medium and examined after 24 and 48 h of incubation. At 24 h, the sensitivity and specificity of each medium were as follows: BEAV, 90.9% and 89.9%, respectively; VRE-BMX, 96.4% and 96.6%, respectively. The positive predictive values (PPV) of VRE-BMX and BEAV at 24 h were 89.8% and 80.7%, respectively. VRE-BMX provided the identification of 10 isolates of vancomycin-resistant
E. faecalis
and 4 isolates of vancomycin-resistant
E. faecium
that were not recovered by BEAV. Further, VRE-BMX was capable of identifying patients colonized with both
E. faecium
and
E. faecalis
, a feature useful for infection control purposes that is not a function of BEAV. In terms of the recovery of vancomycin-resistant
E. faecium
and
E. faecalis
, the sensitivity and PPV were as follows: BEAV, 75.7% and 74.6%, respectively; VRE-BMX, 95.5% and 91.3%, respectively. In this initial evaluation, we found that VRE-BMX provided improved recovery of VRE from stool specimens, with the added advantage of being able to differentiate between vancomycin-resistant
E. faecalis
and
E. faecium
. Extending the incubation period beyond 24 h did not significantly improve the recovery of VRE and resulted in decreased specificity.
Publisher
American Society for Microbiology
Cited by
28 articles.
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