Comparison of two chromogenic media for the detection of vancomycin-resistant enterococcal carriage by nursing home residents

Abstract

We compared ChromID VRE and Brilliance VRE media for the detection of vancomycin-resistant enterococci (VRE). Using a panel of 28 enterococcal isolates, 10 vanA Enterococcus faecium and three vanA Enterococcus faecalis isolates grew as per manufacturers’ instructions whilst growth of two vanC and eight vancomycin-susceptible enterococci was inhibited on both media. Important differences were noted in the selectivity and chromogenic properties of the two media for vanA Enterococcus raffinosus and vanB E. faecium. The two media were further evaluated using 295 stool samples from nursing home residents, 34 of which grew VRE (11.5%). ChromID and Brilliance had comparable sensitivity, which was increased markedly by prolonging incubation to 48 hours (from 29% to 82%, and from 41% to 85%, respectively) and by a pre-enrichment step (to 97% and 100%, respectively). Brilliance VRE agar had higher selectivity at 48 hours, and after pre-enrichment.

Evaluation of a selective chromogenic medium for detecting vancomycin-resistant enterococci

“…Regarding sensitivity, similar results have been obtained in previous studies evaluating the performance of chromID™ VRE. 1 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 In relation to the specificity, previous studies have obtained values higher than 95%, 1 , 7 , 8 , 11 in contrast to the low specificity observed in this study.…”

Defining the Role of the Environment in the Emergence and Persistence of vanA Vancomycin-Resistant Enterococcus (VRE) in an Intensive Care Unit: A Molecular Epidemiological Study

“…Although they are less sensitive, culture-based methods may more closely reflect a patient’s ability to transmit VRE, as positive cultures correlate with higher density of stool and in turn with skin colonization 28 . It is expected that ICU patients would have a high load of VRE carriage, 29 and cultures were incubated for 48 hours, which increases the sensitivity of VRE detection 30 . It is therefore likely that most VRE carriers in the ICU were identified.…”

Consideration of within-patient diversity highlights transmission pathways and antimicrobial resistance gene variability in vancomycin resistantEnterococcus faecium

“…Also, we relied on direct plating to solid VREfm screening agar for inclusion in our study. Previous studies have shown a sensitivity of 58-96% for this approach, rising to 97-100% with a pre-enrichment step (45–47). In our study, P49 carried ST1424, ST80, and ST789 on their first positive screen having been negative for VREfm 11 days previously, suggesting either infection with a mixed population from another host not detected by our sampling strategy or an initial false negative VREfm screen.…”