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.
Highlights
Vancomycin-resistant enterococci (VRE) are an important cause of healthcare-associated infections in Europe and USA, mainly attributed to the global dissemination of hospital-adapted lineages of vanA mediated vancomycin-resistant Enterococcus faecium (VREfm) (Hidron et al, 2008; Lebreton et al, 2013; Werner et al, 2008)
Growth of vanA vancomycin-resistant E. faecalis (VREfs) and VREfm was observed for all tested isolates as per manufacturers’ instructions. vanB VREfm grew well on chromID but showed poor growth on Brilliance, at 24 hours
E. raffinosus grew as colorless colonies on chromID but as purple colonies resembling VREfm on Brilliance
Summary
Vancomycin-resistant enterococci (VRE) are an important cause of healthcare-associated infections in Europe and USA, mainly attributed to the global dissemination of hospital-adapted lineages of vanA mediated vancomycin-resistant Enterococcus faecium (VREfm) (Hidron et al, 2008; Lebreton et al, 2013; Werner et al, 2008). Screening for fecal carriage of VRE has been advocated as part of a bundle of interventions used to control outbreaks in healthcare settings (Cookson et al, 2006; Siegel et al, 2006), and is routinely used in some units for active surveillance (Brown et al, 2006). Brilliance VRE (Oxoid) was not included in this evaluation and chromogenic media were not assessed under different culture conditions such as using pre-enrichment. No comparative studies have been conducted outside the hospital setting where optimising culture conditions to maximise yield would be important for the accurate determination of VRE stool carriage and epidemiology
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