Anomalies in species identification of enterococci from veterinary sources using a commercial biochemical identification system

Aims: A commercial biochemical panel ID kit was used to identify presumptive enterococci isolates of veterinary or agricultural origin obtained during different steps of culture. Methods and Results: Fifty isolates identified as enterococci using a genus PCR assay were tested for genus and species identification using the BBL Crystal Identification Gram-Positive ID kit (Becton Dickinson, Sparks, MD, USA). Following sub-culture of the isolates three times, 59% agreement with the original panel ID was obtained. After four and six sub-cultures, percentage agreement increased to 61 and 64%, respectively. Nineteen of the 50 cultures were identified as both Enterococcus faecalis and E. faecium . Conclusions: As a result of the variability between speciation of isolates following re-culture, additional methods for speciation are warranted. Significance and Impact of the Study: This study suggests that the identification of the genus and species of non-human enterococcal isolates can vary greatly during successive passages when using this kit.