Enterococcus Identification

This version of the course is no longer available.
Need multiple seats for your university or lab? Get a quote
The page below is a sample from the LabCE course Case Studies in Clinical Microbiology. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Case Studies in Clinical Microbiology (online CE course)
Enterococcus Identification

The top image shows the Gram stain of Enterococcus species, demonstrating gram-positive cocci (GPC) arranged in pairs and short chains. The viridans streptococci generally form GPC in long chains; the gram-positive cells of S. pneumoniae, on the other hand, may appear similar in Gram stain.
In the lower image (on the right side of the frame) is shown a 6.5% NaCl tube. The turbidity indicates growth, a unique characteristic for Enterococcus species. Also shown in the lower image (in the left frame) is a bile esculin hydrolysis slant, showing a positive reaction (black pigment) characteristic of Enterococcus species. The streptococci are uniformly negative. Some strains of Leuconostoc species and Pediococcus species can grow in 6.5% NaCl and are bile-esculin positive; however, they should be ruled out because of the negative PYR reaction.