Enterococcus faecium ID from Current Topics in Clinical Microbiology, presented by MediaLab

Recurrent urinary tract infection: Laboratory Identification

Enterococcus faecium ID

As a high percentage of Enterococcus faecium strains carry the Van A gene and are highly resistant to vancomycin. Species identifications are performed in some laboratories where MIC susceptibility testing may not be available.
Methods for the phenotypic separation of E. faecium from E. faecalis are limited.
Illustrated in this photograph are positive reactions for acid production from arabinose and melibiose (yellow color), characteristic of E. faecium. E. faecalis are negative for these reactions.
A few preformed substrates such as beta galactosidase (E. faecium positive, E. faecalis negative) also serve to separate these two species, accomplished by certain commercial systems that include these substrates.
E. faecium is not motile, an additional characteristic helpful to separate vancomycin-resistant Enterococcus species from E. cassiloflavus and E. gallinarum, both of which are motile, and carry the low level resistant gene VAN-c.

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