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July 14, 1975

Identification of Enterococci

Author Affiliations

Georgetown University Hospital Washington, DC

JAMA. 1975;233(2):136. doi:10.1001/jama.1975.03260020022006

To the Editor.—  The multiplicity of media available for identification of enterococcus and the inadequacy of any one of them alone to provide positive identification of the organism is a very practical problem for the average clinical laboratory. As Dr. Demko indicates, increasing the bile concen tration of the medium increases accuracy, but even the 40% concentration Bile Esculin Agar (Difco) will occasionally support the growth of viridans streptococci, falsely identifying the organism as enterococcus.1The important point is that whichever selective medium is used for screening purposes, confirmation of the identity of enterococcus should depend on further tests, preferably growth in 6.5% sodium chloride broth. In addition, an early clue to correct identification may be found from the sensitivity plates, since enterococci are almost invariably resistant to lincomycin and both Streptococcus viridans and nonenterococcal group D organisms are usually sensitive. To summarize, no single test can be used