What are enterococci?

Updated: Jun 10, 2021
  • Author: Susan L Fraser, MD; Chief Editor: John L Brusch, MD, FACP  more...
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Enterococci are part of the normal intestinal flora of humans and animals.The genus Enterococcus includes more than 17 species, although only a few cause clinical infections in humans. They are increasingly recognized as significant human pathogens and pose major therapeutic challenges, including the need for synergistic antibiotic combinations to successfully treat enterococcal infective endocarditis (IE).

Enterococcus species are facultative anaerobic organisms that can survive temperatures of 60°C for short periods and that grow in high salt concentrations. In the laboratory, enterococci are distinguished by their morphologic appearance on Gram stain and culture (gram-positive cocci that grow in chains) and their ability to (1) hydrolyze esculin in the presence of bile, (2) their growth in 6.5% sodium chloride, (3) their hydrolysis of pyrrolidonyl arylamidase and leucine aminopeptidase, and (4) their reaction with group D antiserum. Before they were assigned their own genus, they were classified as group D streptococci.

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