Definition of Enterococcus
Members of the genus Enterococcus are gram positive cocci that occur in single or arranged in pairs or short chains. Cells may appear coccobacillary when gram stains are prepared from growth on solid media. Cells tend to be ovoid and in chains when gram stains are prepared form growth in thioglycolate broth. They are facultative anaerobes that grow at temperatures ranging from 10 to 45oC, with optimum growth at 35oC. They grow in media containing 6.5% NaCl and hydrolyze esculin in presence of 40% bile salts (bile –esculin medium). Some species are motile (E. gallinarum and E. pullorum). Most Enterococcus species hydrolyze L-pyrrolidonyl- β-naphthylamide (PYR) by producing pyrrolidonyl arylamidase (pyrrolidonase or PYRase): exceptions are E. cecorum, E. columbae, E. pallens and E. saccharolyticus. All strains hydrolyze leucine β-napthylamide by producing leucine aminopeptidase (LAPase).
Nearly all strains are homofermentative, gas is not produced, and lactic acid is the end product of glucose fermentation. Most strains produce a cell wall associated glycerol teichoic acid antigen that is referred to as the Lancefield’s serological group D antigen. The guanine and cytosine (G+C) content of DNA ranges from 37 to 45 mol%.
Reference: Topley and Wilson’s Microbiology and Microbial infections, Bacteriology Volume 2
Views – 990