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In: Biology

Are there any tests that distinguish Enterococcus organisms from other Gram positive organisms?

Are there any tests that distinguish Enterococcus organisms from other Gram positive organisms? And what does such a test use that distinguishes them.

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Expert Solution

Bile-esculin test is widely used to differentiate Enterococci and other gram positive organisms. Enterococci are bile tolerant and can hydrolyze esculin to esculetin and it grows well, but non- enterococci grows poorly on bile. It is a low cost, rapid test with good sensitivity and specificity (>90%).

Principle :

Bile-esculin test is based on the ability of certain bacteria, notably the Enterococcus species, to hydrolyze esculin in the presence of bile. Bacteria that are bile-esculin positive are, first of all, able to grow in the presence of bile salts. Hydrolysis of the esculin in the medium results in the formation of glucose and a compound called esculetin.

Esculetin, in turn, reacts with ferric ions (supplied by the inorganic medium component ferric citrate) to form a black diffusible complex which indicates the postive result. i.e the presence of Enterococcus faecalis, Enterococcus faecium, and Streptococcus bovis.


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