What is esculin agar used for?

This is a medium that is both selective and differential. It tests the ability of organisms to hydrolyze esculin in the presence of bile. It is commonly used to identify members of the genus Enterococcus (E faecalis and E.

How is streptococci different from Enterococci?

It is generally accepted that the enterococci and the non-enterococcal group D streptococci have the same LTA antigen which cross-reacts. The only recognized difference is that the non- enterococcal species contain relatively small amounts of the antigen.

What is the purpose of using bile esculin agar with vancomycin?

Remel Bile Esculin Azide Agar w/ 6 µg/ml Vancomycin is a solid medium recommended for use in qualitative procedures as a screening method for primary isolation and presumptive identification of vancomycin-resistant enterococci (VRE) from surveillance cultures.

How is the esculin test used to diagnose enterococci?

Bile-esculin test is widely used to differentiate Enterococci and nonenterococcus group D streptococci, which are bile tolerant and can hydrolyze esculin to esculetin, from non-group D viridans group streptococci, which grow poorly on bile. It is a low cost, rapid test with good sensitivity and specificity (>90%).

How is bile esculin agar used to differentiate Enterococcus?

Bile Esculin Agar is used primarily to differentiate Enterococcus from Streptococcus. Members of the genus Enterococcus are capable of growing in the presence of 4% bile (oxgall) and hydrolyzing esculin to glucose and esculetin. Esculetin combines with ferric ions to produce a black complex.

How does Enterococcus hydrolyze esculin in Gram stain?

Enterococcus hydrolyze esculin to products that react with ferric citrate in the medium to produce insoluble iron salts, resulting in the blackening of the medium. Test results must be interpreted in conjunction with gram stain morphology.

Can a heavy inoculum affect the bile esculin test?

A heavy inoculum on BEA may cause interpretation of the bile esculin test difficult to read. Excess inoculum decreases the ability of the bile to inhibit growth of other gram-positive organisms that may hydrolyze esculin. There are a few streptococci that do not hydrolyze esculin but will grow in the presence of bile.