As a result of nutritional requirements, some organisms may grow poorly or not at all on this medium. St. Louis, Missouri: Elsevier. Bile esculin agar (we do not use bile esculin azide agar, as sodium azide is extremely hazardous) is a selective and differential medium which is used to presumptively identify enterococci  and group D streptococci based on the ability of an organism to hydrolyze esculin. Incubate at 35°-37°C in ambient air for 48 hours. Thus the tolerance to the presence of bile and the hydrolysis of esculin provide the means to presumptively identify organisms. The effects on test performance of the concentration of bile salts, inoculum, and duration of incubation were examined with 110 strains of enterococci, 30 strains of Streptococcus bovis , and 110 strains of non-group D viridans group streptococci. Esculetin, in turn, reacts with ferric ions (supplied by the inorganic medium component ferric citrate) to form a black diffusible complex. It is commonly used to identify members of the genus Enterococcus (E faecalis and E. faecium).. Bailey & Scott’s diagnostic microbiology (Thirteenth edition.). Question: BILE ESCULIN Test *Biochemical Rxn: *Enzyme: *End Product: *Reagent Added: *pH Indicator: 6.5% NaCl Test *Biochemical Rxn: *Enzyme: *End Product: E.faecalis *Reagent Added: *pH Indicator: What Is The Biochemical Reaction For Bile Esculin Test? Bile esculin test is based on the hydrolysis of esculin into glucose and esculetin (6, 7-dihydroxy-coumarin) by a micro-organism that produce an enzyme esculinase. Organisms capable of growth in the presence of 4% bile and able to hydrolyze esculin to esculetin. It tests the ability of organisms to hydrolyze esculin in the presence of bile. Bile esculin agar (we do not use bile esculin azide agar, as sodium azide is extremely hazardous) is a selective and differential medium which is used to presumptively identify enterococci and group D streptococci based on the ability of an organism to hydrolyze esculin. It should be used in conjunction with other biochemical tests to identify cultures of isolated organism. Organisms capable of growth in the presence of 4% bile and able to hydrolyze esculin to esculetin. A heavy inoculum on BEA may cause interpretation of the bile esculin test difficult to read. The first selective ingredient in this agar is bile, which inhibits the growth of Gram-positives other than enterococci and some streptococci species. Excess inoculum decreases the ability of the bile to inhibit growth of other gram-positive organisms that may hydrolyze esculin. Thus the tolerance to the presence of bile and the hydrolysis of esculin provide the means to presumptively identify organisms. A. Bile Esculin Test. ). Thus the bile esculin test is based on the ability of certain bacteria, notably the group D streptococci and Enterococcus species, to hydrolyze esculin in the presence of bile (4% bile salts or 40% bile). Save my name and email in this browser for the next time I comment. The bile-esculin test is a biochemical test performed to differentiate Enterococci and group D Streptococci from non-group D viridans group Streptococci on the basis of their ability to hydrolyze esculin. Growth without blackening of this medium does not constitute a positive test. The test differentiates enterococci and group D streptococci from non–group D viridans streptococci. Esculetin reacts with an iron salt (ferric citrate) in the medium to form a phenolic iron complex which produces a dark brown or black color. This is a medium that is both selective and differential. The bile-esculin test is used to differentiate enterococci and group D streptococci from non-group D viridans group streptococci. Esculin + Acid → β-D-glucose + Esculetin Esculetin + Fe3+ → Dark Brown Color Bile esculin test is widely used to differentiate Enterococci from streptococci, other than streptococcus bovis which are bile tolerant and can hydrolyze esculin to esculetin, it reacts with an iron salt in the medium to form a phenolic iron complex which produces a dark brown or black color. Bile esculin agar is a selective and differential medium which is used to presumptively identify enterococci and group D streptococci based on the ability of an organism to hydrolyze esculin. Bile esculin test is widely used to differentiate Enterococci from streptococci, other than streptococcus bovis which are bile tolerant and can hydrolyze esculin to esculetin, it reacts with an iron salt in the medium to form a phenolic iron complex which produces a dark brown or black color. Observe for growth and blackening of the medium. https://catalog.hardydiagnostics.com/cp_prod/Content/hugo/BileEscAgar.htm, https://www.austincc.edu/microbugz/bile_esculin_test.php.