bile esculin test

Presumptive identification of microorganisms is defined as identification by the colony morphology, growth on selective media, gram stains, or up to three tests 


This test is used most commonly for presumptive identifi- cation of enterococci and members of the Streptococcus bovis group, all of which are positive.

Members of Streptococcus and Enterococcus genus

The carbohydrate esculin (substrate) is hydrolized

bile saltsesculinferric ammonium citratebeef and gelatin extracts

Hydrolyze the carbohydrate esculin in the presence of bile Produce glucose and esculetin Esculetin reacts with ferric ammonium citrate Form a blackish precipitate

The esculetin end-product reacts with ferric citrate forming phenolic iron complexturning the slant dark to black brown

50% or greater

Gram +, specifically the Streptococcus genus and Enterococcus genus

Selective, undefined, and differential-tests the ability of organisms to hydrolize esculin in the presence of bile-Selective ingredient=bile-Differential ingredient=esculin

-Enterococcus faecalis (pathogenic)-Lactobacillus casei (nonpathogenic)

glucose and esculetin

positive

oxgall

• 1.esculetin
• 2.black

48 hours enterococculus faccalis is positive and turns esculin into esculetin. The esculitin reacts with iron and produces a black color giving a positve

citrobacter freundii is negative because it cant hydrolyze esculin

it acts a a differential medium because it contains feeric ammonium citrate to produce the black color then the bile inhibits the growth of a negative

the bile inhibits growth for for others and it has a specialized growth for a positive result

the ferric citrate reacts with the esculin to produce a black color and the bile inhibits the growth of the negative c. freundii

is an enzyme produced by a cell that catalyze reactions outside of the cell

is an enzyme produced by a cell that catalyze reactions inside the cell