What does hektoen Agar contain?

What does hektoen Agar contain?

The nutritional components of Hektoen Agar include a mixture of meat peptone, yeast extract, along with the carbohydrates lactose, sucrose, and salicin. The relatively high levels of carbohydrates and peptone counteract the inhibitory effects that bile salts may have on certain organisms, such as Shigella species.

What makes hektoen enteric agar selective and differential?

Principle. Hektoen enteric agar is a selective as well as differential media for the isolation and differentiation of enteric pathogens from clinical specimens. The presence of the bile salts and dyes inhibits most gram-positive organisms allowing only gram-negative rods to grow on HE agar.

Is hektoen enteric agar complex?

-Hektoen Enteric agar is a complex (chemically undefined), moderately selective, and differential medium designed to isolate Salmonella and Shigella species from other enterics. -HE agar is selective for Gram negatives and is typically used to isolate members of the Enterobacteriaceae.

Which ingredient in hektoen enteric agar produces black precipitate?

The H2S gas reacts with the ferric ammonium citrate, forming a precipitate, resulting in colonies that are black or have a black center (12). Other nonpathogenic enteric organisms, such as Proteus sp. andCitrobacter freundii, also produce H2S, but these organisms are usually inhibited by the bile salts in the HE agar.

Is hektoen enteric agar selective?

BD Hektoen Enteric Agar is a moderately selective and differential medium for the isolation and cultivation of gram-negative enteric micro-organisms, especially for the isolation of Shigella and Salmonella species from fecal specimens.

Is hektoen enteric agar solid or liquid?

Remel Hektoen Enteric (HE) Agar is a solid medium recommended for use in qualitative procedures for the isolation and differentiation of gram-negative enteric pathogens.

How do you make hektoen enteric agar?

Suspend 76.67 grams of Hektoen Enteric Agar in 1000 mls of distilled water. Boil to dissolve the medium completely. Do not autoclave. Store the dehydrated medium at 24°C and the prepared medium at 2-8°C.

What ingredient makes it selective or differential?

This medium is both selective and differential. The selective ingredients are the bile salts and the dye, crystal violet which inhibit the growth of Gram-positive bacteria. The differential ingredient is lactose.

What is the selective component of hektoen enteric agar?

Hektoen enteric (HE) agar is a medium that relies on the use of bile salts for selective inhibition and two indicator systems: bromothymol blue and acid fuchsin as indicators of carbohydrate dissimilation and. ferric iron as an indicator of the formation of hydrogen sulfide from thiosulfate.

Does Pseudomonas aeruginosa grow on hektoen Agar?

HE (Hektoen Enteric Agar) test- no growth seen (blue growth seen on other cultures of P. aeruginosa in class) MAC (MacConkey Agar) test- clear result, no growth seen.

What components of hektoen Agar make it differential?

Hektoen Enteric Agar (HE) is a selective and differential medium designed to isolate and differentiate members of the species Salmonella and Shigella from other Enterobacteriaceae. Bile salts and the dyes bromthymol blue and acid fuchsin inihibit the growth of most Gram positive organisms.

What is Hektoen enteric agar?

Hektoen enteric (HE) agar was developed in 1968 by Sylvia King and William I. Metzger in an effort to increase the recovery of Salmonella and Shigella species over the previously formulated Salmonella-Shigella (SS) Agar. This is also known as HEK and HEA.

What color are E coli colonies on Hektoen agar?

Colonies on Hektoen enteric agar appear green, as do colonies from Salmonella spp. E. coli strains form yellow colonies. The general biochemical characteristics of Shigella exploited are that they are nonlactose-fermenting bacteria that do not produce H 2 S (except for S. flexneri 6 and S. boydii 14) as indicated on triple sugar iron slants.

What is the composition of Hehe agar?

HE agar is composed of proteose peptone, yeast extract, sodium chloride, lactose, sucrose, salicin, bromothymol blue, acid fuchsin, sodium thiosulfate, iron (III) ammonium citrate, bile salts, agar, and distilled or deionized water.

What is enteric agar used to isolate?

Hektoen Enteric Agar is a selective and differential medium designed to isolate and differentiate members of the species Salmonella and Shigella from other Enterobacteriaceae. The medium was introduced in 1968 by Sylvia King and William I. Metzger.