BacterPlate™ Hektoen Enteric Agar (HE)

Ready-to-use medium on 90mm plates for selecting and differentiating pathogenic intestinal bacteria from clinical samples
Code: 05020
Packaging: 10 plates/ box or as per customer request.
Storage Conditions: 2–8°C.
Transportation: Ambient temperature.
Shelf Life: 04 months from the date of manufacture.

INTENDED USE

BacterPlate™ Hektoen Enteric Agar (HE) is a selective medium for the isolation and differentiation of pathogenic enterobacteria from biological samples of animal origin, water samples, dairy products and other food products. It is used in animal health in the context of Salmonella detection in mammals (NF U47-102). The medium is also recommended for the detection of Shigella, in food microbiology (NF EN ISO 21567). BacterPlate™ Hektoen Enteric Agar (HE) can also be used as the second media of choice in the standardized methods for the detection of Salmonella.
The packaging with semi-permeable Cellophane film helps balance the humidity of the environment during storage.

PRINCIPLE

Gram-positive flora are inhibited by bile salts which can also slightly inhibit the growth of a few Gram-negative microorganisms.
The medium contains three carbohydrates: lactose, sucrose and salicin. The high lactose concentration favors the visualization of enterobacteria by avoiding the problem of late fermentations. The other carbohydrates were added to insure a higher degree of differentiation and to reduce the toxicity caused by colored indicators so as to obtain excellent recovery of Shigella.
The principle of visualization is founded on the eventual fermentation of the 3 sugars present in the media. The microorganisms that ferment at least one of them form salmon-colored colonies, the others give rise to blue or green colonies. The color indicator system, composed of bromothymol blue and acid fuchsin, yields orange-yellow colonies for lactose-positive enterobacteria and blue-green colonies in the case of lactose-negative strains.
In the presence of sodium thiosulfate, H₂S producing bacteria reduce ferric ammonium citrate and are detected by darkening due to the production of iron sulfide at the center of the colonies.

Inoculate by streaking onto the ready-to-use medium plates used for the detection of Salmonella or Shigella.
Incubate at 36 ± 1°C for 18 to 24 hours.

RESULTS

Salmonella present green or blue-green colonies, with a black center for the majority of strains.
Shigella present green or bluish droplet-like colonies, without a black center.
Coliforms appear as yellow-salmon colored colonies:

Micoorganisms	Characteristics
Escherichia coli, Citrobacter, Klebsiella, Enterobacter, Arizona, Serratia	Yellow-salmon colonies
Proteus vulgaris	Yellow-salmon colonies with a black center
Proteus mirabilis, Salmonella	Green colonies with a black center
Shigella, Salmonella, Providencia, Proteus morganii, Proteus rettgeri	Green or blue-green colonies
Pseudomonas (oxidase positive)	Small bluish to brownish colonies

BacterLab ensures the quality of each product batch by testing with ATCC reference strains.

Standard Microorganism Strain	Incubation Conditions
S. typhimurium ATCC 14028	18 – 24 hours, 35 – 37⁰ C	Good growth, blue colonies with black centers
S. flexneri ATCC 12022		Good growth, green colonies
E. coli ATCC 35218		Inhibited or no growth
S. aureus ATCC 25923		No growth

For 1 liter of medium