Can you identify “A” & “B” Organisms , On Hektoen Enteric (HE) Agar ?
Question mentioned , this culture media as Hektoen Entoric agar .
Remember , this media usually used to isolate and differentiate Salmonella and Shigella species from other Gram-negative enteric organisms. But because of various color production , we can get clear idea about number of organisms.
This media contain , 3 sugar sources & sodium thiosulfate is as a source of sulfur. Ferric ammonium Citrate is added to react with H2S and form a black precipitate.
Bile salts are included to inhibit most Gram-positive cocci.Proteus and Salmonella species that reduce sulfur to H2S , And form colonies containing a black precipitate. Therefore Organism “B” should be , Proteus or salmonella.
Also lactose fermenters , produce acid & it will produce yellow to salmon-pink color characteristic colonies on Hektoen Entoric agar . Therefore Organism “A” must be , Ecoli bacteria. Because it has ability to ferment lactose as a enteric bacteria.
One response
Hydrogen sulfide producing organism (Black colonies) non H2S producing colonies ( yellow). Black colonies – Salmonella and Yellow colonies Shigella.