Hektoen Enteric Agar vs Brilliant Green Agar (Salmonella De

Yersinia yersinia at GATE.CYBERNEX.NET
Sat Oct 19 13:40:15 EST 1996


Johnny Barone writes,

<Recently, I discovered that both the United States Pharmacopia Compendia 
and the European Pharmacopia Compendia are proposing the use of Hektoen 
Enteric Agar instead of Brilliant Green Agar for Salmonella detection. 
I cannot determine the reason for this change because both agars seem to 
select for Salmonella sp. just as well.
Does anyone have an explaination for this change?>

Wow, good question! I regularly QC test both of these media when they 
come in to the lab I'm working at presently. I just popped open my Difco 
Manual, and according to this, the immediate impression I got was that 
Brilliant Green is actually slightly better - S. typhi (ATCC #19430), S. 
enteritidis (ATCC #13076) *and* S. typhimurium (ATCC # 14028) will all be 
recovered on BG, whereas only the latter two organisms are said to be 
recovered on HE. The lab I work in now only maintains the last of these 
three organisms in stock culture (I just made up a new freeze culture of 
this a couple of weeks ago, in fact!). I use it for testing both of these 
media, and not surprisingly, it grows very well on each.

However, on closer examination of the information in my Difco manual, I 
would ask if it's possible that the sodium thiosulfate and ferric 
ammonium citrate in HE allow for differentiation between  species of 
Salmonella which produce H2S and those which don't. The S. typhimurium I 
use produces blue-green colonies with black centers (it's an H2S 
producer) on HE, and on BG I get the pinkish white colonies and red agar. 
 All Salmonella sp. listed for BG produce pinkish white colonies and 
redden the agar (due to the phenol red in this medium). One more thing, 
Shigella will grow on HE  but is not said to grow on BG....

But these are the only differences I notice between the two media. Do you 
(or does anyone else in here) know if H2S producing Salmonella sp. are 
"worse" than the non-producers?

Do the United States Pharmacopia Compendia and the European Pharmacopia 
Compendia state any reasons for this proposal?

--Yersinia.



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