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Chocolate Agar

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Chocolate Agar

Postby kady123 » Wed Feb 11, 2009 7:42 pm

Hello!
Can the chocolate agar be used instead of plate count agar in food microbiology ( finding total plate count) ?
Thank u
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Postby Sepals » Thu Feb 12, 2009 1:39 pm

Chocolate agar is used to select for certain pathogens, such as Haemophilus. The ingredients are completely different and plate count agar is recommanded for isolating oragnisms from dairy products, so why not stick with it?
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Postby miles500 » Fri Feb 13, 2009 9:39 am

There is no perfect agar that will grow everything, however chocolate agar would inhibit more growth than the PCA. So you would not achieve a true count.
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Postby kady123 » Fri Feb 13, 2009 2:37 pm

it is just because i don't have PCA and i can't order it now...only chocolate is available atm...
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Postby mith » Fri Feb 13, 2009 6:14 pm

did someone say chocolate?
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Postby canalon » Fri Feb 13, 2009 7:26 pm

You would not like that one mith. Chocolate refer to the color, NOT to the ingredient. The color comes from the blood used for the preparation of the medium.
Considering the recipe of PCA I would be more inclined to replace it with something like TSA or LBA, maybe with addition of glucose. But any micro lab should have the ingredients to prepare some.
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any proof. (Ashley Montague)
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Postby JorgeLobo » Mon Feb 16, 2009 2:09 pm

Wrong sepals, chocolate agar is not selective. It's an enruiched medium 1st described in the 1930's for Neisseria gonorrhea cultivation. Generally, it should work as well as PCA but it depends on the material being cultured. It's probably not good for water and there's probably not much if any validation work for other materials.
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Re: Chocolate Agar

Postby Sepals » Fri Feb 20, 2009 3:43 pm

It is when incubated in certain conditions such as 5-10% CO2 for Haemophilus influenza.
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Re: Chocolate Agar

Postby JorgeLobo » Sat Feb 21, 2009 12:56 am

absolute bull - show us the data , pal.
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Re: Chocolate Agar

Postby pnkkmi » Thu Mar 12, 2009 10:19 pm

I am not trained in food microbiology but I'm assuming that it isn't much different than medical microbiology.
The main purpose of chocolate agar is to support the growth of microorganisms that have fastidious growth requirements. Most bacteria will actually grow better on chocolate than on blood agar, which is the primary plating medium in medical micro labs.
Chocolate is a nutrient media, not selective. It is helpful for detecting Haemophilus influenza, which will not grow on regular blood agar due to the lack of v-factor, but it doesn't have any inhibitors, such as anitbiotics or anitfungals, that would inhibit the growth of other organisms. As far as I know, chocolate is almost always paired with a primary agar, such as the blood agar that we use in medical labs.
In suspected cases of H. influenza the chocolate and blood agar plates are compared side by side. If the chocolate has significantly more growth than the blood agar H. influenza may be suspected, but further testing is still needed.
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