MacConkey's Broth Reaction in Coliform Count

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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MacConkey's Broth Reaction in Coliform Count

Post by cloudnine » Wed Sep 07, 2005 3:42 am

in MPN count for coliform bacteria.
i used double strength MacConkey's broth.
the positive reaction is the change in colour, purple to yellow and gas production.

but some tubes turned to white.
please reply why this white colour is formed?
when these tubes are plated on MacConkey's agar, they produced Non-lactose fermentor colonies, they are like Pseudo.

yellow colour, because of lactose fermetation, acid produced reacts with the indicator and the colour changes.
but i don't know changing to white colour.
MaC broth has only lactose as carbon source, i think.
is there other that serves as carbon source, such as Peptone?

best regards.

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Location: Europe

Post by Lukaszos » Sun Sep 11, 2005 9:36 pm

Do Bacterium which you are trying to confirme, come from the environment ??

Best regards

(Sorry for my English)

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Need help

Post by Wrath_ing » Thu Nov 02, 2006 12:23 pm

Hi, can any suggest to me a suitable agar for doing plate count 4 coliform and e. coli? Thx

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Joined: Fri Apr 22, 2005 9:24 am

Post by jes » Tue Nov 07, 2006 12:53 pm

Try EMB agar (Eosine Methylene Blue). It's selective for coliforms and gram-negative bacteria. here's a link:

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