[Microbiology] Re: methylene blue milk
limbic_lesion at hotmail.com
Sun Aug 13 04:17:23 EST 2006
The MB test is an old method used to to assess quality of milk. It is a dye
reduction test where in a fixed aliqout of milk was incubated with a MB
solution. Reduction of the blue color or not within a fixed time gave a "
gun shot" indication of general microbial loading. It was usually
performed as part of a suite of tests with such media as the Croslley Milk
medium and peillicle assay for anaerobes and "bitty cream" formers.
Such tests were superseeded by more accurate specific and quatatative assays
in the Dairy Industry many years ago. I beleive ISO BS and FDA stndards
exist which describe current best practise for the examination of Diary
Theoretically The MB test could be made relatively selective for Group D
strepps perhapes by inclusion of Kanamyciene and Aesculin in the
formualtion and with incubation at 44'c but its hardly worth it as so many
more suitable microbiological media are avialableof the shelf these day.
"JEDilworth" <bactitech at nospamhortonsbay.com> wrote in message
news:kIKdnbv-TrzKOEPZnZ2dnUVZ_u-dnZ2d at buckeye-express.com...
> Group D enterococci are identified in clinical micro labs by either a PYR
> disc, or a combination of bile esculin agar with a 6.5% NaCl broth. I have
> worked in micro for nearly 30 years and have never used or heard of
> methylene blue milk. What type of laboratory (research? clinical?) are
> you working in? I'm not saying that it doesn't work, it's just that I
> never heard of it.
> Group D enterococci are PYR +, BE+, 6.5% NaCl +
> Group D nonenterococci are PYR -, BE+, 6.5% NaCl-
> PYR can be bought commercially in disc form. You smear some of the colony
> on it, wait two minutes, add reagent. If positive, it turns pink. Bile
> esculin agar turns black if positive. Negative is no change from the
> yellowish agar slant. The 6.5% NaCl broth is either cloudy from growth or
> clear from no growth. You can also buy this broth with an indicator. It
> turns from purplish blue to yellow if positive for growth.
> PYR takes 2 minutes; the other two take overnight incubation.
> Judy Dilworth, M.T. (ASCP)
> "vincent setiawan" <vincedemagna at yahoo.com> wrote in message
> news:mailman.567.1155407777.20007.microbio at net.bio.net...
>> i just want to know what's the formula for making methylene blue milk for
>> detecting Streptococcus Group D and how to determine positive and
>> negative reaction
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