[Microbiology] Re: methylene blue milk

N10 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.

Good luck


"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)
> Microbiology
> "vincent setiawan" <vincedemagna at yahoo.com> wrote in message 
> news:mailman.567.1155407777.20007.microbio at net.bio.net...
>> hai
>> 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
>> thanks

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