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May 2006


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Stephanie Thomas <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Wed, 24 May 2006 08:10:39 -0700
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One of my friends wants to know if we can get a sensitivity of <10 cfu/100 mL using a 50 mL sample.Normally for a regular MLT test we use 10 gms or 10 ml into 90 mL buffer or media,  plate duplicate 1 ml aliquots. If no growth, results are expressed as <10 per ml because 1:10 dilution was used. But if we test 50 ml how can we get a result of <10/100 mL. This is a CPMP requirement for bulk prior to aseptic filtration. Even if we do a 1:10, aliquot 25 ml each into 4 large petridishes, can we acieve this result? Or can we extrapolate from a result of <1/10 ml?
  Any suggestions? She said that this material is very expensive and that the manufacturing operations can provide her only 50 ml maximum.
  Final question. What is the difference between bioburden and microbial limits test.  For MLT you do screen for indicator organisms by enriching the media and you do Aerobic plate count plus Yeast and Mold count. For Bioburden, you only look for Total Plate count. But why does some material require only one test over the other?

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