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May 2011

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Subject:
From:
"Wong, Gilman (Hong Kong)" <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Wed, 25 May 2011 09:58:54 -0400
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Dear Carolyn,

1. Since cefuroxime is an antibiotic, addition of Polysorbate 80 will not neutralize antibacterial effect of any antibiotics drug. You can try to add beta-lactamase to neutralize the antibacterial effect of cefuroxime since cefuroxime is belonging to beta-lactam class antibiotics. The amount required to neutralize your product depends on the concentration of cefuroxime in your cream product and to be determine by trials.

2. You can try to add TTC solution (Triphenyltetrazolium Chloride) into your agar medium before pour plating. It is available in sterile, ready-to-use form from many culture media companies like BD etc. Bacterial colonies grow on TTC-containing agar medium will turn to red in colour so that you can distinguish them from your product or other debris. Suggested concentration to be added: 2ml of 0.5% TTC solution to 200ml agar medium or 1ml of 1% TTC solution to 200ml agar medium

3. Neutralizers should be added during sample preparation, i.e. the first 90ml diluent that used to dilute your 10g/ml of product to be tested.



Best regards, 


Gilman Wong, Ph.D


-----Original Message-----
From: The Pharmaceutical Microbiology Forum Email List [mailto:[log in to unmask]] On Behalf Of Carolyn Lim
Sent: Wednesday, May 25, 2011 10:47 AM
To: [log in to unmask]
Subject: [PMFLIST] MLT Validation for cefuroxime and cream products / PET

Dear Forum,

I am performing several validation tests presently and have a few problems
with microbial recovery and neutralizers. I would appreciate any comments or
suggestions you can provide.

1. I performed an MLT validation on a product containing cefuroxime and have
found out that it would require a dilution of up to 1:10^4 before I can
recover any Gram positive bacteria using the pour plate method, even with
the addition of polysorbate 80 (I only tested up to the 0.2% concentration).


Would serial diluting the product 4 times affect the recovery of possible
contaminants in any way? If so, is there a different method I can apply?
(The product is in tablet form.)

2. Is there a specific method to validate the MLT test for cream products? I
have problems with differentiating "pieces" of cream from my bacteria in the
diluent only control (no neutralizer or surface active agents added) when I
carried out the procedure based on the USP <61> guideline. Again, the pour
plate method was used.

3. When do you add in the neutralizer for the PET validation test? Do you
mix it with the agar media at the time of preparation or would you mix them
at the time of mixing with the product? What concentration range would you
suggest is better for using neutralizers?

I just reailzed I had more questions than I thought. Thank you kindly for
reading through. I hope to hear from you soon.

Best regards,
Carolyn

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the scientific community.

Please take a second to visit our sponsors' web sites and say thank you for their support of this service.

Accugenix - http://www.accugenix.com

American Type Culture Collection - http://www.atcc.org

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Rapid Micro Biosystems - http://www.rapidmicrobio.com  (formerly GPS)

Veltek Associates, Inc - http://www.sterile.com

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