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March 2012

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The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
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Thu, 8 Mar 2012 18:29:32 -0800
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Kate Ambrus <[log in to unmask]>
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Yes - in my former positions we have tested preserved antibiotic products. I don't think you need to worry about the concentration of the antibiotic in the case of the AET test. An AET does not have anything to do with the antibiotic - which can be tested in a chemical or microbial assay.
 
What you could do is to assume what your lowest concentration of the preservative would be at the end of shelf life, and test several lower concentrations of the preservative in the AET test.
 
The neutralization of the agents may get tricky - since the antibiotic can inhibit the growth of the test organisms. If I recall we used to place all of the test aliquots and dilutions to be plated into an 0.45 (I think or may have been 0.22) filter, and washed it with a validated volume of a validated diluent. Seems like Flid A or D worked well in most cases. The filters were then placed onto the TSA or SDA media. Reading Aspergillus may be tricky and should probably be done as early as possible. Also we found that Porato Dextrose agar minimized the size of the colonies and often used this media instead of SDA (after sidee by side validation).
 
The preservative was inactivated with a validated diluent media - and taken care of that way.
 
So the validation may be a little tricky, but has been done many times - we used to test antibiotics in ophthalmic solutions. Again - would not vary the concentration of the antibiotic, but would test the AET at the lowest assumed concentraiton of the preservative that would be expected to be in the product at the end of shelf life.
 
Kate Ambrus


________________________________
From: Jelena Peric <[log in to unmask]>
To: [log in to unmask] 
Sent: Thursday, March 8, 2012 2:49 AM
Subject: [PMFLIST] Antimicrobial efficacy

Dear All,
 
 
have you ever tested the antimicrobial efficacy (i.e. efficacy of antimicrobial preservation) according to EP 5.1.3., or USP, on an antibiotic oral solution, or in any other antibiotic preparation that contains preservatives in addition to the antibiotic?
 
The test is usually used to demonstrate that the chosen preservative concentration in a product is effective. During developmental stages of a product, different probes with different preservative concentrations are usually tested in order to demonstrate that the choice of a preservative and its concentration is justified, and that the product still complies even if the preservative content drops for what ever reason during shelf life. 
 
In my case, the situation is more complicated because of the presence of the antibiotic. What would be the right experimental design in my case? 
The simplest way would be to do the test on the final formulation, and to claim that the product is adequately preserved - but by doing so, I would not find out which test microorganisms are inhibited by the preservative, and which ones by the antibiotic, and what happens if the content of any of the antimicrobial substances drops during shelf life.
 
Maybe I should test the final product formulation with the targeted preservative concentration, and than the same formulation but with the preservative concentration lowered (for example, 80% of the targeted concentration). Maybe I should see what happens if the content of the antibiotic drops to 80%, or what happens in the placebo (without the antibiotic) with the targeted preservative concentration or the lowered preservative concentration...
What would you do in this case?
 
Any thoughts will be appreciated,
 
 
Jelena

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The PMFList (http://microbiol.org/PMFList_info.htm) is operated from
The Microbiology Network (http://microbiol.org) and supported by
our sponsors (http://microbiol.org/sponsor.htm) as a service to
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

BD Diagnostic Systems - http://www.bd.com/ds/

Biolog - http://www.biolog.com

Biomerieux - http://industry.biomerieux-usa.com

Biotest - http://www.BiotestUSA.com/micro

Lonza Rapid Testing Solutions - http://www.lonza.com/rts

MicroBioLogics, Inc. - http://www.microbiologics.com

Pall - http://www.pall.com

NovaTek International - http://www.ntint.com

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

Steris - http://www.sterislifesciences.com/

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

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The nature of this service is to provide a medium for communication.  The specific statements and endorsements of individuals participating in the discussions are not necessarily those of The Microbiology Network, Inc., the PMF, or the sponsors of the list.

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