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Microbiology
I need guidance on where to obtain a protocol on how to quantify aerobic heterotrophic in cosmetic grade petrolatum.
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7 Replies
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That’s nice. Is there a question or a request for help in there somewhere?
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Did not find one
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I need a new car.
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Hi Adam,
I suspect your concern is getting microbes in the petrolatum to mix with water in order to be present and uniformly distributed in the solution used for dilution and plating.
I imagine you could use an ordinary APC procedure (1 gram product into 9 mL D/E broth, vortex mix, then plate, then incubate), but you would have to validate recovery using a procedure similar to that laid out in USP <61>.
The duration (>1 min) and temperature (I suggest 35C) of the mixing step will be important. Also, I am specifically recommending D/E broth over letheen, etc.
If recovery verification fails, then try a greater dilution (say 1 ml in 99 ml D/E broth). If that approach is not suitable either, then re-post and I can share some “advanced” techniques.
Good luck!
Ben
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Also you might check out this CTFA test method for some tips on how to recover microorganisms from oil-based test samples.
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Hi,
I am curious to know why you recommend D/E broth over letheen broth? @The_Microbiologist
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Hi Shepard,
D/E broth has more neutralizing chemicals, by mass and number, than ordinary Letheen broth. For instance, it has 10X the lecithin. In my experience, that makes it better for emulsification of oils or oily test materials. Plus I imagine there are all sorts of trace chemicals in petrolatum that could be toxic to bacteria. D/E broth has sodium thiosulfate, sodium bisulfate, and some other goodies in there that may neutralize them and that will increase the odds that our friend Adam will pass his suitability/recovery validation test.
Ben
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