Tony,
My opinion is that the best practice would be your # 2. The object of the
growth promotion test as I see it is to show that low numbers of
microorganisms can indeed grow in the media used for the test under the
conditions of the test. Consequently, it would be best to inoculate your
media fill samples right after the media fill and incubate them along with
the media - all conditions are identical. However, it has been an accepted
practice to inoculate media fill samples for growth promotion AFTER they
have gone through the incubation. Since, incubation of media prior to
inoculation will not effect its growth promotion characteristics it is OK to
do it this way also. It is more expedient and valid to do the former.

[log in to unmask]

        -----Original Message-----
        From:   Tony & Roz Cundell [SMTP:[log in to unmask]]
        Sent:   Wednesday, July 21, 1999 7:07 PM
        To:     [log in to unmask]
        Subject:        [PMFLIST] Growth Promotion Testing Media Fill
Material

        My collaegues and I wish to ask about the industry practice for
        growth-promotion testing soybean-casein digest broth used in media
fills.

        What is the best practice?

        1. Using the USP growth-promotion test for soybean-casein digest
broth which
        I believe is S. aureus, C. albicans and A. niger incubated at 20-25
degree C
        for 5 days.

        2. Using an appropriate range of organisms such as B. substilis, S.
aureus,
        C. albicans and A. niger at the media fill incubation conditions,
i.e., 7
        days at 20-25 degree C followed by 7 days at 30-35 degree C.

        3. Using say B. substilis, S. aureus incubated at 30-35 degree C for
7 days
        and C. albicans and A. niger at 20-25 degree C for 7 days.

        Is it OK to use media fill vials for growth-promotion currently with
the
        media fill incubation or do you need to conduct the the
growth-promotion
        test after the 14 days of incubation?

        Tony Cundell
        Wyeth-Ayerst


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