You might be seeing a media stratification effect from the heat
sterilization process. Has the media been mixed after sterilization?
This might account for the differences between beginning and end of the
The only other problem I have encountered was a bad seal on media that
was sterilized in an autoclave. In this case, the media was
contaminated by the steam (not clean steam) and the media didn't
support any growth. If you used a tank with a jacket to sterilize the
media, you may want to check the tank for cracks. Maybe the heating
media could have leaked into the tank, stratified in a layer that was
filled first and inhibited only B. subtilis growth at the beginning of
Just some thoughts!
IVAX Research, Inc.
On Tuesday, December 16, 2003, at 11:20 AM, Scott Sutton wrote:
> Here is an interesting case study I have been asked to post
> Two aseptic filling lines:
> Line A - Product is filtered sterile immediately before aseptic
> Line B - Product is bulk sterilized (heat) and then aseptically
> The problem:
> Filled bottles (Line B) from the beginning of the run fail GPQ for B
> subtilis (and continue to fail on subsequent challenges of additional
> Bulk media from both lines pass GPQ for all organisms
> Filled units from the end of the run (Line B) pass GPQ
> Filled units from Line A always pass GPQ, no matter from beginning
> or end
> of run
> Both media fills used same manufacturer's lot of TSB
> CIP is validated
> No evidence of sanitizers can be found in the media filled bottles.
> When I first saw this question I thought that the CIP was suspect, but
> been assured that all is in place, and there is no evidence of residual
> sanitizer being washed off the equipment into the filled units. Next
> thought was that they had baked the TSB too much to support B subtilis
> B remember is sterilized in bulk by heat). If so, then why do samples
> the bulk and the end of the fill run support growth? Unfortunately,
> are no retains from the different sampling events to evaluate.
> BTW - all other organisms used for GPQ (based on Sterility Test B/F
> environmental) were fine.
> Anyway, I held this post a couple of days to get the above
> Does anyone have any ideas?
> Scott Sutton
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