David,
This can be dependent on what the finished product is. A contamination that
results directly or indirectly from fecal sources generally consists of
Salmonella and members of the Enterobacteriaceae family which includes E.
coli. If that product is processed for safety such as heat treatment in
excess of 150F, it has been shown that the presence of any member of the
Enterobacteriaceae family, whether E. coli, coliforms or other members, that
the presence of Salmonella is highly likely. A question is what is your
coliform count and more importantly, what is your Total Enterobacteriaceae
Count? The presence of other members of that family rather than just E.
coli may add some information.
It has also been shown that there are only small numbers of E. coli present
in fecal samples. If Salmonella is present, it may be at substantially
higher numbers due to infection or a persistent carrier state.
If you are using an ingredient that may have fecal contamination and is
frozen, it is likely that E. coli will die off at a higher rate than
Salmonella so that Salmonella is present in the final product without the
presence of E. coli. This can also be a result of finished product testing
if the finished product is frozen prior to testing.
Other treatments of ingredients such as irradiation and ethylene oxide may
have similar effects.
Another concern would be a "pocket" of Salmonella contamination on a piece
of equipment within the process. This may contain other bacteria as well as
the Salmonella, but not E. coli.
Conducting a spectrum of tests provides a much broader picture of a
situation and allows for a more in-depth analyses. These tests would
include the common indicator tests such as plate count, coliform count,
Enterobacteriaceae count as well as Salmonella.
I hope this helps
Larry
Larry Wyatt, PhD
Chief Executive Officer
FoodHorizon Inc.
2700 Earl Rudder Freeway
Suite 1301
College Station, TX 77845
Office 979.696.7654
Cell 979.574.1304
_____
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On Behalf
Of david culak
Sent: Tuesday, September 06, 2005 1:44 PM
To: seafood@ucdavis.edu
Subject: Re: Incidence of Salmonella presence with no E. coli evident
Dear Seafood List,
I have a microbiololgical question that I hope some of you may help
shed some light on. I understand that E. coli is used as an indicator
orgainism for the presence of various potential pathogens, of which
Salmonella would be a prime example. Would it be common (would you
expect) for a food to have the presence of Salmonella, but no E. coli ???
This is a situation we have been experiencing in my company i.e. , the
presence of Salmonella in finished product, which has been extensively
tested for E. coli with negative results. We test our finished product for
the presence of both E. coli as well as Salmonella.
Thanks ALL,
David Culak
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