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Microbial Safety: Rapid Methods for Shellfish....
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GRANT NUMBER:  NA47FD0416           NMFS NUMBER:  93-WO-022

REPORT TITLE:  Microbial Safety: Rapid Methods for Shellfish and Seawater-Injured E. coli

AUTHOR:  George W. Chang

PUBLISH DATE:  September 3, 1999

AVAILABLE FROM:  National Marine Fisheries Service, National Program Office, 1315 East-West Highway, Silver Spring, MD 20910.  PHONE: (301) 713-2358

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ABSTRACT

This study addressed two major problems: (1) development of a simple, rapid, sensitive test for fecal contamination in shellfish based on the indole production by Escherich a coli and (2) the need for a reliable test for fecal contamination in seawater.  We found that our "Colitag-S" medium and its indole reaction provided an excellent MPN test for E. coli in shellfish.  It supplies trimethylamine that neutralizes acid produced from glycogen in shellfish tissue, permitting the inclusion of large amounts of shellfish in each culture tube.  This increases sensitivity.  As for resuscitating seawater-injured E. coli for use as a seawater fecal indicator, we found that pyruvate in the medium would greatly enhance the recovery of E. coli injured under laboratory conditions.   However, preliminary studies with field samples were less than promising.  The primary goal, the development and validation of a simple, rapid E. coli test for shellfish tissues, was effectively attained.  The secondary goal of improving resuscitation of seawater-injured E. coli yielded an exciting lead with the discovery of pyruvate-enhanced resuscitation.  However, it should be tested further in waters with higher levels of fecal contamination than those of San Francisco Bay.

 
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