Preliminary evaluation of the depuration of Galveston Bay oysters Crassostrea virginica against Vibrio vulnificus using probiotic bacteria: Inherent variability of autochthonous levels

2001 2001 Jan 21
Williams KR
Fox JM
Mott JB
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High levels of the human health pathogen, Vibrio vulnificus, in Galveston Bay oysters (Crassostrea virginica) are often related to higher summer temperatures in the Gulf of Mexico and lower salinities in the fishing grounds resulting in bacterial cell densities approaching 1,000 c/mL. Mounting public and private sector concern regarding consumption of raw oysters has resulted in the oyster industry's further evaluation of depuration as a means of reducing both health risks and consumers' concerns. This study reports preliminary results of depuration of oysters against V. vulnificus using probiotic bacteria. It focuses on inherent variability in V. vulnificus levels in commercial oyster stocks and summarizes factors relevant to the effective implementation of various depuration methodologies. The following factors could impact results associated with depuration of V. vulnificus from Galveston Bay oysters using probiotic bacteria: Release of gut contents upon stocking and subsequent re-ingestion of bacteria coupled with marked increase in numbers due to proliferation in warm holding tanks could mask actual autochthonous levels of V. vulnificus in oyster. Culturability of probionts and morphological similarities to V. vulnificus on mCPC agar could result in errors in MPN determinations of oyster tissue cell densities and could pose problems for laboratory determination of V. vulnificus (either contamination or elimination in oysters). Data must be normalized to show percent reduction of V. vulnificus over time due to the intrinsic variability in initial levels across oyster stocks (ranging from 180 to 15,000 cfu/g), in order to measure depuration efficacy. Depuration protocols of up to six days with maintenance of constant levels of probiotic bacteria could be commercially impractical, and Availability of probionts/probiotic mixtures with salinity tolerance. The natural variability in V. vulnificus levels of Galveston Bay oysters may make complete depuration highly problematic. Preliminary investigations have shown significant reduction in V. vulnificus. Despite inherent difficulties, further experimentation with multiple probionts and modification of holding and culture protocols is warranted

ASW,USA,Texas,Galveston Bay, Bacteria, Crassostrea, Crassostrea virginica, Disease control, Disease resistance, Eastern oyster, Evaluation, Galveston Bay, Methodology, Oyster culture, Oysters, probiotic bacteria, Q1 01587 Diseases of Cultured Organisms, Q3 01587 Diseases of Cultured Organisms, Risks, Salinity, Salinity tolerance, Self purification, Temperature, Texas, Tolerance, USA, Variability, Vibrio vulnificus