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Applied and Environmental Microbiology, April 2000, p. 1280-1285, Vol. 66, No. 4
Centre for Environment, Fisheries and
Aquaculture Science, Weymouth Laboratory, Weymouth, Dorset DT4 8UB,
England
Received 14 June 1999/Accepted 8 January 2000
Escherichia coli is a widely utilized indicator of the
sanitary quality of bivalve molluscan shellfish sold for human
consumption. However, it is now well documented that shellfish that
meet the E. coli standards for human consumption may
contain human enteric viruses that cause gastroenteritis and hepatitis.
In this study we investigated using F-specific RNA bacteriophage (FRNA
bacteriophage) to indicate the likely presence of such viruses in
shellfish sold for consumption. FRNA bacteriophage and E. coli levels were determined over a 2-year period for oysters
(Crassostrea gigas) harvested from four commercial sites
chosen to represent various degrees of sewage pollution. Three sites
were classified as category B sites under the relevant European
Community (EC) Directive (91/492), which required purification
(depuration) of oysters from these sites before sale. One site was
classified as a category A site, and oysters from this site could be
sold directly without further processing. Samples were tested at the
point of sale following commercial processing and packaging. All of the
shellfish complied with the mandatory EC E. coli standard
(less than 230 per 100 g of shellfish flesh), and the levels of
contamination for more than 90% of the shellfish were at or below the
level of sensitivity of the assay (20 E. coli MPN per
100 g), which indicated good quality based on this criterion. In
contrast, FRNA bacteriophage were frequently detected at levels that
exceeded 1,000 PFU per 100 g. High levels of FRNA bacteriophage
contamination were strongly associated with harvest area fecal
pollution and with shellfish-associated disease outbreaks.
Interestingly, FRNA bacteriophage contamination exhibited a marked
seasonal trend that was consistent with the trend of oyster-associated
gastroenteritis in the United Kingdom. The correlation between FRNA
bacteriophage contamination and health risk was investigated further by
using a reverse transcription-PCR assay for Norwalk-like virus (NLV).
NLV contamination of oysters was detected only at the most polluted
site and also exhibited a seasonal trend that was consistent with the
trend of FRNA bacteriophage contamination and with the incidence of
disease. The results of this study suggest that FRNA bacteriophage
could be used as viral indicators for market-ready oysters.
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Evaluation of F-Specific RNA Bacteriophage as a Candidate Human
Enteric Virus Indicator for Bivalve Molluscan Shellfish
*
Corresponding author. Mailing address: Centre for
Environment, Fisheries and Aquaculture Science, Weymouth Laboratory,
Weymouth, Dorset DT4 8UB, England. Phone: 44 (0) 1305-206600. Fax:
44 (0) 1305-206601. E-mail: w.j.dore{at}cefas.co.uk.
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