Strategies for removal of indicator pathogenic bacteria from commercial harvested shellfish

The Great Bay/Piscataqua River Estuary in New Hampshire and Maine has an abundant oyster resource in sewage-contaminated water. The only approved area in the Maine portion of the Estuary is Spinney Creek, where fecal indicator bacteria are present at reduced levels and Vibrio vulnificus is absent. Spinney Creek Oyster Company (SCOC) of Eliot, Maine, operates relay lagoons and a depuration facility for oysters harvested commercially from restricted areas of the Salmon Falls River in Maine. Oysters naturally contaminated with vibrios and fecal indicator bacteria were used to evaluate depuration and relaying as strategies for eliminating these bacteria from shellfish. Oysters and water were analysed for the presence of total and fecal coliforms, V. vulnificus, V. parahaemolyticus, and total vibrios. Coliforms were always detected at varying levels in water and oyster samples. V. vulnificus was detected consistently during July-October at the harvest site, but never in Spinney Creek water or anywhere else during November-June. Relaying oysters for 7 days to the SCOC relay lagoons consistently decreased levels of fecal coliforms and V. vulnificus. Depuration of oysters for 48 hours significantly reduced total and fecal coliforms, but did not decrease vibrio levels. These results demonstrate the effectiveness of depuration and relaying in reducing fecal contamination in oysters, and a unique, additional benefit of relaying for eliminating otherwise recalcitrant V. vulnificus.


ANW, USA, New Hampshire, Great Bay, Crassostrea, Bivalvia, Vibrio parahaemolyticus, Vibrio vulnificus, Indicator species, Microbial contamination, Bacteria, Oyster culture, Vibriosis, Bacterial counters, Pathogenic bacteria, Self purification

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Jones S, Howell T, O'neill K, Langan R (1992). Strategies for removal of indicator pathogenic bacteria from commercial harvested shellfish. Actes de colloques. Ifremer. Brest [ACTES COLLOQ. IFREMER.]. 1995.

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