E. coli Is a poor end-product criterion for assessing the general microbial risk posed from consuming norovirus contaminated shellfish

Jasmine H Sharp, Katie Clements, Mallory Diggens, James E McDonald, Shelagh K Malham, Davey L Jones

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Abstract

The fecal indicator organism (FIO) Escherichia coli is frequently used as a general indicator of sewage contamination and for evaluating the success of shellfish cleaning (depuration) processes. To evaluate the robustness of this approach, the accumulation, retention, and depuration of non-pathogenic E. coli, pathogenic E. coli O157:H7 and norovirus GII (NoV GII) RNA were evaluated using a combination of culture-based (E. coli) and molecular methods (E. coli, NoV GII) after exposure of mussels (Mytilus edulis) to water contaminated with human feces. We simulated water contamination after a point-source release from a combined sewer overflow (CSO) where untreated wastewater is released directly into the coastal zone. All three microbiological indicators accumulated rapidly in the mussels, reaching close to maximum concentration within 3 h of exposure, demonstrating that short CSO discharges pose an immediate threat to shellfish harvesting areas. Depuration (72 h) in clean water proved partially successful at removing both pathogenic and non-pathogenic E. coli from shellfish tissue, but failed to eradicate NoV GII RNA. We conclude that current EU standards for evaluating microbiological risk in shellfish are inadequate for protecting consumers against exposure to human norovirus GII found in polluted marine waters.
Original languageEnglish
Article number608888
Number of pages14
JournalFrontiers in Microbiology
Volume12
DOIs
Publication statusPublished - 19 Feb 2021

Bibliographical note

This work was supported by the Dwr Cymru/Welsh Water ˆ and James Wilson at Bangor Mussel Producers Ltd. who provided research samples used in the study. Funding was provided by the United Kingdom Natural Environment Research Council (NERC) and the Food Standards Agency (FSA) under the Environmental Microbiology and Human Health (EMHH) Programme (NE/M010996/1). The work was also funded by the European Fisheries Fund (EFF), Bangor Mussel Producers and Dwr Cymru-Welsh Water under the Shellpath Project. The funders had no role in the study design, data collection and interpretation, or the decision to submit the work for publication. Bangor Mussel Producers provided shellfish samples for use in the experiments. Dwr Cymru-Welsh Water provided advice on water quality issues pertinent to the experimental study area.

Keywords

  • STEC
  • food safety
  • microbiological standard
  • mussel (Mytilus edulis)
  • norovirus
  • risk assessment
  • shellfish handling

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