BACKGROUND: Non-cholera Vibrio bacteria are a major cause of foodborne illness in the United States. Raw oysters are commonly implicated in gastroenteritis caused by pathogenic Vibrio parahaemolyticus. In response to outbreaks in 1997-1998, the US Food and Drug Administration developed a nation-wide quantitative microbial risk assessment (QMRA) of V. parahaemolyticus in raw oysters in 2005. The QMRA identified information gaps that new research may address. Incidence of sporadic V. parahaemolyticus illness has recently increased and, as oyster consumption increases and sea temperatures rise, V. parahaemolyticus outbreaks may become more frequent, posing health concerns. Updated and region-specific QMRAs will improve the accuracy and precision of risk of infection estimates.
OBJECTIVE: We identify research to support an updated QMRA of V. parahaemolyticus from oysters harvested in Chesapeake Bay and Puget Sound, focusing on observational and experimental research on post-harvest practices (PHPs) published from 2004 to 2019.
METHODS: A predefined search strategy was applied to PubMed, Embase, Scopus, Science.gov, NAL Agricola, and Google Scholar. Study eligibility criteria were defined using a population, intervention, comparator, and outcome statement. Reviewers independently coded abstracts for inclusion/exclusion using predefined criteria. Data were extracted and study quality and relevance evaluated based on published guidance for food safety risk assessments. Findings were synthesized using a weight of evidence approach.
RESULTS: Of 12,174 articles retrieved, 93 were included for full-text review. Twenty-seven studies were found to be high quality and high relevance, including studies on cold storage, high hydrostatic pressure, depuration, and disinfectant, and other PHPs. High hydrostatic pressure consistently emerged as the most effective PHP in reducing abundance of V. parahaemolyticus.
CONCLUSIONS: Limitations of the knowledge base and review approach involve the type and quantity of data reported. Future research should focus on PHPs for which few or no high quality and high relevance studies exist, such as irradiation and relaying.

Questions related to the safety of alternative water sources, such as recycled water or reclaimed water (including grey water, produced water, return flows, and recycled wastewater), for produce production have been largely un-explored at the detail warranted for protection of public health. Additionally, recent outbreaks of Escherichia coli (E. coli) in fresh produce, in which agricultural water was suspected as the source, coupled with heightened media coverage, have elevated fruit and vegetable safety into the forefront of public attention. Exacerbating these concerns, new Federal regulations released by the U.S. Food and Drug Administration (FDA) as part of implementation of the FDA Food Safety Modernization Act (FSMA), require testing of agricultural water quality for generic E. coli. Here, we present a review of water quality criteria - including surface water, groundwater recreational water, and water reuse - in an attempt to better understand implications of new FDA regulations on irrigated produce. In addition, a Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate risks from pathogen contamination of food crops eaten fresh under the context of FDA regulations to provide perspective on current water reuse regulations across the country. Results indicate that irrigation water containing 126 CFU/100 mL of E. coli correspond to a risk of GI illness (diarrhea) of 9 cases in 100,000,000 persons (a 0.000009% risk) for subsurface irrigation, 1.1 cases in 100,000 persons (a 0.0011% risk) for furrow irrigation, and 1.1 cases in 1000 persons (a 0.11% risk) for sprinkler irrigation of lettuce. In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations. These findings, while limited to a one-time exposure event of lettuce irrigated with water meeting FSMA water quality regulations, highlight the need for additional assessments to determine if the scientific-basis of the regulation is protective of public health.

This paper reviews the latest evidence provided by epidemiological studies and quantitative microbial risk assessments (QMRAs) of infection risk from recreational water use. Studies for review were selected following a PubMed search for articles published between January 2010 and April 2014. Epidemiological studies show a generally elevated risk of gastrointestinal illness in bathers compared to non-bathers but often no clear association with water quality as measured by faecal indicator bacteria; this is especially true where study sites are impacted by non-point source pollution. Evidence from QMRAs support the lack of a consistent water quality association for non-point source-impacted beaches. It is suggested that source attribution, through quantified microbial source apportionment, linked with appropriate use of microbial source tracking methods should be employed as an integral part of future epidemiological surveys.