Bacteroidales as a Fecal Contamination Indicator in Fresh Produce Industry: A Baseline Measurement

Foodborne outbreaks caused by fecal contamination of fresh produce represent a serious concern to public health and the economy. As the consumption of fresh produce increases, public health officials and organizations have pushed for improvements in food safety procedures and environmental assessments to reduce the risk of contamination. Visual inspections and the establishment of "buffer zones" between animal feeding operations and producing fields are the current best practices for environmental assessments. However, a generalized distance guideline and visual inspections may not be enough to account for all environmental risk variables. Here, we report a baseline measurement surveying the background Bacteroidales concentration, as a quantitative fecal contamination indicator, in Californias Salinas Valley. We collected a total of 1632 samples from two romaine lettuce commercial fields at the time of harvesting through two seasons in a year. The Bacteroidales concentration was very low (0 - 2.00 copies/cm2). Furthermore, we established a practical methodology for evaluating the risk of fecal contamination in a real-world setting, complementing the current environmental assessment practices. This method can identify site-specific risks and offer fresh produce stakeholders a more comprehensive understanding of their fields. We anticipate this work can encourage the use of Bacteroidales in the fresh produce industry to monitor fecal contamination and prevent future foodborne outbreaks.