Rain splash-mediated dispersal of Escherichia coli from fecal deposits to field-grown lettuce in the mid- and south Atlantic U.S. regions is affected by mulch type

• Published in: Frontiers in plant science 2024-03, Vol.15, p.1370495-1370495
• Main Authors: Hopper, Adam L, Hudson, Claire L, Klair, Diksha, Ding, Qiao, Gao, Zhujun, Jha, Aprajeeta, Bryan, Austin, Tikekar, Rohan V, Coolong, Timothy, Dunn, Laurel L, Micallef, Shirley A
• Format: Article
• Language: English
• Subjects: bacterial dispersal; fecal contamination; harvest buffer zones; lettuce contamination; Plant Science; preharvest food safety; rain splash
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2024.1370495

Wildlife feces can contaminate vegetables when enteric bacteria are released by rain and splashed onto crops. Regulations require growers to identify and not harvest produce that is likely contaminated, but U.S. federal standards do not define dimensions for no-harvest zones. Moreover, mulching, used to retain soil moisture and maximize crop yield may impact rain-mediated bacterial dispersal from feces. To assess dissemination from a fecal point source to lettuce grown on various mulches, lettuce cv. 'Magenta' was transplanted into raised beds with plastic, biodegradable plastic, straw, or left uncovered at field sites in Maryland and Georgia. Eleven days post-transplant, 10 g of rabbit manure spiked with ~8 log CFU g were deposited in each bed. One day following natural or simulated rain events, lettuce was sampled along 1.5 m transects on either side of fecal deposits. Lettuce-associated was semi-quantified with an MPN assay and dependence on fecal age (stale or fresh), lettuce age (baby leaf or mature head), distance from point source, mulch and post-rain days were statistically evaluated. Distance (