Abstract
In the Northeast USA, the aquaculture of macroalgae is a rapidly growing industry. Within this region, there are no established regulations for farm siting or methods of pathogen detection on macroalgae cultivated or harvested for human consumption. Bacterial pathogens from natural and anthropogenic sources may persist in coastal waters and can potentially contaminate macroalgae. During the winter growing season, sugar kelp Saccharina latissima and adjacent water were sampled from three sites of kelp aquaculture located in adjacent bays of ME, USA. Membrane filtration onto selective media detected Escherichia coli, Vibrio parahaemolyticus, and Vibrio alginolyticus in kelp and water samples at all sites, however plate counts were very low. The foodborne pathogens Salmonella enterica ser. Typhimurium, V. parahaemolyticus, and enterohemorrhagic E. coli O157:H7 were detected on enriched kelp samples from 83%, 78%, and 56% of sampling events, respectively, using molecular methods. Even with low bacterial levels, this frequency of detection confirms the risk of foodborne pathogens present on kelp and recommends the development of best management practices to control microbial growth during kelp harvest and processing. Bacterial plate counts from kelp samples often varied from those of water, indicating the importance of sampling the kelp directly, and that the association between bacterial pathogens on kelp and in the surrounding water should be further investigated. This study provides the first food safety assessment of sea vegetables in this region with the goal of providing data to enable the expansion of its industry.
Highlights
Humans have consumed wild macroalgae for thousands of years and cultivate many species through aquaculture processes (Wells et al 2016)
Samples were collected from two coastal sites of kelp aquaculture in Casco Bay (CB I and II), one being a commercial farm that supplies kelp to the food industry and the other being an educational lease for a local school, and another site in Saco Bay (SB) which was established for research purposes (Fig. 1)
A preliminary study revealed that qPCR-mediated detection of pathogens on kelp was enhanced when samples were subjected to a microbiological enrichment step
Summary
Humans have consumed wild macroalgae for thousands of years and cultivate many species through aquaculture processes (Wells et al 2016). Recently spread into North Atlantic countries, especially within the northeast region of the USA with the culture of sugar kelp (Saccharina latissima; Hafting et al 2015; Cole et al 2017). This region’s market for edible macroalgae, termed sea vegetables, cultivated through aquaculture practices or harvested from wild beds, is growing in popularity due to macroalgal nutrient content, culinary potential, and sustainable farming practices. Guidelines for the detection of acceptable levels of human pathogens on sea vegetables are lacking yet
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