Assessment of bacterial pathogens on edible macroalgae in coastal waters

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.

Lactic acid fermentation in the development of a seaweed sauerkraut‐style product: Microbiological, physicochemical, and sensory evaluation

“…This finding appears to be treatment specific and unrelated to total mesophilic counts (Figure 8), which closely resembled LAB counts in both level and trend. The elevated coliform level in the 75% SK treatment likely due to the slower rate of acidification in the higher inclusion level SK formulations, but calls for further investigation to assess the potential survival of foodborne pathogens such as shigatoxigenic E. coli , which has been detected on freshly harvested SK (Barberi, Byron, Burkholder, St. Gelais, & Williams, 2020) and closely related Salmonella . Fungi were found only sporadically on any of the samples tested during this study (data not shown).…”

Microbiological Food Safety of Seaweeds

“…Pathogens from environmental and anthropogenic sources may persist in coastal waters and can potentially cause contamination. Research on bacterial pathogen contamination of seaweeds is limited, and literature is scarce for some areas e.g., US coastal waters [74] while more literature is found from other parts of the world. Sugar kelp Saccharina latissima and adjacent water were sampled from three sites of seaweed aquaculture located in adjacent bays of Maine, USA, during the winter growing season [74].…”

Antimicrobials from Seaweeds for Food Applications

“…This fact may be due to the initial bacterial load of the macroalgal samples as this may vary depending on the sampling site and also sampling procedures and pore-treatments applied to the biomass prior to their inclusion into food formulations. Recently, Barberi et al [ 145 ] reported the presence of foodborne pathogens, such as S. Typhimurium , V. parahaemolyticus and enterohemorrhagic E. coli O157:H7, on kelp samples analyzed using molecular methods. The authors concluded that although the bacterial counts in the seaweeds were generally low, there is a risk for consumers associated with the presence of foodborne pathogens [ 145 ].…”

“…Recently, Barberi et al [ 145 ] reported the presence of foodborne pathogens, such as S. Typhimurium , V. parahaemolyticus and enterohemorrhagic E. coli O157:H7, on kelp samples analyzed using molecular methods. The authors concluded that although the bacterial counts in the seaweeds were generally low, there is a risk for consumers associated with the presence of foodborne pathogens [ 145 ]. Thus, the pre-treatments of the macroalgal biomass, such as cleaning, drying and extraction procedures used to obtain macroalgal ingredients, may influence considerably the initial microbial loads of meat and other food products formulated using macroalgae and/or macroalgal ingredients.…”