Tetrodotoxins (TTXs) and Vibrio alginolyticus in Mussels from Central Adriatic Sea (Italy): Are They Closely Related?

Tetrodotoxins (TTXs), potent neurotoxins, have become an increasing concern in Europe in recent decades, especially because of their presence in mollusks. The European Food Safety Authority published a Scientific Opinion setting a recommended threshold for TTX in mollusks of 44 mu g equivalent kg(-1) and calling all member states to contribute to an effort to gather data in order to produce a more exhaustive risk assessment. The objective of this work was to assess TTX levels in wild and farmed mussels (Mytilus galloprovincialis) harvested in 2018-2019 along the coastal area of the Marche region in the Central Adriatic Sea (Italy). The presence of Vibrio spp. carrying the non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) genes, which are suspected to be involved in TTX biosynthesis, was also investigated. Out of 158 mussel samples analyzed by hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry (HILIC-MS/MS), 11 (7%) contained the toxins at detectable levels (8-26 mu g kg(-1)) and 3 (2%) contained levels above the EFSA safety threshold (61-76 mu g kg(-1)). Contaminated mussels were all harvested from natural beds in spring or summer. Of the 2019 samples, 70% of them contained V. alginolyticus strains with the NRPS and/or PKS genes. None of the strains containing NRPS and/or PKS genes showed detectable levels of TTXs. TTXs in mussels are not yet a threat in the Marche region nor in Europe, but further investigations are surely needed.

Automated summary

Tetrodotoxins (TTXs) have raised concerns in Europe in recent years, prompting the European Food Safety Authority to set recommended thresholds for TTX in mollusks and call for data collection to conduct a more comprehensive risk assessment. A study in the Marche region of Italy assessed TTX levels in mussels harvested in 2018-2019, as well as the presence of Vibrio spp. carrying genes associated with TTX biosynthesis. The study found some mussels contaminated with TTXs, but further investigation is needed to determine the potential threat of TTXs in the region.