EMERGING ISSUES DUE TO SAXITOXINS AND TETRODOTOXIN IN THE MEDITERRANEAN SEA: AN ANALYTICAL AND MOLECULAR COMBINED APPROACH
C. Dell'Aversano; 1; 2 L. Tartaglione1; 2; A. Turner3; M. G. Giacobbe4; S. Casabianca2; 5; S. Capellacci2; 5; A. Penna2; 5;
Harmful algal blooms (HAB) cause serious impacts to human health, marine environment and economic maritime activities at many coastal sites. Therefore, there is an urgent need for validated analytical methods for determination of toxins in the food chain and of molecular methods for detection and count of HAB species, species-specific identification and reliable quantification of cell densities.
Saxitoxins (STXs) are a group of neurotoxins produced by marine dinoflagellate belonging to genus Alexandrium, Gymnodinium and Pyrodinium that may cause a fatal paralytic syndrome in humans following ingestion of contaminated seafood. Tetrodotoxin (TTX) is also a natural toxin produced by marine bacteria, well known in Japan to cause lethal food poisonings following ingestion of contaminated puffer fish (fugu). Despite presenting different structural features, STXs and TTX exert similar toxic effects and, most importantly in an analytical perspective, they are co-extracted under the same conditions; thus, availability of a methodological approach for their combined detection is desirable.
This study aimed to investigate STX-related risk in the Mediterranean area [1]. Genus- and species-specific primers and probes designed on rDNA ribosomal and STX genes allowed to develop and apply new identification and counting qPCR based assay, which proved to be more rapid, sensitive and specific when applied in the water column. In the recent aquaculture system investigated for the STXs producing species, the sxtA1 gene qPCR assay can support the analytical methods for STX determination in seawater and shellfish especially at early warning stage of toxic blooms. At the same time, three different instrumental platforms and 3 separate analytical methods were used to investigate the presence of a wide array of STXs and TTX in seawater and shellfish (mussels, clams) collected in spring/summer 2015 to 2017 in the Mediterranean Sea. A very high STX contamination in mussels emerged, unprecedentedly found in Italy, with maximum total concentration of 10850 ?g STX eq/kg of shellfish tissue measured in 2016. The sxtA1 gene content was correlated with toxin presence in environmental samples to provide an indication of STX-related risk during a bloom. The amount of sxtA1 gene was in the range of 1.38×105-2.55×108 copies/L and the STX concentrations ranged from 41-201 nmol/L in seawater. In addition, for the first time TTX was detected in Italy in most of the analyzed samples in the range 0.8-6.4 ?g TTX eq/kg.
The recurring blooms of STX-producing species over the 3-year period, the high STX levels and the first finding of TTX in mussels from the Syracuse Bay suggest that human health concerns exist and that monitoring programs of STXs and TTX in seafood should be activated in this geographical area.
References
[1]Chemosphere, 2019, 215, 881-892 doi: 10.1016/j.chemosphere.2018.10.081
2019 - Contributo in atti di convegno
2nd MEETING ON "NATURAL TOXINS", Parma, 18-19/09/2019
Keywords: Harmful Algal Blooms, Saxitoxins, Tetrodotoxin, qPCR assay, Syracuse Bay