The sxt gene and paralytic shellfish poisoning toxins as markers for the monitoring of toxic Alexandrium species blooms

Paralytic shellfish poisoning (PSP) is a serious human illness caused by the ingestion of seafood contaminated with saxitoxin and its derivatives (STXs). These toxins are produced by some species of marine dinoflagellates within the genus Alexandrium. In the Mediterranean Sea, toxic Alexadrium spp. blooms, especially of A. minutum, are frequent and intense with negative impact to coastal ecosystem, aquaculture practices and other economic activities. A large scale study on the sxt gene and toxin distribution and content in toxic dinoflagellate A. minutum of the Mediterranean Sea using both quantitative PCR (qPCR) and HILIC-HRMS techniques was performed. We developed a new qPCR assay for the estimation of the sxtA1 gene copy number in seawater samples during a bloom event in Syracuse Bay (Mediterranean Sea). The linear correlation between sxtA1 gene copy number and microalgal abundance and between the sxtA1 gene and STX content allowed us to rapidly determine the STX-producing cell concentrations of two Alexandrium species in environmental samples. This study described a potential PSP scenario in the Mediterranean Sea.