Assessment of PSP Collected from Targha in Morocco Using the Luminescence of Vibrio fischeri

Abstract

Paralytic shellfish poisoning (PSP) is a public health concern caused by paralytic shellfish toxins that can accumulate in shellfish. This study assessed PSP-associated toxicity in Acanthocardia tuberculata collected from Targha on the Mediterranean coast of Morocco using a Vibrio fischeri-based Bioluminescence Inhibition Assay (BIA) and compared the result with the Mouse Bioassay (MBA). Shellfish extracts were evaluated under defined pH and dilution conditions. The influence of pH on bacterial bioluminescence was examined from pH 1 to 14, and saxitoxin (STX) concentrations of 0.16, 0.33, 0.99, and 1.65 µM were used to establish a calibration response. Complete inhibition of bioluminescence occurred at pH 1, 13, and 14, while a progressive reduction was observed at pH 2 and no substantial inhibition occurred between pH 3 and 12. Increasing STX concentrations produced progressively greater inhibition of V. fischeri bioluminescence. The MBA yielded 92.8 ± 0.1 µM STX equivalents, whereas the BIA yielded 0.40 ± 0.40 µM STX equivalents. Serial dilution of the shellfish extract generally reduced bioluminescence inhibition. The marked difference between the MBA and BIA estimates indicates that the two methods are not directly interchangeable under the evaluated conditions. Nevertheless, the BIA showed practical advantages in simplicity, rapidity, relatively low operational requirements, and avoidance of experimental animals, supporting further evaluation as a complementary screening approach for PSP surveillance.