Utility of a PCR-based method for rapid and specific detection of toxigenic spp. in farm ponds.

is a widespread freshwater cyanobacterium that can produce microcystin, a potent hepatotoxin harmful to animals and humans. Therefore, it is crucial to monitor for the presence of toxigenic spp. to provide early warning of potential microcystin contamination. Microscopy, which has been used traditionally to identify spp., cannot differentiate toxigenic from non-toxigenic . We developed a PCR-based method to detect toxigenic spp. based on detection of the microcystin synthetase C () gene and 16S rRNA gene. Specificity was validated against toxic and nontoxic strains, as well as 4 intergeneric freshwater cyanobacterial strains. Analytical sensitivity was as low as 747 fg/µL genomic DNA (or 3 cells/µL) for toxic . Furthermore, we tested 60 water samples from 4 farm ponds providing drinking water to swine facilities in the midwestern United States using this method. Although all water samples were positive for spp. (i.e., 16S rRNA gene), toxigenic spp. were detected in only 34 samples (57%). Seventeen water samples contained microcystin (0.1-9.1 μg/L) determined with liquid chromatography-mass spectrometry, of which 14 samples (82%) were positive for . A significant correlation was found between the presence of toxigenic spp. and microcystin in water samples ( = 0.0004). Our PCR method can be a low-cost molecular tool for rapid and specific identification of toxigenic spp. in farm ponds, improving detection of microcystin contamination, and ensuring water safety for farm animals.