Ferrihydrite Treatment to Mitigate Inhibition of RT-qPCR Virus Detection from Large-volume Environmental Water Samples

Molecular assays are currently the most widely used method to quantify pathogenic viruses in water; however, their performance is often disrupted by matrices present in environmental samples. The present study used ferrihydrite (Fh) treatment to mitigate inhibition of RT-qPCR virus detection from environmental water concentrates. Fh treatment was performed to improve the detection of spiked Aichi virus 1 (AiV) and Qβ bacteriophage (Qβ) in commercial humic acids and seawater concentrates. The optimal Fh doses were found to be 200, 500, and 1000 mgFe/L for humic acid concentrates at UV of 1.5, 3.0, and 6.0 cm respectively, whereas this value was 1000 mgFe/L for the seawater concentrates at UV of 1.5 cm. At these optimal doses, the recoveries of spiked AiV and Qβ ranged from 2% to 12% in the humic acid and seawater concentrates, respectively. In addition, high levels of indigenous viruses (including AiV ≥ 2.81 log copies/mL and pepper mild mottle virus ≥ 2.77 log copies/mL) were detected from seawater concentrates after Fh treatment, while none were detected without Fh treatment. Fh treatment effectively mitigated the inhibitive effects from environmental water samples.