Comparative efficiency of high-throughput magnetic bead method and polyethylene glycol precipitation for viral enrichment in sewage

Monitoring viral loads in sewage can reflect the prevalence of infections within communities to a certain extent. Methods for concentrating and enriching viruses in sewage are also rapidly evolving. The magnetic bead method has been widely adopted for nucleic acid extraction due to its simplicity and high efficiency. In this study, we designed three pre-treatment procedures (T1: sedimentation for 30 min; T2: low-speed centrifugation at 2,500 × g for 5 min; T3: high-speed centrifugation at 8,000 × g for 5 min) to identify the optimal pre-treatment for enhancing viral nucleic acid enrichment efficiency using the magnetic bead method. Spiked recovery tests were employed to compare the enrichment efficiency of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in sewage between the magnetic bead method and the traditional polyethylene glycol (PEG) precipitation method. Real sewage samples were further used to evaluate both methods for enriching enveloped viruses (SARS-CoV-2, influenza virus) and non-enveloped viruses (Norovirus, Rotavirus, Adenovirus). Results demonstrated that low-speed centrifugation (T2) served as the optimal pre-treatment for the magnetic bead-based enrichment. The high-throughput magnetic bead method achieved significantly higher recovery rates for SARS-CoV-2, Norovirus, and Adenovirus compared to PEG precipitation. Thus, the high-throughput magnetic bead method can be widely applied for the enrichment and concentration of diverse viruses in sewage.