Comparison of Auto Sampling and Passive Sampling Methods for SARS-CoV-2 Detection in Wastewater

Area of Science:

• Environmental microbiology
• Public health surveillance
• Molecular diagnostics

Background:

• Wastewater-based surveillance is crucial for tracking COVID-19 trends.
• Traditional sampling methods (grab, auto-composite) have limitations, especially for small or inaccessible wastewater catchments.
• Passive samplers present a cost-effective and resource-efficient alternative for SARS-CoV-2 monitoring.

Purpose of the Study:

• To compare the effectiveness of passive sampling versus traditional auto-sampling for SARS-CoV-2 detection in wastewater.
• To evaluate a novel 3D-printed passive sampler design.

Main Methods:

• A torpedo-style 3D-printed passive sampler with cotton swabs and filter membranes was deployed alongside an autosampler.
• Samples were collected from a hospital wastewater outflow over a defined period.
• SARS-CoV-2 RNA was detected using reverse transcription and quantitative polymerase chain reaction (RT-qPCR) targeting N1 and N2 genes.

Main Results:

• Passive samplers demonstrated comparable SARS-CoV-2 detection rates and cycle threshold (Ct) values to auto-sampling.
• No significant differences were observed in N1 and N2 Ct values between the two methods.
• Discrepant results on two occasions, with positive passive samples and negative auto-samples, suggest potential benefits of longer passive sampling durations.

Conclusions:

• The passive sampler is a rapid, reliable, and cost-effective method for SARS-CoV-2 detection in wastewater.
• Passive sampling can serve as a viable alternative to traditional methods for wastewater-based surveillance.
• This approach enhances the feasibility of monitoring SARS-CoV-2 in diverse wastewater settings.