Purpose: This study aims to optimize a surface sampling method for virus recovery from nonporous surfaces (NPS) with application in environmental persistence studies.
Methods: Tulane virus (TuV) and Aichivirus (AiV) were selected for NPS sampling optimization. One hundred microliters of virus (104 to 106 PFU/ml) was inoculated onto duplicate NPS (plastic, stainless steel, acrylic) and dried under ambient conditions for one hour. Viruses were recovered using one of three implements (cell scraper, repeated pipetting, or macrofoam swab) combined with one of two eluents (1× phosphate buffered saline (PBS) or 1× PBS + 0.1%Tween 80 (PBST, 1:1 v/v)). For persistence studies, HuNoVs (GI.1; GII.17) and Aiv were evaluated. Virus-inoculated NPS were placed into an environmental chamber at varying temperatures (6°C, 15°C, 22°C) and relative humidity (RH; 60%, 90%) and recovered at specified time points over two-weeks. Virus recovery efficiency and persistence were obtained through plaque assay or RT-qPCR.
Results: The repeated pipetting with PBST method was selected though no significant differences were observed compared to other methods. Recovery efficiencies ranged from 22.1±14.9% to 82.6±38.6% depending on virus and NPS type. Data indicate HuNoV GI.1 is more stable than GII.17 on NPS at 22°C/60%RH with GI.1 detection over 14 days and no signal detected for GII.17 at 3 days. For AiV, a three-log reduction was observed over 14 days on NPS at 22°C/60%RH. Virus persistence at remaining temperature-RH combinations is ongoing.
Significance: Evaluation of surface sampling techniques is typically limited to swabs for application in environmental sampling during HuNoV outbreaks. An optimized virus recovery method for laboratory-based persistence studies has been described here allowing for uniformity across studies.