Feasibility of the Bag-Mediated Filtration System for Environmental Surveillance of Poliovirus in Kenya

Abstract

The bag-mediated filtration system (BMFS) was developed to facilitate poliovirus (PV) environmental surveillance, a supplement to acute flaccid paralysis surveillance in PV eradication efforts. From April to September 2015, environmental samples were collected from four sites in Nairobi, Kenya, and processed using two collection/concentration methodologies: BMFS (> 3 L filtered) and grab sample (1 L collected; 0.5 L concentrated) with two-phase separation. BMFS and two-phase samples were analyzed for PV by the standard World Health Organization poliovirus isolation algorithm followed by intratypic differentiation. BMFS samples were also analyzed by a cell culture independent real-time reverse transcription polymerase chain reaction (rRT-PCR) and an alternative cell culture method (integrated cell culture-rRT-PCR with PLC/PRF/5, L20B, and BGM cell lines). Sabin polioviruses were detected in a majority of samples using BMFS (37/42) and two-phase separation (32/42). There was statistically more frequent detection of Sabin-like PV type 3 in samples concentrated with BMFS (22/42) than by two-phase separation (14/42, p = 0.035), possibly due to greater effective volume assayed (870 mL vs. 150 mL). Despite this effective volume assayed, there was no statistical difference in Sabin-like PV type 1 and Sabin-like PV type 2 detection between these methods (9/42 vs. 8/42, p = 0.80 and 27/42 vs. 32/42, p = 0.18, respectively). This study demonstrated that BMFS can be used for PV environmental surveillance and established a feasible study design for future research.

A comparison of SARS-CoV-2 wastewater concentration methods for environmental surveillance

“…Seeded wastewater samples were aliquoted and concentrated using four methods: the BMFS (with and without Vertrel™ extraction), skimmed-milk flocculation (with and without Vertrel™ extraction), PEG precipitation, or ultrafiltration ( Table 1 ) (Appendix B). The BMFS concentrated an average of 2.63 L ( Table 1 ) of primary wastewater using previously published methods, including filtration, elution, and secondary concentration with a two-hour shake at 200 RPM and pellet resuspension in 4 mL of sterile PBS (pH 7.4) ( Zhou et al, 2019 ; Falman et al, 2019 ; Fagnant et al, 2018 ). Skimmed milk flocculation was also carried out on primary wastewater samples in volumes of 0.1 L, 0.5 L, and 1.0 L following the protocol used during BMFS processing.…”

“…A comparison of concentration methods is necessary to develop effective environmental wastewater surveillance and to standardize the methods being used across communities. To compare and optimize methods currently being used around the world, the following methods were carried out on primary wastewater from three wastewater treatment plants (WWTPs) in the Seattle area: the Bag-Mediated Filtration System (BMFS) ( Zhou et al, 2019 ), modified skimmed milk flocculation from Calgua et al 2008 ( Calgua et al, 2008 ; Falman et al, 2019 ), polyethylene glycol precipitation (PEG) ( Falman et al, 2019 ; Lewis and Metcalf, 1988 ), and ultrafiltration via Millipore filtration concentration ( Ahmed et al, 2020a ). Direct sludge extraction was also carried out on primary sludge samples from the same WWTPs.…”

Validation of the bag‐mediated filtration system for environmental surveillance of poliovirus in Nairobi, Kenya

“…A Y‐adapter was connected to the bag’s outlet, two replicate ViroCap filters preseeded with a known titre of bacteriophage MS2 as previously described (Zhou et al . 2020) were attached to either end and samples were filtered simultaneously by gravity.…”

“…bucket protocol) (Zhou et al 2018), and filtration within 24 h. Collection bags were hung on a tripod stand outside on KEMRI's campus, allowed to settle 15 min and approximately 0Á5 l was drained as waste to remove settled solids. A Y-adapter was connected to the bag's outlet, two replicate ViroCap filters preseeded with a known titre of bacteriophage MS2 as previously described (Zhou et al 2020) were attached to either end and samples were filtered simultaneously by gravity. For filters shipped to UP, a 2% sodium benzoate (Becton Dickinson, Sparks, MD) and 0Á2% calcium propionate (Becton Dickinson) preservative mixture was passed through the filter at KEMRI (Fagnant et al 2017a).…”

“…For BMFS samples processed at UP the following controls were included. Infectious MS2 preseeded onto the ViroCap filters as a BMFS process control, was enumerated in the filter eluate via the double agar layer method using an E. coli F À amp host as previously described (Adams 1959;US EPA 2000;Zhou et al 2020). MS2 recovery efficiency ranged from 0 to 5900%, with a median of 9Á9%.…”