Inactivation of murine norovirus 1 and Bacteroides fragilis phage B40-8 by mesophilic and thermophilic anaerobic digestion of pig slurry

Abstract

Mesophilic (37 degrees C) and thermophilic (52 degrees C) anaerobic digestion of pig slurry induced at least a 4-log decrease in murine norovirus 1, used as a surrogate virus for porcine norovirus, after 13 and 7 days, respectively. Bacteroides fragilis phage B40-8, employed as a universal viral model, was lowered by 2.5 log after 7 days. The viral titer declined due to temperature and matrix effects.

FIG. 1.

Reduction in MNV-1 genomic copies/ml (a) and B. fragilis HSP40-infecting phage B40-8 PFU/ml (b) by mesophilic (37°C) anaerobic digestion (liquid [⧫] and solid [⋄] phases) and by thermophilic (52°C) anaerobic digestion (liquid [▪] and solid [□] phases) of raw pig slurry. Experiments were performed in duplicate. Error bars represent standard deviations (Excel version 2003; Microsoft, Redmond, WA). Detection limits for the liquid phase and the solid phase are depicted by a solid black line and a gray line, respectively.

FIG. 2.

Reduction in MNV-1 genomic copies/ml by mesophilic (37°C) anaerobic digestion (liquid [⧫] and solid [⋄] phases) and by thermophilic (52°C) anaerobic digestion (liquid [▪] and solid [□] phases) of digested pig slurry (a), pasteurized digested pig slurry (b), autoclaved digested pig slurry (c), and autoclaved tap water (d). Experiments were performed in duplicate. Error bars represent standard deviations (Excel version 2003; Microsoft, Redmond, WA). Detection limits for the liquid phase and the solid phase are depicted by a solid black line and a gray line, respectively.

FIG. 3.

Reduction in B. fragilis HSP40-infecting phage B40-8 PFU/ml by mesophilic (37°C) anaerobic digestion (liquid [▴] and solid [▵] phases) and by thermophilic (52°C) anaerobic digestion (liquid [•] and solid [○] phases) of digested pig slurry (a), pasteurized digested pig slurry (b), autoclaved digested pig slurry (c), and autoclaved tap water (d). Experiments were performed in duplicate. Error bars represent standard deviations (Excel version 2003; Microsoft, Redmond, WA). The reduction in B40-8 PFU/ml in tap water is shown as the means from two replicate samples at 37°C (liquid [▴] and solid [▵] phases), whereas the replicates at 52°C are shown separately (liquid [•] and solid [○] phases of replicate 1; liquid [⧫] and solid [⋄] phases of replicate 2). Detection limits for the liquid phase and the solid phase are depicted by a solid black line and a gray line, respectively.