Development of a feasible method to extract somatic coliphages from sludge, soil and treated biowaste

Extraction of viruses and bacteriophages from sludge, soil and treated biowaste requires homogenization, elution, clarification and detoxification–decontamination steps. Seeding these matrixes with bacteriophages does not reproduce what happens in nature. Therefore, naturally occurring matrixes, raw sludge, digested and dewatered sludge and compost, containing high numbers of somatic coliphages, and soils contaminated with wastewater or raw sludge were used in the extraction assays. Based on eluting the bacteriophages with beef extract, a feasible method in which the different steps had been optimized has been established. The method is feasible, repeatable, robust and applicable in routine laboratories. Digested and dewatered sludge has been probed to be useful as a reference material for validation studies and for “in lab” quality control. The established method includes homogenization by magnetic stirring, elution (which is performed at the same time that homogenization) with 10% beef extract at neutral pH, clarification by centrifuging at 4000 × g and decontamination by filtration through low protein binding 0.22 μm diameter pore size membrane filters.