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Comparison of glass wool and glass powder methods for concentration of viruses from treated waste waters.

Enumeration of cultivable virus particle in sewage requires the samples to be concentrated. Two adsorption-elution methods, the glass wool cartridge method and the glass powder fluid layer method were compared. Firstly, it was demonstrated that virus could be readily recovered from the head, first 25 ml, of eluate of glass wool rather than from a reconcentration of the entire eluate, either by organic flocculation: 83% of positivity vs 44% respectively or double precipitation by PEG: 85% of positivity vs 61% respectively. Concentration on glass wool allowed the rescue of a greater number of positive samples (33/35) than on glass powder (16/35) as well as a higher mean titer of indigenous viruses, respectively 19 MPNCU/l vs 6 MPNCU/l (F1(34) = 36.02, P < 0.0001). Enteroviruses were the most frequently isolated viruses: found in 34/35 samples by either method, in 32/35 samples by glass wool, and in 14/35 samples by glass powder. Of the 12 enterovirus types identified by either method, a majority was Echovirus 6 (10 samples), Echovirus 11 (7 samples), Coxsackievirus B5 (4 samples) and also Coxsackievirus A7, A16, A21, B1, B6, Echovirus 1, 4, 12 and 19. Adenovirus types 1 and 5 were isolated from 4 samples by either method.