Virus detection in soils: a comparison of four recovery methods

Among nine eluents tested, 0.5% (w/v) isoelectric casein at pH 9.0 and 0.5% (w/v) non-fat dry milk (pH 9.0) were the most efficient in eluting poliovirus type 1 (Sabin) from Eustis fine sand. However, no significant difference was found between the overall (elution followed by concentration) virus recoveries by non-fat dry milk, isoelectric casein, beef extract, and glycine-EDTA methods. High overall recovery (75%) of low input (200 PFU) of viruses from 100 g of soil was achieved by the isoelectric casein method. It was found that the recovery efficiency of this method was not significantly affected by the soil type, following examination of four Florida soils. The mean overall recovery for the four soils was 50%. For other enteroviruses, the overall recovery for coxsackie B3 was 88% but was significantly lower (23%) for echovirus 4. Examination of the efficiency of the casein method under field conditions showed that it was possible to recovery low poliovirus numbers from soil (0.9-1.3 PFU/g soil).