The effect of pre-treatment and sonication of centrifugal ultrafiltration devices on virus recovery.

Enteric viruses such as norovirus (NV) and hepatitis A (HAV) are responsible for a large proportion of food and water-borne illnesses. Most human pathogenic enteric viruses cannot be cultured so they must be detected by molecular techniques. Male specific (F(+)) RNA coliphages, a potential surrogate for human enteric viruses, can be detected by culture and molecular assays. Numbers of viruses and F-RNA coliphages in contaminated food or water may be too low for direct detection. Ultrafiltration is a general concentration method for all virus types but there is little information on the recovery efficiency of F-RNA coliphages and enteric viruses. The recovery of F-RNA coliphage MS2 was only 25% by plaque assay in initial trials. The objective was to optimize the recovery of concentrated MS2 from Microsep 100K ultrafiltration devices. The mean recovery of MS2 increased significantly to 85% by plaque assay and 65% by real-time RT-PCR when ultrafiltration devices were treated with 1% BSA before concentration and then ultrasonicated after concentration. The method was validated with MS2, HAV, NV and feline calicivirus (FCV) in water and spinach eluate. The recovery of MS2, HAV and NV was significantly higher from concentrates obtained from water with treated devices than untreated devices but not significantly different for FCV or from spinach eluate. To our knowledge, this is the first study to use ultrasonication as a post-treatment step to increase recovery of viruses from ultrafiltration devices.