A study has been undertaken to determine a suitable method for virus isolation from sewage samples in Sao Paulo State, Brazil. The samples were concentrated by the following methods: adsorption on aluminum hydroxide flocs; precipitation by aluminum sulfate; adsorption to and elution from membrane filters followed by organic flocculation; direct organic flocculation as a single-step concentration method and electropositive cartridge filter, AMF Cuno. The BS-C-1 cell line and the plaque technique were used for virus assay.
Out of the methods employed, the Al(OH)3, method presented the best recovery rates (185.6 PFU), followed by AMF Cuno method (58.0 PFU), organic flocculation as a second-step concentration method (40.6 PFU), direct organic flocculation (24.3 PFU) and adsorption on Al2SO4). (6.0 PFU). From a total of 1,037 viruses isolated, 176 strains were identified: 110 were Coxsackie B virus (62.5%), 57 were poliovirus (32.4%) and 7 were Echovirus (4.0%). Two virus strains remained untyped.