Preliminary evaluation of the ELISA as a tool for the detection of rotaviruses in activated sewage sludge.

Samples of activated sludge were taken in three different treatment plants near Nancy (France) and in West Berlin (F.R.G.), and were investigated for their content of rotaviruses. After elution with beef extract (0.25%, pH 7.3) and ultrasonication, the samples were concentrated by protamine flocculation and, in a few cases, in parallel by ultracentrifugation. A commercially available ELISA test kit (Rotazyme, Abbott Diagnostics) was routinely used for rotavirus detection. Although both the Rotazyme and a laboratory-designed ELISA gave positive results for the suldge concentrates, confirmation with a blocking test and electron microscope (EM) was negative in all cases so far investigated. Therefore, the exclusive use of ELISA cannot be recommended for similar investigations as it may lead to false positive results. In this light, an additional verification step with neutralizing antibodies should be included by the ELISA kits' manufacturers to enable a quick confirmation of the user's results.