Saturday, August 13, 2011

Methods of laboratory diagnosis for viruse, microscopy

nullnull Direct Microscopy :
Electron microscope (EM) with negative staining methods can be used to directly examine specimens for the presence of viral particles. EM is particularly helpful to detect non cultivatable or fastidious viruses. The major limitation are low sensitivity and specificity, the expertise needed, successful detection requires the presence of 105 or greater particles/ml. EM is effective for identification of virus morphologically by family, which may be sufficient clinically in many cases, and can be enhanced by use of antibodies (immune EM), which permits identification of specific viruses (Petric and Szymanski, 2000).
Immunofluorescence (IF):
The direct staining of clinical specimens using monoclonal or polyclonal antibodies (Abs) bound to fluorescent dye. This may be direct or indirect techniques. In direct IF, a single fluorochrome-labeled Ab is used. Indirect IF uses two Abs, one specific for the Ag and a second fluorochrome-labeled Ab to the immunoglobulin (Madeley and Peiris, 2002).

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