DETECTION OF VIRUSES BY ELECTRON-MICROSCOPY - AN EFFICIENT APPROACH

Wetting of grids is the most important aspect of the detection of viru ses by electron microscopy. Carbon or plastic/carbon coated grids used in most electron microscopy laboratories are negatively charged and h ydrophobic (Sogo, Portman, Kaufman and Koller, 1975. J. Microsc. 104, 187-198.). Most viruses are negatively charged at pH 6.0-7.0 which doe s not allow them to adhere effectively to the support film. Viruses ar e then washed away or form clumps on the grid making detection more di fficult. A suitable wetting agent, 0.l% poly-L-lysine hydrobromide (MW 35000) has been used for the detection of plant viruses (Roberts, per sonal communication). This chemical was used for processing faecal sam ples from patients with gastroenteritis for electron microscopy. The r esult showed a significant increase in terms of virus concentration on the grids.and an increase in the general detection rate of positive s amples. A study was then undertaken comparing the treatment method of grids using faecal samples. The grids were treated and not treated wit h poly-L-lysine hydrobromide. (C) 1998 Elsevier Science B.V.