Demonstration of microorganisms in tissues by the ABT and KOH-ABT topo-optical reactions.

The aldehyde-bisulphite-toluidine blue (ABT) reaction, as a selective topo-optical test of vicinal OH and amino-OH groups is suited for the selective demonstration in tissues of microorganisms of polysaccharide containing cells. Alkaline pretreatment of the polysaccharide cell walls, releases, by splitting the O-acyl radicals, further vicinal OH groups for the ABT reaction, thus actually increases the sensitivity of the method. The topo-optical reactions are characterized by a strong birefringence induced by oriented dye-binding, due to the linear arrangement of polysaccharides composing the cell wall. Differences in the character of birefringence have made it possible to work out a new method for the analysis of the cell wall ultrastructure as well as to demonstrate microorganisms in tissues. The practical value of the reactions is illustrated by examples.