Factors Affecting the Beading of the Tubercle Bacillus Stained by the Ziehl-Neelsen Technique

Abstract

The production of beads in films of tubercle bacilli stained by the Ziehl-Neelsen technique is greatly influenced by the prepn. of basic fuchsin used in the staining process. Films stained with pararosaniline acetate present numerous beaded forms, whereas those stained with pararosaniline hydrochloride present no beads, or only a few. The conc. of the dye soln. likewise has a definite bearing on the production of the beaded forms. With all prepns. qf fuchsin, addition of electrolytes (NaCl, Na acetate, etc.) greatly increases the number of beads. Washing of the stained prepn. with neutral alcohol following the decolorization with acid alcohol destroys all or a large majority of the beads. The effect of electrolytes and of alcohol on the production and destruction of the beads can be directly followed under the microscope in wet prepns. Before any attempt can be made to correlate the staining character of the tubercle bacillus with its biol. properties (age, virulence, etc.) it is essential to gain a better understanding of the many factors which affect the result of the staining process.