[The informative value of various methods for identifying acid-fast bacilli in relation to the degree of tuberculosis process activity].

Carbol fuchsin (Ziehl-Neelsen) staining is a major method used since the late nineteenth century to detect Mycobacterium tuberculosis in the tissues. At the same time, the number of mycobacteria does not frequently show a clinical and morphological correspondence to the activity of the infectious process.

OBJECTIVE: To reveal the morphological characteristics of Mycobacterium tuberculosis in patients with long-lasting tuberculosis.

MATERIAL AND METHODS: Twenty-four autopsies of verified fibrous-cavernous tuberculosis were examined. Paraffin sections were stained with hematoxylin and eosin, carbol fuchsin (Ziehl-Neelsen), or auramine-rhodamine (followed by luminescence microscopic examination); an immunohistochemical (IHC) study with serum to PAV (Protein antigen B) was conducted.

RESULTS AND DISCUSSION: The changes characteristic of progressive tuberculosis were revealed in all the cases. The Ziehl-Neelsen staining revealed isolated clusters of acid-fast bacilli (a total of 1,000 in less than 10 fields of view). When stained with auramine-rhodamine, the number of found mycobacteria proved to be significantly larger (a total of 1,000 to 10,000 in 10-50 fields of view) and that was greatest in the IHC study (a total of over 10,000 in more than 50 fields of view). At the same type, all types of studies revealed that the localization of mycobacteria was exclusively extracellular. The Ziehl-Neelsen staining indicated that the proportion of typical bacilli was much higher (85-95%; mean 88.13±2.14) than that (50-85%; mean 64.38±4.24%) identified when stained with auramine-rhodamine and even more significantly more than that (50-70%; mean 57.29±2.78%) detected during the IHC study. The indicators were equally different for the atypical morphological forms of mycobacteria identified in minimal quantities by the Ziehl-Nielsen staining and in large quantities by fluorescence and IHC studies.

CONCLUSION: There is evidence for the ability of mycobacteria to have morphological polymorphism and for the need to clarify the pathogenesis of tuberculosis.