Cell wall deficient forms of mycobacteria: A review

Abstract

Cell wall deficient (CWD)-forms or L-forms of bacteria are characterized by a complete or partial loss of cell wall components and by the change of cellular shape. CWD-forms (spheroplasts) of bacteria are commonly prepared in vitro and are used for various practical applications. However, very little is known about the conditions required for the formation of CWD-forms of bacteria and mycobacteria in vivo and their significance in aetiology of various chronic diseases of humans (tuberculosis, sarcoidosis, and Crohn's disease) and animals (paratuberculosis). It is quite difficult to detect CWD-forms of mycobacteria in biological material and the possibilities of their detection by microscopy, culture, DNA hybridization techniques and other methods are limited. This obviously leads to a relatively small amount of published data on the detection and the isolation of CWD-forms of mycobacteria both from human or veterinary biological material, which can lead to the conclusion of a non-infectious origin of the diseases. The present review also includes studies performed by authors from the former Soviet Union and likely represents the first complete summarization of their knowledge in this sphere. However, certain results may be viewed as somewhat controversial. Accordingly, more attention should be paid to the research of cell wall deficient forms, not only in association with chronic and latent mycobacterial infections.