Atypical Forms of M. tuberculosis

¹ Missouri State Sanatorium.

Atypical forms of M. tuberculosis have been discussed from the earliest identification of variations to the present time, and instead of being a mystery, it is all within the laws of biology. While there may be phenomena not yet clearly understood in the life of bacteria, the mutation theory of DeVries seems to be adequate to explain most of the changes that have appeared and are continuing to appear as they do in other forms of life.

Even before the recent work, the mutation theory was plausible; where changes could be demonstrated by stimulants, such as the x-ray and chemicals on certain species of life. The biochemical and x-ray identification of the structure of giant molecules in the chromosomes are more revealing and convincing. Sometimes major displacements occur within the molecule so that the new molecule is sufficiently different to result in variation of the progeny. These changes are a continuing process throughout life on the earth and help explain the presence of the widespread of life. When there has been a radical change in the environment, a mutant may result and will grow when all the other forms, including the parent strains, are suppressed or are over-grown.

Use of antimicrobial drugs has brought the phenomenon into clear perspective. The drugs have blocked the formation of new molecules leaving the mutants free to overgrow the parents as resistant forms. The question whether drugs cause mutation is still unanswered, but the wiping out of the sensitive parent forms no doubt leaves a greater number of atypical bacilli.

Attempts are being made to classify the various atypical forms. Many of them still retain varying degrees of virulence for the human host and thereby create problems.