Mycobacterium fallax sp. nov.

A new species, Mycobacterium fallax, is described. A study of 22 strains showed that they form a homogeneous group with an internal phenotypic similarity value of 94.6 ± 4.1%. The colony morphology resembled that of Mycobacterium tuberculosis, with cord formation on solid medium. The characteristic features of these strains were that they were nonchromogenic and grew rapidly at 30° but slowly at 37°. Most formed a thermolabile catalase and produced nitrate reductase. A lipid analysis showed that tuberculostearic acid was present and that only α-mycolic acids were formed. These α-mycolic acids were di- and tri-unsaturated acids, a feature that has not been described previously in the mycobacteria. The type strain has been deposited in the Collection Nationale de Cultures de Microorganismes, Paris, France, as strain CIP 8139.