Acid-fast bacilli found in sphagnum vegetation of coastal Norway containing Mycobacterium leprae-specific phenolic glycolipid-I.

In the grey layer of sphagnum vegetation originating from former leprosy-endemic regions of coastal Norway, acid-fast bacilli (AFB) containing Mycobacterium leprae-specific phenolic glycolipid I (PGL-I) on the surface have been found. These AFB survived in foot pads of nude mice with multiplication but without swelling. This contrasts to experimental leprosy with clinically derived M. leprae where swelling and unlimited multiplication takes place. The naturally occurring AFB may be of a lower pathogenicity than M. leprae obtained from clinical cases. The possibility of M. leprae surviving in sphagnum vegetation was assessed by inoculation of clinically derived M. leprae into the grey layer of the sphagnum. It multiplied more than tenfold and retained its pathogenicity in nude mice for 16 weeks, the duration of the experiment. The lack of pathogenicity of sphagnum-derived, M. leprae-like mycobacteria may be relevant to the decline of leprosy in Norway.