Microbiology: culture in vitro
Claims of successful culture have been made in the past but none have been substantiated and M. leprae has not yet been successfully cultured in vitro. There have been many reports of cultivation in artificial media of acid-fast bacilli from the skin or other tissues of leprosy patients and many authors have claimed such bacilli to be true leprosy bacilli, but no satisfactory evidence of this has been produced. Most of the organisms isolated in culture from lepromatous tissues appear to be mycobacteria related to M. avium complex.
Incubation period
In leprosy, both the reference points for measuring the incubation period, the time of infection and the time of onset of disease, are difficult to define; the former because of the lack of adequate immunological tools and the latter because of the insidious nature of the onset of leprosy. Even so, several investigators have attempted to measure the inclubation period for leprosy. The minimum incubation period reported is as short as a few weeks and this is based on the occurrence very occasionally of leprosy among young infants (Montestruc & Berdonneau, 1954). The maximum incubation period reported is as long as 30 years or over as observed among war veterans known to have been exposed for short periods in endemic areas but otherwise living in non-endemic areas.