Historical Perspective

The first report of reliable cultivation of MAP was published in 1912 and was both detailed and rigorous (Twort and Ingram, 1912). The study was stimulated by the challenge to grow an or­ganism that was obviously present in the lesions of affected livestock but clearly different from Mycobacterium bovis, which was prevalent at the time.

Twort and Ingram studied the active ingre­dient from M. phlei and found that it could be extracted in hot ethanol. They showed that in­clusion of egg in culture media was beneficial, that extracted liver broth and agar media were less suitable than a clotted egg medium, that albumin was not needed for growth and that glycerol was beneficial. MAP grew at 28-43°C. They described the morphology of in vitro grown MAP, showed that it was non-spore forming, non-motile, acid-fast, was a strict aerobe when growing but was not killed in the absence of oxygen for 3 months at 39°C. They reported a slow rate of growth with tiny discrete colonies forming in 3-5 weeks. Cultures were not killed by light and were resistant to disinfectants.

In summary, much of the useful knowledge about cultivation of MAP was provided in one paper in 1912. This breakthrough enabled ad­ditional work that has been of enormous benefit, including the evaluation of alternative culture media, assessment of decontamination solu­tions and improvements to sample preparation protocols (Minett, 1942; Merkal et al., 1982). Although progress was made prior to the mo­lecular era, including the realization that there were different strains of MAP with distinct cul­tural requirements, substantial advances have been made since, particularly with the introduc­tion of PCR to identify the presence and also the growth of MAP in cultures.

is still being determined (Janagama et al., 2009; Wang et al., 2016). Exceptions to the rule of my­cobactin dependence for primary isolation are discussed below.

18.3