Mycobacterium-induced infectious granuloma in Xenopus: histopathology and transmissibility.

The acid-fast bacteria present in the transmissible putative Xenopus lymphosarcoma (px1) (M. Balls, Cancer Res., 22: 1142-1154, 1962) were isolated and identified as Mycobacterium marinum. M. marinum induces an infectious granuloma in Xenopus which is histopathologically indistinguishable from Xenopus "lymphosarcoma" (px1). It had been reported that the filtrate (0.22-micron pore size) and the supernate of ultracentrifugation (20,000 x g) of the pxl tissue homogenate were bacteria free and could transmit the disease (R.H. Clothier and M. Balls, Oncology, 28: 445-457, 1973; R.H. Clothier and M. Balls, Oncology, 28: 458-480, 1973). Both features, however, also correspond to the transmission of M. marinum-induced granuloma. The granuloma induced by the ultrafiltrate of granulomatous tissue homogenate may be due to the granulomatogenic component of the bacteria-containing tissue, since no bacteria were detected in such filtrate. The 100,000 x g centrifugation supernate of the same homogenate, however, contains bacteria which induce granuloma. Since no other feature of pxl corresponds to neoplasia, it is concluded that as diagnosed by Dawe [C.J. Dawe, Natl. Cancer Inst. Monogr., 32: 7-28, 1969; C.J. Dawe. In: M. Mizell (ed.), Recent Results in Cancer Research, pp. 429-440. New York: Springer-Verlag, 1969; C.J. Dawe. In: R.M. Dutcher (ed.), Comparative Leukemia Research. Bibliotheca Haematologica pp. 634-637. New York: Karger, 1970], this spontaneous abnormal growth of Xenopus actually is an infectious granuloma.