Studies on Stachybotrys alternans. II. Occurrence, morphology and toxigenicity.

Three types of biological methods were compared as detectors of stachybotrys toxin. The seven preparations tested represented “crude” or partially purified toxins produced by different strains of Stachybotrys alternans and toxic fractions obtained by partial purification of the product of one strain. The order of sensitivity of the methods was almost invariably: the mouse fibroblast test most sensitive, the rabbit skin test next, and the brine shrimp (Artemia salina) test last. A conspicuous variation by preparation in relative sensitivity of the mouse fibroblast test and the rabbit skin test was revealed, however. The variation ranged from a sensitivity of the rabbit skin test approximately 2.5 times higher than that in the mouse fibroblast tests to the other limit when the mouse fibroblast test was 80 times more sensitive than the rabbit skin test. The variation is interpreted to provide the first experimental proof of heterogeneity in biological effect based on chemical differences among the compounds constituting “stachybotrys toxin”. The toxic fractions obtained by purification of two crude preparations and identified as toxic by the mouse fibroblast test showed different patterns of distribution of toxicity. The results demonstrate that qualitative differences may exist in the chemical structure of the population of toxic compounds of “stachybotrys toxin” produced by different strains of S. alternans.