THE RELATIONSHIP BETWEEN THE DOWNY AND GRANULAR FORMS OF TRICHOPHYTON-MENTAGROPHYTES

[摘要] The downy and granular forms of Trichophyton mentagrophytes represent 2 cultural forms of a single species. Expts. indicate that the downy type culture has less virulence for the guinea pig and the dog. Clinical data indicate that they are also less virulent for man. Virulence of the downy type culture may be enhanced by serial passage on guinea pigs. The guinea pig passage strains are also more virulent for both the guinea pig and the dog. In 2 instances, the increased virulence of the downy type culture was accompanied by a morphological change to a granular type culture. The relationship of these 2 cultural types to the epidemiology of T. mentagrophytes infections is discussed. Although neither downy or granular type cultures are isolated strictly from specific clinical entities, the downy type culture is most commonly isolated from chronic, low-grade infections, and the granular type culture is most commonly isolated from acute supperative lesions, particularly those acquired from animals. The fact that the virulence of the downy type culture can be enhanced by animal passage, and that this increase in virulence may be accompanied by a change to the granular type culture appears to explain these phenomena. Evidence is presented suggesting that T. interdigitale should not be considered as a species distinct from T. mentagrophytes.