Effect of Temperature on Growth as a Differentiating Characteristic between Human and Nonhuman Isolates of Basidiobolus Species.

Since Basidiobolus ranarum (Eidam, Beitr. Biol. Pflanz. 4:181, 1886) was first reported as a cause of subcutaneous phycomycosis in human beings (Lie Kian Joe et al., Arch. Dermatol. 74:378, 1956), some question has prevailed as to the validity of the specific identification (Drechsler, Am. J. Botany 45:632, 1958). The isolates from man were reported as B. ranarum initially, even though some cultural differences were noted when compared with isolates from nature (Lie Kian Joe et al., Arch. Dermatol. 74:378, 1956; Emmons et al., Mycologia 49:1, 1957). These differences were discounted inasmuch as they were thought to fall within the range of variability. Drechsler (Am. J. Botany 45:632, 1958), however, feels that the species causing human disease differs significantly from the description of B. ranarum, which is usually saprophytic on the excrement of frogs and lizards and which is thought to pass an undetermined period of time within certain insects. One primary difference which this investigator emphasizes is the smoothness of the zygospores of the pathogen of man as opposed to the rough surface of this morphological form produced by species isolated from nature. In studying the immunological and pathological properties of B. ranarum isolated from human and nonhuman sources, a fortuitous observation led to an investigation of the temperatures at which growth occurred, the results of which are reported herein. B. ranarum RSA 334, B. meristosporus RSA 964, and B. microsporus RSA 977, all from nonhuman sources, were obtained from R. K. Benjamin. B. ranarum 6A and 6C were isolated by the authors from feces of the green chameleon found near New Orleans, La. Strains isolated from human lesions were obtained from C. W.