Ringworm infections caused by Microsporum persicolor in persons from eastern United States were described. Two cases—first, tinea of feet; and second, tinea of face—were observed in patients from Baltimore. The third case was manifested in a facial lesion of a patient from Philadelphia. The identification of the three isolates was confirmed by mating studies with the tester strains of Nannizzia persicolor. The three isolates proved to be of the plus mating type. Thus, M persicolor was reported for the first time as the cause of human ringworm in the United States.
Padhye AA, Blank F, Koblenzer PJ, Spatz S, Ajello L. Microsporum persicolor Infection in the United States. Arch Dermatol. 1973;108(4):561-562. doi:10.1001/archderm.1973.01620250045014