THE HUMAN SCALP AS A HABITAT FOR YEASTS 85 isolated. The groups surveyed were considered to be composed of normal young adults. The culture media used for primary isolation were Littman Oxgall Agar (Difco-pH 7), Littman Oxgall Agar with 2 per cent sesame oil (pH 6.8) and Yeast Morphology Agar (Difco-pH 5). Streptomycin sulfate (30 micrograms per mi.) was added to each of the three media after steriliza- tion and cooling to 45øC. Prior to pouring the plates which were to con- rain 2 per cent sesame oil, the oil was shaken vigorously with melted Litt- man Oxgall Agar in order to form an emulsion. Each culture was in- cubated for three days at 35øC. and then for two weeks at 25øC. The techniques and media used in the determination of the morphological and physiological properties of each yeast isolate are those described by Lodder and Kreger-Van Rij (5). RESULTS Yeasts capable of growing on one or more of the media used in this study were isolated from 122 of the 189 individuals participating in the survey. This represents 65 per cent of the total. In some instances more than one yeast was present in the scalp of the same person, resulting in a total of 145 identifiable yeasts which could be maintained in subculture. Three members of the Dermatiatiae were also isolated. These are sometimes called the "Black Yeasts" because of their color. Since they are be- lieved to represent a yeast-like phase of certain molds they were not in- cluded in this survey. All the yeasts identified in this survey were found to be members of the Cryt)tococcaceae. No metfiber of the ascospore forming family Endomy- cetaceae and the ballistospore forming family Sporobolomycetaceae was found. It was also noted that the two yeasts most commonly identified with pathological conditions in man are not scalp inhabitants. These are C. albicans and Cr. neoformans. The predominant yeast was P. ovale which was found in 46 individuals. Other workers have reported the occurrence of P. ovale on the scalp as being between 70 and 94 per cent but this percentage was reached by a direct smear from the scalp and not by growth on isolation media. The other two most common yeasts were C. parapsilosis in 32 individuals and Rh. mucilaginosa in 26 individuals. In all, there were fourteen different species of yeasts identified. These are listed in Table 1. Each of the 14 species of yeasts isolated in this survey were studied to determine which of them had been isolated from the human skin by previ- ous workers and if possible to draw inferences concerning their possible role as scalp pathogens. Table 2 represents a compilation of the work of previous investigators. It wouJd appear, based upon the f_re•quency of occurrence that only, P.

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE 1--IDENTIFIABLE YEASTS ISOLATED FROM THE SCALPS OF 189 HUMANS Number of Frequency Organism Isolates Percentage Pityrosporum ovale 46 31.72 Candida parapsilosis 32 22.07 Rhodotorula mucilaginosa 26 17.93 Cryptococcus diJfiuens 9 6.20 Torulopsisfamata 8 5.52 Cryplococcus albidus 7 4.83 Rhodotorula minuta 4 2.76 Candida mycoderma 3 2.07 Trichosporon cutaneum 3 2.07 Torulopsis inconspicua 2 1.38 Cryptococcus laurentii 2 1.38 Rhodotorulaflava 1 0 69 Rhodotorula rubra 1 0.69 Candida scotti 1 0.69 145 100.00 ovale, C. parapsilosis, and Rh. mucilaginosa are prevalent enough in the human scalp to warrant serious consideration. The case for and against P. ovale has already been discussed. In view of the frequency with which C. parapsilosis has been isolated from onychomycotic infections and be- cause of its proven keratinolytic nature this organism could be added to the list of possible pathogens. Rh. mucilaginosa, on the other hand, has not been recorded as being associated with any skin pathological condition except in one instance. The monograph of Lodder and Kreger-Van Rij (5) makes a single reference to its isolation by Wolfram and Zach from diseased nails in 1934. Because of the higher incidence of Rh. mucilag- inosa in the air than upon human skin Cormell and Skinner (8) refer to this organism as an adventitious saprophyte. TABLE 2--COMPARATIVE STUDIES OF YEASTS ISOLATED FROM VARIOUS SKIN SURFACES Organism A B C D E F G P. ovale * C. parapsilosis * Rh. mucilaginosa * * * Cr. diffluens * * T. f amata * Cr. albidus * * Rh. minuta * C. mycoderma * Trich. cutaneum * T. inconspicua * Cr. laurentii * * Rh. tiara Rh. rubra * * C. scotti * * * * * * * * * * * * * A--Lodder and Kreger-Van Rij. B--Huxley and Hurd. C--Connell and Skinner. D-- Croft and Black. E--DiMenna. F--Sturde. G--Rieth.