Selective and Differential Media for Isolation and Tentative Identification of Each Species of Pityrosporum Residing on Normal or Diseased Human Skin

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Abstract
Selective and differential media were designed for each species of Pityrosporum; P. pachydermatis, P. ovale, and P. orbiculare in order to make feasible a quantitative cultivation. Medium for P. pachydermatis (medium A) was composed of 1% trypticase peptone (BBL), 0.5% yeast extract (BBL), 0.3% glucose, 0.2% NaCl, 1.2% KH2 PO4 (anhydrous), 1.5% agar, 0.01% ampicillin, and 0.025% cycloheximide with a pH of 5.5. Medium for P. ovale (medium B) was medium A supplemented with 0.05% sodium acetate (anhydrous), 0.2% Tween 80, and 0.025% (selective medium) or 0.075% (differential medium) sodium laurate. Medium for P. orbiculare was medium B (devoid of laurate) supplemented with 2% olive oil, 0.25% glycerol, 0.25% gall powder, 0.05% sodium palmitate, 0.05% sodium stearate, 0.05% sodium oleate and 8% (selective medium) or 10% (differential medium) sodium lactate and an increase in Tween to 1%. For isolation of Pityrosporum, specimens were suspended in 0.1% Tween 80 solution and inoculated onto agar plates of three selective media. The plates were incubated aerobically at 37 C for 8-10 days under conditions of prevention of water loss from the media. The plating efficiency of each selective medium, expressed as a ratio of cultural counts to microscopic counts was generally over 70%. Species of Pityrosporum could also be identified when we inoculated the cell suspension onto differential agar plates and incubated the preparations at 37 C for 7 days.