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

Abstract

Selective and differential media were designed for each species of Pityrosporum ; P. pachydermatis, P. ouale, 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 P04 (anhydrous), 1.5% agar, 0.01% ampicillin, and 0.025% cycloheximide with a pH of 5.5. Medium for P. ouale (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.

Malassezia pachydermatis: a review

“…The latter characteristic was first reported by Ushijima eta!. [49], who devised selective and differential media for lipid-dependent Malassezia yeasts. Supplementation with laurate (750 mg mi-1 ) leads to the complete growth inhibition of M. pachydermatis.…”

“…pachydermatis was first demonstrated on bovine serum agar [48] and further confirmed using Sabouraud glucose agar and Sabouraud glucose liquid medium, supplemented with casein [46]. M. pachydermatis is resistant to cycloheximide (1000 ppm) (2,44,49]. In fact, increased growth has even been observed with high concentrations of cycloheximide (2000 ppm) [50].…”

Immunology of Diseases Associated withMalasseziaSpecies

“…The difficulty in culturing the organism was explained by Benham in 1939, when she observed the need for a "fatty substance" in the growth medium (45). Once this lipid requirement had been established, it paved the way for the formulation of various culture media that could reliably recover and maintain the organism (135,245,288,325,444,445), enabling work on the taxonomy, physiology, and biochemistry of the genus to be undertaken.…”

Usefulness of Modified Dixon's Medium for Quantitative Culture ofMalasseziaSpecies from Canine Skin

“…However, specific media with lipid supplementation have been devised to culture Malassezia yeasts: modified Dixon's (mDixon) medium, 10,21,27 Leeming's medium, 17 and Ushijima's medium. 26 These media would be appropriate for the isolation of all Malassezia species, i.e., M. pachydermatis as well as lipid-dependent Malassezia species that have been recovered occasionally from canine 22,24 and feline skin. 3,5 Specific media would also allow the isolation of M. pachydermatis strains with exacting culture requirements.…”