Revised Culture-Based System for Identification of Malassezia Species

Abstract

Forty-six strains of Malassezia spp. with atypical biochemical features were isolated from 366 fresh clinical isolates from human subjects and dogs. Isolates obtained in this study included 2 (4.7%) lipiddependent M. pachydermatis isolates; 1 (2.4%) precipitate-producing and 6 (14.6%) non-polyethoxylated castor oil (Cremophor EL)-assimilating M. furfur isolates; and 37 (34.3%) M. slooffiae isolates that were esculin hydrolyzing, 17 (15.7%) that were non-tolerant of growth at 40°C, and 2 (1.9%) that assimilated polyethoxylated castor oil. Although their colony morphologies and sizes were characteristic on CHROMagar Malassezia medium (CHROM), all strains of M. furfur developed large pale pink and wrinkled colonies, and all strains of M. slooffiae developed small (<1 mm) pale pink colonies on CHROM. These atypical strains were distinguishable by the appearance of their colonies grown on CHROM. Three clinically important Malassezia species, M. globosa, M. restricta, and M. furfur, were correctly identified by their biochemical characteristics and colony morphologies. The results presented here indicate that our proposed identification system will be useful as a routine tool for the identification of clinically important Malassezia species in clinical laboratories.Members of the genus Malassezia are among the microbiological flora of the skin of homoiothermic animals. Most species of this genus are lipid-dependent yeasts which colonize the seborrheic part of the skin, and they have been reported to be associated with pityriasis versicolor, seborrheic dermatitis, Malassezia folliculitis, and atopic dermatitis (1,6,19,20,24,29). Although M. furfur was previously thought to be the causative agent or trigger factor in all of these skin disorders, Guého et al. (9) reclassified this genus into five species in 1996. Malassezia has since been reclassified into seven species based on molecular biological analysis of nuclear ribosomal DNA/ RNA (9, 10), and the results agreed with those of mitochondrial ribosomal DNA analyses (30). As members of the genus Malassezia share similar morphological and biochemical characteristics, it was thought that differentiating between them based on phenotypic features would be difficult. While molecular biological techniques are the most reliable for the identification of Malassezia, they are not available in most clinical laboratories. Therefore, culture methods for the identification of Malassezia species are required. Some of these identification or differentiation methods have been reported previously. Guillot et al. reported a method of identification based on lipid usage pattern, catalase reaction, growth temperature, and cell shape (11). Hammer and Riley reported the production of a precipitate by some Malassezia strains on Dixon's agar (12); for example, M. furfur, M. obtusa, and M. slooffiae were precipitate-negative strains, while M. sympodialis and M. globosa were precipitate-positive strains. Mayser et al. reported that some Malassezia species hydrolyzed esculin and assimilated pol...

Genotyping of <i>Malassezia pachydermatis</i> Isolates from Canine Healthy Skin and Lesional Skin of Atopic Dermatitis in Japan, Korea and Taiwan

“…Samples were obtained from healthy skin (24 dogs) and from skin lesions of atopic dermatitis (42 dogs). Each sample was derived from at least 3 areas of the external ear, paw, and abdominal regions and samples were cultured using CHROMagar Malassezia medium (CHROMagarm, Paris, France) [2].…”

“…Samples were obtained from healthy skin (24 dogs) and from skin lesions of atopic dermatitis (42 dogs). Each sample was derived from at least 3 areas of the external ear, paw, and abdominal regions and samples were cultured using CHROMagar Malassezia medium (CHROMagarm, Paris, France) [2].Isolates of M. pachydermatis(n=182) were identified phenotypically based on morphology and on their ability to grow on medium with no lipid supplementation [1]. The isolates were divided into two groups: Group I consisted of 72 (3 strains per 1 dog) isolates collected from the healthy skin of 24 healthy dogs, and Group II consisted of 110 (2 or 3 isolates per 1 patient) isolates collected from the atopic dermatitis skin lesions of 42 dogs (25 isolates from Japan, 22 isolates from Korea and 63 isolates from Taiwan).…”

Prevalence of Malassezia species in patients with pityriasis versicolor in Rosario, Argentina

“…The scheme used for the identification of the isolates proposed by Kaneko et al, 26 showed good results in our laboratory to identify species. All the clinical isolates showed positive catalase reaction.…”

“…Moreover, the new scheme proposed by Kaneko et al 26 that requires modified CHROMagar-Malassezia medium, SGA, Tween 60-Esculin agar (EA), Cremophor El agar (CrEl) and catalase reaction, was proved. The latter scheme uses the following culture media:…”

“…15,18 Nowadays, the Japanese system of identification has been proposed. 25,26 It requires subculturing the isolated strain on several media as CHROMagar-Malassezia (CHROMM), Sabouraud Glucose Agar, Cremophor EL agar or Tween 60-Esculin agar. 2 The aim of this research was to evaluate the prevalence of Malassezia species in the superficial infection of the stratum corneum (pityriasis versicolor) in Rosario city, and to analyze their distribution according to patients' characteristics such as age, gender and site of lesions.…”