FEMS Yeast Research 5 (2005) 1101–1113 www.fems-microbiology.org MiniReview Malassezia Baillon, emerging clinical yeasts Roma Batra a,1, Teun Boekhout b,*, Eveline Gue´ho c, F. Javier Caban˜es d, Thomas L. Dawson Jr. e, Aditya K. Gupta a,f a Mediprobe Research, London, Ont., Canada b Centraalbureau voor Schimmelcultures, Uppsalalaan 8, 85167 Utrecht, The Netherlands c 5 rue de la Huchette, F-61400 Mauves sur Huisne, France d Departament de Sanitat i dÕ Anatomia Animals, Universitat Auto`noma de Barcelona, Bellaterra, Barcelona E-08193, Spain e Beauty Care Technology Division, Procter & Gamble Company, Cincinnati, USA f Division of Dermatology, Department of Medicine, Sunnybrook and WomenÕs College Health Science Center (Sunnybrook site) and the University of Toronto, Toronto, Ont., Canada Received 1 November 2004; received in revised form 11 May 2005; accepted 18 May 2005 First published online 12 July 2005 Abstract The human and animal pathogenic yeast genus Malassezia has received considerable attention in recent years from dermatolo- gists, other clinicians, veterinarians and mycologists. Some points highlighted in this review include recent advances in the techno- logical developments related to detection, identification, and classification of Malassezia species. The clinical association of Malassezia species with a number of mammalian dermatological diseases including dandruff, seborrhoeic dermatitis, pityriasis ver- sicolor, psoriasis, folliculitis and otitis is also discussed. Ó 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved. Keywords: Malassezia; Yeast; Identification; Animals; Disease 1. Introduction a positive staining reaction with Diazonium Blue B (DBB) [3]. The genus was named in 1889 by Baillon Members of the genus Malassezia are opportunistic [6] with the species M. furfur, to accommodate the fila- yeasts of increasing importance, due in large part to ad- mentous fungus observed in scales of the human skin vances in detection and culture methodology which have disease pityriasis versicolor (PV). Pityrosporum [7] has both allowed their investigation and revealed their been proposed as an alternative generic name, but be- importance in human and animal disease [1,2]. The cause Malassezia had been published earlier this name genus Malassezia belongs to the basidiomycetous yeasts has nomenclatural priority. The genus remained limited and is classified in the Malasseziales (Ustilaginomycetes, to M. furfur and M. pachydermatis for a long time. M. Basidiomycota) [3–5]. The cells show a multilayered cell pachydermatis is lipophilic but not lipid-dependent, wall, enteroblastic budding (Fig. 1), urease activity, and and usually occurs on animals [8]. For many years all pathologies caused by M. furfur sensu lato, particularly disorders of the skin such as dandruff, seborrhoeic * Corresponding author. Tel.: +31 30 212 2671; dermatitis (D/SD), pityriasis versicolor (PV), and follic- fax: +31 30 251 2097. E-mail address: [email protected] (T. Boekhout). ulitis, were ascribed to a single species [9]. Only the re- 1 Present address: W281N4904, Theodores Cove, Pewaukee, WI, cent recognition of a number of new species and the USA. development of methods to differentiate them has 1567-1356/$22.00 Ó 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.femsyr.2005.05.006 1102 R. Batra et al. / FEMS Yeast Research 5 (2005) 1101–1113 C ° , (w) , (w) v À + )+ À , (w) + -Glucosidase Growth at 37 b À ÀÀ Fig. 1. Morphology of Malassezia cells. (A) Budding cells of M. À pachydermatis viewed by scanning electron microscopy. (B) M. furfur under bright field microscopy. ) À borrhoeic dermatitis; SD/AN, seborrhoeic Catalase +, w +, ( + ÀÀ ++ + changed this approach [2,10]. The 28S-rDNA sequences )+,( revealed seven distinct genetic entities [11], which are À , (w) + + + now widely accepted as species (M. furfur, M. obtusa, 1 EL À ? ?+?+ À , growth may be inhibited near the well where the substrate is M. globosa, M. slooffiae, M. sympodialis, M. pachyder- 1 matis,andM. restricta) [10]. Since then, five new Malas- )+,( sezia species have been reported (M. dermatis [12], M. À , (w) ÀÀ À À equi [13], M. japonica [14], M. nana [15], and M. yama- À toensis [16]), but further biochemical and molecular )+,( characterization will be required for their acceptance À as distinct species. Biochemical identification tests for 2 3 À À Malassezia species include catalase and b-glucosidase activity, and evaluation of growth with cremophor EL )+,( À and Tweens 20, 40, 60, 80, using the diffusion method 2 3 ++++ +++ in Sabouraud glucose agar (Table 1, Fig. 2) [1,4,10,17]. w+ )+ + À )+,( , opaque zone may occur. 2 3 À ,w 1 ++,++ + Tween 20 Tween 40 Tween++++W,(+)+? 60 Tween 80 Cremophor ÀÀ ++++? +? + ÀÀ À ÀÀÀÀÀ 2. Malassezia species À M. furfur is morphologically heterogeneous with glo- bose, oval or cylindrical yeast cells. This species can be identified by its ability to grow at 37 °C, strong catalase , (w) + dependency ++,( À activity, absence or a very weak b-glucosidase activity, and equal growth in the presence of cremophor EL (=castor oil) and Tweens 20, 40, 60, 80 as sole lipid sources [4,17]. Strains of M. furfur showed two different karyotypes [18], but demonstrated high percentages of DNA/DNA reassociation and high ribosomal RNA similarity [10,11]. Some strains are able to produce fila- Globose, ellipsoidal, cylindrical Globose + Globose, ellipsoidal + ments, either spontaneously or under particular culture [1,2,10,12,14–17,24,26–28,30–33,36,38–42,55,57,62,63,65,72,80,82–84,92,95,96,99–101] conditions [19]. Strains of the species originate from var- ious hosts, body sites and diseases. However, M. furfur was not observed in recent epidemiological surveys of species healthy persons and patients with pityriasis versicolor (PV) and seborrhoeic dermatitis (SD) or with only PV [20,21]. This absence may, perhaps, be caused by the iso- Malassezia lation protocols used, or may arise from competition be- AD Ellipsoidal, globose + AD, AN, HS, OE, PV low, S, SD low AN, AD, P, PVSD high, high, SD/D high AD, HS, SD Ellipsoidal + AD, HS scalp, P, SD, SD/D high AD, HSAN, HS, P, PV, Globose, SD ellipsoidal + Ellipsoidal, cylindrical + +, w, ( AN, OEAN, HS, OE, SD Ellipsoidal, cylindrical + Ellipsoidal + v + + w ? + ? + AN, OE, S, SD/AN Ellipsoidal AD, AN, HS, P, PV, SD Ellipsoidal + tween different skin-inhabiting species of Malassezia. Using the same isolation protocol, the species has been isolated from systemic and mucosal sites, such as urine, , growth may occur at some distance from the well where the substrate is placed; vagina and blood, or exposed sites such as nails (E. Gue´- 2 ho, unpublished data). It has also been isolated from Table 1 Salient characteristics of M. dermatis Species Occurrence Cell morphology Lipid M. furfur M. globosa M. yamatoensis dermatitis in animals; SD/D, seborrhoeic dermatitis/dandruff; SD; w, weak; v, variable; ( ) indicate rare deviations from main pattern; AD, atopic dermatitis; AN, non-human animals; HS, healthy human skin; OE, otitis externa; P, psoriasis; PV, pityriasis versicolor; S, sepsis; SD, se placed; M. restricta M. japonica M. slooffiae M. nana M. obtusa M. pachydermatis animals [22–24]. M. furfur is the only Malassezia species M. sympodialis R. Batra et al. / FEMS Yeast Research 5 (2005) 1101–1113 1103 their esters. All isolates grow well at 37 °C, and some primary cultures show a certain lipid-dependence [28,29]. These weakly-lipid-dependent isolates may have smaller colonies than those growing on regular Sabou- raud dextrose agar. Differences in catalase and b-gluco- sidase expression, that can be absent, weak or positive depending on the strain, and differences in reactivity to cremophor EL and Tweens 20, 40, 60, 80 occur in all rDNA genotypes [4,17]. These different compounds, particularly cremophor EL and Tween 20, may be more or less inhibitory. In this case, growth may occur only at some distance from the compound-containing well where the compound is more diluted, or it may occur within the inhibitory area as secondary growth [30]. M. pachydermatis occurs rarely on humans, although it has been found to cause septic epidemics, usually in neonates receiving intravenous lipid supplementation [31,32]. M. pachydermatis is well-known as a normal cutaneous inhabitant of numerous warm-blooded ani- mals. Seborrhoeic dermatitis and otitis associated with this lipophilic yeast are now commonly recognized, especially in dogs [33]. M. sympodialis corresponds with the former serovar AofM. furfur [10,34] and is characterized by a strong b-glucosidase activity and growth at 37 °C, but cremo- phor EL as a lipid supplement does not allow good growth. The yeast cells are small and ovoid. The species is commonly isolated from healthy as well as diseased skin [20]. Its role as a pathogen has not yet been eluci- dated. Indeed, M. sympodialis is often present in skin le- sions, but usually associated with the more abundantly occurring M. globosa [35]. M. sympodialis has also been isolated from healthy feline skin [36]. Fig. 2. Assimilation patterns of Tween 20, 40, 60 and 80 (Clockwise M. globosa corresponds with serovar B of M. furfur from bar) and Cremophor EL (center). (A) M. sympodialis; (B) M. [10,34] but has spherical yeast cells only [10]. Buds are restricta. also spherical and emerge from the mother yeast through a narrow site, contrary to the patterns seen in other Malassezia spp. The species corresponds to the to be isolated from non-mammalian sources, in one case original description of P. orbiculare obtained from a from a hospital room floor [25]. PV case [37]. M. globosa is able to produce filaments, M. slooffiae may be misidentified as M. furfur, but it in particular in primary cultures. The yeast does not can be differentiated by its absence of growth with crem- grow at 37 °C or does so very poorly, does not grow ophor EL [4,10].