Malassezia Yeasts Research Articles

Editorial

In this issue, guidelines on two more very important conditions in veterinary dermatology are published. These documents adopt the same successful format developed and sponsored by the World Association for Veterinary Dermatology (WAVD) as used for the guidelines on infections caused by meticillin-resistant staphylococci, and on dermatophytosis of small animals that were published in Veterinary Dermatology volume 28, issue three of June 2017.1 The new guidelines deal with the diagnosis and treatment of demodicosis in dogs and cats, chaired by Ralf Mueller, and the biology, diagnosis and treatment of Malassezia dermatitis in dogs and cats, chaired by Ross Bond. They have already been presented in draft form at the North American Veterinary Dermatology Forum in Maui, Hawaii, and at the ESVD-ECVD Congress in Dubrovnik, Croatia, in 2018. The Malassezia guidelines were also presented at the Malassezia workshop of the International Society for Human and Animal Mycology (ISHAM) in Utrecht, the Netherlands in 2018. The guidelines comprehensively review the literature relating to these diseases, focusing on clinical signs, diagnosis and treatment, and they concisely summarise the consensus recommendations providing easy access to this essential information at the beginning of each text. Importantly, they also identify areas where lack of knowledge makes treatment and prevention of these conditions more difficult and where further research is needed. The Malassezia guidelines provide, in addition, a detailed review of the biology of this genus and illustrate the emerging knowledge that has led to the development of its taxonomy and the identification of multiple species of the organism. This examination of historical aspects of Malassezia yeasts as skin pathogens illustrates the way in which World War I and World War II retarded knowledge of the organism and its diseases both in animals and in man. The demodicosis guidelines also touch on sociological factors when they describe how the use of the isoxazoline drug, fluralaner, could be used to allow breeding of healthy puppies from bitches that are susceptible to generalised demodicosis and would otherwise have offspring likely to develop this disease. However, the authors warn against the temptation to adopt this approach as it would be likely to further increase susceptible canine populations. The importance of sociological factors in the management of disease both in animals and in man was a feature examined by Tony Barnett in an editorial accompanying the first set of WAVD guidelines.2 He reminded us that preparation of guidelines and their adoption depend not only on scientific knowledge and the approach taken by clinicians but also on attitudes towards the diseases and their control amongst dog breeders and owners. Such attitudes influence the demand for fashionable breeds, possibly promoting the breeding of dogs with increased susceptibility to diseases such as Malassezia dermatitis and demodicosis. We still need to find ways of informing potential owners about such issues and enabling them to understand the suffering and difficulties of management which are imposed on such animals. The WAVD has a continuing programme of guideline preparation aimed at promoting best practice in veterinary dermatology. Two more guidelines are currently reaching the final stages. They will deal with equine hypersensitivity, chaired by Rosanna Marsella, and best clinical practices in otitis of dogs and cats, chaired by Jim Noxon and will be presented at the 9th World Congress of Veterinary Dermatology in Sydney, Australia, in October 2020. All of the WAVD guidelines are to be published in Veterinary Dermatology with open access or free access so as to maximise their availability to and use by veterinary practitioners, both specialists and those in general practice, and also to research workers.

PH-Dependent Expression, Stability, and Activity of Malassezia restricta MrLip5 Lipase.

BackgroundThe lipophilic yeasts Malassezia spp. are normally resident on the surface of the human body, and often associated with various skin diseases. Of the 18 known Malassezia spp., Malassezia restricta is the most predominantly identified Malassezia sp. found on the human skin. Malassezia possesses a large number of genes encoding lipases to degrade human sebum triglycerides into fatty acids, which are required not only for their growth, but also trigger skin diseases. Previously, we have shown that MrLIP5 (MRET_0930), one of the 12 lipase genes in the genome of M. restricta, and is the most frequently expressed lipase gene in the scalp of patients with dandruff.ObjectiveIn this study, we aimed to analyze the activity, stability, and expression of MrLip5, with particular focus on pH.MethodsWe heterologously expressed MrLip5 in Escherichia coli, and purified and analyzed its activity and expression under different pH conditions.ResultsWe found that MrLip5 was most active and stable and highly expressed under alkaline conditions, which is similar to that of the diseased skin surface.ConclusionOur results suggest that the activity and expression of MrLip5 are pH-dependent, and that this lipase may play an essential role at the M. restricta-host interface during disease progression.

Occurrence of Malassezia Spp. on Healthy Human Skin

Abstract The genus Malassezia currently includes seventeen species that have been isolated from healthy and diseased human and other animal skin. Malassezia are implicated in a range of cutaneous diseases in humans: pityriasis versicolor, atopic or seborrheic dermatitis, dandruff, folliculitis and psoriasis. The outbreak of the disease depends on the interaction between the host immune system and Malassezia species. Malassezia stimulates both the cellular and humoral immune response in humans. Although Malassezia species have been associated with various dermatological diseases in people, the detailed pathological role of Malassezia remains obscured. Malassezia yeasts require lipids for their growth and therefore to a greater extent they colonize the sites with more sebaceous glands. The ecosystem on skin is complex and its balance depends on several factors. The aim of this study was to determine the presence of Malassezia yeasts in clinically normal skin of 42 healthy, randomly selected individuals of different ages. In the group of people examined, up to 30 persons (71.4 %) represented by children, adults and the elderly were positive to Malassezia yeasts. It has been shown that the back is an area with a higher incidence (66.7 %) of observed yeast compared to the head (40.5 %).

Antifungal in vitro Activity of Essential Oils against Clinical Isolates of Malassezia pachydermatis from Canine Ears: A Report from a Practice Laboratory

Background: The yeast Malassezia pachydermatis is a commensal but also the most isolated pathogenic yeast in canine otitis externa. Essential oils (EOs) exhibit antimicrobial activity and thus could be an alternative for treatment of otitis. Objective: The aim of this study was to analyse the in vitro efficacy of EOs against M. pachydermatis isolates from canine ears. Materials and Methods: Twenty-two EOs were tested for their in vitro activity against 15 M. pachydermatis isolates by agar disc diffusion. In addition, diluted EOs were tested and volatile antifungal activity was analysed by vapour assay. Results: Most EOs showed in vitro efficacy against M. pachydermatis. A different susceptibility pattern of tested isolates was found. Overall, the most potential EO was lemon grass. Also, cinnamon leaf, clove, manuka, Indian melissa, oregano, palmarosa, and winter savory oil exhibited a strong antifungal activity. Volatile activity was proven by the inhibiting effect in vapour assay. Conclusion: EOs show in vitro activity against M. pachydermatis. This study gives scientific background for the use of EOs in veterinary medicine. Diverse susceptibility patterns of different M. pachydermatis strains emphasise the helpfulness of an aromatogram as one lead for the best choice of an EO for therapy.

Malassezia colonisation on a reconstructed human epidermis: Imaging studies.

Biofilm formation represents a major microbial virulence attribute especially at epithelial surfaces such as the skin. Malassezia biofilm formation at the skin surface has not yet been addressed. The present study aimed to evaluate Malassezia colonisation pattern on a reconstructed human epidermis (RhE) by imaging techniques. Malassezia clinical isolates were previously isolated from volunteers with pityriasis versicolor and seborrhoeic dermatitis. Yeast of two strains of Mfurfur and Msympodialis were inoculated onto the SkinEthic™ RHE. The tissues were processed for light microscopy, wide-field fluorescence microscopy and scanning electron microscopy. Colonisation of the RhE surface with aggregates of Malassezia yeast entrapped in a multilayer sheet with variable amount of extracellular matrix was unveiled by imaging techniques following 24, 48, 72 and 96hours of incubation. Whenever yeast were suspended in RPMI medium supplemented with lipids, the biofilm substantially increased with a dense extracellular matrix in which the yeast cells were embedded. Slight differences were found in the biofilm architectural structure between the two tested species with an apparently higher entrapment and viscosity in Mfurfur biofilm. Skin isolates of Mfurfur and Msympodialis were capable of forming biofilm in vitro at the epidermal surface simulating in vivo conditions. Following 24hours of incubation, without added lipids, rudimental matrix was barely visible, conversely to the reported at plastic surfaces. The amount of biofilm apparently increased progressively from 48 to 96hours. A structural heterogeneity of biofilm between species was found.

Seborrheic dermatitis—Looking beyond Malassezia

Seborrhoeic Dermatitis (SD) is a very common chronic and/or relapsing inflammatory skin disorder whose pathophysiology remains poorly understood. Yeast of the genus Malassezia has long been regarded as a main predisposing factor, even though causal relationship has not been firmly established. Additional predisposing factors have been described, including sebaceous activity, host immunity (especially HIV infection), epidermal barrier integrity, skin microbiota, endocrine and neurologic factors, and environmental influences. Genetic studies in humans and mouse models-with particularly interesting insights from examining the Mpzl3 knockout mice and their SD-like skin phenotype, and patients carrying a ZNF750 mutation-highlight defects in host immunity, epidermal barrier and sebaceous activity. After synthesizing key evidence from the literature, we propose that intrinsic host factors, such as changes in the amount or composition of sebum and/or defective epidermal barrier, rather than Malassezia, may form the basis of SD pathobiology. We argue that these intrinsic changes provide favourable conditions for the commensal Malassezia to over-colonize and elicit host inflammatory response. Aberrant host immune activity or failure to clear skin microbes may bypass the initial epidermal or sebaceous abnormalities. We delineate specific future clinical investigations, complemented by studies in suitable SD animal models, that dissect the roles of different epidermal compartments and immune components as well as their crosstalk and interactions with the skin microbiota during the process of SD. This research perspective beyond the conventional Malassezia-centric view of SD pathogenesis is expected to enable the development of better therapeutic interventions for the management of recurrent SD.

Onychomycosis Caused by Malassezia pachydermatis in a Dog

Background: Malassezia species are commensal skin organisms of warm-blooded vertebrates that can act as opportunistic pathogens. Malassezia pachydermatis is of importance in both veterinary and human medicine. Recognised initially as causes of infection of the skin, they are now known to be superficial commensals as well as potential causes of infections in domestic animals and more serious human conditions such as fungemia. They have also been implicated in the pathogenesis of allergic and other inflammatory diseases. Onychomycosis is defined as fungal infection of the claw (nail disease) caused by dermatophytes (Microsporum and Trichophyton genus), non-dermatophyte molds (hyaline and dematiaceous) and/or yeasts. The objective of this work was to report a case of canine onychomycosis by Malassezia pachydermatis based on reference standard diagnostics of this pathology.Case: A 9-year-old male West Highland White Terrier presented history of claw abnormality: brown staining and partly brittle. The dog has no apparent history of trauma on the affected claw and no skin disease was reported. Direct examination of claw was performed using the tape strip technique revealed Malassezia organisms. Nail fragments were cultured onto Sabouraud Dextrose Agar with Chloramphenicol and Cycloheximide. After 10 days of incubation (32ºC) nail fragments allowed the isolation of pure colonies of Malassezia pachydermatis. The histopathological evaluation was performed by Sector of Veterinary Clinical Pathology, Faculdade de Veterinária (FAVET/UFRGS) and fungal infection due to Malassezia pachydermatis was confirmed by histopathologic examination (Hematoxylin and eosin and Grocott’s methenamine silver stain) of the nail, that revealed abundant yeasts (blastoconidia).Discussion: Fungal infection of the skin, hair and nails are common and are primary caused by the dermatophyte molds. Non-dermatophyte molds isolated from nails constitute a long list, but only a few species cause onychomycoses. These include Scopulariopsis brevicaulis, Fusarium sp., Acremonium spp., Aspergillus spp., Penicillium spp. Yeasts like Malassezia and Candida spp. are saprophytes and usually represent incidental contaminants associated with a non-sterile specimen at mycological culture, however in some cases they may parasite the nails and become an etiological agent of the disease. M. pachydermatis, normally present on the skin and in the ear canal of dogs and cats, can act as opportunistic pathogenic microbe and frequently causes dermatitis and otitis in mammals. In the case of onychomycosis, there is little evidence that Malassezia yeasts are implicated in nail plate invasion, although this may be a rare occurrence. All species of the genus are obligatory lipid-dependent forms, with the exception of M. pachydermatis, as well as absence of keratinolytic ability. Malassezia organisms were commonly retrieved from the subungual claw fold region of normal healthy dogs (should be considered resident microflora of the normal canine claw fold). Some authors suggests that high numbers of yeast can be detected on cytological evaluation of the skin surface of the canine claw fold from allergic dogs in both the absence and presence of concurrent signs of pruritus and paronychia.

Topical Non-Pharmacological Treatment for Facial Seborrheic Dermatitis.

Facial seborrheic dermatitis (FSD) is a chronic and relapsing inflammatory skin disorder occurring in areas of the face rich in sebaceous glands. It clinically manifests as erythematous scaly macules or plaques, often associated with pruritus. Although the pathogenesis of seborrheic dermatitis is not yet fully understood, Malassezia yeast, hormones, sebum levels, and immune response are known to play important roles. Additional factors including drugs, cold temperatures, and stress may exacerbate the condition. Currently, the available treatments do not cure the disease but relieve symptoms. Various pharmacological treatments are available, including antifungal agents, keratolytics, topical low-potency steroids, and calcineurin inhibitors. All of them provide several benefits, but they also have potential side effects. Seborrheic dermatitis tends to have a chronic, recurrent course. To avoid the long-term use of drugs, topical non-pharmacological products such as cosmetics or medical devices may improve clinical outcomes. Products with antimicrobial and anti-inflammatory ingredients such as zinc, piroctone olamine, dihydroavenanthramide, biosaccharide gum-2, and stearyl glycyrrhetinate may speed FSD recovery and avoid flare-ups. Finally, the use of specific cleansers, moisturizers, and sunscreens formulated as light creams or gel/creams should be strongly recommended to all FSD patients. We provide a brief review of the most used non-pharmacological cleansers, topical gel/creams, and specific sunscreens in the management of FSD.

Human thioredoxin, a damage-associated molecular pattern and Malassezia-crossreactive autoallergen, modulates immune responses via the C-type lectin receptors Dectin-1 and Dectin-2

Human thioredoxin (hTrx), which can be secreted from cells upon stress, functions in allergic skin inflammation as a T cell antigen due to homology and cross-reactivity with the fungal allergen Mala s13 of the skin-colonizing yeast Malassezia sympodialis. Recent studies have shown that cell wall polysaccharides of Malassezia are detected by the immune system via the C-type lectin receptors Dectin-1 and Dectin-2, which are expressed on myeloid cells. Therefore, this study aimed to investigate a putative interaction between Dectin-1, Dectin-2 and the allergens Mala s13 and hTrx. Stimulation of human monocyte-derived dendritic cells or macrophages with Mala s13 or hTrx resulted in remarkable secretion of IL-1β and IL-23. Blocking experiments suggest that hTrx induces IL-23 by Dectin-1 binding and IL-1β by binding to either Dectin-1 or Dectin-2. Regarding Mala s13, Dectin-1 appears to be involved in IL-1β signaling. Interference of Syk kinase function was performed to investigate downstream signaling, which led to diminished hTrx responses. In our experiments, we observed rapid internalization of Mala s13 and hTrx upon cell contact and we were able to confirm direct interaction with Dectin-1 as well as Dectin-2 applying a fusion protein screening platform. We hypothesize that this cytokine response may result in a Th2/Th17-polarizing milieu, which may play a key role during the allergic sensitization in the skin, where allergen presentation to T cells is accompanied by microbial colonization and skin inflammation.

Malassezia interaction with a reconstructed human epidermis: Keratinocyte immune response.

The immediate immune response developed by the keratinocytes against Malassezia yeasts has been addressed yielding conflicting results. This study aims the assessment of cytokines and antimicrobial peptides gene expression elicited by M. sympodialis and M. furfur once in contact with a reconstructed human epidermis. A yeast suspension was prepared in RPMI 1640 medium (Sigma-Aldrich, St. Louis, MO) supplemented with Tween 60 and oleic acid to obtain approximately 1 × 106 cells in a volume of 100μL. Clinical isolates of M. sympodialis (from pityriasis versicolor) and M. furfur (from seborrhoeic dermatitis) were inoculated, separately, onto a reconstructed human epidermis. A distinct expression pattern was found between the two tested species, with a tendency for overexpression of pro-inflammatory cytokines very soon after infection, whereas no significant expression or gene downregulation was often noticed following 24 and 48h of incubation. A possible Malassezia species-dependent immune response pattern is highlighted.

Investigation on Microecology of Hair Root Fungi in Androgenetic Alopecia Patients.

This study focused on the differences in hairy root fungal microecology between androgenetic alopecia patients and healthy individuals. Light microscopy was used to observe the morphology of hairy roots. Morphological observations were also performed in the positive specimens using scanning electron microscopy and transmission electron microscopy. The high-throughput sequencing method was used to detect the fungal microecology of hairy roots at different sites. Moreover, the comparison of fungal loads of Malassezia in different group and scalp area were tested by PCR. The fungi in the hair root observed by optical microscopy are mainly Malassezia yeast. The positive rate of Malassezia in the hair loss group (60%) was higher than that in the control group (40%). The detection efficiency of Malassezia examined by scanning electron microscopy was higher than that by light microscopy. Results acquired from high-throughput molecular sequencing of fungi suggested that Ascomycota was the dominant species, whereas in the occipital hair roots of the control group Basidiomycota was the dominant species in the hair loss group. Malassezia followed by Trichosporon were the most abundant fungal genera. The changes in abundance at the top and occipital region of the control group were more significant than those of the genus Fusarium, followed by Epicoccum and Malassezia. The load of Malassezia located on calvaria in the alopecia group was significantly higher than that in the control group. In the alopecia group, the load of Malassezia on the scalp was higher than that on the occipital region. The load of Malassezia globosa and Malassezia restricta in the hair loss group was higher on calvaria and occipital areas. Malassezia had a positive correlation with the incidence of androgenic alopecia.

Advancing Functional Genetics Through Agrobacterium-Mediated Insertional Mutagenesis and CRISPR/Cas9 in the Commensal and Pathogenic Yeast Malassezia.

Malassezia encompasses a monophyletic group of basidiomycetous yeasts naturally found on the skin of humans and other animals. Malassezia species have lost genes for lipid biosynthesis, and are therefore lipid-dependent and difficult to manipulate under laboratory conditions. In this study, we applied a recently-developed Agrobacterium tumefaciens-mediated transformation protocol to perform transfer (T)-DNA random insertional mutagenesis in Malassezia furfur A total of 767 transformants were screened for sensitivity to 10 different stresses, and 19 mutants that exhibited a phenotype different from the wild type were further characterized. The majority of these strains had single T-DNA insertions, which were identified within open reading frames of genes, untranslated regions, and intergenic regions. Some T-DNA insertions generated chromosomal rearrangements while others could not be characterized. To validate the findings of our forward genetic screen, a novel clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system was developed to generate targeted deletion mutants for two genes identified in the screen: CDC55 and PDR10 This system is based on cotransformation of M. furfur mediated by A. tumefaciens, to deliver both a CAS9-gRNA construct that induces double-strand DNA breaks and a gene replacement allele that serves as a homology-directed repair template. Targeted deletion mutants for both CDC55 and PDR10 were readily generated with this method. This study demonstrates the feasibility and reliability of A. tumefaciens-mediated transformation to aid in the identification of gene functions in M. furfur, through both insertional mutagenesis and CRISPR/Cas9-mediated targeted gene deletion.

The lipid profile of three Malassezia species assessed by Raman spectroscopy and discriminant analysis

Malassezia yeasts constitute the major eukaryotic cutaneous flora of homoeothermic vertebrates. These lipophilic yeasts are able to cause, trigger, or aggravate common skin diseases under favorable conditions. Species identification and subspecies differentiation is currently based on morphological characteristics, lipid assimilation profile, and molecular tests. Mass spectrometry has been also reported as a reliable, yet costly and labor-intensive, method to classify Malassezia yeasts. Here, we introduce Raman spectroscopy as a new molecular technique able to differentiate three phylogenetically close Malassezia species (M.globosa, M.pachydermatis, and M.sympodialis) by examining their lipid metabolic profile. Using Raman spectroscopy, lipid fingerprints of Malassezia cultures on Leeming-Notman agar, were analyzed by spectral bands assignment and partial least squares discriminant analysis. Our results demonstrate differential utilization of lipid supplements among these three species and the ability of Raman spectroscopy to rapidly and accurately discriminate them by predictive modelling.

Malassezia-derived aryl hydrocarbon receptor ligands enhance the CCL20/Th17/soluble CD163 pathogenic axis in extra-mammary Paget's disease.

Malassezia yeast play a role in the pathogenesis of chronic dermatitis, especially in apocrine areas, by polarizing the local immunologic background to a Th2/Th17 state through aryl hydrocarbon receptor (AhR)-dependent pathways. Extra-mammary Paget's disease (EMPD) is an adenocarcinoma of apocrine origin, and except for cases associated with Malassezia yeast and their metabolites, the lesions typically develop in areas not exposed to environmental material. The purpose of this study was to investigate (a) the immunomodulatory effects of Malassezia metabolites on normal human keratinocytes (NHKCs), focusing on interleukin (IL)-17 and related cytokines/chemokines (IL-23, IL-36γ, CCL20), (b) the expression of these factors in lesion-affected skin in EMPD and (c) the activation of tumor-associated macrophages (TAMs) by these factors. Malassezia metabolites augmented the expression of cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1), CCL20 and IL-36γ mRNA in NHKCs in vitro. In lesion-affected skin of patients with EMPD, epidermal keratinocytes expressed CYP1A1 and CCL20. In addition, Paget cells expressed CCL20 and IL-23. IL-17-producing cells were distributed adjacent to Paget cells. Compared to healthy donors, patients with EMPD exhibited significantly increased serum levels of soluble (s)CD163, CXCL5, CXCL10 and CCL20. In addition, serum levels of sCD163 decreased significantly following tumor resection. Our study demonstrates a possible mechanism for the development of EMPD involving AhR-mediated signalling by epidermal keratinocytes and RANKL-induced recruitment of Th17 cells and TAMs.

In vitro efficacy of antifungal agents alone and in shampoo formulation against dandruff‐associated Malassezia spp. and Staphylococcus spp.

Dandruff is a complex skin condition characterized by unpleasant itching and flaking of the scalp. It is primarily attributed to the over colonization of Malassezia yeasts such as Malassezia globosa and Malassezia restricta. Some studies also suggest the involvement of staphylococci bacteria in dandruff disease pathogenesis. We aimed to access the effectiveness of anti-dandruff treatments by determining the efficacy of the active antifungal agents alone or in commercial shampoo formulations against Malassezia and Staphylococcus. The minimum inhibitory concentrations of three anti-dandruff shampoo antifungals (zinc pyrithione, ketoconazole and ciclopirox) and the witch hazel extract, hamamelitannin were tested against commensal Malassezia and Staphylococcus species using broth microdilution methods. In experiments simulating shampoo exposure and washing conditions on the scalp, we also tested the ability of the above agents in shampoo formulation (Head and Shoulders® (H&S), Ketomed® , Sebiprox® , Erol Healthcare Hair Shampoo® respectively) along with a generic over-the-shelf shampoo to inhibit microbial growth. Ketomed® and H&S shampoo were the most effective treatments against Malassezia in invitro assays and washing simulation experiments. Erol Healthcare Hair Shampoo® was less effective against Malassezia as it required a longer contact time to achieve growth inhibition for some species. Sebiprox® showed variable efficacy in washing and contact time experiments whereas the generic over-the-shelf shampoo was the least effective in inhibiting Malassezia and Staphylococcus growth. From these findings, it is reasonable that patients with dandruff may benefit from applying specific antifungal shampoo although results may vary with microbial species, time of contact and shampoo formulation components.

Antifungal activity of selected Malassezia indolic compounds detected in culture.

Malassezia yeasts produce bioactive indolic substances when grown on L-tryptophan agar. A panel of these substances was tested against commensal and opportunistic fungi, the Minimum Inhibitory Concentration (MIC) was determined and the potential for in loco antifungal activity on the skin was assessed. Eight indoles were included (malassezin, pityriacitrin, indirubin, indolo[3,2-b]carbazole, 6-formylindolo[3,2-b]carbazole, tryptanthrin, 6-hydroxymethylindolo[3,2-b]carbazole and 6-methylindolo[3,2-b]carbazole) and were tested against 40 fungal strains [yeasts: Malassezia spp.(N=9); Cryptococcus spp.(N=10); Candida spp.(N=7); Yarrowia lipolytica(N=1); Exophialla dermatitidis (N=2); moulds: Aspergillus spp.(N=7); Fusarium spp.(N=2); Rhizopus oryzae(N=2)]. The concentration of 5/8 of the tested indoles on diseased skin was calculated from published data. Kruskal-Wallis and Mann-Whitney U tests were employed for group susceptibility evaluation in 33 strains. The MIC range was 0.125-32μg/mL, and the median log2 MIC was four. Indirubin was the most potent antifungal agent and differed significantly from the others. The highest median MIC was found for FICZ. Malassezia with Candida strains were more susceptible compared to Cryptococcus and Aspergillus, and this inhibitory activity was predicted to be valid also on human skin. Malassezia yeasts produce indolic species that inhibit an array of clinically significant yeasts and moulds.

Efficacy and tolerability of 1% ciclopirox shampoo in the treatment of moderate-to-severe scalp seborrheic dermatitis: a multicenter, prospective, assessor-blinded trial.

Seborrheic dermatitis (SD) is a very common inflammatory skin disease. It occurs in 1-3% of the population. The most supported pathogenetic theory links SD to dandruff via a common etiology, yeasts of the genus Malassezia. Ketoconazole and ciclopirox (CPX) shampoo are considered as the first line treatment of SD of the scalp. CPX is a broad-spectrum, hydroxypyridone-derived, synthetic antifungal agent with anti-bacterial, anti-inflammatory, and anti-oxidant properties. The aim of this study was to assess the efficacy and tolerability of 1% CPX shampoo in SD of the scalp. A total of 40 patients, 31 men and 9 women, mean age 33±6 years, with scalp SD of moderate-to-severe grade were enrolled, after their informed consent, in this 12-week prospective assessor-blinded trial. One-percent CPX shampoo (5 mL) was applied twice a week for 12 weeks. The primary efficacy parameter was the Total Dandruff Severity Score (TDSS), based on 4-point ordinal scales describing signs and symptoms (scaling, inflammation, and itching) of the disease, evaluated in an assessor-blinded fashion, at baseline and after 6 and 12 weeks. Secondary outcomes were the single items of the TDSS and the evaluation of local tolerability. At baseline the TDSS was 17±5. After 1% CPX TDSS was reduced to 10±5 at week 6 and to 6.6±4 at the end of study period (P=0.0001; ANOVA test). This difference represents a 62% reduction in comparison with baseline. At week 12, the reduction of scaling, inflammation and itching scores were -55%, -65%, and -69%, respectively. The product was very well tolerated. No side effects were reported or observed during the study. The study supports the use of 1% CPX shampoo in the treatment of SD of the scalp. CPX shampoo was able to reduce desquamation, inflammation and itching associated with scalp SD. Furthermore, 1% CPX shampoo was found to be safe and well tolerated.

Secreted Hydrolytic and Haemolytic Activities of Malassezia Clinical Strains.

Malassezia yeasts are opportunistic pathogens associated with a number of skin diseases in animals and humans. The free fatty acids released through these organisms' lipase and phospholipase activities trigger inflammation in the host; thus, these lipase and phospholipase activities are widely recognised as some of the most important factors in Malassezia pathogenesis. In this study, we sought to investigate and examine the relationship between these secreted hydrolytic activities and haemolytic activity in newly isolated Malassezia clinical strains. This characterisation was expected to elucidate pathogenicity of this fungus. We isolated 35 clinical strains of Malassezia spp.; the most frequently isolated species were M. sympodialis and M. furfur. Next, we analysed the hydrolytic activities of all of these clinical isolates; all of these strains (except for one M. dermatis isolate) showed detectable lipase and phospholipase activities against 4-nitrophenyl palmitate and L-α-phosphatidylcholine, dipalmitoyl, respectively. Most of the M. globosa isolates showed higher lipase activities than isolates of other Malassezia species. In terms of phospholipase activity, no significant difference was observed among species of Malassezia, although one isolate of M. globosa showed considerably higher phospholipase activity than the others. All tested strains also exhibited haemolytic activity, both as determined using 5% (v/v) sheep blood agar (halo assay) and by quantitative assay. Although all tested strains showed detectable haemolytic activity, we did not observe an apparent correlation between the secreted lipase and phospholipase activities and haemolytic activity. We infer that the haemolytic activities of Malassezia spp. are mediated by non-enzymatic factor(s) that are present in the secreted samples.

Malassezia: The Forbidden Kingdom Opens

Malassezia yeast exist on all humans and have long been associated with healthy and diseased skin. Inthisissue of Cell Host & Microbe, Sparber etal. (2019) and Limon etal. (2019) present murine models for Malassezia/host interaction and describe a role for Malassezia in inflammatory skin and gut disease.

The Skin Commensal Yeast Malassezia Triggers a Type 17 Response that Coordinates Anti-fungal Immunity and Exacerbates Skin Inflammation

Commensal fungi of the mammalian skin, such as those of the genus Malassezia, are associated with atopic dermatitis and other common inflammatory skin disorders. Understanding of the causative relationship between fungal commensalism and disease manifestation remains incomplete. By developing a murine epicutaneous infection model, we found Malassezia spp. selectively induce IL-17 and related cytokines. This response is key in preventing fungal overgrowth on the skin, as disruption of the IL-23-IL-17 axis compromises Malassezia-specific cutaneous immunity. Under conditions of impaired skin integrity, mimicking a hallmark of atopic dermatitis, the presence of Malassezia dramatically aggravates cutaneous inflammation, which again was IL-23 and IL-17 dependent. Consistently, we found a CCR6+ Th17 subset of memory Tcells to be Malassezia specific in both healthy individuals and atopic dermatitis patients, whereby the latter showed enhanced frequency of these cells. Thus, the Malassezia-induced type 17 response is pivotal in orchestrating antifungal immunity and in actively promoting skin inflammation.