Modulating the skin mycobiome-bacteriome and treating seborrheic dermatitis with a probiotic-enriched oily suspension.

Seborrheic dermatitis (SD) affects 2-5% of the global population, with imbalances in the skin microbiome implicated in its development. This study assessed the impact of an oily suspension containing Lactobacillus crispatus P17631 and Lacticaseibacillus paracasei I1688 (termed EUTOPLAC) on SD symptoms and the skin mycobiome-bacteriome modulation. 25 SD patients were treated with EUTOPLAC for a week. Symptom severity and skin mycobiome-bacteriome changes were measured at the start of the treatment (T0), after seven days (T8), and three weeks post-treatment (T28). Results indicated symptom improvement post-EUTOPLAC, with notable reductions in the Malassezia genus. Concurrently, bacterial shifts were observed, including a decrease in Staphylococcus and an increase in Lactobacillus and Lacticaseibacillus. Network analysis highlighted post-EUTOPLAC instability in fungal and bacterial interactions, with increased negative correlations between Malassezia and Lactobacillus and Lacticaseibacillus genera. The study suggests EUTOPLAC's potential as a targeted SD treatment, reducing symptoms and modulating the mycobiome-bacteriome composition.

Lesional skin of seborrheic dermatitis patients is characterized by skin barrier dysfunction and correlating alterations in the stratum corneum ceramide composition.

Seborrheic dermatitis (SD) is a chronic inflammatory skin disease characterized by erythematous papulosquamous lesions in sebum rich areas such as the face and scalp. Its pathogenesis appears multifactorial with a disbalanced immune system, Malassezia driven microbial involvement and skin barrier perturbations. Microbial involvement has been well described in SD, but skin barrier involvement remains to be properly elucidated. To determine whether barrier impairment is a critical factor of inflammation in SD alongside microbial dysbiosis, a cross-sectional study was performed in 37 patients with mild-to-moderate facial SD. Their lesional and non-lesional skin was comprehensively and non-invasively assessed with standardized 2D-photography, optical coherence tomography (OCT), microbial profiling including Malassezia species identification, functional skin barrier assessments and ceramide profiling. The presence of inflammation was established through significant increases in erythema, epidermal thickness, vascularization and superficial roughness in lesional skin compared to non-lesional skin. Lesional skin showed a perturbed skin barrier with an underlying skewed ceramide subclass composition, impaired chain elongation and increased chain unsaturation. Changes in ceramide composition correlated with barrier impairment indicating interdependency of the functional barrier and ceramide composition. Lesional skin showed significantly increased Staphylococcus and decreased Cutibacterium abundances but similar Malassezia abundances and mycobial composition compared to non-lesional skin. Principal component analysis highlighted barrier properties as main discriminating features. To conclude, SD is associated with skin barrier dysfunction and changes in the ceramide composition. No significant differences in the abundance of Malassezia were observed. Restoring the cutaneous barrier might be a valid therapeutic approach in the treatment of facial SD.

Part 1: Understanding the role of Malassezia spp. in skin disorders: Malassezia yeasts as commensal or pathogenic organisms of human and animal skin.

INTRODUCTION: Malassezia spp. are a group of lipid-dependent basidiomycetes yeasts acting as commensal organisms of the human and animal skin. However, under some not well-defined circumstances, these yeasts may switch to opportunistic pathogens triggering a number of skin disorders with different clinical presentations. The genus comprises of 18 lipid-dependent species with a variable distribution in the hosts and pathologies thus suggesting a host- and microbe-specific interactions. AREA COVERED: This review highlighted and discussed the most recent literature regarding the genus Malassezia as a commensal or pathogenic organisms highlighting Malassezia-associated skin disorders in humans and animals and their antifungal susceptibility profile. A literature search of Malassezia associated skin disorders was performed via PubMed and Google scholar (up to May 2023), using the different keywords mainly associated with Malassezia skin disorders and Malassezia antifungal resistance. EXPERT OPINION: Malassezia yeasts are part of the skin mycobiota and their life cycle is strictly associated with the environment in which they live. The biochemical, physiological, or immunological condition of the host skin selects Malassezia spp. or genotypes able to survive in a specific environment by changing their metabolisms, thus producing virulence factors or metabolites which can cause skin disorders with different clinical presentations.

MALASSEZIA COLONIZATION CORRELATES WITH THE SEVERITY OF SEBORRHEIC DERMATITIS.

OBJECTIVE: The aim: To compare the number of fungi of the genus Malassezia on inflated and healthy areas of the skin and to correlate them with the severity of seborrheic dermatitis. PATIENTS AND METHODS: Materials and methods: 168 patients with typical manifestations of seborrheic dermatitis on the scalp and face and 30 healthy individuals were recruited. SD severity was assessed by SEDASI. Samples from lesions on scalp, face and intact chest skin were cultivated and/or stained with methylene blue or cotton and inoculated onto Malassezia Leeming & Notman Agar Modified (MLNA). RESULTS: Results: A statistical difference in colonization intensity between all body zones (Dwass-Steel-Critchlow-Flinger pairwise comparisons p≤0,001). Face zone with lesions of SD patients was two times more colonized with funguses than in the control group (38,5 vs 16,5 p=0,003). The sternal area with no skin lesions was more colonized in the SD group (25,0 vs 9,0 p=0,013). The SEDASI was positively correlated with the amount of CFU on the face (Spearman's rho 0,849; p≤0,001) and trunk (0,714; p≤0,001). CONCLUSION: Conclusions: Our results demonstrate that inflamed seborrheic areas are more colonized with Malassezia fungi than intact areas. The intensity of Malassezia growth is correlated with the severity of the symptoms of seborrheic dermatitis. The level of colonization may be a potential biomarker to indicate the efficiency of new treatment approaches.

Seborrheic dermatitis: topical therapeutics and formulation design.

Seborrheic dermatitis (SD) is a common dermatological disorder with symptoms that include skin flaking, erythema and pruritus. This review discusses the topical products available for treating SD, which target several aspects of disease pathobiology, including cutaneous microbial dysbiosis (driven by Malassezia yeast), inflammation, sebum production and skin barrier disruption. Among the various treatments available, zinc pyrithione (ZnPT) based products that exhibit anti-fungal action are the market leaders. A skin compartment approach is presented here for combining ZnPT exposure information with threshold levels for anti-fungal efficacy and toxicity, overall providing a comprehensive picture of ZnPT therapeutics and safety. While Malassezia yeast on the surface are effectively targeted, yeast residing beyond the superficial follicle may not receive adequate ZnPT for anti-fungal effect forming the basis for skin re-colonisation. Levels entering systemic circulation from topical delivery are well below toxic thresholds, however the elevated zinc levels within the viable epidermis warrants further investigation. Strategies to improve formulation design can be broadly classified as influencing 1) topical delivery, 2) therapeutic bioactivity, 3) skin mildness, and 4) sensory attributes. Successful SD treatment ultimately requires formulations that can balance efficacy, safety, and consumer appeal.

Analysis of cutaneous bacterial microbiota of Thai patients with seborrheic dermatitis.

Seborrheic dermatitis (SD) is a chronic inflammatory skin condition that occurs in body areas that contain profuse sebaceous glands. Skin microbiota are diverse across ethnic groups and its dysbiosis has been implicated in the pathogenesis of SD. Here, we reported the contribution of cutaneous bacterial microbiota to SD in the Thai population. Healthy individuals and patients with scalp SD were recruited into the study. Normal skin, scalp skin lesion (SL) and non-lesion sites (SNL) samples were collected using a tape stripping method and next-generation sequencing of 16S rRNA for microbiome analysis. Although bacterial diversity in all sample groups was not statistically different, a population of bacteria commonly found on skin of scalp showed signs of dysbiosis. Apart from the reduction of Corynebacterium spp., SD-specific microbiota was dominated by Firmicutes at taxa level and Pseudomonas spp., Staphylococcus spp. and Micrococcus spp. at genus level. The dysbiosis of the skin microbiota in SD was specifically described as an alteration of bacteria populations commonly found on scalp skin, implying that managing and controlling the cutaneous bacterial microbiome can alleviate and prevent SD and pave the way for the development of new SD treatments.

Malassezia virulence factors and their role in dermatological disorders.

Malassezia is a commensal fungus that constitutes normal skin microbiota. However, in certain conditions and individuals, it may transform into a pathogenic yeast with multiple associated dermatological disorders and various clinical manifestations. This phenomenon is influenced by a unique host-agent interaction that triggers the production of several virulence factors, such as indoles, reactive oxygen species, azelaic acid, hyphae formation, and biofilm formation. This review article discusses Malassezia virulence factors that contribute to the transformation of Malassezia from commensal to pathogenic as well as their role in dermatological disorders, including pityriasis versicolor, seborrheic dermatitis, Malassezia folliculitis, atopic dermatitis, and psoriasis.

Genome of Malassezia arunalokei and Its Distribution on Facial Skin.

Malassezia is a fungal genus found on the skin of humans and warm-blooded animals, with 18 species reported to date. In this study, we sequenced and annotated the genome of Malassezia arunalokei, which is the most recently identified Malassezia species, and compared it with Malassezia restricta, the predominant isolate from human skin. Additionally, we reanalyzed previously reported mycobiome data sets with a species-level resolution to investigate M. arunalokei distribution within the mycobiota of human facial skin. We discovered that the M. arunalokei genome is 7.24 Mbp in size and encodes 4,117 protein-coding genes, all of which were clustered with M. restricta. We also found that the average nucleotide identity value of the M. arunalokei genome was 93.5, compared with the genomes of three M. restricta strains, including M. restricta KCTC 27527. Our findings demonstrate that they indeed belong to different species and that M. arunalokei may have experienced specific gene loss events during speciation. Furthermore, our study showed that M. arunalokei was diverged from M. restricta approximately 7.1 million years ago and indicated that M. arunalokei is the most recently diverged species in the Malassezia lineage to date. Finally, our analysis of the facial mycobiome of previously recruited cohorts revealed that M. arunalokei abundance is not associated with seborrheic dermatitis/dandruff or acne, but was revealed to be more abundant on the forehead and cheek than on the scalp. IMPORTANCEMalassezia is the fungus predominantly residing on the human skin and causes various skin diseases, including seborrheic dermatitis and dandruff. To date, 18 species have been reported, and among them, M. restricta is the most predominant on human skin, especially on the scalp. In this study, we sequenced and analyzed the genome of M. arunalokei, which is the most recently identified Malassezia species, and compared it with M. restricta. Moreover, we analyzed the fungal microbiome to investigate the M. arunalokei distribution on human facial skin. We found that M. arunalokei may have experienced specific gene loss events during speciation. Our study also showed that M. arunalokei was diverged from M. restricta approximately 7.1 million years ago and indicated that M. arunalokei is the most recently diverged species in the Malassezia lineage. Finally, our analysis of the facial mycobiome revealed that M. arunalokei has higher relative abundance on the forehead and cheek than the scalp.

Effectiveness of FastFung agar in the isolation of Malassezia furfur from skin samples.

BACKGROUND: Lipophilic basidiomycetous yeasts of the Malassezia genus can cause various skin diseases, such as seborrheic dermatitis, pityriasis versicolor, folliculitis and atopic dermatitis, and even life-threatening fungemia in newborns and immunocompromised individuals. Routine mycological media used in clinical practice do not contain sufficient lipid ingredients required for the growth of Malassezia species. A recently developed medium, FastFung agar, is promising for culturing fastidious fungal species. METHODS: In this study, we compared FastFung agar and mDixon agar for culturing Malassezia species from nasolabial fold and retroauricular specimens of 83 healthy individuals and 187 and 57 patients with acne vulgaris and seborrheic dermatitis, respectively. RESULTS: Malassezia species were identified using conventional tests and matrix-assisted laser desorption/ionisation mass spectrometry. In total, 96 of 654 samples (14.6%) contained Malassezia species. The total isolation rate was significantly higher in patients with seborrheic dermatitis (40.4%) than in healthy volunteers (21.7%; p < .05), and the rate of M. furfur isolation was significantly higher for patients with acne vulgaris (13.9%) and seborrheic dermatitis (24.6%) than for healthy individuals (1.5%; p < .05). FastFung agar was superior to mDixon agar in M. furfur isolation (p = .004) but showed similar performance in the case of non-M. furfur species (p > .05). Among cultured Malassezia species, perfect agreement between mDixon agar and FastFung agar was found only for M. globosa (κ = 0.90). CONCLUSION: Our results indicate that FastFung agar favours the growth of Malassezia species and should be useful in clinical mycology laboratories.

Presence of Malassezia Hyphae Is Correlated with Pathogenesis of Seborrheic Dermatitis.

Seborrheic dermatitis (SD) is a common, chronic, and relapsing skin disease. The roles of Malassezia spp. in the pathogenesis of SD are still not clear due to the lack of direct evidence for the existence of hyphae within affected skin tissues. We set out to elucidate if Malassezia mycelium contributes to the onset and development of SD and if Malassezia mycelium is correlated with the clinical severity of SD patients. We detected Malassezia hyphae in patients with SD using potassium hydroxide (KOH) and calcofluor white (CFW) staining. Fluorescent microscopy was performed for the analysis of fungal cell wall and morphological characteristics of Malassezia under CFW staining. Culture growth in modified Dixon agar was used for DNA extraction and sequencing, and Malassezia species were confirmed by a sequencing data BLAST search against the NCBI database. We demonstrated that Malassezia hyphae were positively correlated with the clinical severity of SD patients (P = 3.1738 × 10-11). All the patients responded well to antifungal treatment. There is no significant difference for species dominance across the variant groups. However, the exact molecular mechanisms of how Malassezia spp. affect SD need to be further explored. The results show that Malassezia spp. in the hyphal stage are restricted to SD patients compared with healthy controls, suggesting that the presence of Malassezia hyphae contributes to the pathogenesis of SD. The results highlight the importance of the antifungal therapy for the future treatment of SD patients. IMPORTANCE Our results support the proposal that the hyphal form of Malassezia could be one of the pathogenic factors that contribute to SD, which has been previously less well studied. This clinical observation paves the way for further investigations of the molecular mechanisms of Malassezia hyphal pathogenicity in SD.

Ketoconazole beyond antifungal activity: Bioinformatics-based hypothesis on lipid metabolism in dandruff and seborrheic dermatitis.

The role of Malassezia yeasts in dandruff and seborrheic dermatitis is unclear; however, antifungal therapy with ketoconazole is commonly used. We propose that ketoconazole shifts skin lipid profile, affects Malassezia lipid metabolism and favours biotin-producing bacteria. Biotin regulates inflammatory response and cell proliferation, contributing to symptom improvement.

Evaluation of a new-formula shampoo containing 6% glycyrrhetinic acid complex for scalp seborrheic dermatitis: A pilot study.

BACKGROUND: Scalp seborrheic dermatitis (SD) is a chronic inflammatory dermatosis associated with sebum imbalance and proliferation of Malassezia species. Various antifungal shampoos are commonly used for scalp SD. AIMS: Glycyrrhetinic acid is known to have antioxidative, anti-inflammatory, and anti-allergic effects. This study was designed to evaluate the effectiveness of a new-formula shampoo that contains glycyrrhetinic acid for the treatment of scalp SD. PATIENTS/METHODS: Thirty-four patients were enrolled and treated with the 6% glycyrrhetinic acid complex shampoo. Efficacy was assessed clinically with Dermatology Life Quality Index (DLQI) and Adherent Scalp Flaking Score (ASFS) by the same dermatologist at baseline, week 2, and week 5. Among the 24 subjects with the most significant clinical improvement, four common microorganisms from scalp samples were analyzed by quantitative polymerase chain reaction (qPCR) at baseline, and week 5. RESULTS: The DLQI and ASFS at week 2 and week 5 improved significantly relative to baseline. The bacteria profiles showed a significant increase of Cutibacterium acnes and a decrease of Staphylococcus epidermidis at week 5. The fungi profiles showed significant decreases of both Malassezia restricta and Malassezia globosa. The ratio of C. acne to S. epidermidis increased significantly from 0.93 at baseline to 1.55 at week 5. The ratio of M. restricta to M. globosa decreased from 5.02 at baseline to 1.00 at week 5. CONCLUSIONS: The effectiveness of this new regimen was objectively demonstrated at the clinical and microbiological levels. This new formula may alleviate the bacterial and fungal dysbiosis in scalp SD.

Essential Oils as Potential Source of Anti-dandruff Agents: A Review.

BACKGROUND: Dandruff is a frequent occurring scalp problem that causes significant discomfort to approximately 50% population at some stage of life, especially post-puberty and preadult age. OBJECTIVES: In this review, we aim to summarise the recent findings regarding anti-fungal properties of herbal essential oils against pathogens involved in dandruff prognosis. METHODS: A literature search of studies published between 2000 and 2020 was conducted over databases: PubMed, Google Scholar, Scopus, and Science Direct. Literature was explored using the guidelines given in Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). RESULTS: Dandruff, characterised by clinical symptoms of dryness, pruritis, scaly, and flaky scalp, is considered as a primary manifestation of seborrheic dermatitis. Amongst various etiological and pathophysiological factors, significant role of yeasts, primarily, species of Malassezia, Candida, has been strongly correlated with dandruff, while incidences of M. furfur, M. restricta and M. globosa are high compared to others. Due to relapse of symptoms with withdrawal of conventional anti-dandruff products, patients find best alternatives in natural products. Essential oils of herbal origin such as tea tree oil, lime oil, rosemary oil, have gained global importance in dermatology. These oils are rich in aromatic secondary metabolites, especially terpenes and phenolic components that impart substantial antimicrobial properties and resisting biofilm production. CONCLUSION: On the basis of the available information, we can conclude that essential oils have huge potential to be developed as anti-dandruff products, however, further studies are warranted to establish their efficacy in dandruff cure.

Continuous clinical improvement of mild-to-moderate seborrheic dermatitis and rebalancing of the scalp microbiome using a selenium disulfide-based shampoo after an initial treatment with ketoconazole.

OBJECTIVE: Scalp seborrheic dermatitis (SD) is a chronic, relapsing, and inflammatory scalp disease. Studies indicate a global bacterial and fungal microbiota shift of scalp SD, as compared to healthy scalp. Ketoconazole and selenium disulfide (SeS2 ) improve clinical signs and symptoms in both scalp dandruff and SD. AIM: The main objective of this study was to investigate the changes in the scalp microbiota diversity and counts in subjects with scalp SD during a two-phase treatment period. MATERIAL AND METHODS: The scalp microbiota and clinical efficacy were investigated in 68 subjects with mild-to-moderate scalp SD after an initial one-month treatment with 2% ketoconazole, and after a 2-month maintenance phase, either with a 1% SeS2 -based shampoo or its vehicle. RESULTS: Thirty one subjects in the active and 37 subjects in the vehicle group participated. Ketoconazole provided an improvement of clinical symptoms (adherent (-1.75 p < 0.05), non-adherent (-1.5, p < 0.05)) flakes and erythema (scores 1.67-0.93, p < 0.001), in an increased fungal diversity and in a significant (p < 0.005) decrease of Malassezia spp. SeS2 provided an additional clinical improvement (-0.8; p = 0.0002 and -0.7; p = 0.0081 for adherent and non-adherent flakes, respectively, at Day 84) compared to the vehicle associated with a low Malassezia spp. count and an additional significant (p < 0.001) decrease of the Staphylococcus spp. level. CONCLUSION: Selenium disulfide provides an additional benefit on the scalp microbiota and in clinical symptoms of SD and dandruff after treatment with ketoconazole. The results confirm the role of Staphylococcus spp. in scalp SD and open possible perspectives for preventing relapses.

Skin microbiome alterations in seborrheic dermatitis and dandruff: A systematic review.

Seborrheic dermatitis (SD) and dandruff (DF) are common chronic inflammatory skin diseases characterized by recurrent greasy scales, sometimes with erythema and itchiness. Although the exact pathophysiology of the disease is still unclear, current theories highlight the role of microbes on the skin surface in the pathogenesis of SD. Here, we conducted a systematic review to investigate the skin microbiome alterations in patients with SD/DF. We searched Medline/PubMed, Embase and Web of Science for research studies published in English between 1 January 2000 and 31 December 2020. A total of 12 studies with 706 SD/DF samples and 379 healthy samples were included in this study. The scalp and face were predominated by the fungi of Ascomycota and Basidiomycota and the bacteria of Actinobacteria and Firmicutes. In general, the included studies demonstrated an increased Malassezia restricta/Malassezia globosa ratio and a reduction in the Cutibaterium/Staphylococcus ratio in the setting of SD/DF. Staphylococcus was associated with epidermal barrier damage, including elevated levels of trans-epidermal water loss and pH, while Cutibacterium had a positive correlation with water content. Malassezia was also found to be related to an increased itching score and disease severity. Further studies focusing on the interactions between various microbes and the host and microbes can help us to better understand the pathogenesis of SD/DF.

Composition of cutaneous bacterial microbiome in seborrheic dermatitis patients: A cross-sectional study.

BACKGROUND: Seborrheic dermatitis (SD) is a chronic inflammatory skin disease with a multifactorial aetiology. Malassezia yeasts have been associated with the disease but the role of bacterial composition in SD has not been thoroughly investigated. OBJECTIVES: To profile the bacterial microbiome of SD patients and compare this with the microbiome of individuals with no inflammatory skin disease (controls). METHODS: This was a cross sectional study embedded in a population-based study. Skin swabs were taken from naso-labial fold from patients with seborrheic dermatitis (lesional skin: n = 22; non-lesional skin SD: n = 75) and controls (n = 465). Sample collection began in 2016 at the research facility and is still ongoing. Shannon and Chao1 α- diversity metrics were calculated per group. Associations between the microbiome composition of cases and controls was calculated using multivariate statistics (permANOVA) and univariate statistics. RESULTS: We found an increased α-diversity between SD lesional cases versus controls (Shannon diversity: Kruskal-Wallis rank sum: Chi-squared: 19.06; global p-value = 7.7x10-5). Multivariate statistical analysis showed significant associations in microbiome composition when comparing lesional SD skin to controls (p-value = 0.03;R2 = 0.1%). Seven out of 13 amplicon sequence variants (ASVs) that were significantly different between controls and lesional cases were members of the genus Staphylococcus, most of which showed increased composition in lesional cases, and were closely related to S. capitis S. caprae and S. epidermidis. CONCLUSION: Microbiome composition differs in patients with seborrheic dermatitis and individuals without diseases. Differences were mainly found in the genus Staphylococcus.

Malassezia and Staphylococcus dominate scalp microbiome for seborrheic dermatitis.

Seborrheic dermatitis (SD) is a common disease of the human scalp that causes physical damage and psychological problems for patients. Studies have indicated that dysbiosis of the scalp microbiome results in SD. However, the specific fungal and bacterial microbiome changes related to SD remain elusive. To further investigate the fungal and bacterial microbiome changes associated with SD, we recruited 57 SD patients and 53 healthy individuals and explored their scalp microbiomes using next generation sequencing and the QIIME and LEfSe bioinformatics tools. Skin pH, sebum secretion, hydration, and trans-epidermal water loss (TWEL) were also measured at the scalp. We found no statistically significant differences between the normal and lesion sites in SD patients with different subtypes of dandruff and erythema. However, the fungal and bacterial microbiome could differentiate SD patients from healthy controls. The presence of Malassezia and Aspergillus was both found to be potential fungal biomarkers for SD, while Staphylococcus and Pseudomonas were found to be potential bacterial biomarkers. The fungal and bacterial microbiome were divided into three clusters through co-abundance analysis and their correlations with host factors indicated the interactions and potential cooperation and resistance between microbe communities and host. Our research showed the skin microbe dysbiosis of SD and highlighted specific microorganisms that may serve as potential biomarkers of SD. The etiology of SD is multi-pathogenetic-dependent on the linkage of several microbes with host. Scalp microbiome homeostasis could be a promising new target in the risk assessment, prevention, and treatment of SD disease.

An update on the microbiology, immunology and genetics of seborrheic dermatitis.

The underlying mechanism of seborrheic dermatitis (SD) is poorly understood but major scientific progress has been made in recent years related to microbiology, immunology and genetics. In light of this, the major goal of this article was to summarize the most recent articles on SD, specifically related to underlying pathophysiology. SD results from Malassezia hydrolysation of free fatty acids with activation of the immune system by the way of pattern recognition receptors, inflammasome, IL-1ß and NF-kB. M. restricta and M. globosa are likely the most virulent subspecies, producing large quantities of irritating oleic acids, leading to IL-8 and IL-17 activation. IL-17 and IL-4 might play a big role in pathogenesis, but this needs to be further studied using novel biologics. No clear genetic predisposition has been established; however, recent studies implicated certain increased-risk human leucocyte antigen (HLA) alleles, such as A*32, DQB1*05 and DRB1*01 as well as possible associations with psoriasis and atopic dermatitis (AD) through the LCE3 gene cluster while SD, and SD-like syndromes, shares genetic mutations that appear to impair the ability of the immune system to restrict Malassezia growth, partially due to complement system dysfunction. A paucity of studies exists looking at the relationship between SD and systemic disease. In HIV, SD is thought to be secondary to a combination of immune dysregulation and disruption in skin microbiota with unhindered Malassezia proliferation. In Parkinson's disease, SD is most likely secondary to parasympathetic hyperactivity with increased sebum production as well as facial immobility which leads to sebum accumulation.

Guinea pig seborrheic dermatitis model of Malassezia restricta and the utility of luliconazole.

Seborrheic dermatitis (SD) is a multifactorial disease in which Malassezia restricta has been proposed as the predominant pathogenic factor. However, experimental evidence supporting this hypothesis is limited. A guinea pig SD model using a clinical isolate of M. restricta was used to elucidate the pathogenicity of M. restricta. Also, the efficacy of 1% luliconazole (LLCZ) cream, a topical imidazole derivative, against M. restricta was compared with that of a 2% ketoconazole (KCZ) cream in the same guinea pig model. Dorsal skin hairs of guinea pig were clipped and treated with M. restricta by single or repeated inoculations without occlusion. Skin manifestations were examined macroscopically and histologically. A quantitative polymerase chain reaction (PCR) assay was also performed for mycological evaluation. An inflammatory response mimicking SD occurred after repeated as well as single inoculation but not in abraded skin. The inflammation score attained its maximum on day 11 and persisted until day 52. The yeast form of the fungal elements was distributed on the surface of stratum corneum and around the follicular orifices, and an epidermal and dermal histological reaction was observed. Application of 1% LLCZ or 2% KCZ cream significantly improved the skin manifestations and decreased the quantity of M. restricta rDNA in the skin lesions. The efficacy of topical antifungal drugs suggested that M. restricta is a pathogenic factor contributing to SD.

Isolation of Malassezia spp. in HIV-positive patients with and without seborrheic dermatitis.

BACKGROUND: Malassezia, a skin saprophyte, is frequently isolated from patients with seborrheic dermatitis, which is one of the most common dermatoses in HIV-infected patients. Its role in pathophysiology has not been defined. OBJECTIVE: To determine whether patients living with HIV and seborrheic dermatitis have more Malassezia than those without seborrheic dermatitis. METHOD: This is an descriptive, observational, prospective cross-sectional study to which all adult patients living with HIV that attend the infectious disease outpatient clinic at the Dr. Manuel Gea González General Hospital were invited. Patients presenting with scale and erythema were included in Group 1, while patients without erythema were included in Group 2. Samples were taken from all patients for smear and culture. RESULTS: Thirty patients were included in each group. All patients with seborrheic dermatitis had a positive smear, with varying amounts of yeasts. In the control group, 36.7% of patients had a negative smear. The results are statistically significant, as well as the number of colonies in the cultures. Study limitations The study used a small sample size and the subspecies were not identified. CONCLUSIONS: Patients with clinical manifestations of seborrheic dermatitis have larger amounts of Malassezia. Further studies need to be performed to analyze if the greater amount is related to imbalances in the microbiota of the skin.