Mechanisms of microbial pathogenesis and the role of the skin microbiome in psoriasis: A review.

The pathogenesis of psoriasis may involve a breakdown of immune tolerance to cutaneous microorganisms. Psoriasis is associated with a higher incidence of Crohn disease and periodontitis, two diseases involving impaired tolerance and abnormal immune activation in response to intestinal and oral microbiota, respectively. In addition, guttate and chronic plaque psoriasis are associated with Streptococcus pyogenes colonization. The aim of this review is to characterize the microorganisms implicated in psoriasis by examining results of major association studies and possible mechanisms of pathogenesis. Although studies show relative increases in Streptococcus and Staphylococcus and decreases in Malassezia and Cutibacterium, they differ in methods of sampling and methods of microbial analysis. As such, no definitive associations between microbes and psoriasis have been found to date. It also remains unclear if changes in the microbiomal composition have a causal association with psoriasis or are simply a consequence of the inflammatory microenvironment. Techniques enabling strain-level analysis rather than species-level analysis of the skin microbiome are likely necessary to determine microbiomal signatures of psoriasis. Future investigations may lead to new diagnostic tests and novel treatments, such as probiotics or bacterial transplantation.

Evaluation of selected Indian medicinal plants for antagonistic potential against Malassezia spp. and the synergistic effect of embelin in combination with ketoconazole.

The genus Malassezia comprises of extremely lipophilic yeasts secreting lipases as a vital factor for survival. They are emerging as opportunistic pathogens in medical microbiology and dermatology by causing recurring and recalcitrant infection. Combinatorial therapy is a constructive way to combat infectious diseases. In that prospect, totally 16 Indian medicinal plants were screened, among which a maximum degree of antimicrobial activity was ascertained in Embelia ribes. Subsequently embelin was identified as the bioactive principle with antagonistic potential by comparative antimicrobial assay and FTIR analysis. The MIC of embelin was determined as 400 µg/ml exhibiting ∼75% of growth inhibition. Further, a fungistatic activity based on anti-lipase potential (65-89%) of embelin has been clearly substantiated by XTT and lipase assay. In addition, embelin exhibited a synergistic effect with the antifungal drug ketoconazole (KTZ) against four different Malassezia spp. with FIC index of 0.5. Therefore, the combinations of embelin and KTZ may represent a promising therapeutic regimen to treat Malassezia infections with subjugated clinical and environmental toxicity. To the best of our knowledge, this is the first report delineating the anti-lipase activity of embelin and in vitro synergistic interaction between embelin and KTZ against Malassezia spp.

Traditional Mediterranean plants: characterization and use of an essential oils mixture to treat Malassezia otitis externa in atopic dogs.

Several plants extracts from Mediterranean countries are traditionally employed in skin troubles both in humans and in animals. Malassezia pachydermatis is a lipophylic yeast responsible for otitis externa and dermatitis in dogs and for cutaneous and systemic disease in humans. Five mixtures of essential oils obtained from Mediterranean plants (Citrus paradisi, Salvia sclarea, Ocimum basilicum, Rosmarinus officinalis, Citrus limon, Anthemis nobilis, Lavandula hybrida and Thymus vulgaris) provided with antifungal and/or anti-inflammatory action assayed in vitro, were tested in vivo versus M. pachydermatis to treat once daily for 2 weeks 25 atopic dogs with Malassezia otitis externa. Mixture composed by C. limon 1%, S. sclarea 0,5%, R. officinalis 1%, A. nobilis 0,5% yielded excellent results in all treated dogs. Despite of clinical resolution after all treatments the number of blastospores did not decrease. This study confirms recent findings suggesting a multifactorial alternative approach for the management of canine Malassezia otitis.

Malassezia growth on peritumoral skin after routine methyl-5-aminolevulinate photodynamic therapy for actinic keratosis and nonmelanoma skin cancer / Crecimiento de Malassezia en Piel Peritumoral Tras Terapia Fotodinámica con Metil-5-aminolevulinato para Queratosis Actínica y Cáncer de Piel No Melanoma

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Effects of AV119, a natural sugar from avocado, on Malassezia furfur invasiveness and on the expression of HBD-2 and cytokines in human keratinocytes.

AV119 is a patented blend of two sugars from avocado that can induce human beta-defensin-2 production by normal human keratinocytes. In this study, we analysed the effect of AV119 on growth and invasiveness of Malassezia furfur, a dimorphic, lipid-dependent yeast that is part of the normal human cutaneous commensal flora. The ability to modulate the expression of the proinflammatory and immunomodulatory cytokines in normal human keratinocytes was also investigated. Microbiological assay demonstrated that this sugar induced the aggregation of yeast cells and inhibited the invasiveness of M. furfur, without affecting its growth. Real-time PCR analysis demonstrated that AV119 was able to modulate the HBD-2 response in treated keratinocytes, reaching a maximum after 48-h treatment, and to induce the recovery of a satisfactory proinflammatory response in human keratinocytes. As AV119 can induce aggregation of yeast cells, thus inhibiting their penetration into the keratinocytes, the sugar could be used in the preparation of cosmetics or pharmacological drugs to inhibit colonization of the skin by pathogenic strains of M. furfur.

Comparison of an antifungal agent with a mixture of antifungal, antibiotic and corticosteroid agents for the treatment of Malassezia species otitis in dogs.

Twenty dogs with otitis externa in both ears and numerous Malassezia species yeasts on cytological examination were treated in one ear with a combination product containing clotrimazole, marbofloxacin and dexamethasone, and in the other ear with a topical antifungal containing miconazole. The effects of the treatments were analysed on the basis of the scores for pruritus, erythema and amount of cerumen, and the number of yeasts on cytological smears. There were reductions in the counts of Malassezia species after both treatments, but the combination product gave significantly greater reductions in erythema, cerumen and pruritus.

Isolation, characterization and molecular cloning of a lipolytic enzyme secreted from Malassezia pachydermatis.

Lipophilic Malassezia species may induce catheter-associated sepsis in premature neonates and immunocompromised patients receiving parenteral lipid emulsions. To assess the participation of lipolytic enzymes in the pathogenesis of this yeast, we cloned a gene encoding the enzyme. A lipolytic enzyme in the culture supernatant of Malassezia pachydermatis was purified 210-fold to homogeneity. The enzyme showed high esterase activity toward p-nitrophenyl octanoate. The cDNA encoding the enzyme was cloned using a degenerate oligonucleotide primer constructed from the N-terminal amino acid sequence. The cDNA consisted of 1582 bp, including an open reading frame encoding 470 amino acids. The first 19 amino acids and the following 13 amino-acid sequence were predicted to be the signal peptides for secretion and prosequence, respectively. The predicted molecular mass of the 438-amino acid mature protein was 48 kDa. Analysis of the deduced amino acid sequence revealed that it contains the consensus motif (Gly-X-Ser-X-Gly), which is conserved among lipolytic enzymes. Homology investigations showed that the enzyme has similarities principally with 11 lipases produced by Candida albicans (29-34% identity) and some other yeast lipases.

[The history of dandruff and dandruff in history. A homage to Raymond Sabouraud]. / Histoire des pellicules et pellicules de l'histoire. Un hommage à Raymond Sabouraud.

In one of his books, written at the beginning of this century, Raymond Sabouraud devotes some 280 pages to the history of dandruff. Their reading illustrates how, from the Greeks to Sabouraud's era, this desquamative disease has been subjected to endless doctrinal and scientific conflicts, long before the so-called "present" controversies. One of the early conflicts, between Celsus and Galen, lies in the nature of the squames, i. e. dry or exudating, leading to the inclusion (or non inclusion) or pityriasis in the group of desquamative diseases, such as psoriasis or ichytosis. Translated into Latin (furfur, porrigo) and into Arabic, the word pityriasis was replaced in the Middle Age by tinea which then referred to any disease of the human scalp. With Plenk, Lorry, Willan and others, the 18th century brought a new attitude of mind where observation took precedence over doctrine, but owing to the lack of experimental approach there was no adequate description of the squames and their anatomical origin. This was the case with Hebra who, in the 19th century, claimed that dandruff was nothing but a sebaceous disease. This major turn resulted for decades in a confusion between dandruff and seborrhoea. In the late 19th century, bacteriological studies were decisive steps taken by Rivolta, Malassez and Sabouraud. The presence on scalps affected with dandruff of a bottle-shaped "fungus" (Pityrosporum ovale was initially not regarded as a yeast) was taken as being the definite cause of the disease. The Sabouraud dogma was born, but as early as 1877 it was denied by Vidal who observed these "spores" on healthy scalps.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of microorganisms in dandruff.

The role of microorganisms in dandruff was studied, by suppressing individually and then collectively the three major components of the scalp microflora. The effect on dandruff was assessed subjectively by clinical grading and objectively by the corneocyte count. No effect on dandruff was demonstrated when scalp organisms were suppressed. In the second group of experiments, dandruff was suppressed by selenium sulfide shampooling and the effect of continued suppression of Pityrosporum with topically applied amphotericin was measured. According to our criteria, dandruff returned to pretreatment levels, despite continued suppression of Pityrosporum. The studies demonstrate that the increased number of scalp microorganisms found in dandruff occurs as a secondary event to increased nutrients and that scalp organisms play no primary role in the pathogenesis of dandruff.