Differential Expression of Extracellular Lipase and Protease Activities of Mycelial and Yeast Forms in Malassezia furfur

Comparative transcriptome analysis to unveil genes affecting the host cuticle destruction in Metarhizium rileyi

Insect pathogenic fungi, also known as entomopathogenic fungi, are one of the largest insect pathogenic microorganism communities, represented by Beauveria spp. and Metarhizium spp. Entomopathogenic fungi have been proved to be a great substitute for chemical pesticide in agriculture. In fact, a lot of functional genes were also already characterized in entomopathogenic fungi, but more depth of exploration is still needed to reveal their complicated pathogenic mechanism to insects. Metarhizium rileyi (Nomuraea rileyi) is a great potential biocontrol fungus that can parasitize more than 40 distinct species (mainly Lepidoptera: Noctuidae) to cause large-scale infectious diseases within insect population. In this study, a comparative analysis of transcriptome profile was performed with topical inoculation and hemolymph injection to character the infectious pattern of M. rileyi. Appressorium and multiple hydrolases are indispensable constituents to break the insect host primary cuticle defense in entomopathogenic fungi. Within our transcriptome data, numerous transcripts related to destruction of insect cuticle rather growth regulations were obtained. Most importantly, some unreported ribosomal protein genes and novel unannotated protein (hypothetical protein) genes were proved to participate in the course of pathogenic regulation. Our current data provide a higher efficiency gene library for virulence factors screen in M. rileyi, and this library may be also useful for furnishing valuable information on entomopathogenic fungal pathogenic mechanisms to host.

Part 2: Understanding the role of Malassezia spp. in skin disorders: pathogenesis of Malassezia associated skin infections

INTRODUCTION

Malassezia is a major component of the skin microbiome, a lipophilic symbiotic organism of the mammalian skin, which can switch to opportunistic pathogens triggering multiple dermatological disorders in humans and animals. This phenomenon is favored by endogenous and exogenous host predisposing factors, which may switch Malassezia from a commensal to a pathogenic phenotype.

AREA COVERED

This review summarizes and discusses the most recent literature on the pathogenesis of Malassezia yeasts, which ultimately results in skin disorders with different clinical presentation. A literature search of Malassezia pathogenesis was performed via PubMed and Google scholar (up to May 2023), using the following keywords: Pathogenesis and Malassezia;host risk factors and Malassezia, Malassezia and skin disorders; Malassezia and virulence factors: Malassezia and metabolite production; Immunology and Malassezia.

EXPERT OPINION

Malassezia yeasts can maintain skin homeostasis being part of the cutaneous mycobiota; however, when the environmental or host conditions change, these yeasts are endowed with a remarkable plasticity and adaptation by modifying their metabolism and thus contributing to the appearance or aggravation of human and animal skin disorders.

Comparison of virulence factors and susceptibility profiles of Malassezia furfur from pityriasis versicolor patients and bloodstream infections of preterm infants

In spite of the increasing medical interest in Malassezia yeasts, the virulence factors of Malassezia furfur causing bloodstream infections (BSI) were never investigated. Therefore, phospholipase (Pz), lipase (Lz), hemolysin (Hz), biofilm production, and in vitro antifungal susceptibility profiles were evaluated in M. furfur strains, isolated from both pityriasis versicolor (PV) patients (n = 18; Group 1) or from preterm infants BSI (n = 21; Group 2). All the test stains exhibited Pz activity, whereas 92.3% and 97.4% of strains exhibited Lz and Hz activities, respectively. Pz, Lz, and Hz activities were higher (i.e., lower values) within Group 1 strains (i.e., 0.48, 0.40, and 0.77) than those within Group 2 (i.e., 0.54, 0.54, and 0.81). The biofilm production was higher within Malassezia isolates from Group 2 (0.95 ± 0.3) than from Group 1 (0.72 ± 0.4). Itraconazole and posaconazole were the most active drugs against M. furfur, followed by amphotericin B and fluconazole. The minimum inhibitory concentrations (MIC) values varied according to the origin of M. furfur strains being statistically lower in M. furfur from Group 1 than from Group 2. This study suggests that M. furfur strains produce hydrolytic enzymes and biofilm when causing PV and BSI. Data show that the phospholipase activity, biofilm production, and a reduced antifungal susceptibility profile might favor M. furfur BSI, whereas lipase and hemolytic activities might display a synergic role in skin infection.

Antifungal Effect of Antimicrobial Photodynamic Therapy Mediated by Haematoporphyrin Monomethyl Ether and Aloe Emodin on Malassezia furfur

Infectious dermatological diseases caused by Malassezia furfur are often chronic, recurrent, and recalcitrant. Current therapeutic options are usually tedious, repetitive, and associated with adverse effects. Alternatives that broaden the treatment options and reduce side effects for patients are needed. Antimicrobial photodynamic therapy (aPDT) is an emerging approach that is quite suitable for superficial infections. The aim of this study is to investigate the antimicrobial efficacy and effect of aPDT mediated by haematoporphyrin monomethyl ether (HMME) and aloe emodin (AE) on clinical isolates of M. furfur in vitro. The photodynamic antimicrobial efficacy of HMME and AE against M. furfur was assessed by colony forming unit (CFU) assay. The uptake of HMME and AE by M. furfur cells was investigated by fluorescence microscopy. Reactive oxygen species (ROS) probe and flow cytometry were employed to evaluate the intracellular ROS level. The effect of HMME and AE-mediated aPDT on secreted protease and lipase activity of M. furfur was also investigated. The results showed that HMME and AE in the presence of light effectively inactivated M. furfur cells in a photosensitizer (PS) concentration and light energy dose-dependent manner. AE exhibited higher antimicrobial efficacy against M. furfur than HMME under the same irradiation condition. HMME and AE-mediated aPDT disturbed the fungal cell envelop, significantly increased the intracellular ROS level, and effectively inhibited the activity of secreted protease and lipase of M. furfur cells. The results suggest that HMME and AE have potential to serve as PSs in the photodynamic treatment of dermatological diseases caused by M. furfur, but further ex vivo or in vivo experiments are needed to verify that they can meet the requirements for clinical practice.

Exploring the antifungal activity and mechanism of action of Zingiberaceae rhizome extracts against Malassezia furfur

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizomes from members of Zingiberaceae have long been used in Thai traditional medicine to treat cutaneous fungal infections, including Malassezia-related skin disorders. Alpinia galanga, Curcuma longa, Zingiber cassumunar, and Zingiber officinale are particularly popular in folk remedies.

AIM OF THE STUDY

On account of the application background in traditional medicine, the present study aims to screen and determine the composition and possible mechanism of the rhizome extracts of selected Zingiberaceae and corresponding fractions against M. furfur.

MATERIALS AND METHODS

All solvent extracts (ethanol, methanol, and n-hexane) obtained from each plant were screened for anti-Malassezia activity by agar disc diffusion assay. The MIC and MFC values of the potent rhizome extract and its bioactive fraction isolated by TLC were determined using broth dilution assay followed by chemical characterization using GC-MS. The anti-Malassezia mechanism was investigated by macroscopic and microscopic observation of cells grown in the yeast phase and hyphal phase.

RESULTS

The primary screening results showed that the n-hexane extract from A. galanga possessed the most significant anti-Malassezia activity. The MIC and MFC values of this extract were in a range of 0.04-0.08 mg/mL and 0.04-0.16 mg/mL, respectively. The TLC purification of the n-hexane extract from A. galanga gave a total of nine fractions, of which only a single exhibited anti-Malassezia activity. The GC-MS analysis of the rhizome extract and the derivative fraction revealed that the major constituents were (2,6-dimethylphenyl)borate followed by a trace content of 1,8-cineol and hydrocarbons. For the antifungal mechanism of the fraction, treatments of the fraction led to morphological changes in cell size and shape, exerted massive vacuoles in yeast form, and inhibited the transition to hyphae but not likely affected chitin contents of the cell wall of M. furfur.

CONCLUSIONS

According to the results, the n-hexane extract of A. galanga rhizome exhibits promising anti-Malassezia potential. The inhibitory effect on virulent hyphal growth supports that A. galanga is a valuable source of natural antifungal agents for further pharmaceutical research.

Skin Commensal Fungus Malassezia and Its Lipases

Malassezia is the most abundant genus in the fungal microflora found on human skin, and it is associated with various skin diseases. Among the 18 different species of Malassezia that have been identified to date, M. restricta and M. globosa are the most predominant fungal species found on human skin. Several studies have suggested a possible link between Malassezia and skin disorders. However, our knowledge on the physiology and pathogenesis of Malassezia in human body is still limited. Malassezia is unable to synthesize fatty acids; hence, it uptakes external fatty acids as a nutrient source for survival, a characteristic compensated by the secretion of lipases and degradation of sebum to produce and uptake external fatty acids. Although it has been reported that the activity of secreted lipases may contribute to pathogenesis of Malassezia, majority of the data were indirect evidences; therefore, enzymes' role in the pathogenesis of Malassezia infections is still largely unknown. This review focuses on the recent advances on Malassezia in the context of an emerging interest for lipases and summarizes the existing knowledge on Malassezia, diseases associated with the fungus, and the role of the reported lipases in its physiology and pathogenesis.

Ambient pH regulates secretion of lipases in Malassezia furfur

Malassezia is a lipophilic cutaneous commensal yeast and associated with various skin disorders. The yeast also causes bloodstream infection via intravascular catheters and can be detected even in human gut microbiota. Ambient pH is one of the major factors that affect the physiology and metabolism of several pathogenic microorganisms. Although dynamic changes of pH environment in different parts of the body is a great challenge for Malassezia to confront, the role that ambient pH plays in Malassezia is largely unknown. In this study, we investigated the impact of ambient pH on physiology and expression of lipases in M. furfur grown under different pH conditions. The yeast was able to grow in media ranging from pH 4 to 10 without morphological alteration. Elevation in pH value enhanced the extracellular lipase activity but decreased that of intracellular lipase. The qPCR results revealed that a set of functional lipase genes, LIP3-6, were constitutively expressed regardless of pH conditions or exposure time. Based on the data, we conclude that the external pH plays a promotional role in the secretion of lipases but exerts less effect on transcription of the genes and morphology in M. furfur.

Malassezia colonisation on a reconstructed human epidermis: Imaging studies

BACKGROUND

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.

OBJECTIVE

The present study aimed to evaluate Malassezia colonisation pattern on a reconstructed human epidermis (RhE) by imaging techniques.

METHODS

Malassezia clinical isolates were previously isolated from volunteers with pityriasis versicolor and seborrhoeic dermatitis. Yeast of two strains of M furfur and M sympodialis were inoculated onto the SkinEthic^™ RHE. The tissues were processed for light microscopy, wide-field fluorescence microscopy and scanning electron microscopy.

RESULTS

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 96 hours 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 M furfur biofilm.

CONCLUSION

Skin isolates of M furfur and M sympodialis were capable of forming biofilm in vitro at the epidermal surface simulating in vivo conditions. Following 24 hours 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 96 hours. A structural heterogeneity of biofilm between species was found.

Investigation on Microecology of Hair Root Fungi in Androgenetic Alopecia Patients

BACKGROUND

This study focused on the differences in hairy root fungal microecology between androgenetic alopecia patients and healthy individuals.

METHODS

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.

RESULTS

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.

CONCLUSION

Malassezia had a positive correlation with the incidence of androgenic alopecia.