Biofilm formation, adherence, and hydrophobicity of M. sympodialis, M. globosa, and M. slooffiae from clinical isolates and normal skinVirulence factors of M. sympodialis, M. globosa and M. slooffiae

Exploring the antibiofilm efficacy of cinnamaldehyde against Malassezia globosa associated pityriasis versicolor

BACKGROUND

Malassezia globosa is a commensal basidiomycetous yeast occurring on the skin that causes pityriasis versicolor (PV) and seborrheic dermatitis, but that has also been implicated in other dermatoses. Cinnamaldehyde (CM) has antibacterial, antioxidant, and anti-inflammatory activities, but the effect of CM on M. globosa-infected PV has not been clarified.

PURPOSE

The study aimed to investigate the possible antifungal and antibiofilm activities of CM against M. globosa-infected PV in vivo and in vitro.

METHODS

The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of CM against M. globosa. The crystal violet staining assay and XTT assay were used to investigate the inhibition of CM on biofilm formation and the eradication of mature biofilms. The visualizations of the biofilm and cell distribution in the biofilm matrix were performed with a scanning electron microscope and confocal laser scanning microscope. The kits of antioxidant kinase were used to determine the activities of oxidative stress markers in M. globosa-stimulated HaCaT cells. Western blot assays were used to evaluate the role of TLR2/NF-κB in vitro. Furthermore, the protective effect of CM was assessed in M. globosa-associated PV mice. The expressions of inflammatory cytokines and apoptosis were screened using ELISA assays. The expressions of interleukin-6 and tumor necrosis factor-α were measured by an immunohistochemistry method in vivo.

RESULTS

Our results showed that the MIC of CM against planktonic cells of M. globosa was 4 µg/ml and treatment with 20 × MIC CM eradicated mature biofilms of M. globosa. In vitro, after CM treatment the levels of oxidative stress indicators (i.e., superoxide dismutase, catalase, glutathione) significantly increased, while the levels of malondialdehyde decreased. In addition, the expression of TLR2/NF-κB in HaCaT cells was significantly reduced after CM treatment. On the other hand, an in vivo therapeutic effect of CM was assessed against M. globosa-infected mice. The fungal load on the skin decreased after treatment with CM compared to the M. globosa-infected group. In addition, the uninfected animals showed a normal skin structure, whereas, the M. globosa-infected mice showed extensive infiltration of neutrophils in skin tissues that improved after treatment with CM. Meanwhile, the levels of inflammatory and apoptotic factors improved after CM treatment.

CONCLUSION

Our results showed that CM inhibits the biofilm formation of M. globosa and eradicates mature biofilms of M. globosa. Treatment with CM significantly decreased oxidative stress, apoptosis, and inflammatory markers in the skin tissue and HaCaT cells. Hence, this study suggests that CM is a good candidate therapeutic agent against M. globosa-induced PV infections because of its antifungal, antibiofilm, and anti-inflammatory properties.

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 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.

Skin Microbiome, Metabolome and Skin Phenome, from the Perspectives of Skin as an Ecosystem

Skin is a complex ecosystem colonized by millions of microorganisms, including bacteria, fungi, and viruses. Skin microbiota is believed to exert critical functions in maintaining host skin health. Profiling the structure of skin microbial community is the first step to overview the ecosystem. However, the community composition is highly individualized and extremely complex. To explore the fundamental factors driving the complexity of the ecosystem, namely the selection pressures, we review the present studies on skin microbiome from the perspectives of ecology. This review summarizes the following: (1) the composition of substances/nutrients in the cutaneous ecological environment that are derived from the host and the environment, highlighting their proposed function on skin microbiota; (2) the features of dominant skin commensals to occupy ecological niches, through self-adaptation and microbe-microbe interactions; (3) how skin microbes, by their structures or bioactive molecules, reshape host skin phenotypes, including skin immunity, maintenance of skin physiology such as pH and hydration, ultraviolet (UV) protection, odor production, and wound healing. This review aims to re-examine the host-microbe interactions from the ecological perspectives and hopefully to give new inspiration to this field.

Virulence factors of Malassezia strains isolated from pityriasis versicolor patients and healthy individuals

Over the last decade, Malassezia species have emerged as increasingly important pathogens associated with a wide range of dermatological disorders and bloodstream infections. The pathogenesis of Malassezia yeasts is not completely clear but it seems to be strictly related to Malassezia strains and hosts and need to be better investigated. This study aimed to assess the enzymatic activities, biofilm formation and in vitro antifungal profiles of Malassezia spp. from Pityriasis versicolor and heathy patients. The potential relationship between virulence attributes, the antifungal profiles and the origin of strains were also assessed. A total of 44 Malassezia strains isolated from patients with (n = 31) and without (n = 13) Pityriasis versicolor (PV) were employed to evaluate phospholipase (Pz), lipase (Lz), hemolytic (Hz) activities and biofilm formation. In addition, in vitro antifungal susceptibility testing was conducted using the CLSI broth microdilution with some modifications. A high percentage of strains produced phospholipase, lipase, hemolysins and biofilm regardless of their clinical origin. The highest number of strains producing high enzymatic activities came from PV patients. A correlation between the intensity of hydrolytic activities (lipase and phospholipase activities) and the hemolytic activity was detected. Positive associations between Lz and the low fluconazole susceptibility and Hz and biofilm formation were observed. These results suggest that enzyme patterns and biofilm formation together with antifungal profiles play a role in the pathogenicity of Malassezia spp. and might explain the implication of some Malassezia spp. in invasive fungal infections and in the development of inflammation.

Amplicon-based sequencing and co-occurence network analysis reveals notable differences of microbial community structure in healthy and dandruff scalps

Background

Dandruff is a chronic, recurring, and common scalp problem that is caused by several etiopathogeneses with complex mechanisms. Management of this condition is typically achieved via antifungal therapies. However, the precise roles played by microbiota in the development of the condition have not been elucidated. Despite their omnipresence on human scalp little is known about the co-occurrence/co-exclusion network of cutaneous microbiota.

Results

We characterized the scalp and hair surface bacterial and fungal communities of 95 dandruff-afflicted and healthy individuals residing in China. The degree distributions of co-occurrence/co-exclusion network in fungi-bacteria and bacteria-bacteria were higher in the healthy group (P < 0.0001), whereas the betweenness values are higher in the dandruff group (P < 0.01). Meanwhile, the co-occurrence/co-exclusion network among fungi-fungi and fungi-bacteria showed that compared to the healthy group, the dandruff group had more positive links (P < 0.0001). In addition, we observed that Malassezia slooffiae, Malassezia japonica and Malassezia furfur, were more abundant in the dandruff group than in the healthy group. These microbiota were co-exclusion by either multiple bacterial genera or Malassezia sp. in healthy group. The lactic acid bacteria on the scalp and hair surface, especially the genera Lactobacillus and Lactococcus, exhibit a negative correlation with multiple bacterial genera on the scalp and hair surface. Lactobacillus plantarum and Pediococcus lactis isolated on the healthy human scalp can inhibit the growth of Staphylococcus epidermidis in vitro.

Conclusions

We showed that microbial networks on scalp and hair surface with dandruff were less integrated than their healthy counterparts, with lower node degree and more positive and stronger links which were deemed to be unstable and may be more susceptible to environmental fluctuations. Lactobacillus bacteria have extensive interactions with other bacteria or fungi in the scalp and hair surface micro-ecological network and can be used as targets for improving scalp health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08534-4.

Malassezia in Inflammatory Bowel Disease: Accomplice of Evoking Tumorigenesis

Accumulating evidence indicates that patients with inflammatory bowel disease (IBD) have a significantly higher risk of developing different cancers, while the exact mechanism involved is not yet fully understood. Malassezia is a lipid-dependent opportunistic yeast, which colonizes on mammalian skin and internal organs. Also, dysbiosis in fungal communities accompanied by high level of Malassezia are fairly common in inflammatory diseases such as IBD and various cancers. In cancer patients, higher levels of Malassezia are associated with worse prognosis. Once it is ablated in tumor-bearing mice, their prognostic conditions will be improved. Moreover, Malassezia manifests multiple proinflammatory biological properties, such as destruction of epithelial barrier, enrichment of inflammatory factors, and degradation of extracellular matrix (ECM), all of which have been reported to contribute to tumor initiation and malignant progression. Based on these facts, we hypothesize that high levels of Malassezia together with mycobiome dysbiosis in patients with IBD, would aggravate the microecological imbalance, worsen the inflammatory response, and further promote tumorigenesis and deterioration. Herein, we will discuss the detrimental properties of Malassezia and explore the key role of this fungus in the correlation between IBD and cancer, in order to take early surveillance and intervention to minimize the cancer risk in individuals with IBD.

The Crosstalk Between Saliva Bacteria and Fungi in Early Childhood Caries

Early childhood caries (ECC) is the most prevalent oral disease in children, which greatly affects the quality of life and health condition of the patients. Although co-infection of oral streptococci and fungi has been well recognized in the development of ECC, the correlation between other core members of oral mycobiome and ECC progression remains unclear. In the current study, saliva samples obtained from severe ECC (SECC), ECC, and caries-free children were collected, and both V3–V4 16S rRNA and ITS1 rRNA gene amplicon sequencing were performed to investigate the salivary bacterial and fungal profiles. Significant alteration of salivary fungal community in SECC/ECC children was observed compared with the caries-free control. The typing analysis determined the fungal community into five fungal types, which influenced the structure of salivary bacteria. By performing Spearman correlation analysis, carious phenotypes were positively related to Fusobacterium but negatively linked to Neocosmospora, and a significant correlation of cross-kingdom taxonomic pairs was identified. Our work demonstrated the interactions between oral bacteria and fungi at the community level, which may advance our knowledge on the etiological role of bacteria/fungi in the development of ECC and promote better management of this disease.

BSC2 induces multidrug resistance via contributing to the formation of biofilm in Saccharomyces cerevisiae

Biofilm plays an important role in fungal multidrug resistance (MDR). Our previous studies showed that BSC2 is involved in resistance to amphotericin B (AMB) through antioxidation in Saccharomyces cerevisiae. In this study, the overexpression of BSC2 and IRC23 induced strong MDR in S. cerevisiae. BSC2-overexpression affected cellular flocculation, cell surface hydrophobicity, biofilm formation and invasive growth. However, it failed to induce caspofungin (CAS) resistance and affect the invasive growth in FLO mutant strains (FLO11Δ, FLO1Δ, FLO8Δ and TUP1Δ). Furthermore, the overexpression of BSC2 compensated for chitin synthesis defects to maintain the cell wall integrity and significantly reduced the cell morphology abnormality induced by CAS. However, it could not repair the cell wall damage caused by CAS in the FLO mutant strains. Although BSC2 overexpression increased the level of mannose in the cell wall, DPM1 overexpression in both BY4741 and bsc2∆ could confer resistance to CAS and AMB. In addition, BSC2 overexpression significantly increased the mRNA expression of FLO11, FLO1, FLO8 and TUP1. BSC2 may function as a regulator of FLO genes and be involved in cell wall integrity in yeast. Taken together, our data demonstrate that BSC2 induces MDR in a FLO pathway-dependent manner via contributing to the formation of biofilms in S. cerevisiae. TAKE AWAYS: Overexpression of BSC2 induced strong MDR in S. cerevisiae. BSC2 affected cellular flocculation, CSH, biofilm formation and invasive growth. BSC2 could not repair the cell wall damage caused by CAS in the FLO mutants. BSC2 may function as a regulator of FLO genes to maintain cell wall integrity. BSC2 promotes biofilm formation in a FLO pathway-dependent manner to induce MDR.

Role of Cell Surface Hydrophobicity in the Pathogenesis of Medically-Significant Fungi

Cell surface hydrophobicity (CSH) is an important cellular biophysical parameter which affects both cell-cell and cell-surface interactions. In dimorphic fungi, multiple factors including the temperature-induced shift between mold and yeast forms have strong effects on CSH with higher hydrophobicity more common at the lower temperatures conducive to filamentous cell growth. Some strains of Cryptococcus neoformans exhibit high CSH despite the presence of the hydrophilic capsule. Among individual yeast colonies from the same isolate, distinct morphologies can correspond to differences in CSH. These differences in CSH are frequently associated with altered virulence in medically-significant fungi and can impact the efficacy of antifungal therapies. The mechanisms for the maintenance of CSH in pathogenic fungi remain poorly understood, but an appreciation of this fundamental cellular parameter is important for understanding its contributions to such phenomena as biofilm formation and virulence.