Real-Time PCR Identification of Six Malassezia Species

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.

Detection of bile acids in bronchoalveolar lavage fluid defines the inflammatory and microbial landscape of the lower airways in infants with cystic fibrosis

BACKGROUND

Cystic Fibrosis (CF) is a genetic condition characterized by neutrophilic inflammation and recurrent infection of the airways. How these processes are initiated and perpetuated in CF remains largely unknown. We have demonstrated a link between the intestinal microbiota-related metabolites bile acids (BA) and inflammation in the bronchoalveolar lavage fluid (BALF) from children with stable CF lung disease. To establish if BA indicate early pathological processes in CF lung disease, we combined targeted mass spectrometry and amplicon sequencing-based microbial characterization of 121 BALF specimens collected from 12-month old infants with CF enrolled in the COMBAT-CF study, a multicentre randomized placebo-controlled clinical trial comparing azithromycin versus placebo. We evaluated whether detection of BA in BALF is associated with the establishment of the inflammatory and microbial landscape of early CF lung disease, and whether azithromycin, a motilin agonist that has been demonstrated to reduce aspiration of gastric contents, alters the odds of detecting BA in BALF. We also explored how different prophylactic antibiotics regimens impact the early life BALF microbiota.

RESULTS

Detection of BA in BALF was strongly associated with biomarkers of airway inflammation, more exacerbation episodes during the first year of life, increased use of oral antibiotics with prolonged treatment periods, a higher degree of structural lung damage, and distinct microbial profiles. Treatment with azithromycin, a motilin agonist, which has been reported to reduce aspiration of gastric contents, did not reduce the odds of detecting BA in BALF. Culture and molecular methods showed that azithromycin does not alter bacterial load or diversity in BALF. Conversely, penicillin-type prophylaxis reduced the odds of detecting BAs in BALF, which was associated with elevated levels of circulating biomarkers of cholestasis. We also observed that environmental factors such as penicillin-type prophylaxis or BAs detection were linked to distinct early microbial communities of the CF airways, which were associated with different inflammatory landscapes but not with structural lung damage.

CONCLUSIONS

Detection of BA in BALF portend early pathological events in CF lung disease. Benefits early in life associated with azithromycin are not linked to its antimicrobial properties. Video Abstract.

Genotypic Analysis of the Population Structure in Malassezia globosa and Malassezia restricta

The molecular characterization of Malassezia spp. isolates from animals and humans has not been thoroughly studied. Although a range of molecular methods has been developed for diagnosing Malassezia species, they have several drawbacks, such as inefficiency in differentiating all the species, high cost and questionable reproducibility. The present study aimed to develop VNTR markers for genotyping Malassezia isolated from clinical and animal samples. A total of 44 M. globosa and 24 M. restricta isolates were analyzed. Twelve VNTR markers were selected on seven different chromosomes (I, II, III, IV, V, VII and IX), six for each Malassezia species. The highest discriminatory power for a single locus was obtained with the STR-MG1 marker (0.829) and STR-MR2 marker (0.818) for M. globosa and M. restricta, respectively. After the analysis of multiple loci, 24 genotypes were noted among 44 isolates in M. globosa, with a discrimination index D of 0.943 and 15 genotypes were noted among 24 isolates in M. restricta, with a discrimination index D of 0.967. An endogenous infection was detected in two patients. Different genotypes of M. globosa strains colonized one patient. Interestingly, VNTR markers analysis revealed a carriage between a breeder and his dog in three cases for M. globosa and two for M. restricta. The FST (0.018 to 0.057) values indicate a low differentiation between the three populations of M. globosa. These results suggest a dominant clonal mode of reproduction in M. globosa. The typing of M. restricta showed a genotypic diversity of the strains, which can cause various skin pathologies. However, patient five was colonized with strains having the same genotype collected from different body parts (back, shoulder). VNTR analysis was capable of identifying species with high accuracy and reliability. More importantly, the method would facilitate monitoring Malassezia colonization in domestic animals and humans. It was shown that the patterns are stable and the method is discriminant, making it a powerful tool for epidemiological purposes.

Production and Quantification of Virulence Factors in Malassezia Species

Seventy-seven strains of Malassezia were included in this study. Biofilm and hydrolytic enzyme production were studied by using specific solid media. The Real-Time reverse transcriptase qPCR method was applied to determine the overexpression of genes encoding the extracellular enzymes. All included Malassezia species produced biofilms. No statistically significant difference was observed between Malassezia species in biofilm formation (p = 0.567). All Malassezia species produced lipase, and 95% of Malassezia globosa showed a strong enzymatic activity (Pz = 0.55 ± 0.02). A statistically significant difference was observed between the mean keratinase indices of Malassezia slooffiae and the other Malassezia species (p = 0.005). The overexpression of one or more genes was observed in 100% of strains isolated from patients with folliculitis, 87.5% - with pityriasis versicolor, and 57.14% of the control group isolates. A statistically significant difference in the lipase gene expression (p = 0.042) was between the strains from patients with folliculitis and the control group. This investigation provides more information about the frequency of the production of the major enzymes considered virulence factors of Malassezia species. Interestingly, the overexpression of one or more genes was observed in strains isolated from patients with Malassezia disorders.

Malassezia: Zoonotic Implications, Parallels and Differences in Colonization and Disease in Humans and Animals

Malassezia spp. are commensals of the skin, oral/sinonasal cavity, lower respiratory and gastrointestinal tract. Eighteen species have been recovered from humans, other mammals and birds. They can also be isolated from diverse environments, suggesting an evolutionary trajectory of adaption from an ecological niche in plants and soil to the mucocutaneous ecosystem of warm-blooded vertebrates. In humans, dogs and cats, Malassezia-associated dermatological conditions share some commonalities. Otomycosis is common in companion animals but is rare in humans. Systemic infections, which are increasingly reported in humans, have yet to be recognized in animals. Malassezia species have also been identified as pathogenetic contributors to some chronic human diseases. While Malassezia species are host-adapted, some species are zoophilic and can cause fungemia, with outbreaks in neonatal intensive care wards associated with temporary colonization of healthcare worker’s hands from contact with their pets. Although standardization is lacking, susceptibility testing is usually performed using a modified broth microdilution method. Antifungal susceptibility can vary depending on Malassezia species, body location, infection type, disease duration, presence of co-morbidities and immunosuppression. Antifungal resistance mechanisms include biofilm formation, mutations or overexpression of ERG11, overexpression of efflux pumps and gene rearrangements or overexpression in chromosome 4.

Conventional therapy and new antifungal drugs against Malassezia infections

Malassezia yeasts are commensal microorganisms occurring on the skin of humans and animals causing dermatological disorders or systemic infections in severely immunocompromised hosts. Despite attempts to control such yeast infections with topical and systemic antifungals, recurrence of clinical signs of skin infections as well as treatment failure in preventing or treating Malassezia furfur fungemia have been reported most likely due to wrong management of these infections (e.g., due to early termination of treatment) or due to the occurrence of resistant phenomena. Standardized methods for in vitro antifungal susceptibility tests of these yeasts are still lacking, thus resulting in variable susceptibility profiles to azoles among Malassezia spp. and a lack of clinical breakpoints. The inherent limitations to the current pharmacological treatments for Malassezia infections both in humans and animals, stimulated the interest of the scientific community to discover new, effective antifungal drugs or substances to treat these infections. In this review, data about the in vivo and in vitro antifungal activity of the most commonly employed drugs (i.e., azoles, polyenes, allylamines, and echinocandins) against Malassezia yeasts, with a focus on human bloodstream infections, are summarized and their clinical implications are discussed. In addition, the usefulness of alternative compounds is discussed.

Epidemiological characterization of pityriasis versicolor and distribution of Malassezia species among students in Hai Phong city, Vietnam

Background and Purpose:

Pityriasis versicolor (PV) is a common fungal skin infection caused by Malassezia species. Previous studies have shown that the prevalence of PV is influenced by geographic factors. The aim of the current study was to find the epidemiological characteristics of PV and distribution of Malassezia species in the secondary school students living in Hai Phong city, Vietnam.

Materials and Methods:

This study was conducted on 1357 students within the age range of 10 - 16 years selected from four secondary schools in Hai Phong city. The students were screened for PV skin lesions from August 2016 to December 2017. The isolates of Malassezia from PV patients were analyzed by performing direct microscopy and culturing on modified Dixon agar plates, containing gentamicin, at 32oC for 7 days. In the next stage, the fungal strains obtained from patients with positive fungal cultures were identified using the CHROMagarTM Malassezia medium, polymerase chain reaction-restriction fragment length polymorphism techniques, and D1/D2 rDNA genome sequencing.

Results:

Pityriasis versicolor was diagnosed in 305 (22.48%) students and confirmed by clinical appearance and direct examination. A total of 293 (96.07%) samples grew on modified Dixon agar. With regard to demographic characteristics, 50.49% of the PV cases were female, and 57.38% of cases resided in urban areas. Furthermore, 88.52% of the subjects had the illness duration of more than 6 months. Hypopigmented and erythematous skin lesions were also observed in the research participants, with hypopigmentation being the most frequent condition (97.05%). Most of the Malassezia fungal strains were isolated from the back (39.56%), face (23.99%), and chest (16.51%). Malassezia furfur and M. japonica accounted for PV in 96.25% and 3.75% of the cases, respectively. Furthermore, Malassezia furfur was distributed in both rural and urban areas, while M. japonica was found only in the urban areas.

Conclusion:

The findings of the present study were indicative of the high prevalence of Malassezia yeasts, mostly M. furfur, among the students in Hai Phong city, Vietnam

Detection of meat from horse, donkey and their hybrids (mule/hinny) by duplex real-time fluorescent PCR

Meat adulteration is currently a common practice worldwide. In China, adulteration of donkey meat products with the similar species (horse and mule/hinny) meat and mislabeling are becoming widespread concerns. In this study, a sensitive and species-specific duplex real-time PCR assay based on the simultaneous amplification of fragments of the creatine kinase muscle gene family, was developed and optimized for the identification of horse, donkey and mule /hinny species in raw and heat-processed meat products. Duplex real-time PCR results showed different fluorescence amplification curves for horse and donkey. Both kinds of fluorescence amplification curves appeared simultaneously for mule/hinny. The limit of detection (LOD) of the method was up to 0.01 ng /μL. The method and strategy developed in this study could be applied to detect the presence of adulterants from horse and mule /hinny meat in raw donkey meat and meat products.

Comparison of Three Skin Sampling Methods and Two Media for Culturing Malassezia Yeast

Malassezia is a lipid-dependent commensal yeast of the human skin. The different culture media and skin sampling methods used to grow these fastidious yeasts are a source of heterogeneity in culture-based epidemiological study results. This study aimed to compare the performances of three methods of skin sampling, and two culture media for the detection of Malassezia yeasts by culture from the human skin. Three skin sampling methods, namely sterile gauze, dry swab, and Transwab^TM with transport medium, were applied on 10 healthy volunteers at 5 distinct body sites. Each sample was further inoculated onto either the novel FastFung medium or the reference Dixon agar for the detection of Malassezia spp. by culture. At least one colony of Malassezia spp. grew on 93/300 (31%) of the cultures, corresponding to 150 samplings. The positive culture rate was 67%, 18%, and 15% (P < 10⁻³), for samples collected with sterile gauze, Transwab^TM, and dry swab, respectively. The positive culture rate was 62% and 38% (P < 0.003) by using the FastFung and the Dixon media, respectively. Our results showed that sterile gauze rubbing skin sampling followed by inoculation on FastFung medium should be implemented in the routine clinical laboratory procedure for Malassezia spp. cultivation.

A case of anti- pityriasis versicolor therapy that preserves healthy mycobiome

Background

The impact of Malassezia yeasts on skin mycobiome and health has received considerable attention recently. Pityriasis versicolor (PV), a common dermatosis caused by Malassezia genus worldwide, is a manifestation of dysbiosis. PV can be associated with hyper- and/or hypopigmented skin lesions. This disease entity is characterized by high percentage of relapses, which demands a proper antifungal therapy that is based on unambiguous species identification and drug susceptibility testing.

Case presentation

Comprehensive analysis of PV case in man presenting simultaneously hyper- and hypopigmented skin lesions was performed. Conventional and molecular diagnostic procedures revealed Malassezia furfur and Malassezia sympodialis, respectively as etiological agents of skin lesions observed. Susceptibility tests showed significantly lowered sensitivity of M. furfur cells to fluconazole. Based on susceptibility profiles local antifungal therapy with drugs characterized by entirely different mechanism of action was included.

Conclusions

Our study indicates that cases of PV represented by two types of skin lesions in one patient may be associated with distinct Malassezia species. Moreover, as observed in this case, each of the isolated etiological agents of PV may differ significantly in susceptibility to antifungals. This can significantly complicate the treatment of dermatosis, which by definition is associated with a significant percentage of relapses. In the presented case localized topical treatment was sufficient and successful while allowing maintaining the physiological mycobiome.

Biology, diagnosis and treatment of Malassezia dermatitis in dogs and cats Clinical Consensus Guidelines of the World Association for Veterinary Dermatology

BACKGROUND

The genus Malassezia is comprised of a group of lipophilic yeasts that have evolved as skin commensals and opportunistic cutaneous pathogens of a variety of mammals and birds.

OBJECTIVES

The objective of this document is to provide the veterinary community and other interested parties with current information on the ecology, pathophysiology, diagnosis, treatment and prevention of skin diseases associated with Malassezia yeasts in dogs and cats.

METHODS AND MATERIAL

The authors served as a Guideline Panel (GP) and reviewed the literature available prior to October 2018. The GP prepared a detailed literature review and made recommendations on selected topics. The World Association of Veterinary Dermatology (WAVD) Clinical Consensus Guideline committee provided guidance and oversight for this process. The document was presented at two international meetings of veterinary dermatology societies and one international mycology workshop; it was made available for comment on the WAVD website for a period of six months. Comments were shared with the GP electronically and responses incorporated into the final document.

CONCLUSIONS AND CLINICAL IMPORTANCE

There has been a remarkable expansion of knowledge on Malassezia yeasts and their role in animal disease, particularly since the early 1990's. Malassezia dermatitis in dogs and cats has evolved from a disease of obscurity and controversy on its existence, to now being a routine diagnosis in general veterinary practice. Clinical signs are well recognised and diagnostic approaches are well developed. A range of topical and systemic therapies is known to be effective, especially when predisposing factors are identified and corrected.

Quantification of Malassezia pachydermatis by real-time PCR in swabs from the external ear canal of dogs

Malassezia pachydermatis is part of the normal microbiota of canine skin and external ear canal, and is also associated with otitis externa in dogs. Laboratory detection of Malassezia otitis relies on the presence of elevated numbers of the yeast on cytologic examination of otic exudate. Although cytology has high specificity, it has low sensitivity, resulting in false-negatives and posing a challenge for clinicians to accurately diagnose Malassezia otitis. We developed a quantitative PCR (qPCR) to detect and quantify M. pachydermatis yeasts and validate the method with swabs from external ear canals of dogs. Our qPCR uses the β-tubulin gene, a single-copy gene, as a target. The limit of quantification was established as 0.18 ng/reaction, equivalent to 2.0 × 10⁴ genome equivalents (gEq). Swabs from healthy dogs yielded quantification values of ≤2.7 × 10⁴ gEq in the qPCR, whereas swabs from dogs with otitis yielded quantification values of ≥2.5 × 10⁵ gEq. Our qPCR assay provides accurate quantification of M. pachydermatis yeasts from swab samples from dogs, is more sensitive than cytology, and could be used to monitor response to treatment. Our assay could also be valuable in a research setting to better understand the pathogenesis of M. pachydermatis.