Monitoring spread of Malassezia infections in a neonatal intensive care unit by PCR-mediated genetic typing

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.

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.

Susceptibilities of Malassezia strains from pityriasis versicolor, Malassezia folliculitis and seborrheic dermatitis to antifungal drugs

The human pathogenic yeast genus Malassezia may be an etiological agent of skin disorders and has received considerable attention from dermatologists in recent years. To investigate the different susceptibilities of Malassezia species to four antifungal drugs, we isolated a total of 244 Malassezia strains and identified six species of Malassezia from patients with clinical skin diseases. The minimum inhibitory concentration (MIC) of the four antifungal drugs was obtained by comparing the susceptibility of the isolated Malassezia strains to four antifungal drugs (ketoconazole (KTZ), itraconazole (ITZ), fluconazole (FLC) and amphotericin B (Am B)). We demonstrated that M. furfur, M. sympodialis, M. pachydermatis and M. globosa are the most common Malassezia species in the three skin diseases. The MICs of KTZ, ITZ, FLC and Am B against M. furfur, M. sympodialis, M. pachydermatis and M. globosa ranged from 0.03 - 16 mg/L, 0.03 - 2.0 mg/L, 0.03 - 8 mg/L, and 13 - 64 mg/L, respectively. The sensitivities of Malassezia to the four antifungal drugs from high to low were ITZ ≥ KTZ > Am B > FLC. The susceptibilities of the various Malassezia species to the four antifungal drugs were different, and the susceptibility of M. furfur to KTZ was significantly different from those of the three skin diseases (pityriasis versicolor, Malassezia folliculitis and seborrheic dermatitis). Our results suggested that the MIC analysis of the four antifungal drugs would be helpful in preventing drug resistance in the clinical screening of Malassezia and choosing better antifungal drugs to treat Malassezia-associated skin diseases.

Systemic Infection Caused by Malassezia pachydermatis in Infants: Case Series and Review of the Literature

BACKGROUND

Malassezia pachydermatis is a rare cause of systemic infection in infants.

METHODS

A total of 4 cases of M. pachydermatis fungemia that occurred in our neonatal intensive care unit over a 21-month period were reviewed, as well as 27 cases reported in the literature since 1988.

RESULTS

The patients were preterm with multiple complications and had birth weights ranging from 490 to 810 g and gestational age between 23 and 26 weeks. All patients had received prophylactic fluconazole, broad-spectrum antibiotics and parenteral lipid supplements before fungemia onset, which occurred between the age of 7 and 28 days. Symptoms were nonspecific and thrombocytopenia was the primary laboratory finding. All patients received intravenous antifungal treatment and recovered from their infection. The 27 cases from review of the literature also indicated that the infected infants were extremely low birth weight (77.8%), with multiple underlying diseases (94.7%), receiving lipid-supplementation (100%) from a central vascular catheter. Most infants received antifungal treatment (73.1%) and catheter removal (73.1%) as the management.

CONCLUSIONS

M. pachydermatis is a pathogenic agent that causes late onset sepsis in critically ill low birth weight infants with generally good outcomes. Targeted antifungal treatment as well as catheter removal appear to be key factors for infection management.

Malassezia Yeasts in Veterinary Dermatology: An Updated Overview

Lipophilic yeasts of the genus Malassezia are important skin commensals and opportunistic skin pathogens in a variety of animals. The species M. pachydermatis was first isolated from the skin of a captive Indian rhinoceros with an exfoliative dermatitis in 1925, recognized as an important otic pathogen of dogs in the 1950's, and finally accepted, after several years of controversy, as a common cause of canine dermatitis in the 1990's. Since then, there has been considerable research into the biology of Malassezia yeasts and their interaction with their animal hosts. In dogs and cats, M. pachydermatis is associated with ceruminous otitis externa and a "seborrhoeic" dermatitis, wherein pruritic, erythematous skin lesions, often with brown/black greasy, malodourous material matting hairs, preferentially develop in intertriginous areas. Skin disease is favored by folds, underlying hypersensitivity disorders, endocrinopathies, defects of cornification, and in cats, various visceral paraneoplastic syndromes. Diagnosis is based on detecting the yeast in compatible skin lesions, usually by cytology, and observing a clinical and mycological response to therapy. Treatment normally comprises topical or systemic azole therapy, often with miconazole-chlorhexidine shampoos or oral itraconazole or ketoconazole. Management of concurrent diseases is important to minimize relapses. Historically, wild-type Malassezia isolates from dogs and cats were typically susceptible to azoles, with the exception of fluconazole, but emerging azole resistance in field strains has recently been associated with either mutations or quadruplication of the ERG11 gene. These observations have prompted increased interest in alternative topical antifungal drugs, such as chlorhexidine, and various essential oils. Further clinical trials are awaited with interest.

Isolation of Malassezia species from healthy cats and cats with otitis

Lipid-dependent Malassezia species have recently been cultured from veterinary specimens. The identification of Malassezia species isolates from animals is important to clarify the epidemiology of these lipophilic yeasts. Malassezia species were cultured from the external ear canals of 63 out of 99 cats with otitis and 12 of 52 (23%) healthy control cats. The rate of isolation in affected animals versus controls was highly significant ( P<0.01). Malassezia pachydermatis was isolated as a pure culture in 33 (45.2%) cats, associated with Malassezia globosa and Malassezia furfur in 20 (50%) and 17 (42.5%) animals, respectively. Three different species were isolated simultaneously in three cats (two cats with M pachydermatis, M globosa and M furfur, one subject with M pachydermatis, M furfur and Malassezia sympodialis). M globosa was isolated as the sole species in two animals. The present work confirms the presence of some lipid-dependent species of Malassezia in both healthy and otitic cats.

Malassezia-Can it be Ignored?

Genus Malassezia comprises of 14 species of “yeast like fungi,” 13 of which are lipophilic and 1 is nonlipophilic. They are known commensals and in predisposed individuals they commonly cause a spectrum of chronic recurrent infections. They rarely also cause serious illnesses like catheter-related blood stream infections, CAPD associated peritonitis etc., Though these fungi have been known to man for over 150 years, their fastidious nature and cumbersome culture and speciation techniques have restricted research. Since the last taxonomic revision, seven new species have been added to this genus. Their ability to evade the host immune system and virulence has increased the spectrum of the diseases caused by them. These agents have been implicated as causal agents in common diseases like atopic dermatitis recently. Though culture-based research is difficult, the new molecular analysis techniques and facilities have increased research in this field such that we can devote more attention to this genus to study in detail, their characteristics and their growing implications implications in the clinical scenario.

Biofilm formation in Malassezia pachydermatis strains isolated from dogs decreases susceptibility to ketoconazole and itraconazole

Malassezia pachydermatis is a commonly isolated yeast in veterinary dermatology that can produce biofilms in vitro and in vivo, lowering its susceptibility to antimicrobial drugs. The aim of this study was to determine and compare the in vitro susceptibility of planktonic cells and biofilms of M. pachydermatis isolates to ketoconazole and itraconazole. The presence of biofilm formation was confirmed by crystal violet staining and absorbance measurement at 595 nm wavelength, and by a scanning electron microscopy method. Cell viability was determined by the Celltiter 96 Aqueous One solution assay containing a water-soluble tetrazolium compound (MTS) with absorbance measurement at 490 nm. Planktonic cell minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) of ketoconazole and itraconazole were very low: MIC90 and MFC90 were 0.032 and 0.125 μg/ml for ketoconazole, while 0.063 and 0.25 μg/ml for itraconazole, respectively. Also, the half maximal effective concentrations (EC50) of itraconazole were higher for planktonic cells and biofilms compared to ketoconazole. The EC50 values of ketoconazole were 18-169 times higher and those of itraconazole 13-124 times higher for biofilms than for planktonic cells. Biofilm EC50 levels exceeded MICs 103-2060 times for ketoconazole and 84-1400 times for itraconazole. No significant difference was found between these values of the two substances. In conclusion, biofilms of all examined M. pachydermatis strains were much less susceptible to ketoconazole and itraconazole than their planktonic forms.

Molecular analysis of Malassezia pachydermatis isolated from canine skin and ear in Korea

We investigated Malassezia species and genotypes colonizing dogs, comparing those recovered from the ear canal with those from other anatomical body sites, as well as from diseased and healthy skin. The Malassezia isolates were obtained from four types of skin samples, i.e., diseased ear, diseased skin, healthy ear, and healthy skin. Sequences of the 26S ribosomal DNA region, the intergenic spacer 1 (IGS-1) and the internal transcribed spacer 1 (ITS-1) DNA region were analyzed. These confirmed the presence of Malassezia pachydermatis, which could be separated into three main sequence genotype groups (A, B, C). Genotype A was the most common, only two genotype B isolates were recovered from diseased skin lesion and genotype C was more likely to be isolated from ear samples than from other healthy or diseased-skin sites. The present findings provide the basis for further studies of genotypic diversity in M. pachydermatis, as well as their pathogenic potential.

The Malassezia genus in skin and systemic diseases

In the last 15 years, the genus Malassezia has been a topic of intense basic research on taxonomy, physiology, biochemistry, ecology, immunology, and metabolomics. Currently, the genus encompasses 14 species. The 1996 revision of the genus resulted in seven accepted taxa: M. furfur, M. pachydermatis, M. sympodialis, M. globosa, M. obtusa, M. restricta, and M. slooffiae. In the last decade, seven new taxa isolated from healthy and lesional human and animal skin have been accepted: M. dermatis, M. japonica, M. yamatoensis, M. nana, M. caprae, M. equina, and M. cuniculi. However, forthcoming multidisciplinary research is expected to show the etiopathological relationships between these new species and skin diseases. Hitherto, basic and clinical research has established etiological links between Malassezia yeasts, pityriasis versicolor, and sepsis of neonates and immunocompromised individuals. Their role in aggravating seborrheic dermatitis, dandruff, folliculitis, and onychomycosis, though often supported by histopathological evidence and favorable antifungal therapeutic outcomes, remains under investigation. A close association between skin and Malassezia IgE binding allergens in atopic eczema has been shown, while laboratory data support a role in psoriasis exacerbations. Finally, metabolomic research resulted in the proposal of a hypothesis on the contribution of Malassezia-synthesized aryl hydrocarbon receptor (AhR) ligands to basal cell carcinoma through UV radiation-induced carcinogenesis.

Advances in the identification of Malassezia

Members of the genus Malassezia are lypophilic and/or lipid-dependent, unipolar budding yeasts that can become pathogenic under the influence of particular predisposing factors (e.g., changes in the cutaneous microenvironment and/or alterations in host defences). This genus comprises at least 14 species, which have been identified traditionally based on their morphology and biochemical features. However, phenetic characteristics often do not allow the identification or delineation of closely related Malassezia spp., such that molecular tools need to be used to assist in fundamental studies of the epidemiology and ecology of Malassezia as well as aspects of the pathogenesis and disease caused by members of this genus. This article briefly reviews the morphological and biochemical methods commonly used for the identification of Malassezia as well as DNA technological methods that have been established for the specific identification of members of this genus and the diagnosis of their infections. New avenues for the development of improved molecular-diagnostic methods to overcome diagnostic limitations and to underpin fundamental investigations of this interesting group of yeasts are proposed.

CHARACTERIZATION OF TYPICAL AND ATYPICAL MALASSEZIA SPP. FROM CATTLE AND DOG BY RANDOM AMPLIFIED POLYMORPHIC DNA ANALYSIS

ABSTRACT There are few numbers of biochemical tests for specie classification in the genus Malassezia and these can to fail in the identification of the atypical isolates. In this study, typical and atypical isolates were analysed by random amplification of polymorphic DNA (RAPD) to compare with biochemical-physiological characteristics of the Malassezia species from bovine and canine ears. RAPD band patterns using OPA4 primer clustered all isolates according its biochemicalphysiological characteristics in the species from cattle and dog. Malassezia nana and M. sympodialis isolates were sub-clustered in separated sub-branches and both were from a different branch of the other species. The DNA pattern of the two atypical lipid-dependent M. pachydermatis strains was similar with of other typical strains but it did not show the one specific band of 200bp. Future studies in the specific RAPD bands of genetic profiles can be important to corroborate the identification of typical and atypical isolates of the genus Malassezia.

The range of molecular methods for typing Malassezia

PURPOSE OF REVIEW

The recent sequencing of the whole genome of Malassezia globosa and M. restricta forms the basis for molecular epidemiology studies and instigates investigations into their respective virulence factors. Thus, reviewing current knowledge on Malassezia molecular typing methods would reveal the pros and cons of each method and would highlight potential scarcity of epidemiological data regarding this ubiquitous fungal commensal and pathogen.

RECENT FINDINGS

Methods employed for Malassezia molecular typing can be categorized into those detecting sequence variations of strains and those that selectively amplify polymorphic DNA markers for discriminating Malassezia species subtypes. The former exploit rRNA gene sequence variations in order to trace M. globosa, M. restricta and M.pachydermatis subtypes associated with specific skin diseases, or detect M. furfur geographical variations. Polymorphic DNA amplification methods, such as amplified fragment length polymorphism analysis, demonstrated association of M. furfur subtypes with the origin of the strain (skin or systemic isolate), whereas PCR-fingerprinting of the mini-satellite DNA clustered M. furfur strains according to their geographic origin and disease origin. Moreover, much typing work has already been performed regarding the zoophilic species M. pachydermatis and the relevant methods can be adapted for studying the anthropophilic Malassezia species.

SUMMARY

In the near future, molecular typing will be a powerful tool in epidemiological studies that could be employed for the elucidation of the pathobiology of Malassezia species in associated skin diseases

RAPD differentiation of Malassezia spp. from cattle, dogs and humans

The molecular characterization of Malassezia spp. isolates from animals and humans has not been thoroughly studied. We have analysed the DNA profile by random amplified polymorphic DNA (RAPD)-PCR to compare the genetic diversity between isolates from the external ears of cattle, dogs and humans. The analysis of electrophoretic profiles on 8% polyacrylamide gel and their phenograms showed genetic heterogeneity between RAPD profiles of Malassezia furfur and Malassezia slooffiae isolates from humans and cattle and between Malassezia pachydermatis isolates from dogs and cattle. Intra-species variations in DNA pattern of Malassezia isolates and the presence of specific genetic types in cattle, dogs or humans were observed. A review of genetic heterogeneity of these yeast in veterinary and human medicine studies is given considering a possible transmission animal to human or human to animal. Additional studies must clarify the differences between the RAPD band patterns observed in this and other studies, which would facilitate monitoring of Malassezia spp. carriage in domestic animals and in humans.

Molecular characterization of Malassezia sympodialis and Malassezia furfur from cattle with and without otitis

A molecular study of Malassezia strains isolated from cattle with or without otitis was carried out by random amplified polymorphic DNA analysis (RAPD). DNA was extracted and purified from nine strains of Malassezia sympodialis and fourteen of Malassezia furfur. These microorganisms were collected from eight different bovine herds in Minas Gerais state, Brazil. The RAPD analysis and phenograms did not show the formation of genetically distinct groups among the strain isolated from cattle with or without otitis raised in the same herds. Genetic heterogeneity was observed among Malassezia strains from different geographic origins. These data suggest that genetically similar M. sympodialis and M. furfur strains found as members of the normal ear microbiota could become opportunistically active in the inflammatory process in cattle.

[Concordance between phenotypical features and PCR-REA for the identification of Malassezia spp]

The genus Malassezia has been recently revised and nowadays includes 11 species that cannot always be differentiated from each other by physiological and morphological tests. This study was aimed to evaluate the correlation between a molecular method and conventional phenotypic features in the identification of Malassezia spp. To achieve this aim, 92 Argentinean clinical strains isolated between 2001 and 2005 were analyzed along with three reference strains (Malassezia furfur CBS 7019, Malassezia sympodialis CBS 7222 and Malassezia slooffiae CBS 7956). By using PCR and restriction enzyme analysis with three different DNA endonucleases (PCR-REA), the molecular method consistently identified all three reference strains and all 92 clinical isolates as follows: 63 M. sympodialis, 18 M. furfur, 10 Malassezia globosa and one Malassezia obtusa. Phenotypic studies undentified 85 clinical isolates and two of the reference strains (total agreement > 91%). In particular for M. sympodialis, M. furfur and M. globosa, the species more frequently involved in human pathology, the agreement ranged between 84 and 96%. This result suggests that phenotypic studies are suitable for the presumptive identification of important Malassezia species in the clinical medical mycology laboratories where molecular methodologies are not available.

Molecular characterization of Malassezia isolates from dogs using three distinct genetic markers in nuclear DNA

Little precise information is available on the systematics, genetics, ecology and epidemiology of yeasts of the genus Malassezia from different animal species. In the present study, one hundred and four isolates of Malassezia (lipid dependent or non-lipid dependent) from dogs were characterized by their chitin synthase 2 gene (CHS2), and the large subunit (LSU) and the first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA sequences, and compared genetically with well-defined reference strains of Malassezia pachydermatis and heterologous species, including Malassezia furfur and Candida albicans. For each locus examined, three main sequence types (i.e. A, B and C) represented all of the 104 isolates, which were designated as genotypes A, B and C, respectively. A fourth, minor sequence type was also defined for the ITS-1. The nucleotide differences among genotypes was consistent with the magnitudes of intraspecific variability reported in previous studies. The genetic analysis of the sequence data sets (for individual loci) showed that all Malassezia genotypes clustered (with moderate to strong support) with the reference sequences of M. pachydermatis to the exclusion of the outgroups M. furfur and C. albicans. The present study reveals that multiple genetic variants of M. pachydermatis occur on dogs. The multilocus approach employed herein provides a foundation for future investigations of M. pachydermatis from other animals and humans, and their ecology and epidemiology.

Update on the genusMalassezia

Malassezia yeasts are commensals of normal human skin, but also cause pityriasis versicolor, seborrhoeic dermatitis and evidence is accumulating that they play a significant role in atopic eczema/dermatitis syndrome (AEDS; formerly atopic dermatitis). The taxonomy of the genus has changed considerably and is likely to change more in the future. Our understanding of the interaction between Malassezia and the host demonstrates that it has the paradoxical ability to both stimulate and suppress the immune response directed against it and there is a fine balance in its existence at the interface between commensalism and pathogenicity.

Malassezia species isolated from lesional and non-lesional skin in patients with pityriasis versicolor

Pityriasis versicolor (PV) is a superficial fungal infection where Malassezia species play a definite causative role, but the clinical significance of each of these species is not fully understood. The aim of our study was to analyse the prevalence of Malassezia species in PV lesions and to examine if the range of species varies with patient sex, age, direct microscopy findings and some clinical data. Ninety patients with PV completed the study. The samples were obtained by scraping the skin surface, both from lesional and non-lesional skin and then incubated on Sabouraud dextrose agar and modified Dixon agar. The yeast isolated were identified according to their macroscopic and microscoipic features and physiological characteristics. In PV lesions, the most common species was M. globosa (63%), followed by M. sympodialis (14%), M. furfur (10%), M. obtusa (8%) and M. slooffiae (4%). The most frequently isolated species from clinically healthy skin were M. globosa (49%), M. sympodialis (37%) and M. furfur (5%). We found significant difference in the distribution of Malassezia species between lesional and non-lesional skin and in the distribution of Malassezia species according to the direct microscopy findings. M. globosa in its mycelial phase is the predominant species involved in the aetiology of PV.

Microcoding and flow cytometry as a high-throughput fungal identification system for Malassezia species

Yeasts of the genus Malassezia have been associated with a variety of dermatological disorders in humans and domestic animals. With the recent recognition of new members of the genus, new questions are emerging with regard to the pathogenesis and epidemiology of the new species. As new species are recognized, a precise and comprehensive identification system is needed. Herein is described a bead suspension culture-based array that combines the specificity and reliability of nucleic acid hybridization analysis with the speed and sensitivity of the Luminex analyser. The developed 16-plex array consisted of species- and group-specific capture probes that acted as 'microcodes' for species identification. The probes, which were designed from sequence analysis in the D1/D2 region of rRNA and internal transcribed spacer (ITS) regions, were covalently bound to unique sets of fluorescent beads. Upon hybridization, the biotinylated amplicon was detected by the addition of a fluorochrome coupled to a reporter molecule. The hybridized beads were subsequently analysed by flow cytometric techniques. The developed array, which allowed the detection of species in a multiplex and high-throughput format, was accurate and fast, since it allowed precise identification of species and required less than 1 h following PCR amplification. The described protocol, which can integrate uniplex or multiplex PCR reactions, permitted the simultaneous detection of target sequences in a single reaction, and allowed single mismatch discrimination between probe and non-target sequences. The assay has the capability to be expanded to include other medically important pathogenic species in a single or multiplex array format.

Invasive fungal infections caused by Candida and Malassezia species in the neonatal intensive care unit

Premature infants in the neonatal intensive care unit (NICU) are at particular risk of invasive fungal infections, and unfortunately, the incidence of fungal septicemia appears to be increasing. Invasive infections caused by species of Candida or Malassezia have been documented in the NICU and are often associated with significant morbidity and mortality. Controversies regarding the diagnosis, treatment, and prevention of such diseases exist. The purpose of this review is to describe the epidemiology, clinical manifestations, diagnostic techniques, treatment, and prevention of invasive infection due to Candida and Malassezia species in the neonatal intensive care setting.

Diversity and evolution of non-Saccharomycesyeast populations during wine fermentation: effect of grape ripeness and cold maceration

We have evaluated the effect of grape maturity and cold maceration prior to fermentation on the yeast ecology during wine fermentation. Non-Saccharomyces strains were selectively isolated and identified using two rapid PCR techniques, namely enterobacterial repetitve intergenic consensus-PCR and PCR-intron splice sites, in various wine fermentation conditions. These identifications were further complemented and confirmed by restriction fragment length poymorphism and sequencing analysis of the 5.8S-ITS and D1/D2 ribosomal regions, respectively. Eleven species belonging to five genera were identified. Candida stellata, Hanseniaspora uvarum and Hanseniaspora osmophila were the dominant species, representing almost 90% of the isolates. Minor strains presented different species of the genera Candida, Issatchenkia, Zygoascus and Zygosaccharomyces. Selective isolation made it possible to isolate some species that were hardly related to the wine-making process, such as Issatchenkia hanoiensis, a new species that has only been described recently.

Malassezia Baillon, emerging clinical yeasts

The human and animal pathogenic yeast genus Malassezia has received considerable attention in recent years from dermatologists, other clinicians, veterinarians and mycologists. Some points highlighted in this review include recent advances in the technological developments related to detection, identification, and classification of Malassezia species. The clinical association of Malassezia species with a number of mammalian dermatological diseases including dandruff, seborrhoeic dermatitis, pityriasis versicolor, psoriasis, folliculitis and otitis is also discussed.

Genetic typing of Malassezia pachydermatis from different domestic animals

In the present study, random amplification of polymorphic DNA, which detects DNA polymorphism in fungal genomic DNA, was applied for genetic typing of Malassezia pachydermatis isolates. Fifty-five isolates from different domestic animals and body sites and the neotype strain CBS 1879 were characterized. Primers M13 and OPT-20 were used to analyse their genetic relatedness and similarity. This technique allowed us to distinguish four different genetic types. The predominant genetic type was observed in isolates recovered from different anatomical locations in all animals. It was the only genetic type found in cats, horse, goat and pig. The other three genetic types were observed only in isolates from external ear canals of dogs. Types II and IV were only recovered from external otitic ears and type III from healthy ears. An animal was colonised by more than one type of M. pachydermatis and different genetic types were detected in the same body site. Some genetic types were only isolated from diseased skin.

Malassezia pachydermatis carriage in dog owners

Malassezia pachydermatis is commonly carried on the hands of dog owners and may cause disease in immunocompromised persons.

Yeasts of the genus Malassezia serve as both commensal microorganisms and pathogens on the skin of humans and domestic animals. Although rare, cases of life-threatening fungemia in people have been attributed to Malassezia pachydermatis, for which dogs are a natural host. Zoonotic transfer has been documented from dogs to immunocompromised patients by healthcare workers who own dogs. We investigated the role of pet dogs as risk factors for mechanical carriage of M. pachydermatis on human hands. Dogs and their owners were sampled as pairs, by fungal culture and nested polymerase chain reaction (PCR). Although fungal culture was not a reliable means by which to detect carriage of the yeast on human hands, PCR identified M. pachydermatis on most (≈93%) human participants. Human carriage of ubiquitous opportunistic pathogens such as M. pachydermatis underscores the importance of good hand hygiene by healthcare professionals.

Skin diseases associated with Malassezia species

The yeasts of the genus Malassezia have been associated with a number of diseases affecting the human skin, such as pityriasis versicolor, Malassezia (Pityrosporum) folliculitis, seborrheic dermatitis and dandruff, atopic dermatitis, psoriasis, and--less commonly--with other dermatologic disorders such as confluent and reticulated papillomatosis, onychomycosis, and transient acantholytic dermatosis. Although Malassezia yeasts are a part of the normal microflora, under certain conditions they can cause superficial skin infection. The study of the clinical role of Malassezia species has been surrounded by controversy because of their fastidious nature in vitro, and relative difficulty in isolation, cultivation, and identification. Many studies have been published in the past few years after the taxonomic revision carried out in 1996 in which 7 species were recognized. Two new species have been recently described, one of which has been isolated from patients with atopic dermatitis. This review focuses on the clinical, mycologic, and immunologic aspects of the various skin diseases associated with Malassezia. It also highlights the importance of individual Malassezia species in the different dermatologic disorders related to these yeasts.

Madurella mycetomatis strains from mycetoma lesions in Sudanese patients are clonal

Molecular diversity among clinical isolates of Madurella mycetomatis, the prime fungal agent of human mycetoma in Sudan, could possibly explain the diverse clinical presentations of this severely debilitating infectious disease. In addition, culture-independent DNA-mediated typing tests need to be developed for this organism, since M. mycetomatis DNA, but not the organism itself, can be identified in soil, the material from which infections are thought to originate. A collection of 38 different clinical M. mycetomatis isolates was characterized by large-scale random amplification of polymorphic DNA using 20 different primer species. These analyses, involving at least 2,600 annealing sites, showed a complete lack of DNA fingerprint variation among the various isolates. From the resulting homogeneous DNA fingerprints, seven fragments were cloned and sequenced, and novel, species-specific PCR restriction fragment length polymorphism (RFLP) tests were designed. The seven PCR RFLP tests were successfully performed on the 38 different M. mycetomatis strains. However, again all M. mycetomatis DNA patterns obtained appeared to be identical, whereas patterns produced using DNAs from other fungal species were clearly discriminatory. These results suggest that there is little genetic variation among clinically relevant M. mycetomatis strains from Sudan. The data tentatively imply that different manifestations of mycetoma are due to differences in host susceptibility rather than differential virulence of the causative agent.

In vitro susceptibilities of Malassezia species to a new triazole, albaconazole (UR-9825), and other antifungal compounds

The in vitro activity of the new triazole albaconazole (UR-9825) in comparison with those of flucytosine, fluconazole, ketoconazole, itraconazole, and voriconazole against 70 strains of Malassezia spp. was determined by a microdilution method using a colorimetric indicator for metabolic activity. Albaconazole showed an in vitro profile similar to those of the different antifungals tested (MIC Collapse

Key Words Collapse

MESH Headings

• Antifungal Agents/pharmacology
• Drug Resistance, Fungal
• Fluconazole/pharmacology
• Flucytosine/pharmacology
• In Vitro Techniques
• Itraconazole/pharmacology
• Ketoconazole/pharmacology
• Malassezia/drug effects
• Microbial Sensitivity Tests
• Pyrimidines/pharmacology
• Quinazolines/pharmacology
• Triazoles/pharmacology
• Voriconazole

Collapse

Grants Collapse

Affiliation(s)

Margarita Garau Department of Microbiology, Hospital Universitario 12 de Octubre, Madrid, Spain
Manolo Pereiro
Amalia del Palacio

Collapse

Fast, noninvasive method for molecular detection and differentiation of Malassezia yeast species on human skin and application of the method to dandruff microbiology

Malassezia fungi have been the suspected cause of dandruff for more than a century. Previously referred to as Pityrosporum ovale, Pityrosporum orbiculare, or Malassezia, these fungi are now known to consist of at least seven Malassezia species. Each species has a specific ecological niche, as well as specific biochemical and genetic characteristics. Malassezia yeasts have fastidious culture conditions and exceedingly different growth rates. Therefore, the results of surveys of Malassezia based on culture methods can be difficult to interpret. We developed a molecular technique, terminal fragment length polymorphism analysis, to more accurately survey the ecology of Malassezia yeasts without bias from culture. This technique involves fluorescent nested PCR of the intergenic transcribed spacer (ITS) ITS I and ITS II region ribosomal gene clusters. All known Malassezia species can be differentiated by unique ITS fragment lengths. We have used this technique to directly analyze scalp samples from subjects enrolled in a demographic scalp health study. Results for subjects assigned composite adherent scalp flaking scores (ASFS) <10 were compared to those for subjects assigned composite ASFS >24. Malassezia restricta and M. globosa were found to be the predominant Malassezia species present in both groups. Importantly, we found no evidence of M. furfur in either group, indicating that M. furfur can be eliminated as the causal organism for dandruff. Both groups also showed the presence of non-Malassezia fungi. This method, particularly when it is used in combination with existing fungal ITS databases, is expected to be useful in the diagnosis of multiple other fungal infections.

Differentiation of Malassezia furfur and Malassezia sympodialis by glycine utilization

The genus Malassezia has been revised to include six lipophilic species and one nonlipophilic species. These Malassezia species have been investigated to differentiate their morphological and physiological characteristics. However, assimilation of amino acids as a nitrogen source by these species was not well elucidated. In the present study, isolates of Malassezia species were examined with a glycine medium (containing 7-266 mmol glycine, 7.4 mmol KH(2)PO(4), 4.1 mmol MgSO(4)7H(2)O, 29.6 mmol thiamine, 0.5% Tween-80 and 2% agar) and a modified Dixon glycine medium (0.6% peptone, 3.6% malt extract, 2% ox-bile, 1% Tween-40, 0.2% glycerol, 0.2% oleic acid, 7 mmol glycine and 2% agar). All M. furfur isolates developed on the glycine medium, assimilating glycine at concentrations of at least 7 mmol l(-1). However, the other six Malassezia species were unable to grow on the glycine medium. Also, many colonies of M. furfur grew rapidly, within 2-3 days on the modified Dixon glycine medium, although the other six species showed slow and poor development. From these results, it was suggested that M. furfur might be able to utilize glycine as a single nitrogen source, which the other Malassezia species could not. Therefore, glycine medium was recommended for the differentiation of M. furfur from other species of Malassezia.

Homogeneous cell suspension of Malassezia pachydermatis obtained with an ultrasonic homogenizer

It is difficult to produce homogeneous cell suspensions of Malassezia pachydermatis, since yeast cells paste up and form many clumps. However, homogeneous fungal suspensions are required for susceptibility examinations and biochemical analyses. Although several types of trials have been carried out using glass homogenizers and many types of agents to obtain homogeneous fungal suspension. They have not yielded good results. We therefore attempted to use an ultrasonic homogenizer to separate clumps of yeast cells into separate individual cells. We succeeded in this fashion in producing homogeneous cell suspensions of M. pachydermatis. These results indicate that an ultrasonic homogenizer can be used to prepare homogeneous fungal suspensions of M. pachydermatis.

Identification of Malassezia species from patient skin scales by PCR-RFLP

OBJECTIVE

This study was aimed at the development of a DNA-based procedure directly applicable to pathological skin scales and at the assessment of its value in rapid laboratory confirmation and identification of each of the seven Malassezia species. These lipophilic basidiomycetous yeasts in predisposed individuals are involved in pityriasis versicolor, seborrheic dermatitis, blepharitis, folliculitis, atopic dermatitis and fungemia. Standard identification procedures to species level are available, but so far no system for direct detection and characterization of Malassezia species in clinical specimens is available.

METHODS

Malassezia DNA was extracted from pathological skin scales by a modified hexadecyltrimethylammonium bromide (CTAB) method and amplified by single and nested polymerase chain reaction (PCR), assays using the general fungal ITS 1/4 and 3/4 primers for amplification of sequences from the Malassezia major ribosomal DNA complex. Restriction fragment length polymorphism (RFLP) analysis of PCR products was used in subsequent species identification. DNA extracted from culture-positive skin scales was also tested by PCR and the RFLP patterns obtained were analyzed.

RESULTS

A total of 36 isolates were tested. Distinct pure culture and skin-scale ITS 3/4 HinfI and AluI restriction patterns differentially identified M. furfur, M. globosa, M. restricta, M. sympodialis, M. pachydermatis, M. obtusa and M. slooffiae. Malassezia DNA was extracted from pathological skin scales and RFLP identified solitary and multiple Malassezia species in the same specimen. Molecular identification was confirmed by cultures and biochemical tests. Concurrent detection and identification of Candida and Yarrowia species was also feasible from skin scales.

CONCLUSION

The proposed method, described for the first time, could provide a sensitive and rapid detection and identification system for Malassezia species, which may be applied to epidemiological surveys and routine practice.

Identification and typing of Malassezia yeasts using amplified fragment length polymorphism (AFLP), random amplified polymorphic DNA (RAPD) and denaturing gradient gel electrophoresis (DGGE)

Three molecular tools, amplified fragment length polymorphism (AFLP), denaturing gradient gel electrophoresis (DGGE) and random amplified polymorphic DNA (RAPD) analysis, were explored for their usefulness to identify isolates of Malassezia yeasts. All seven species could be separated by AFLP and DGGE. Using AFLP, four genotypes could be distinguished within M. furfur. AFLP genotype 4 contained only isolates from deep human sources, and ca. 80% of these isolates were from patients with systemic disease. Most of the systemic isolates belonged to a single RAPD genotype. This suggests that systemic conditions strongly select for a particular genotype. Although the clinical use of DGGE may be limited due to technical demands, it remains a powerful tool for the analysis of complex clinical samples.

A single PCR-restriction endonuclease analysis for rapid identification of Malassezia species

AIMS

The present study describes a system based on PCR and restriction endonuclease analysis (REA) to distinguish the seven currently recognized Malassezia species.

METHODS AND RESULTS

Fifty-five representative yeast isolates were examined. A single primer pair was designed to amplify the large subunit ribosomal RNA (LSU rRNA) gene of the seven Malassezia species, and identification was achieved by digestion of the PCR products with three restriction endonucleases: BanI, HaeII and MspI. A specific restriction endonuclease analysis pattern was determined for each species investigated. Moreover, PCR-REA allowed the detection and characterization of mixtures of several Malassezia species.

CONCLUSION

PCR-REA of only the LSU rRNA gene is a reliable and rapid method to distinguish all Malassezia species.

SIGNIFICANCE AND IMPACT OF THE STUDY

PCR-REA represents a considerable saving in time over currently available identification procedures. This method should be evaluated on clinical material directly.

Molecular characterization of Yarrowia lipolytica and Candida zeylanoides isolated from poultry

Yeast isolates from raw and processed poultry products were characterized using PCR amplification of the internally transcribed spacer (ITS) 5.8S ribosomal DNA region (ITS-PCR), restriction analysis of amplified products, randomly amplified polymorphic DNA (RAPD) analysis, and pulsed-field gel electrophoresis (PFGE). ITS-PCR resulted in single fragments of 350 and 650 bp, respectively, from eight strains of Yarrowia lipolytica and seven strains of Candida zeylanoides. Digestion of amplicons with HinfI and HaeIII produced two fragments of 200 and 150 bp from Y. lipolytica and three fragments of 350, 150, and 100 bp from C. zeylanoides, respectively. Although these fragments showed species-specific patterns and confirmed species identification, characterization did not enable intraspecies typing. Contour-clamped heterogeneous electric field PFGE separated chromosomal DNA of Y. lipolytica into three to five bands, most larger than 2 Mbp, whereas six to eight bands in the range of 750 to 2,200 bp were obtained from C. zeylanoides. Karyotypes of both yeasts showed different polymorphic patterns among strains. RAPD analysis, using enterobacterial repetitive intergenic sequences as primers, discriminated between strains within the same species. Cluster analysis of patterns formed groups that correlated with the source of isolation. For ITS-PCR, extraction of DNA by boiling yeast cells was successfully used.

Susceptibility testing of Malassezia species using the urea broth microdilution method

A urea broth microdilution method to assay the susceptibilities of seven Malassezia species was developed. This method indicated the same sensitivities as the agar plate dilution method for isolates of Malassezia furfur, M. pachydermatis, M. slooffiae, and M. sympodialis.

Atypical lipid-dependent Malassezia species isolated from dogs with otitis externa

During a survey of the occurrence of Malassezia species in the external ear canals of dogs with chronic otitis externa, lipid-dependent Malassezia species were isolated in three dogs. These species were identified as Malassezia furfur and M. obtusa but showed atypical assimilation patterns. To our knowledge, this is the first report of the isolation of lipid-dependent species of the genus Malassezia in association with canine otitis.

Fast, simple and highly sensitive double-rounded polymerase chain reaction assay to detect medically relevant fungi in dermatological specimens

BACKGROUND

Early detection of fungal infection is essential for beginning of prompt and specific therapy. In this study we describe a rapid and sensitive procedure to detect, by polymerase chain reaction (PCR) assays, a wide range of medically important opportunistic and pathogenic fungi in dermal specimens from dermatomycoses-affected patients.

MATERIALS AND METHODS

Three primer pairs, amplifying fragments of the highly conserved gene coding for small ribosomal RNA (18S rDNA) and the adjacent internal transcribed spacer (ITS) rDNA, previously published by others, were probed on DNA from pure cultures of medically relevant human and animal fungal species. In order to evaluate the specificity of the assay, amplifications of control DNAs from other eukaryotes and prokaryotes were also carried out, and they gave negative results.

RESULTS

These primer sets, in single amplification or double-rounded PCR assays, allowed specific amplification when applied to a wide number of fungal DNA from human and animal tissue specimens, including dermatophytes (genera Trichophyton, Microsporum), several yeast species (Candida, Saccharomyces, Cryptococcus, Malassezia) and moulds (Aspergillus, Penicillium). The PCR assay was able to detect as little as 10 pg of fungal DNA, corresponding to approximately 25 fungal genomes per sample specimen. A small-scale DNA extraction method was also developed. This simple, time-saving and sensitive procedure was successfully applied to 40 human and veterinary specimens, and the diagnosis was confirmed with cultural techniques, being shown to work even in the presence of other lesions or contaminating organisms.

CONCLUSIONS

This method allows early recognition of fungal pathogen cells in clinical samples as an alternative tool to conventional detection techniques.