Cryptic Diversity of Malassezia pachydermatis from Healthy and Diseased Domestic Animals

Comparative analysis of the distribution and antifungal susceptibility of yeast species in cat facial hair and human nails

Zoonotic yeast species have been implicated in disease development in both humans and cats. This study analyzed the yeast mycobiota present in feline facial hair and human nails and explored potential interspecies associations. A total of 118 biological specimens were examined, including 59 feline facial hair and 59 human nail samples. DNA extraction and DNA sequencing were performed to identify the specific yeast species. The most predominant yeast species in humans and cats were selected for antifungal susceptibility testing (itraconazole, ketoconazole, miconazole, and terbinafine). The findings unveiled diverse yeast species in cats and humans. Malassezia pachydermatis (45.8%) and Malassezia furfur (30.5%) were the most common yeast species in cats and humans, respectively. However, no significant correlation was detected between the yeast species identified in cats and their owners residing in the same household (p > 0.05). Miconazole exhibited the highest minimum inhibitory concentrations (MICs) against Malassezia pachydermatis and Malassezia furfur in both cat and human isolates, whereas terbinafine showed the lowest MICs against most Malassezia pachydermatis and Malassezia furfur in both cat and human isolates. Diverse yeast species in cat facial hair and human nails suggest possible cross-contamination among humans, pets, and environments.

Malassezia pachydermatis from brown bear: A comprehensive analysis reveals novel genotypes and distribution of all detected variants in domestic and wild animals

Malassezia pachydermatis (phylum Basidiomycota, class Malasseziomycetes) is a zoophilic opportunistic pathogen with recognized potential for invasive infections in humans. Although this pathogenic yeast is widespread in nature, it has been primarily studied in domestic animals, so available data on its genotypes in the wild are limited. In this study, 80 yeast isolates recovered from 42 brown bears (Ursus arctos) were identified as M. pachydermatis by a culture-based approach. MALDI-TOF mass spectrometry (MS) was used to endorse conventional identification. The majority of samples exhibited a high score fluctuation, with 42.5% of isolates generating the best scores in the range confident only for genus identification. However, the use of young biomass significantly improved the identification of M. pachydermatis at the species confidence level (98.8%). Importantly, the same MALDI-TOF MS efficiency would be achieved regardless of colony age if the cut-off value was lowered to ≥1.7. Genotyping of LSU, ITS1, CHS2, and β-tubulin markers identified four distinct genotypes in M. pachydermatis isolates. The most prevalent among them was the genotype previously found in dogs, indicating its transmission potential and adaptation to distantly related hosts. The other three genotypes are described for the first time in this study. However, only one of the genotypes consisted of all four loci with bear-specific sequences, indicating the formation of a strain specifically adapted to brown bears. Finally, we evaluated the specificity of the spectral profiles of the detected genotypes. MALDI-TOF MS exhibited great potential to detect subtle differences between all M. pachydermatis isolates and revealed distinct spectral profiles of bear-specific genotypes.

ERG11 Gene Variability and Azole Susceptibility in Malassezia pachydermatis

Malassezia pachydermatis is part of the normal skin microbiota of various animal species but under certain circumstances becomes an opportunistic pathogen producing otitis and dermatitis. Commonly these Malassezia diseases are effectively treated using azoles. However, some cases of treatment failure have been reported. Alterations in the ERG11 gene have been associated with in vitro azole resistance in M. pachydermatis. In the present study, in vitro antifungal susceptibility of 89 different strains of M. pachydermatis isolated from different animal species and health status was studied. The susceptibility to fluconazole (FLZ), itraconazole (ITZ), ketoconazole and amphotericin B was tested by a disk diffusion method and 17 strains were also subjected to an ITZ E-test. Mueller-Hinton supplemented with 2% glucose and methylene blue was used as culture medium in both susceptibility assays. Multilocus sequence typing was performed in 30 selected strains using D1D2, ITS, CHS2 and β-tubulin genes. Also, ERG11 gene was sequenced. The four antifungals tested were highly effective against most of the strains. Only two strains showed no inhibition zone to antifungals and a strain showed an increased MIC to ITZ. The study of the ERG11 sequences revealed a high diversity of DNA sequences and a total of 23 amino acid substitutions, from which only two have been previously described. Also, three deleterious substitutions (A302T, G459D and G461D) previously associated with azole resistance in this yeast were recovered. A correlation between certain genotypes and ERG11 mutations was observed. Some of the ERG11 mutations recovered were correlated with a reduced susceptibility to azoles.

Effect of an anti-inflammatory pomegranate otic treatment on the clinical evolution and microbiota profile of dogs with otitis externa

BACKGROUND

Canine otitis externa (OE) is a common disease characterised by inflammation of the epithelial tissue of the external ear canal. Secondary infections are frequent, and Malassezia pachydermatis and Staphylococcus pseudintermedius are routinely isolated and treated with antifungal and antibiotic compounds.

HYPOTHESIS/OBJECTIVES

To analyse the otitis ear microbiome before and after a treatment with prednisolone plus pomegranate or antimicrobial drugs ANIMALS: 15 dogs with nonpurulent OE.

METHODS AND MATERIALS

A 30 day, double-blinded, multicentre, randomized and controlled parallel-group (1:1) trial was conducted in 15 dogs with nonpurulent OE, following two different topical treatments (prednisolone plus pomegranate versus prednisolone plus antibiotic and antifungal drugs). On days (D)0, D15 and D30, serum and skin otic samples were collected, and clinical examination and microbiome analysis (bacteria and fungi) were performed. Results were compared with validated otitis clinical scores to assess the effectiveness of both treatments.

RESULTS

Nine bacterial and four fungal families were detected during the three time-points tested. An increase in fungal diversity (Shannon index) and composition was the most significant change observed after both treatments. At treatment D15 and D30, the reduction in clinical signs was statistically significant in both treatment groups (P ≤ 0.05). Prednisolone plus pomegranate cleanser treatment was able to control the clinical signs of otitis as well as the bacterial and fungal overgrowth.

CONCLUSIONS AND CLINICAL IMPORTANCE

Mild otitis cases associated with microbial overgrowth may be managed with topical antiseptic and anti-inflammatory agents without the need for antibiotic and/or antifungal compounds.

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.

Characterization of the species Malassezia pachydermatis and re-evaluation of its lipid dependence using a synthetic agar medium

The genus Malassezia includes lipophilic yeasts, which are part of the skin microbiota of various mammals and birds. Unlike the rest of Malassezia species, M. pachydermatis is described as non-lipid-dependent, as it is able to grow on Sabouraud glucose agar (SGA) without lipid supplementation. In this study we have examined the phenotypic variability within M. pachydermatis and confirmed its lipid-dependent nature using a synthetic agar medium. We used a selection of representative non-lipid-dependent strains from different animal species and three atypical lipid-dependent strains of this species, which were not able to grow after multiple passages on SGA. More than 400 lipid-dependent Malassezia isolates from animals were studied in order to detect the three lipid-dependent strains of M. pachydermatis. The identity of the atypical strains was confirmed by DNA sequencing. On the other hand, we have modified the Tween diffusion test, which is widely used in the characterization of these yeasts, by using a synthetic agar-based medium instead of SGA. This modification has proved to be useful for differentiation of M. pachydermatis strains, providing reproducible results and a straightforward interpretation. The finding of these peculiar lipid-dependent strains exemplifies the large variability within the species M. pachydermatis, which involves rare atypical strains with particular growth requirements.

Highly efficient transformation system for Malassezia furfur and Malassezia pachydermatis using Agrobacterium tumefaciens-mediated transformation

Malassezia spp. are part of the normal human and animal mycobiota but are also associated with a variety of dermatological diseases. The absence of a transformation system hampered studies to reveal mechanisms underlying the switch from the non-pathogenic to pathogenic life style. Here we describe, a highly efficient Agrobacterium-mediated genetic transformation system for Malassezia furfur and M. pachydermatis. A binary T-DNA vector with the hygromycin B phosphotransferase (hpt) selection marker and the green fluorescent protein gene (gfp) was introduced in M. furfur and M. pachydermatis by combining the transformation protocols of Agaricus bisporus and Cryptococcus neoformans. Optimal temperature and co-cultivation time for transformation were 5 and 7days at 19°C and 24°C, respectively. Transformation efficiency was 0.75-1.5% for M. furfur and 0.6-7.5% for M. pachydermatis. Integration of the hpt resistance cassette and gfp was verified using PCR and fluorescence microscopy, respectively. The T-DNA was mitotically stable in approximately 80% of the transformants after 10 times sub-culturing in the absence of hygromycin. Improving transformation protocols contribute to study the biology and pathophysiology of Malassezia.