Aristea Velegraki

The Malassezia Genus in Skin and Systemic Diseases

SUMMARY 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.

EUCAST Definitive Document EDef 7.1: method for the determination of broth dilution MICs of antifungal agents for fermentative yeasts: Subcommittee on Antifungal Susceptibility Testing (AFST) of the ESCMID European Committee for Antimicrobial Susceptibility Testing (EUCAST)∗

Antifungal susceptibility tests are performed on fungi that cause disease, especially if they belong to a species exhibiting resistance to commonly used antifungal agents. Antifungal susceptibility testing is also important for resistance surveillance, for epidemiological studies and for comparing the in-vitro activity of new and existing agents. Dilution methods are used to establish the MICs of antimicrobial agents. These are the reference methods for antimicrobial susceptibility testing, and are used mainly to establish the activity of a new antifungal agent, to confirm the susceptibility of organisms that give equivocal results in routine tests, and to determine the susceptibility of fungi where routine dilution tests may be unreliable. Fungi are tested for their ability to produce visible growth in microdilution plate wells containing broth culture media and serial dilutions of the antifungal agents (broth microdilution). The MIC is defined as the lowest concentration (in mg ⁄ L) of an antifungal agent that inhibits the growth of a fungus. The MIC provides information concerning the susceptibility or resistance of an organism to the antifungal agent and can help in making correct treatment decisions. The method described in this document is intended for testing the susceptibility of yeasts that cause clinically significant infections (primarily Candida spp.). The method encompasses only those yeasts that are able to ferment glucose. Thus, the susceptibility of non-fermentative yeasts, e.g., Cryptococcus neoformans, cannot be determined by the current procedure, and the method is not suitable for testing the yeast forms of dimorphic fungi.

EUCAST Definitive Document EDef 7.1: method for the determination of broth dilution MICs of antifungal agents for fermentative yeasts

Antifungal susceptibility tests are performed on fungi that cause disease, especially if they belong to a species exhibiting resistance to commonly used antifungal agents. Antifungal susceptibility testing is also important for resistance surveillance, for epidemiological studies and for comparing the in-vitro activity of new and existing agents. Dilution methods are used to establish the MICs of antimicrobial agents. These are the reference methods for antimicrobial susceptibility testing, and are used mainly to establish the activity of a new antifungal agent, to confirm the susceptibility of organisms that give equivocal results in routine tests, and to determine the susceptibility of fungi where routine dilution tests may be unreliable. Fungi are tested for their ability to produce visible growth in microdilution plate wells containing broth culture media and serial dilutions of the antifungal agents (broth microdilution). The MIC is defined as the lowest concentration (in mg ⁄ L) of an antifungal agent that inhibits the growth of a fungus. The MIC provides information concerning the susceptibility or resistance of an organism to the antifungal agent and can help in making correct treatment decisions. The method described in this document is intended for testing the susceptibility of yeasts that cause clinically significant infections (primarily Candida spp.). The method encompasses only those yeasts that are able to ferment glucose. Thus, the susceptibility of non-fermentative yeasts, e.g., Cryptococcus neoformans, cannot be determined by the current procedure, and the method is not suitable for testing the yeast forms of dimorphic fungi.

Candidal overgrowth in diabetic patients: potential predisposing factors

This study was designed to investigate the potential factors that influence the prevalence of the oral carriage of Candida species in patients with type II diabetes mellitus. One hundred and twenty‐eight diabetic patients (68 males and 60 females, mean age 54 ± 7 years) were sequentially enrolled along with 84 (44 males and 40 females mean age 52 ± 8 years) healthy subjects. Samples were obtained by swabbing the oral mucosa of all participants. Yeast isolates were identified by germ tube test, with API 32 ID system, and by chlamydospore production on ‘cornmeal’ Tween‐80 agar. Candida spp. was recovered from the oral cavity of 64% of the diabetic group, in contrast to 40% of the control group. Candida albicans was the most frequently isolated species in both groups. Potential etiologic factors such as xerostomia, dentures, age, gender and diabetes on oral carriage of Candida spp. were evaluated. The oral carriage of Candida spp. was significantly higher in ‘diabetic’ patients compared with the healthy subjects but it seems that parameters such as xerostomia, dentures, age, gender and glycemic control cannot be directly associated with Candida growth in the oral cavity in the presence of diabetes.

Autochthonous and dormant Cryptococcus gattii infections in Europe

Dormant infections can become reactivated years after having been acquired on another continent.

Distribution of Malassezia species in pityriasis versicolor and seborrhoeic dermatitis in Greece. Typing of the major pityriasis versicolor isolate M. globosa.

Background  The expansion of the genus Malassezia has generated interest in the epidemiological investigation of the distribution of new species in a range of dermatoses, on which variable results have been reported from different geographical regions. No data are thus far available from South‐east Europe (Greece).

Results from a Prospective, International, Epidemiologic Study of Invasive Candidiasis in Children and Neonates

Background: Candida species are the third most common cause of pediatric health care–associated bloodstream infection in the United States and Europe. To our knowledge, this report from the International Pediatric Fungal Network is the largest prospective, multicenter observational study dedicated to pediatric and neonatal invasive candidiasis. Methods: From 2007 to 2011, we enrolled 196 pediatric and 25 neonatal patients with invasive candidiasis. Results: Non-albicans Candida species predominated in pediatric (56%) and neonatal (52%) age groups, yet Candida albicans was the most common species in both groups. Successful treatment responses were observed in pediatric (76%) and neonatal patients (92%). Infection with Candida parapsilosis led to successful responses in pediatric (92%) and neonatal (100%) patients, whereas infection with Candida glabrata was associated with a lower successful outcome in pediatric patients (55%). The most commonly used primary antifungal therapies for pediatric invasive candidiasis were fluconazole (21%), liposomal amphotericin B (20%) and micafungin (18%). Outcome of pediatric invasive candidiasis was similar in response to polyenes (73%), triazoles (67%) and echinocandins (73%). The most commonly used primary antifungal therapies for neonatal invasive candidiasis were fluconazole (32%), caspofungin (24%) and liposomal amphotericin B (16%) and micafungin (8%). Outcomes of neonatal candidiasis by antifungal class again revealed similar response rates among the classes. Conclusions: We found a predominance of non-albicans Candida infection in children and similar outcomes based on antifungal class used. This international collaborative study sets the foundation for large epidemiologic studies focusing on the unique features of neonatal and pediatric candidiasis and comparative studies of therapeutic interventions in these populations.

Use of Fatty Acid RPMI 1640 Media for Testing Susceptibilities of Eight Malassezia Species to the New Triazole Posaconazole and to Six Established Antifungal Agents by a Modified NCCLS M27-A2 Microdilution Method and Etest

A novel formulation of RPMI 1640 medium for susceptibility testing of Malassezia yeasts by broth microdilution (BMD) and Etest is proposed. A modification of the NCCLS M27-A2 BMD method was used to test 53 isolates of Malassezia furfur (12 isolates), M. sympodialis (8 isolates), M. slooffiae (4 isolates), M. globosa (22 isolates), M. obtusa (2 isolates), M. restricta (2 isolates), M. pachydermatis (1 isolates), and M. dermatis (2 isolates) against amphotericin B, ketoconazole, itraconazole, fluconazole, voriconazole, terbinafine, and posaconazole by BMD and Etest. RPMI and antibiotic medium 3 (AM3) were supplemented with glucose, bile salts, a mixture of fatty acids, and n-octadecanoate fatty acids and Tween 20. M. furfur ATCC 14521 and M. globosa ATCC 96807 were used as quality control strains. Depending on the species, MICs were read after 48 or 72 h of incubation at 32 degrees C. Low azole and terbinafine MICs were recorded for all Malassezia species, whereas amphotericin B displayed higher MICs (>/=16 microg/ml) against M. furfur, M. restricta, M. globosa, and M. slooffiae strains, which were AM3 confirmed. Agreement of the two methods was 84 to 97%, and intraclass correlation coefficients were statistically significant (P < 0.001). Because of higher amphotericin B MICs provided by Etest for strains also displaying high BMD MICs (>/=1 microg/ml), agreement was poorer. The proposed media are used for the first time and can support optimum growth of eight Malassezia species for recording concordant BMD and Etest MICs.

Proposed nomenclature for Pseudallescheria, Scedosporium and related genera

As a result of fundamental changes in the International Code of Nomenclature on the use of separate names for sexual and asexual stages of fungi, generic names of many groups should be reconsidered. Members of the ECMM/ISHAM working group on Pseudallescheria/Scedosporium infections herein advocate a novel nomenclature for genera and species in Pseudallescheria, Scedosporium and allied taxa. The generic names Parascedosporium, Lomentospora, Petriella, Petriellopsis, and Scedosporium are proposed for a lineage within Microascaceae with mostly Scedosporium anamorphs producing slimy, annellidic conidia. Considering that Scedosporium has priority over Pseudallescheria and that Scedosporium prolificans is phylogenetically distinct from the other Scedosporium species, some name changes are proposed. Pseudallescheria minutispora and Petriellidium desertorum are renamed as Scedosporium minutisporum and S. desertorum, respectively. Scedosporium prolificans is renamed as Lomentospora prolificans.

AhR Ligands, Malassezin, and Indolo[3,2-b]Carbazole are Selectively Produced by Malassezia furfur Strains Isolated from Seborrheic Dermatitis

Malassezia yeasts are connected with seborrheic dermatitis (SD) whereas M. furfur pathogenicity is associated with the production of bioactive indoles. In this study, the production of indoles by M. furfur isolates from healthy and diseased skin was compared, the respective HPLC patterns were analyzed, and substances that are preferentially synthesized by strains isolated from SD lesions were isolated and characterized. Malassezin, pityriacitrin, indole-3-carbaldehyde, and indolo[3,2-b]carbazole (ICZ) were isolated by HPLC from extracts of M. furfur grown in L-tryptophan agar, and identified by nuclear magnetic resonance and mass spectroscopy. Of these, ICZ, a potent ligand of the aryl hydrocarbon receptor (AhR), is described for the first time to our knowledge as a M. furfur metabolite. HPLC-photodiode array detection analysis of strain extracts from 7 healthy subjects and 10 SD patients showed that M. furfur isolates from only SD patients consistently produce malassezin and ICZ. This discriminatory production of AhR agonists provides initial evidence for a previously unreported mechanism triggering development of SD and indicates that the variable pathogenicity patterns recorded for M. furfur-associated SD conditions may be attributed to selective production (P<0.001) of measurable bioactive indoles.