Haemolytic and co-haemolytic (CAMP-like) activity in dermatophytes

PubMedID: 25476038Dermatophytes are some of the most common fungal pathogens in both humans and animals. These fungi release enzymes (e.g., keratinases) that play roles in their pathogenesis. Little is known about their haemolytic and co-haemolytic (CAMP-like) activities; however, in bacteria, these components play significant roles in pathogenesis. This study characterised these two factors in 45 dermatophyte strains (representing the genera Arthroderma, Epidermophyton, Microsporum and Trichophyton) using Columbia agar (CA) supplemented with 5% bovine, ovine and equine erythrocytes. Haemolysis was best observed on CA supplemented with ovine erythrocytes followed by equine and bovine erythrocytes, while CAMP-like reactions occurred using bovine and ovine but not equine erythrocytes. Haemolytic and CAMP-like activities were best observed using ovine and bovine erythrocytes in CA in 44 and 38 strains at 7 and 3 days respectively. Most dermatophytes recovered from both symptomatic and asymptomatic lesions had haemolytic and CAMP-like activities. We suggest that the haemolytic and CAMP-like activities are not correlated with ecological characteristics, isolation sites or clinical manifestations of dermatophytic fungi. We also believe that this study has the potential to contribute to the existing literature on dermatophytes and dermatophyte pathogenesis. © 2014 Blackwell Verlag GmbH

Comparison of the contamination rates of culture media used for isolation and identification of dermatophytes

PubMedID: 26281324Background/aim: Mycological media that promote spore production are essential for the diagnosis of dermatophytosis. However, these culture media frequently become contaminated by multiple fungal or bacterial species during culture. The aim of this study was to compare the contamination rates of 6 culture media used for the isolation and identification of dermatophytes, including Borelli’s lactritmel agar (BLA), brain-heart infusion agar (BHIA), Lowenstein–Jensen agar (LJA), malt extract agar (MEA), potato dextrose agar (PDA), and Sabouraud glucose agar (SGA). Materials and methods: Agar plates were inoculated with 43 well-characterized dermatophyte strains, belonging to the genera Arthroderma, Epidermophyton, Microsporum, or Trichophyton. The agar plates were incubated at 26 °C and examined every 5 days for 1 month. Results: By the end of the incubation period, 97 of the 258 plates (37.6%) were contaminated by fungi. No bacteria were detected. Overall, BLA demonstrated the lowest rate of contamination, followed by SGA, MEA, BHIA, PDA, and LJA. Sequencing of the internal transcribed spacer region rDNA of the contaminant fungi revealed that Aspergillus and Penicillium species were the most common contaminants. Conclusion: Tese results suggest that nonenriched culture media types, such as BLA or SGA, reduced contamination during dermatophyte subculture. © TÜBİTAK

The Use of Albino Adult Hair and Blond Prepubertal Hair Yields Equivalent Results in an In Vitro Hair Perforation Test to Differentiate Between Different Dermatophytic Fungi

PubMedID: 23591622An in vitro hair perforation test is used to differentiate isolates of Trichophyton mentagrophytes and Trichophyton rubrum complexes because morphological criteria are insufficient. Here, we performed in vitro hair perforation tests using blond prepubertal hair and albino adult hair to determine whether they differentiate between fungal species. We tested 43 well-characterized dermatophyte strains, Arthroderma spp. [n = 4], Epidermophyton floccosum [n = 1], Microsporum spp. [n = 8], and Trichophyton spp. [n = 30], and examined hair perforation at 3-30 days postinoculation (p.i.). The perforation times were not significantly different between the two hair types (P > 0.05). The T. mentagrophytes complex strains perforated hair 4-5 days p.i., whereas T. rubrum complex strains perforated hair 13-30 days p.i., except for Trichophyton violaceum, which perforated hair after 6-7 days. Thus, the hair perforation test is highly sensitive (100 %) and specific (100 %) for differentiating T. mentagrophytes from T. rubrum complexes 5 days p.i. At 14 and 30 days, the sensitivity and negative predictive value of the test remained unchanged (100 %), but the specificity was reduced (64.3 and 14.3 %, respectively). Consistent with previous reports, we observed "perforating organs" of zoophilic Microsporum canis and geophilic Microsporum gypseum at 4 and 3 days, respectively. This paper offers a "low-cost" and "low-tech" alternative to differentiating dermatophyte species where standard morphological techniques fail and/or where molecular techniques are not a viable option. © 2013 Springer Science+Business Media Dordrecht

Overview of selected virulence attributes in Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Trichophyton rubrum, and Exophiala dermatitidis

PubMedID: 29102684The incidence of fungal diseases has been increasing since 1980, and is associated with excessive morbidity and mortality, particularly among immunosuppressed patients. Of the known 625 pathogenic fungal species, infections caused by the genera Aspergillus, Candida, Cryptococcus, and Trichophyton are responsible for more than 300 million estimated episodes of acute or chronic infections worldwide. In addition, a rather neglected group of opportunistic fungi known as black yeasts and their filamentous relatives cause a wide variety of recalcitrant infections in both immunocompetent and immunosuppressed hosts. This article provides an overview of selected virulence factors that are known to suppress host immunity and enhance the infectivity of these fungi. © 2017 Elsevier Inc

Massive contamination of Exophiala dermatitidis and E. phaeomuriformis in railway stations in subtropical Turkey

In order to reveal the source of contamination of opportunistic fungi, their natural habitat has to be understood. Black yeast-like fungi are abundant in man-made environments, particularly in those that are rich in toxic hydrocarbons such as railway ties. In this study, we investigated the presence of black fungi on creosote-treated oak railway ties and concrete sleepers stained with petroleum oil. Samples were collected at two central stations in Turkish cities, Mersin and Adana, and from Tarsus town station located between these two. The sample locations had subtropical climates. A total of 570 railway samples, including 320 from oak and 250 from concrete, were collected. Cotton swabs moistened with sterile physiological saline were applied to the ties and inoculated onto malt extract agar followed by incubation at 37 °C. Overall, we recovered 97 black yeast-like fungi (17.0 % positive). Sixty-three fungi (19.7 %) were collected from creosote-treated oak, whereas 34 isolates (13.6 %) were derived from concrete; the difference was significant (P = 0.05). Identification using rDNA internal transcribed spacer revealed Exophiala dermatitidis (57.7 %) and Exophiala phaeomuriformis (42.3 %). This study suggested that hydrocarbons enrich these opportunistic black yeasts. An eventual health risk is discussed

Virulence markers of opportunistic black yeast in Exophiala

PubMedID: 26857806The black yeast genus Exophiala is known to cause a wide variety of diseases in severely ill individuals but can also affect immunocompetent individuals. Virulence markers and other physiological parameters were tested in eight clinical and 218 environmental strains, with a specific focus on human-dominated habitats for the latter. Urease and catalase were consistently present in all samples; four strains expressed proteinase and three strains expressed DNase, whereas none of the strains showed phospholipase, haemolysis, or co-haemolysis activities. Biofilm formation was identified in 30 (13.8%) of the environmental isolates, particularly in strains from dishwashers, and was noted in only two (25%) of the clinical strains. These results indicate that virulence factors are inconsistently present in the investigated Exophiala species, suggesting opportunism rather than pathogenicity. © 2016 Blackwell Verlag GmbH

MTL genotypes, phenotypic switching, and susceptibility profiles of Candida parapsilosis species group compared to Lodderomyces elongisporus

PubMedID: 28771588Reference isolates of Candida parapsilosis (n = 8), Candida metapsilosis (n = 6), Candida orthopsilosis (n = 7), and Lodderomyces elongisporus (n = 11) were analyzed to gain insight into their pathobiology and virulence mechanisms. Initial evaluation using BBL Chromagar Candida medium misidentified L. elongisporus isolates as C. albicans. Polymerase chain reaction analysis of isolate MTL idiomorphs revealed that all C. parapsilosis isolates were MTLa homozygous and no MTL ?1, ?2, a1, or a2 gene was detected in L. elongisporus isolates. For C. orthopsilosis, two isolates were MTLa homozygous and five were MTL-heterozygous. Similarly, one C. metapsilosis isolate was MTL? homozygous whereas five were MTL-heterozygous. Isolate phenotypic switching analysis revealed potential phenotypic switching in the MTL? homozygous C. metapsilosis isolate, resulting in concomitant elongated cell formation. Minimum inhibitory concentrations of fluconazole (FLC) and FK506, alone or in combination, were determined by checkerboard assay, with data analyzed using the fractional inhibitory concentration index model. Synergistic or additive effects of these compounds were commonly observed in C. parapsilosis and L. elongisporus isolates. No killer activity was observed in the studied isolates, as determined phenotypically. No significant difference in virulence was seen for the four species in a Galleria mellonella model (P > 0.05). In conclusion, our results demonstrated phenotypic switching of C. metapsilosis CBS 2315 and that FLC and FK506 represent a promising drug combination against C. parapsilosis and L. elongisporus. The findings of the present study contribute to our understanding of the biology, diagnosis, and new possible treatments of the C. parapsilosis species group and L. elongisporus. © 2017 Döğen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Duke University R01 AI50113-13, R37 MERIT Award AI39115-19 North Carolina State UniversityThis work was supported by NIH/NIAID R37 MERIT Award AI39115-19, and NIH/NIAID R01 AI50113-13 provided support to J.H. The authors are grateful to Shawn Lockhart, PhD, for kindly providing L. elongisporus strains. We thank Valerie Knowlton, Research Assistant, at the Center for Electron Microscopy (North Carolina State University, Raleigh, NC) for her expert help with the electron microscopy experiments. The authors also acknowledge the valuable assistance of members of the Heitman laboratory at the Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, with laboratory analyses

Mating type (MAT) locus and possible sexuality of the opportunistic pathogen Exophiala dermatitidis

PubMedID: 30611834Sexual reproduction among the black yeasts is generally limited to environmental saprobic species and is rarely observed among opportunists in humans. To date, a complete sexual cycle has not been observed in Exophiala dermatitidis. In this study, we aimed to gain insight into the reproductive mode of E. dermatitidis by characterizing its mating type (MAT) locus, conducting MAT screening of environmental and clinical isolates, examining the expression of the MAT genes and analyzing the virulence of the isolates of different mating types. Similar to other members of the Pezizomycotina, the E. dermatitidis genome harbors a high mobility group (HMG) domain gene (MAT1-2-1) in the vicinity of the SLA2 and APN2 genes. The MAT loci of 74 E. dermatitidis isolates (11 clinical and 63 environmental) were screened by PCR, and the surrounding region was amplified using long-range PCR. Sequencing of the ~ 12-kb PCR product of a MAT1-1 isolate revealed an ?-box gene (MAT1-1-1). The MAT1-1 idiomorph was 3544-bp long and harbored the MAT1-1-1 and MAT1-1-4 genes. The MAT1-2 idiomorph was longer, 3771-bp, and harbored only the MAT1-2-1 gene. This structure suggests a heterothallic reproduction mode. The distribution of MAT among 74 isolates was ~ 1:1 with a MAT1-1:MAT1-2 ratio of 35:39. RT-PCR analysis indicated that the MAT genes are transcribed. No significant difference was detected in the virulence of isolates representing different mating types using a Galleria mellonella model (P > 0.05). Collectively, E. dermatitidis is the first opportunistic black yeast in which both MAT idiomorphs have been characterized. The occurrence of isolates bearing both idiomorphs, their approximately equal distribution, and the expression of the MAT genes suggest that E. dermatitidis might reproduce sexually. © 2019 Elsevier Inc.R01 AI50113-14, AI39115-20 215S106The molecular mating-type study was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) , grant no. 215S106 , to B. M. The virulence study was supported by NIH/NIAID R37 MERIT Award AI39115-20 and NIH/NIAID R01 AI50113-14 to J.H. The sponsors did not have any role in the design of the study; the collection, analysis, and interpretation of data; the writing of the paper; and the decision to submit the paper for publication

Whole-genome analysis illustrates global clonal population structure of the ubiquitous dermatophyte pathogen trichophyton rubrum

PubMedID: 29467168Dermatophytes include fungal species that infect humans, as well as those that also infect other animals or only grow in the environment. The dermatophyte species Trichophyton rubrum is a frequent cause of skin infection in immunocompetent individuals. While members of the T. rubrum species complex have been further categorized based on various morphologies, their population structure and ability to undergo sexual reproduction are not well understood. In this study, we analyze a large set of T. rubrum and T. interdigitale isolates to examine mating types, evidence of mating, and genetic variation. We find that nearly all isolates of T. rubrum are of a single mating type, and that incubation with T. rubrum “morphotype” megninii isolates of the other mating type failed to induce sexual development. While the region around the mating type locus is characterized by a higher frequency of SNPs compared to other genomic regions, we find that the population is remarkably clonal, with highly conserved gene content, low levels of variation, and little evidence of recombination. These results support a model of recent transition to asexual growth when this species specialized to growth on human hosts. © 2018 Persinoti et al.National Human Genome Research Institute: U54-HG-003067 AI-39115-20, RO1 award AI-50113-13 Fundação de Amparo à Pesquisa do Estado de São Paulo: 13/19195-6, 12/22232-8 National Council for Scientific Research: 1059B191501539 Broad InstituteWe thank the Broad Institute Genomics Platform for generating the DNA sequence described here, Yonathan Lewit for technical assistance, and Cecelia Wall for providing helpful comments on the manuscript. Financial support was provided by the National Human Genome Research Institute (grant number U54-HG-003067) to the Broad Institute, and by National Institutes of Health/National Institute of Allergy and Infectious Diseases R37 Method to Extend Research in Time award AI-39115-20 and RO1 award AI-50113-13 to J.H. This study was supported by The Scientific and Technological Research Council of Turkey-2219 Research Fellowship Programme for International Researchers project number 1059B191501539 to A.D. and by Brazilian funding agency Fundação de Amparo à Pesquisa do Estado de São Paulo Postdoctoral Fellowships 12/22232-8 and 13/19195-6 to G.F.P

Dishwashers are a major source of human opportunistic yeast-like fungi in indoor environments in Mersin, Turkey

The natural habitat of opportunistic fungal pathogens is outside of the host; therefore, it is crucial to understand their ecology and routes of transmission. In this study, we investigated the presence of black and filamentous fungi in moist indoor environments in the city of Mersin in subtropical Turkey. In total, 177 private dwellings were screened and 893 samples obtained using cotton swabs and moistened with physiological saline from dishwashers, washing machines, refrigerators, bath-tubs, bathroom walls, and shower heads. These were then inoculated onto malt extract agar supplemented with chloramphenicol, followed by incubation at 37°C. Thirty samples (3.4%) were positive for fungi, which were then identified by sequencing the rDNA internal transcribed spacer region. Exophiala dermatitidis was the most common species (23), followed by E. phaeomuriformis (three), Magnusiomyces capitatus (two), and Candida parapsilosis (two). Genotype A of E. dermatitidis (14) was more prevalent than genotypes B (eight) and C (one) and E. phaeomuriformis was also represented by two genotypes. Our findings suggest that dishwashers are a major indoor niche for thermophilic black yeasts. The occurrence of the opportunistic filamentous fungus M. capitatus in dishwashers is consistent with a recent report