Host-fungus Relationship Research Articles

Clinical Significance of Dermatophytes and Their Pathogenesis

Despite the superfi cial localization of most dermatophytosis, host-fungus relationship in these infections is complex and still poorly elucidated. Though many efforts have been accomplished to characterize secreted dermatophytic proteases at the molecular level, only punctual insights have been afforded into other aspects of the pathogenesis of dermatophytosis, such as fungal adhesion, regulation of gene expression during the infection process, and immunomodulation by fungal factors. However, new genetic tools were recently developed, allowing a more rapid and high-throughput functional investigation of dermatophyte genes and the identifi cation of new putative virulence factors. In addition, sophisticated in vitro infection models are now used and will open the way to a more comprehensive view of the interactions between these fungi and host epidermal cells, especially keratinocytes.

Divergent host use among cryptic species in the fungivorous ciid beetle Octotemnus laminifrons (Motschulsky, 1860), with descriptions of three new species from Japan

AbstractInsect–host fungus associations are important ecological features that affect population dynamics and interspecific interactions. However, details of host fungus relationships in fungivorous beetles remain unclear due to incompletely revised taxonomy and insufficient host records. We conducted a taxonomic study of the ciid beetle Octotemnus laminifrons (Coleoptera: Ciidae) and its cryptic species in Japan and investigated fungal host‐use by these ciid beetles. Maximum‐likelihood phylogenetic analysis of mitochondrial cytochrome c oxidase subunit I fragments and two nuclear markers recovered four well‐supported, reciprocally monophyletic groups among specimens previously identified as O. laminifrons. Quantitative analyses of genital structures revealed diagnostic differences among these four lineages. These molecular and morphological analyses indicate that the ciid beetles currently identified as O. laminifrons actually comprise four species: O. laminifrons (Motschulsky, 1860), O. assimilis Kobayashi & Sota sp.n., O. crassus Kobayashi & Sota sp.n. and O. kawanabei Kobayashi & Sota sp.n. Here we provide a redescription and lectotype designation for O. laminifrons and descriptions of the three new species. These species showed different patterns of fungal host‐use among four Trametes and one Lenzites species. We also studied the phylogenetic relationships among these four species based on restriction‐site associated DNA (RAD) sequence data, which provided a more reliable phylogenetic tree. We discuss shifts in their fungal host use. Our results demonstrate that closely related, congeneric fungivorous insects exhibit different utility patterns for closely related fungal species, a phenomenon that has rarely been reported previously.

Unusual Specific Lesion of Pleura as Result of Delay in Diagnosis of Chronic Pulmonary Aspergillosis: A Case Presentation

The fungus Aspergillus spp. causes infections in immunocompromised hosts and produces a variety of clinical syndromes including lung tracheobronchial, chronic necrotizing or cavitary pulmonary and allergic bronchopulmonary manifestations, as well as aspergilloma, depending on the type of host-fungus relationship involved. Aspergilloma is usually colonized by Aspergillus spp. lesions in the bronchial tree, while invasive or semi-invasive forms are characterized by the presence of hyphae below its basement membrane. The objective of the present study was to describe the case of a patient with chronic pulmonary aspergillosis in the form of cavitary lesions of lung with infiltrates complicated by pleural empyema, including the clinical course, diagnostic approach and paraclinical care provided. The patient was a 28-year-old female with a history of thymoma who initially presented with febrile and pneumonia 12 years after surgical treatment of tumor. Traditional antibiotic treatment to pneumonia provided no improvement in the patient’s condition and computed tomography of the thorax revealed cavities of destruction and pulmonary opacities. Later a bronchopleural fistula (BPF) was formed. A pleura lesion biopsy was performed after Video assisted thorascopic surgery (VATS) revision of pleural cavity showed a white exophytic lesion and pathological changes of pleura. Since pathologic examination revealed numerous septate fungal hyphae exhibiting 45° branching compatible with Aspergillus spp., the patient was treated with voriconazole. We emphasized on the reasons of delay of true diagnosis due to mistakes in management and treatment of clinical syndromes for a long time. In patients with tumor pathology in anamnesis who present with febrile and respiratory symptoms, it is essential to consider fungi as potential etiologic agents including Aspergillus spp., which is common and causes a variety of clinical syndromes.

Identification of Candida Species Using MP65 Gene and Evaluation of the Candida albicans MP65 Gene Expression in BALB/C Mice.

Background:Systemic candidiasis is a major public health concern. In particular, in immunocompromised people, such as patients with neutropenia, patients with Acquired Immune Deficiency Syndrome (AIDS) and cancer who are undergoing antiballistic chemotherapy or bone marrow transplants, and people with diabetes. Since the clinical signs and symptoms are nonspecific, early diagnosis is often difficult. The 65-kDa mannoprotein (MP65) gene of Candida albicans is appropriate for detection and identification of systemic candidiasis. This gene encodes a putative b-glucanase mannoprotein of 65 kDa, which plays a major role in the host-fungus relationship, morphogenesis and pathogenicity.Objectives:The current study aimed to identify different species of Candida (C. albicans, C. glabrata and C. parapsilosis) using the Polymerase Chain Reaction (PCR) technique and also to evaluate C. albicans MP65 gene expression in BALB/C mice.Materials and Methods:All yeast isolates were identified on cornmeal agar supplemented with tween-80, germ tube formation in serum, and assimilation of carbon sources in the API 20 C AUX yeast identification system. Polymerase Chain Reaction was performed on all samples using species-specific primers for the MP65 65 kDa gene. After RNA extraction, cDNA synthesis was performed by the Maxime RT Pre Mix kit. Candida albicans MP65 gene expression was evaluated by quantitative Real-Time (q Real-Time) and Real-Time (RT) PCR techniques. The 2-ΔΔCT method was used to analyze relative changes in gene expression of MP65. For statistical analysis, nonparametric Wilcoxon test was applied using the SPSS version 16 software.Results:Using biochemical methods, one hundred, six and one isolates of clinical samples were determined as C. albicans, C. glabrata and C. parapsilosis, respectively. Species-specific primers for PCR experiments were applied to clinical specimens, and in all cases a single expected band for C. albicans, C. glabrata and C. parapsilosis was obtained (475, 361 and 124 base pairs, respectively). All species isolated by culture methods (100% positivity) were evaluated with PCR using species-specific primers to identify Candida species. Relative expression of Mp65 genes increased significantly after C. albicans injection into the mice (P < 0.05).Conclusions:The results of the current study showed that the PCR method is reproducible for rapid identification of Candida species with specific primers. Mp65 gene expression of C. albicans after injection into the mice was 2.3 folds higher than before injection, with this difference being significant. These results indicated that increase of Mp65 gene expression might be an early stage of infection; however definitive conclusions require further studies.

Characterization of host–fungus interactions among wood decay fungi associated with Khaya senegalensis (Desr.) A. Juss (Meliaceae) in Singapore

SummaryTree pruning creates wounds that are amenable for wood decay fungi colonization. To characterize the dynamic host–fungus interactions at this location in Senegal mahogany (Khaya senegalensis), in vitro and in vivo pathogenicity tests were conducted with wood decay fungi associated with this tropical tree species. Fomitiporella caryophylii, Hymenochaete murina and Phellinus noxius isolates were included in this experiment following their frequent isolation from Senegal mahogany pruning wounds. The evaluated isolates demonstrated unique host interactions in laboratory tests that suggest equally divergent prognoses for living Senegal mahoganies affected by these fungi. Although all evaluated fungal isolates successfully breached naturally induced reaction zones, P. noxius alone caused significant mass loss to incubated wood blocks. In addition, P. noxius caused extensive wood decay after inoculation in living hosts, successfully illustrating Koch's postulates for this host–fungus relationship. The wood decay ability, invasiveness and facultative parasitism demonstrated by P. noxius suggest its dominant role in wood decay columns below pruning wounds on living Senegal mahoganies. These results highlight the importance of characterizing specific host–fungus interactions and their implications for wood decay severity below pruning wounds in living trees.

Aspergilosis invasiva pulmonar: reporte de un caso

The fungus Aspergillus spp. causes infections in immunocompromised hosts and produces a variety of clinical syndromes including lung tracheobronchial, chronic necrotizing pulmonary and allergic bronchopulmonary manifestations, as well as aspergilloma, depending on the type of host-fungus relationship involved. Aspergilloma is usually colonized by Aspergillus spp. lesions in the bronchial tree, while invasive forms are characterized by the presence of hyphae below its basement membrane. The objective of the present study was to describe the case of a pediatric patient with invasive pulmonary aspergillosis in the form of pseudomembranous tracheobronchitis, including the clinical course, diagnostic approach and paraclinical care provided. The patient was a 5-year-old female with a history of Fanconi anemia who presented with febrile neutropenia and pneumonia. Antibiotic treatment with cefepime provided no improvement in the patient´s condition and computed tomography of the thorax revealed bibasilar pulmonary opacities. Bronchoalveolar lavage and a lesion biopsy were performed after diagnostic bronchoscopy showed a white exophytic lesion. Since pathologic examination revealed numerous septate fungal hyphae exhibiting 45° branching compatible with Aspergillus spp., the patient was treated with voriconazole. Bronchoalveolar lavage culture produced fungi of the Aspergillus flavi complex. A review of pulmonary Aspergillus spp. infection in children is also included, with emphasis on the management and treatment of clinical syndromes. In pediatric patients with hematological diseases who present with febrile neutropenia and respiratory symptoms, it is essential to consider fungi as potential etiologic agents including Aspergillus spp., which is common and causes a variety of clinical syndromes.

The cross-talk between opportunistic fungi and the mammalian host via microbiota's metabolism.

An increased understanding of the importance of microbiota in shaping the host's immune and metabolic activities has rendered fungal interactions with their hosts more complex than previously appreciated. It is now clear that a three-way interaction between host, fungi, and microbiota dictates the types of host-fungus relationship. Indeed, microbial dysbiosis predisposes to a variety of chronic fungal infections and diseases at local and distant sites. By correlating changes in metabolite profiles with microbiota metagenomic composition, we have defined a functional node whereby certain bacteria species contribute to host-fungal symbiosis and mucosal homeostasis. A tryptophan catabolic pathway is exploited by commensal lactobacilli and the mammalian host to increase fitness in response to Candida albicans by inducing resistance and tolerance mechanisms of antifungal immunity. Much like lactobacilli in the gut, Firmicutes change significantly in the airways during aspergillosis. The aryl hydrocarbon receptor has a pivotal role in connecting tryptophan catabolism by microbial communities and the host's own pathway of tryptophan degradation through the enzyme indoleamine 2,3-dioxygenase 1. These data suggest that the study of the human microbiota in the trans-omics era, with a focus on metagenomics and metabonomics, is providing novel insights into the regulation of host immune responsiveness to fungi.

Antifungal Th Immunity: Growing up in Family

Fungal diseases represent an important paradigm in immunology since they can result from either the lack of recognition or over-activation of the inflammatory response. Current understanding of the pathophysiology underlying fungal infections and diseases highlights the multiple cell populations and cell-signaling pathways involved in these conditions. A systems biology approach that integrates investigations of immunity at the systems-level is required to generate novel insights into this complexity and to decipher the dynamics of the host–fungus interaction. It is becoming clear that a three-way interaction between the host, microbiota, and fungi dictates the types of host–fungus relationship. Tryptophan metabolism helps support this interaction, being exploited by the mammalian host and commensals to increase fitness in response to fungi via resistance and tolerance mechanisms of antifungal immunity. The cellular and molecular mechanisms that provide immune homeostasis with the fungal biota and its possible rupture in fungal infections and diseases will be discussed within the expanding role of antifungal Th cell responses.

皮膚糸状菌のヒト角層での寄生形態の走査型電子顕微鏡観察

Electron microscopic techniques have been widely used to investigate the pathogenesis of dermatophytosis. In this article, morphological studies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) concerned with the dermatophyte infection process are literary reviewed and we introduced our morphological study observing the parasitic form of dermatophytes in the lesional cornified layer. Various experimental models have been established to study fungal adhesion and invasion to the skin surface in the early stage of infection by several authors.In these studies, arthroconidial adherence to corneocytes and germination was demonstrated by SEM and TEM. To understand the host-fungus relationship in dermatophytosis, it is also important to identify parasitic forms of fungi and morphological changes of corneocytes in the lesion. The three-dimensional structure of growing or parasitic dermatophytes in the lesional cornified cell layer was observed using the adhesive strip method in tinea cruris and tinea glabrosa. In tinea unguium, however, it is difficult to apply this method because of subungual hyperkeratosis. We introduce the alkaline treatment method for SEM for use in observing fungal elements in a subungual hyperkeratotic lesion and scales in dermatophytosis. With this technique, small pieces of nails or scales were fixed with 2.5% glutaraldehyde, and were treated with low concentrations of alkaline and subjected to the conventional procedure for SEM observation. This method is applicable to various skin lesions, such as tinea unguium, tinea pedis and tinea capitis to investigate the parasitic forms of dermatophytes and the spatial relationship with corneocytes and is useful to understand the infection process of dermatophytosis.

The MP65 gene is required for cell wall integrity, adherence to epithelial cells and biofilm formation in Candida albicans

BackgroundThe MP65 gene of Candida albicans (orf19.1779) encodes a putative β-glucanase mannoprotein of 65 kDa, which plays a main role in a host-fungus relationship, morphogenesis and pathogenicity. In this study, we performed an extensive analysis of a mp65Δ mutant to assess the role of this protein in cell wall integrity, adherence to epithelial cells and biofilm formation.ResultsThe mp65Δ mutant showed a high sensitivity to a range of cell wall-perturbing and degrading agents, especially Congo red, which induced morphological changes such as swelling, clumping and formation of hyphae. The mp65Δ mutant showed an activation of two MAPKs (Mkc1p and Cek1p), a high level of expression of two stress-related genes (DDR48 and SOD5), and a modulated expression of β-glucan epitopes, but no gross changes in cell wall polysaccharide composition. Interestingly, the mp65Δ mutant displayed a marked reduction in adhesion to BEC and Caco-2 cells and severe defects in biofilm formation when compared to the wild type. All of the mentioned properties were totally or partially recovered in a revertant strain, demonstrating the specificity of gene deletion.ConclusionsWe demonstrate that the MP65 gene of Candida albicans plays a significant role in maintaining cell wall integrity, as well as in adherence to epithelia and biofilm formation, which are major virulence attributes of this fungus.

Pathogenesis of Dermatophytosis

Despite the superficial localization of most dermatophytosis, host-fungus relationship in these infections is complex and still poorly elucidated. Though many efforts have been accomplished to characterize secreted dermatophytic proteases at the molecular level, only punctual insights have been afforded into other aspects of the pathogenesis of dermatophytosis, such as fungal adhesion, regulation of gene expression during the infection process, and immunomodulation by fungal factors. However, new genetic tools were recently developed, allowing a more rapid and high-throughput functional investigation of dermatophyte genes and the identification of new putative virulence factors. In addition, sophisticated in vitro infection models are now used and will open the way to a more comprehensive view of the interactions between these fungi and host epidermal cells, especially keratinocytes.

Compatibilidade simbiótica de fungos micorrízicos arbusculares com espécies arbóreas tropicais

A revegetação com espécies arbóreas é uma estratégia adequada, quando se pretende a reabilitação de terras degradadas. Entretanto, o estabelecimento e o crescimento destas em solos pobres em nutrientes dependem de diversos fatores como a capacidade de formar e beneficiar-se das micorrizas. No presente estudo, realizado em casa de vegetação na Universidade Federal de Lavras, Minas Gerais- Brasil, avaliaram-se aspectos da relação fungos micorrízicos arbusculares e espécies arbóreas do sudeste brasileiro. Os fungos estudados foram: Scutellospora pellucida, Acaulospora scrobiculata, Entrophospora colombiana, Gigaspora gigantea, Gigaspora margarita, Glomus etunicatum, Scutellospora gregaria, Glomus clarum e isolados oriundos de agrossistemas e de mata, os quais foram inoculados em dezesseis espécies vegetais: Luehea grandiflora, Cecropia pachystachya, Schinus terebinthifolius, Machaerium nyctitans, Senna macranthera, Senna spectabilis, Solanum granuloso-leprosum, Caesalpinea ferrea, Tabebuia serratifolia, Maclura tinctoria, Guazuma ulmifolia, Acacia polyphylla, Mimosa caesalpiniaefolia, Enterolobium contortisiliquum, Trema micrantha e Cedrela fissilis. Estas espécies apresentaram comportamento diferenciado em relação à susceptibilidade aos fungos e às respostas em crescimento decorrentes da inoculação. A amplitude de eficiência simbiótica dos fungos variou muito, sendo o Gl. clarum, E. colombiana, S. pellucida e Gl. etunicatum os fungos de maior amplitude, beneficiando mais de 80 % das espécies vegetais estudadas, e a A. scrobiculata a espécie de comportamento mais restrito em relação aos hospedeiros. A análise da compatibilidade fungo-hospedeiro e o comportamento geral das espécies em associação indicam a ocorrência de seletividade diferenciada na relação fungo-hospedeiro, existindo combinações de eficiência simbiótica muito variável para as plantas hospedeiras. A importância destes resultados para a revegetação de áreas degradadas é discutida.

Structurally preserved ascomycetous fungi from the Maastrichtian type area (NE Belgium)

Various structurally preserved ascomycetous fungus structures found in and on leaves of the Late Maastrichtian conifer Brachyphyllum patens (Cheirolepidiaceae?) are described: (1) stomatal hypostromata with attached hyphae and a probable fruit body ( Pteropus brachyphylli, gen. et sp. nov., Venturiaceae); (2) nonstomatal epicuticular stromata, including a thyriothecium with septate spores (?Micropeltidaceae, ?Microthyriaceae); (3) nonstomatal subcuticular stromata (?Phacidiaceae, ?Rhytismataceae); and (4) unidentified epicuticular and endophytical hyphae. Pteropus brachyphylli is considered as a close relative of extant Phaeocryptopus (Venturiaceae), species of which infect leaves of conifers belonging to the Araucariaceae, Cupressaceae, Pinaceae and Podocarpaceae. Pteropus brachyphylli may have been closely associated with cheirolepidiaceous conifers, which became extinct near the end of the Cretaceous. To date, it is the only fossil representative of Phaeocryptopus-like fungi. Pteropus brachyphylli is believed to have occupied a niche comparable to that of its modern relatives, which are weak parasites or sometimes saprophytes. Its presence in the Late Maastrichtian sets a minimum age of c. 66.5 million years for the kind of host–fungus relationships as nowadays present between conifers and Phaeocryptopus species.

Humoral and cellular immune response to a Microsporum canis recombinant keratinolytic metalloprotease (r-MEP3) in experimentally infected guinea pigs.

In order to better understand the host-fungus relationship in Microsporum canis dermatophytosis and to identify major fungal antigens, the immune response to a crude exoantigen preparation and to a purified recombinant keratinolytic metalloprotease (r-MEP3) was evaluated in guinea pigs experimentally infected with M. canis. Humoral and cellular immune responses were assessed from day 0 to day 57 post-infection (PI), the former by enzyme-linked immunosorbent assay (ELISA) and the latter via a lymphocyte proliferation assay. Infected guinea pigs developed humoral and cellular responses to both M. canis exoantigen and r-MEP3, while no specific immune response to these antigens was observed in control animals. This is the first report on the development of both humoral and cell-mediated immune responses to a purified keratinase in M. canis dermatophytosis.

Comparison of oral fluconazole and amphotericin B in the prophylaxis of fungal infection in neutropenic patients treated for acute leukemia

Forty patients with acute leukemia (age 16-71 years, 13 females, 27 males) with induced neutropenia due to chemotherapy received either 50 mg fluconazole or 800 mg amphotericin B per day orally as prophylaxis against fungal infection. Nasal and genital swabs, mouth washings, urine, stool and blood serum were taken for mycological and serological examination before and weekly during one episode of neutropenia (less than 10(9) granulocytes/l) per patient. The quantitative determination of the yeast concentration in stool specimens demonstrated that amphotericin B led to intestinal yeast count reduction in only one third of the patients and could not prevent the increase of the intestinal yeast flora in another third of the patients. Beyond that the quantitative determination of yeast colonization in oropharynx, genital region, blood and stool did not prove to be a reliable tool for evaluating the host-fungus relationship during neutropenia. On the other hand mycoserology reflected episodes of candidosis well. 19 patients treated with fluconazole showed only minor titer increases. In 21 patients treated with amphotericin B, four fungemias were found: two by both hemagglutination (HAT) and immunofluorescence (IFT), one by IFT and one by antigen detection (Ramco Cand-Tec) alone. In only one of these cases yeast cells were released in urine. From these results is concluded that control of serology is essential in studies of that type and that fluconazole seems to provide better protection from candidosis than amphotericin B during induced neutropenia.

Dermatophytes in a population of bank voles and woodmice

A population of bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus) inhabiting an oak wood in Somerset was examined for dermatophytes at monthly intervals for 2 years. The marked animals were frequently retrapped, allowing a study of host fungus relationship over a period of time. Microsporum persicolor (Sabouraud) Guiart er Grigorakis and Trichophyton mentagrophytes (Robin) Blanchard were isolated from both animal species, but M. persicolor predominated in bank voles and T. mentagrophytes in wood mice. In their most favoured host, both dermatophyte species often persisted for several months, but in the less favoured host they were never isolated at more than one sampling. Males of both animal species were infected more often than females. The existing evidence for the geophilic nature of both fungi is reviewed and shown to be very weak, especially for M. persicolor. This is the first report from Great Britain of T. mentagrophytes infection of wood mice not in contact with human habitation.