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Peptide synthetase gene in Trichoderma virens.

Trichoderma virens (synonym, Gliocladium virens), a deuteromycete fungus, suppresses soilborne plant diseases caused by a number of fungi and is used as a biocontrol agent. Several traits that may contribute to the antagonistic interactions of T. virens with disease-causing fungi involve the production of peptide metabolites (e.g., the antibiotic gliotoxin and siderophores used for iron acquisition). We cloned a 5,056-bp partial cDNA encoding a putative peptide synthetase (Psy1) from T. virens using conserved motifs found within the adenylate domain of peptide synthetases. Sequence similarities with conserved motifs of the adenylation domain, acyl transfer, and two condensation domains support identification of the Psy1 gene as a gene that encodes a peptide synthetase. Disruption of the native Psy1 gene through gene replacement was used to identify the function of this gene. Psy1 disruptants produced normal amounts of gliotoxin but grew poorly under low-iron conditions, suggesting that Psy1 plays a role in siderophore production. Psy1 disruptants cannot produce the major T. virens siderophore dimerum acid, a dipetide of acylated N(delta)-hydroxyornithine. Biocontrol activity against damping-off diseases caused by Pythium ultimum and Rhizoctonia solani was not reduced by the Psy1 disruption, suggesting that iron competition through dimerum acid production does not contribute significantly to disease suppression activity under the conditions used.

Amino Acid Sequence↗

Production of prostaglandins and leukotrienes by pathogenic fungi.

These studies demonstrate that pathogenic fungi (dermatophytic, subcutaneous, and systemic) have the ability to produce eicosanoids both from simple metabolites and from arachidonic acid. Host-derived eicosanoids have been previously demonstrated to enhance fungal colonization and atopic disease development. Thus, fungus-derived eicosanoids represent a potential class of novel virulence factors.

Cysteine↗

Biotyping and virulence properties of skin isolates of Candida parapsilosis.

The biotype and virulence of skin isolates of Candida parapsilosis were compared with blood isolates of the same fungus. Morphotype, resistotype, and electrophoretic karyotype determinations did not reveal any special cluster with a unique or dominant pathogenic feature among all of the isolates, regardless of their source. However, all cutaneous isolates had uniformly elevated secretory aspartyl-protease (Sap) activity, more than four times higher than the enzyme activity of the blood isolates. They were also highly vaginopathic in a rat vaginitis model, being significantly more virulent than blood isolates in this infection model. In contrast, skin isolates were nonpathogenic in systemic infection of cyclophosphamide-immunodepressed mice, while some blood isolates were, in this model, highly pathogenic (median survival time, 2 days, with internal organ invasion at autopsy). Finally, skin isolates did not differ, as a whole, from blood isolates in their adherence to plastic. This property was associated with a morphotype, as defined by a colony with continuous fringe, which was present among both skin and blood isolates. While confirming the genetic heterogenicity of C. parapsilosis, our data strongly suggest that the potential of this fungus to cause mucosal disease is associated with Sap production and is substantially distinct from that of systemic invasion.

AIDS-Related Opportunistic Infections↗

First case of Arthrographis kalrae ethmoid sinusitis and ophthalmitis in the People's Republic of China.

We present here the first case in the People's Republic of China of human disease caused by the fungus Arthrographis kalrae. The male patient had fungal panophthalmitis and invasive sinusitis involving the maxillary and ethmoid sinuses. He was an apparently healthy man before receiving trauma to his left eye. He complained of pain and loss of visual acuity in the injured eye, which displayed redness and edema and eventually discharged pus. His symptoms became more severe after he was treated with steroids and several antibacterial agents. A computed tomography scan of the left eye revealed that the maxillary and ethmoid sinuses were involved. A smear of purulent material from the left eye orbit revealed fungal elements, and cultures of the material grew a fungus. The isolate was identified as A. kalrae based on gross and microscopic morphologies, biochemical assays, and DNA sequence analysis. The patient received amphotericin B intravenously, itraconazole orally, and atomized allitridum by nebulizing allitridum therapy. The patient's wound healed following surgical intervention, but the patient lost the use of his left eye. This case should remind ophthalmologists and other clinicians to consider the possibility of infections being fungal when antibacterial agents have no effect and the patient's condition worsens.

Adult↗

Review of fungus-induced asthmatic reactions.

Fungus-induced obstructive airway disease in atopic individuals can be differentiated into two categories: first, uncomplicated asthmatic reactions due to high but transient exposure to fungal spores (fungal asthma), resulting in a TH2-type response with immunoglobulin E-mediated reactions and eosinophilic inflammation; and second, a more complex asthmatic reaction due to colonization of the mucus-epithelial surface by virulent protease-producing fungi. The latter condition stimulates as exaggerated immunological response including all subclasses of antibodies directed against the microorganism and an intense eosinophilic infiltrate of the airways. The authors propose that the exaggerated inflammatory response in allergic bronchopulmonary fungosis damages epithelial cells and underlying tissue cells, resulting in inefficient elimination of the microorganisms and damage to matrix proteins of the lung tissue by proteases released by both the fungi and degranulating eosinophils. The positive effects of corticosteroids in the treatment of allergic bronchopulmonary aspergillosis probably results from the dampening of the inflammatory response and an increase of the efficiency of killing the fungi. Sensitization to fungi is high in childhood and declines rapidly with age, suggesting that younger children may be less proficient in clearing fungi from the airways. We propose that insufficient treatment of fungal asthma may result in damage to the bronchial mucosa and formation of bronchiectasis.

Antigens, Fungal↗

Inhibition of the transcription factors NF-kappa B and AP-1 underlies loss of cytokine gene expression in rat alveolar macrophages treated with a diffusible product from the spores of Aspergillus fumigatus.

The spores of Aspergillus fumigatus have a survival advantage over other respirable fungal spores in the lung, leading to a number of lung diseases associated with this fungus. We have hypothesized that a component on the spore surface can inhibit the activation of alveolar macrophages, known to play an essential role in immune regulation in the lung. A diffusible product from the spores of A. fumigatus (AfD) inhibited the production of tumor necrosis factor alpha (TNF alpha) protein by alveolar macrophages in an enzyme-linked immunosorbent assay. Using a semiquantitative reverse transcription-polymerase chain reaction, we also demonstrated a potent inhibitory effect of AfD on the production of proinflammatory cytokine transcripts in rat alveolar macrophages. The inhibition occurred at the level of transcription, with AfD inhibiting the synthesis of TNF alpha-and interleukin 6 (IL-6)-specific mRNA transcripts. No effect was seen on the synthesis of interleukin 1 beta (IL-1 beta) cytokine transcripts or on the expression of the housekeeping gene beta-actin. Furthermore, AfD specifically inhibited the activation of nuclear transcription factors NF-kappa B and AP-1, both of which are required for the coordinate upregulation of transcription of the proinflammatory cytokines TNF alpha, IL-1 beta, and IL-6. We conclude that AfD can inhibit normal alveolar macrophage responses by selectively inhibiting the production of key inflammatory cytokines, and that the mechanism of inhibition is primarily at the level of transcriptional activation.

Animals↗

A fatal pseudo-tumour: disseminated basidiobolomycosis.

BACKGROUND: Basidiobolomycosis is a rare disease caused by the fungus Basidiobolus ranarum, member of the class Zygomycetes, order Entomophthorales, found worldwide. Usually basidiobolomycosis is a subcutaneous infection but rarely gastrointestinal manifestations have been described; 13 adults and 10 children and a few retroperitoneal or pulmonary cases. In gastrointestinal basidiobolomycosis the colon is most frequently involved, usually presenting with subacute mild abdominal pain. In contrast to children only very few described adult patients had hepatic masses. Definitive diagnosis requires culture, serological testing can be helpful. The fungal morphology and the Splendore-Hoeppli phenomenon are characteristic histological features. There are no prominent risk factors. Usually surgery and prolonged antifungal therapy are required. CASE PRESENTATION: A 61 year old man presented with progressive left abdominal pain and constipation since a few months. Colonoscopy showed an obstructing tumour in the descending colon, and a hemicolectomy was performed. Histology showed inflammation, possibly caused by a fungal or parasitic infection, without definite identification of an organism. A few weeks postoperatively a CT scan made because of abdominal discomfort, revealed a livermass (6 cm). Treatment with metronidazole, directed against an amoebic liver abscess, was unsuccessful. He developed a marked eosinophilia (27.7%). A liver biopsy was performed and the patient was referred to a university hospital.A repeated CT scan showed a livermass of 9 cm diameter. Review of colon and liver biopsy samples showed extensive necrosis and histiocytes, multinucleated giant cells and numerous eosinophils. Grocott stained sections contained unusually large hyphae surrounded by strongly eosinophilic material in haematoxylin and eosin stained sections (Splendore-Hoeppli phenomenon). A presumptive diagnosis of Basidiobolus spp. infection was made and treated with amphotericin B (Itraconazol contra-indicated because of renal insufficiency). A few days later the patient died of a septic shock. After autopsy Basidiobolus ranarum was cultured from liver, gallbladder and colon. CONCLUSION: Our patient died of gastrointestinal basidiobolomycosis with an obstructing colon tumour and a large hepatic mass. This was a rare presentation of basidiobolomycosis and the second fatal case described worldwide.

Entomophthorales↗

Infection of malaria (Anopheles gambiae s.s.) and filariasis (Culex quinquefasciatus) vectors with the entomopathogenic fungus Metarhizium anisopliae.

BACKGROUND: Current intra-domiciliary vector control depends on the application of residual insecticides and/or repellents. Although biological control agents have been developed against aquatic mosquito stages, none are available for adults. Following successful use of an entomopathogenic fungus against tsetse flies (Diptera: Glossinidae) we investigated the potency of this fungus as a biological control agent for adult malaria and filariasis vector mosquitoes. METHODS: In the laboratory, both sexes of Anopheles gambiae sensu stricto and Culex quinquefasciatus were passively contaminated with dry conidia of Metarhizium anisopliae. Pathogenicity of this fungus for An. gambiae was further tested for varying exposure times and different doses of oil-formulated conidia. RESULTS: Comparison of Gompertz survival curves and LT50 values for treated and untreated specimens showed that, for both species, infected mosquitoes died significantly earlier (p < 0.0001) than uninfected control groups. No differences in LT50 values were found for different exposure times (24, 48 hrs or continuous exposure) of An. gambiae to dry conidia. Exposure to oil-formulated conidia (doses ranging from 1.6 x 10(7) to 1.6 x 10(10) conidia/m2) gave LT50 values of 9.69 +/- 1.24 (lowest dose) to 5.89 +/- 0.35 days (highest dose), with infection percentages ranging from 4.4-83.7%. CONCLUSION: Our study marks the first to use an entomopathogenic fungus against adult Afrotropical disease vectors. Given its high pathogenicity for both adult Anopheles and Culex mosquitoes we recommend development of novel targeted indoor application methods for the control of endophagic host-seeking females.

Age Factors↗

Blasticidin S deaminase gene (BSD): a new selection marker gene for transformation of Arabidopsis thaliana and Nicotiana tabacum.

Arabidopsis thaliana and Nicotiana tabacum were transformed to blasticidin S (BS) resistance with BSD (the BS deaminase gene from Aspergillus terreus) using the Agrobacterium-mediated transformation method. Expression of BSD allowed direct selection of transformants by the fungicide, and both kinds of transgenic plants showed high level of resistance phenotype at 100 ppm of BS sprayed on the leaves. Using Botrytis cinerea, the causal fungus of gray mold disease, it was exemplified that application of BS could control the disease in transgenic tobacco with negligible phytotoxicity.

Aminohydrolases↗

Histologic features of zygomycosis: emphasis on perineural invasion and fungal morphology.

OBJECTIVE: Invasive zygomycosis is rapidly progressive and is associated with angioinvasion and infarction. Invasive disease requires emergent surgical and medical intervention. Because it is important for surgical pathologists to recognize these fungi and their preferential sites of growth, the objective of this article is to describe the fungal morphology and histopathologic findings in biopsies from patients with zygomycotic disease, with emphasis on preferential sites of fungal growth. DESIGN: Medical record and histologic review identified 20 patients with zygomycosis. Inclusion criteria included the presence of typical ribbonlike hyphae and positive culture, a clinical history of invasive zygomycosis, or both. The histologic features of disease and the fungal morphology were assessed. RESULTS: Fungus ball (15%), rhinocerebral (55%), and pulmonary (30%) disease were the types of disease represented. The inflammatory responses were predominantly neutrophilic (50%), predominantly granulomatous (5%), pyogranulomatous (25%), or absent (20%). Invasive disease was characterized by prominent infarcts (94%), angioinvasion (100%), and, surprisingly, prominent perineural invasion (90%) in biopsies that contained nerves for evaluation. At least rare hyphal septa were always seen (100%), and most branches (95%) varied from 45 degrees to 90 degrees. CONCLUSIONS: As known to mycologists, zygomycetes are pauciseptate, rather than aseptate, molds. Therefore, the presence of an occasional septum is expected. Perineural invasion is a common finding in invasive zygomycosis, as are angioinvasion and infarcts. Therefore, prior to excluding the presence of these fungi in biopsies suspected to contain zygomycetes, the perineural space should be carefully examined.

Aspergillosis↗

[Tibial abscess caused by histoplasma capsulatum].

Disseminated histoplasmosis is the most serious form of the disease produced by the fungus Histoplasma capsulatum. Histoplasmosis was first described by Darling in 1906, and it is endemic in certain areas of Central and Southeastern regions of USA, and most Latin America countries, including the Pampa húmeda and Mesopotamia regions in Argentina, but in other continents it has a limited regional distribution. Lung involvement predominates in 90% of cases, but H. capsulatum may involve bone and soft tissues. Bone lesions without other signs of infection are very rare, and are often misdiagnosed as cancer. We report a case of disseminated histoplasmosis in a man with a myelodysplasia who presented a left tibial abscess, without any clinical evidence of pulmonary involvement. The patient was successfully treated with itraconazole.

Abscess↗