Outbreak of acute histoplasmosis in a family group: identification of the infection source

An outbreak of acute histoplasmosis occurring in 4 members of the same family, two women, a girl and a male, is reported. The index case presented acute respiratory symptoms, severe enough to require hospitalization. In the remaining persons, the infection was asymptomatic but was evidenced by reactive histoplasmin serologic tests. Search for the common source of infection led to an enriched soil obtained in a local nursery for growing in-door plants. BALB/c mice were inoculated with suspensions of soils from the potted plants. Histoplasma capsulatum var. capsulatum was isolated from various internal organs of the mice. Although histoplasmosis is observed more frequently in persons with occupations implying risk of exposure and is connected to rural areas, outbreaks and intra-family cases are now common in urban areas. This is due to massive urbanization, deforestation, demolitions and the use of soils enriched with organic compounds, mainly bird/bat excrements. This report calls the attention on the danger involved in using such enriched soils for plant nutrition.     

Identification of the infectious source of an unusual outbreak of histoplasmosis, in a hotel in Acapulco, state of Guerrero, Mexico

Three isolates of Histoplasma capsulatum were identified from mice lung, liver, and spleen inoculated with soil samples of the X hotel's ornamental potted plants that had been fertilized with organic material known as compost. The presence of H. capsulatum in the original compost was detected using the dot-enzyme-linked immunosorbent assay. Nested-PCR, using a specific protein Hcp100 coding gene sequence, confirmed the fungal identification associated with an unusual histoplasmosis outbreak in Acapulco. Although, diversity between the H. capsulatum isolate from the hotel and some clinical isolates from Guerrero (positive controls) was observed using random amplification of polymorphic DNA based-PCR, sequence analyses of H-anti and ole fragment genes revealed a high homology (92-99%) between them.     

A murine monoclonal antibody exhibiting high species specificity for Histoplasma capsulatum var. capsulatum.

A monoclonal antibody (mAb) exhibiting a high degree of species specificity for the yeast phase of the dimorphic fungus Histoplasma capsulatum was produced by a modification of the standard mAb production protocol. The technique for generating mAbs involved the use of the immunosuppressive drug cyclophosphamide to diminish the response in mice to immunodominant cross-reactive epitopes. This mAb exhibited clear specificity and did not react by ELISA with the closely related genera Blastomyces, Paracoccidioides and Sporothrix. In Western blots it recognized a linear determinant on a 70-75 kDa molecule in H. capsulatum antigen, with an extremely faint reactivity to antigens of identical molecular mass derived from Sporothrix and Paracoccidioides, and no reactivity against Blastomyces antigen.     

Histoplasma capsulatum isolated from Didelphis albiventris (Marsupialia: Didelphidae) in the State of Minas Gerais, Brazil

We report the isolation of Histoplasma capsulatum from a culture of the viscera of Didelphis albiventris, one of the marsupial species found in Brazil. To our knowledge, this is the first report of the isolation of this fungus from this mammalian species. This finding confirms the ubiquitous presence of H. capsulatum in nature.     

Effect of antilymphocyte serum on animals experimentally infected with Histoplasma capsulatum or Cryptococcus neoformans

The anti-mouse and anti-guinea pig antilymphocyte sera (ALS) prepared for this study were shown to contain cytoxic and leucoagglutinating antibodies, and were capable of producing severe lymphopenia in these animals. Guinea pigs treated weekly with ALS were more susceptible to development of fatal infection when inoculated with Histoplasma capsulatum. No fatalities occurred in guinea pigs infected with equal doses of H. capsulatum but treated with normal rabbit serum (NRS) or saline. The time necessary to reach 50% fatality in mice infected with Cryptococcus neoformans was greatly reduced by pretreatment with ALS in comparison with infected controls treated with NRS or saline. When low dosages were used (0.1 ld(50)), the effect was even more pronounced. Spleen homogenates from mice infected with equal dosages of H. capsulatum and treated with ALS or NRS were cultured. More than 150 times as many organisms were present in the spleens of the ALS-treated group. Similar results were obtained from culturing the lungs and liver. Delayed hypersensitive skin reactions were radically decreased or abrogated in H. capsulatum-infected guinea pigs inoculated intraperitoneally with ALS 12 hr before skin testing with histoplasmin. When ALS was given weekly, the influence on skin reactivity was less notable. Given intradermally, ALS was shown to inhibit the delayed reaction to histoplasmin within a radius of 40 mm.     

Inhibition of growth of Histoplasma capsulatum by lymphokine-stimulated macrophages

Peritoneal cells from mice immunized by sublethal infection inhibit the intracellular growth of Histoplasma capsulatum in vitro. Lymphokines generated in cultures of immune splenocytes stimulated with Histoplasma antigen activate normal macrophages to inhibit the intracellular growth of the fungus. Such lymphokines may inhibit the intracellular growth of H. capsulatum by 60 to 80% but have no direct effect on the viability of the fungus extracellularly. The lymphokine preparations have high interferon activity that is heat stable and acid labile. The cells in the spleen that are responsible for lymphokine production are T lymphocytes, but the help of other cells such as macrophages is essential for maximal production.     

来自土壤的金孢属四个新记录种

【背景】金孢属是一类重要的嗜角蛋白真菌资源。【目的】对我国甘肃省和云南省土壤中的金孢属资源进行调查。【方法】采集不同环境中的土壤样品,利用鸡毛和头发对土壤样品中的这类资源进行钓饵,分离目标菌株;基于形态特征和ITSrDNA序列进行系统发育分析相结合的方法进行菌株的鉴定。【结果】从土壤中分离发现5个金孢属菌株,其中菌株H5.11在形态上与节状金孢模式菌株的形态特征非常相近,而且系统发育中与GenBank上报道的该种序列以较高的支持率聚在一个亚分支;H10.10菌株的形态特征与乔治金孢模式标本的形态非常吻合,培养基上均呈现红色,同时系统发育分析结果表明该菌株与GenBank上报道的序列较好的聚在一个亚分支中;EB8803M和EB8801M两个菌株在形态特征上与水生金孢模式标本的描述非常吻合,系统发育分析结果显示它们与网上该种序列能较好地聚在一个亚分支中;O1菌株在形态特征上与轮带金孢模式标本的描述非常吻合,其系统发育表明它与GenBank已报道菌株序列能较好聚在一起。因此将它们鉴定为节状金孢Chrysosporiumarticulatum、乔治金孢C.georgiae、水生金孢C.submersum和轮带金孢C.zonatum。【结论】这4个种均为中国新记录种。     

Histoplasma capsulatum molecular genetics, pathogenesis, and responsiveness to its environment

Histoplasma capsulatum is a thermally dimorphic ascomycete that is a significant cause of respiratory and systemic disease in mammals including humans, especially immunocompromised individuals such as AIDS patients. As an environmental mold found in the soil, it is a successful member of a competitive polymicrobial ecosystem. Its host-adapted yeast form is a facultative intracellular pathogen of mammalian macrophages. H. capsulatum faces a variety of environmental changes during the course of infection and must survive under harsh conditions or modulate its microenvironment to achieve success as a pathogen. Histoplasmosis may be considered the fungal homolog of the bacterial infection tuberculosis, since both H. capsulatum and Mycobacterium tuberculosis exploit the macrophage as a host cell and can cause acute or persistent pulmonary and disseminated infection and reactivation disease. The identification and functional analysis of biologically or pathogenically important H. capsulatum genes have been greatly facilitated by the development of molecular genetic experimental capabilities in this organism. This review focuses on responsiveness of this fungus to its environment, including differential expression of genes and adaptive phenotypic traits.     

Effect of Histoplasmosis on Antibody Response to an Erythrocyte Antigen

Infection of mice with Histoplasma capsulatum depressed their ability to form agglutinins against foreign erythrocytes. Animals previously inoculated with 10(8) yeast cells of H. capsulatum showed the most significant depression, occurring when erythrocytes were injected 8 days after infection. The average log(2) hemagglutinin titer was 2.7 compared to 8.0 for the control (noninfected) group. In general, depression of hemagglutinin response in all infected mice was greatest 8 days after infection, but response was back to near normal after 16 days and stayed at that level for the remaining time tested (24 days).     

Knocking on the right door and making a comfortable home: Histoplasma capsulatum intracellular pathogenesis

Histoplasma capsulatum is a successful intracellular pathogen of mammalian macrophages. As such, this fungus must survive and/or subvert hostile environmental onslaughts in a professionally antimicrobial host cell. H. capsulatum uses different host receptors for binding to macrophages (beta 2 integrins) than it uses for binding to dendritic cells (the fibronectin receptor); the fungus experiences different degrees of success in survival in these two cells. Surface expression of HSP60 as the specific adhesin for macrophage beta 2 integrins represents a novel mechanism for binding. Long considered a resident of the phagolysosome, H. capsulatum may also reside in a modified phagosome without experiencing phagolysosomal fusion. H. capsulatum must compete with the host to acquire the essential nutrient iron, and has several potential mechanisms for accomplishing this necessary feat. Finally, H. capsulatum displays morphotype-specific expression of several genes, and a calcium-binding protein expressed only by the pathogenic yeast phase has been demonstrated as essential for full virulence. An organism's environment is of great importance to its success or failure, and H. capsulatum is good at finding or making the right environment in the host.     

一个分离自冬虫夏草的金孢霉新种

从采自四川理县米亚洛的冬虫夏草(Cordyceps sinensis(Serk.)Sacc.)内菌核中分离得一金孢霉新种,中国金孢霉(Chrysosporium sinense Liang)。此菌与本属已知种的鉴别特征是:形成较多孢梗束,生长最适温低于20℃且大量形成壁光滑的间生分生孢子。本文还对虫草无性型的确定作了扼要地讨论。     

Adhesion of Histoplasma capsulatum to pneumocytes and biofilm formation on an abiotic surface

The pathogenic fungus, Histoplasma capsulatum, causes the respiratory and systemic disease 'histoplasmosis'. This disease is primarily acquired via inhalation of aerosolized microconidia or hyphal fragments of H. capsulatum. Evolution of this respiratory disease depends on the ability of H. capsulatum yeasts to survive and replicate within alveolar macrophages. It is known that adhesion to host cells is the first step in colonization and biofilm formation. Some microorganisms become attached to biological and non-biological surfaces due to the formation of biofilms. Based on the importance of biofilms and their persistence on host tissues and cell surfaces, the present study was designed to investigate biofilm formation by H. capsulatum yeasts, as well as their ability to adhere to pneumocyte cells. H. capsulatum biofilm assays were performed in vitro using two different clinical strains of the fungus and biofilms were characterized using scanning electron microscopy. The biofilms were measured using a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium-hydroxide (XTT) reduction assay. The results showed that both the H. capsulatum strains tested were very efficient at adhering to host cells and forming biofilm. Therefore, this is a possible survival strategy adopted by this fungus.     

Development and Use of a Polyvalent Conjugate to Differentiate Histoplasma capsulatum and Histoplasma duboisii from Other Pathogens

Previous investigations have demonstrated the existence of five Histoplasma capsulatum serotypes. Available specific fluorescent-antibody reagents stain only four of the five serotypes. Antibodies produced against the most complete H. capsulatum serotype were labeled with fluorescein isothiocyanate to develop a reagent specific for H. capsulatum that was reactive with all the known serotypes. The unadsorbed reagent not only stained all the H. capsulatum serotypes, but it also stained cultures of Blastomyces dermatitidis, H. duboisii, several Candida species, and a variety of other fungi. Adsorption of the conjugate with antigens of C. albicans produced a reagent that intensely stained only H. capsulatum, H. duboisii, and B. dermatitidis. Differentiation of B. dermatitidis from the Histoplasma species was accomplished by application of a B. dermatitidis specific fluorescent antibody to antigens positive with the H. capsulatum reagent. At present, differentiation of H. capsulatum from H. duboisii may be accomplished only by animal inoculation. Our data substantiate the antigenic relationships hypothesized earlier, and they indicate that H. capsulatum shares at least two antigens with the other fungi that were studied.     

Efficacy of cell-free antigens in evaluating cell immunity and inducing protection in a murine model of histoplasmosis

Histoplasma capsulatum is a dimorphic pathogenic fungus that causes a wide spectrum of disease when mycelial fragments are inhaled. Resistance to H. capsulatum is dependent on cellular immunity mediated by T cells and macrophages. Here we standardized the production of extracts containing cell-free antigens (CFAgs) and observed their efficacy in evaluating cellular immunity during murine histoplasmosis. CFAgs induced a more potent delayed-type hypersensitivity (DTH) response in H. capsulatum-infected mice than did histoplasmin-a classical antigen. This DTH response to CFAgs is able to determine the immune status of infected mice and to predict their death. Moreover, CFAgs stimulated spleen cells from immune mice to produce higher amounts of gamma interferon (IFN-gamma) in vitro. Finally, immunization with CFAgs protected against a lethal inoculum of H. capsulatum. These results demonstrate that CFAgs may be useful for the evaluation of cellular immune response and as a potential source for the development of a vaccine against histoplasmosis.     

Parasitic and Saprophytic Abilities of the Nematode-Attacking Fungus Hirsutella rhossiliensis

The ability of Hirsutella rhossiliensis to colonize various substrates in sterile and nonsterile soil was measured. Hirsutella rhossiliensis was recovered from 67% and 77% of living, inoculated Criconemella xenoplax incubated in sterile and nonsterile soil, respectively. In contrast, the fungus was recovered from 100% and 18% of heat-killed, inoculated nematodes incubated on sterile and nonsterile soil, respectively. Hirsutella rhossiliensis was readily recovered from inoculated, autoclaved wheat seeds incubated in sterile soil but not from seeds incubated in nonsterile soil. Autoclaved peach roots were a poor substrate for the fungus. Germination of H. rhossiliensis spores incubated on agar disks above soil was about 90% regardless of soil treatment. However, germ tube length was greatly suppressed by nonsterile soil. Our results suggest that H. rhossiliensis is a better parasite than saprophyte and that the fungus may be specialized for attacking nematodes.     

秸秆覆盖免耕土壤真菌群落结构与生态特征研究

不同耕作方法土壤真菌群落结构和生态特征分析表明,翻耕0－10cm土层土壤真菌群落含有29种真菌,其中以Chrysosporium merdarium为优势种;翻耕10－20cm土层含有17种真菌,以Sterile black A为优势种：翻耕20－30cm土层含有10种真菌,其中以Chaetomium bostrychodes为优势种,铁茬0－10cm含16种真菌,其中Sterile black A是优势种;铁茬10－20cm土层含有26种真菌,优势种为Sterile black A;铁茬20－30cm含有14种真菌,其中Chaetomium bostrychodes为优势种,免耕0－10cm土层由23种真菌构成,Trichoderma viride和T.koningii为优势种,免耕10－20cm土层由14个种类构成,Talaromyces trachyspermus为优势种,免耕20－30cm土壤由9种真菌组成,其中Talaromyces trachypermus为优势种,免耕土壤真菌群落的多样性和均匀度指数均较高,主成分分析表明,土壤耕作形成了特征性的真菌区系。     

VEA1 is required for cleistothecial formation and virulence in Histoplasma capsulatum

Histoplasma capsulatum is a pathogenic fungus dependent on dimorphism for virulence. Among the four described Velvet family genes, two of them, Ryp2 and Ryp3, have been shown to be required for dimorphism. It is known that Velvet A (VeA) is necessary for sexual development and toxin production in Aspergillus nidulans. However, the role of the VeA ortholog in H. capsulatum has not yet been explored. Vea1, H. capsulatum homolog of VeA, was studied to determine its role in cleistothecial formation, dimorphism, and virulence. H. capsulatum Vea1 restores cleistothecial formation and partially restores sterigmatocystin production in an A. nidulans veA deletion strain. Furthermore, silencing VEA1 in an H. capsulatum strain capable of forming cleistothecia abolishes cleistothecial formation. Silenced strains also switch to mycelial phase faster, and show impaired switching to the yeast phase once in mycelial phase. Virulence in mice and macrophages is attenuated in VEA1 silenced strains and silenced strains demonstrate increased sensitivity during growth under acidic conditions. These results indicate that H. capsulatum Vea1 shares a similar role in development as VeA. H. capsulatum is also more susceptible to growth in acidic conditions when VEA1 is silenced, which may contribute to the silenced strains' attenuated virulence in mice and macrophages.     

Purification and characterization of a cysteine dioxygenase from the yeast phase of Histoplasma capsulatum

A cysteine dioxygenase, cysteine oxidase (EC 1.13.11.20), has been purified from the cytosolic fraction of yeast phase cells of the dimorphic fungus Histoplasma capsulatum. The cysteine oxidase is an iron-containing dioxygenase with a molecular weight of 10500 (+/- 1500) and is present only in the yeast phase of the fungus. The enzyme is highly specific for L-cysteine, with a Km of 2 X 10(-5) M in vitro. The product of cysteine oxidation is cysteinesulfinic acid, as analyzed by thin-layer chromatography and mass spectroscopy. To our knowledge, this is the first cysteine oxidase isolated from a fungus, and it probably plays an important role in the mycelial to yeast phase transition of H. capsulatum during which redox potential and cysteine levels are crucial factors.     

Morphological characterization of in-vitro human hair keratinolysis,produced by identified wild strains of Chrysosporium species

Chrysosporium species were isolated from soil and keratinized material. Primary isolation was performed following the general method of hair baiting on modified Czapek-agar media with washed, defated and sterilized human hair fragments added. Strains were maintained in test tubes of potato dextrose agar at 29 degrees C and cultivated on phytone yeast extract agar at 28 degrees C for 14 days for identification. Isolates were characterized using Van Oorschot's key. Keratinolytic activity was expressed following a subjective scale representing degree/severity of attack upon hair surface and presence of fungal structures observed in substrate. Culture results and characterization methods were effective for soil Chrysosporium strain isolation. A new hair attack mode is described. Of 71 keratinolytic fungal isolates, eight (12%) Chrysosporium species were identified. One keratinolytic Chrysosporium sp. isolate is yet to be identified.