Specific immunological test for the rapid identification of members of the genus Histoplasma

Challenges in Serologic Diagnostics of Neglected Human Systemic Mycoses: An Overview on Characterization of New Targets

Systemic mycoses have been viewed as neglected diseases and they are responsible for deaths and disabilities around the world. Rapid, low-cost, simple, highly-specific and sensitive diagnostic tests are critical components of patient care, disease control and active surveillance. However, the diagnosis of fungal infections represents a great challenge because of the decline in the expertise needed for identifying fungi, and a reduced number of instruments and assays specific to fungal identification. Unfortunately, time of diagnosis is one of the most important risk factors for mortality rates from many of the systemic mycoses. In addition, phenotypic and biochemical identification methods are often time-consuming, which has created an increasing demand for new methods of fungal identification. In this review, we discuss the current context of the diagnosis of the main systemic mycoses and propose alternative approaches for the identification of new targets for fungal pathogens, which can help in the development of new diagnostic tests.

Prevalence of pulmonary mycoses in smear-negative patients with suspected tuberculosis in the Brazilian Amazon

BACKGROUND

Pulmonary mycoses resemble clinically and radiologically chronic pulmonary tuberculosis. Studies describing the prevalence, etiology and clinical features of pulmonary mycosis are of crucial importance in the Brazilian Amazon.

AIMS

To estimate the frequency of pulmonary mycoses in smear-negative tuberculosis patients; to describe their demographic, epidemiological, and clinical characteristics; and to evaluate diagnostic methods.

METHODS

A cross-sectional study was conducted at two tuberculosis reference institutions in Amazonas, Brazil. We included 213 patients and collected clinical data, blood and induced sputum to perform serological, direct microscopy, microbiologic culture and PCR-based assays to identify infections caused by Aspergillus fumigatus, Paracoccidioides brasiliensis, Histoplasma capsulatum, Cryptococcus, and HIV. Chest computed tomography was also performed.

RESULTS

Pulmonary mycoses were diagnosed in 7% (15/213) of the cases, comprising ten aspergillosis cases, three cases of paracoccidioidomycosis and one case each of histoplasmosis and cryptococcosis. Among the patients with pulmonary mycoses, 86.7% were former tuberculosis patients. The most significant clinical characteristics associated with pulmonary mycoses were cavity-shaped lung injuries, prolonged chronic cough and hemoptysis.

CONCLUSIONS

Our study confirmed the high prevalence of pulmonary mycoses in smear-negative tuberculosis patients in the Brazilian Amazon.

Novel clinical and dual infection by Histoplasma capsulatum genotypes in HIV patients from Northeastern, Brazil

Histoplasmosis is a worldwide-distributed deep mycosis that affects healthy and immunocompromised hosts. Severe and disseminated disease is especially common in HIV-infected patients. At least 11 phylogenetic species are recognized and the majority of diversity is found in Latin America. The northeastern region of Brazil has one of the highest HIV/AIDS prevalence in Latin America and Ceará State has one of the highest death rates due to histoplasmosis in the world, where the mortality rate varies between 33-42%. The phylogenetic distribution and population genetic structure of 51 clinical isolates from Northeast Brazil was studied. For that morphological characteristics, exoantigens profile, and fungal mating types were evaluated. The genotypes were deduced by a MSLT in order to define local population structure of this fungal pathogen. In addition, the relationships of H. capsulatum genotypes with clinically relevant phenotypes and clinical aspects were investigated. The results suggest two cryptic species, herein named population Northeast BR1 and population Northeast BR2. These populations are recombining, exhibit a high level of haplotype diversity, and contain different ratios of mating types MAT1-1 and MAT1-2. However, differences in phenotypes or clinical aspects were not observed within these new cryptic species. A HIV patient can be co-infected by two or more genotypes from Northeast BR1 and/or Northeast BR2, which may have significant impact on disease progression due to the impaired immune response. We hypothesize that co-infections could be the result of multiple exposure events and may indicate higher risk of disseminated histoplasmosis, especially in HIV infected patients.

Fast protocol for the production of Histoplasma capsulatum antigens for antibody detection in the immunodiagnosis of histoplasmosis

BACKGROUND

Current methods for the production of Histoplasma capsulatum antigens are problematic in terms of standardization, specificity, stability, repeatability and reproducibility.

AIMS

In this study, we sought to optimize the methodology for producing H. capsulatum antigens, and to evaluate its applicability.

METHODS

Antigenic preparations obtained from 12 H. capsulatum isolates were evaluated by double immunodiffusion and immunoblotting assays against homologous and heterologous sera.

RESULTS

The evaluated and optimized protocol allowed a more stable production, as well as repeatable, reproducible, with shorter culture time and less costly. By double immunodiffusion and immunoblotting assays, the best pattern of reactivity was observed for antigens obtained with 33 days of culture from the isolates 200 and 406 against the M antigen and for the isolate 200 with 15 days against H antigen. The SDS-PAGE presented antigenic components of molecular masses between 17 and 119kDa. The immunoblotting sensitivity was 95.5% and 100% with histoplasmosis sera from ill patients and sera from H. capsulatum infected but otherwise healthy patients, respectively, to the antigen derived from isolates 200 and 406.

CONCLUSIONS

We suggest the employment of the antigen from isolate 200, with 15 or 30 days of culture, in the double immunodiffusion and immunoblotting assays due to its good ability to discriminate both sera from patients with histoplasmosis illness and histoplasmosis infection, in addition to its high specificity against heterologous sera.

Immuno-identification of cultures of fungi pathogenic to man

Because isolates of the fungal pathogensBlastomyces dermatitidis. Coccidioides immitis, Histoplasma capsulatum, andParacoccidioides brasiliensis frequently vary widely in gross and microscopic features and are often difficult or impossible to convert to their tissue forms, a simple diagnostic procedure not dependent upon sporulation is needed to identify them specifically and rapidly. The exoantigen technique has been found to meet this need effectively. On the basis of studies with 166Histoplasma spp. isolates, 128C. immitis isolates, 59B. dermatitidis isolates, 30P. brasiliensis isolates, and 181 saprophytes, we determined that the exoantigen test is valuable for the presumptive identification of the four fungal pathogens studied. All of the positive reactions have correlated with the cultural, histologic, or other available laboratory data, and we are unaware of any false positive or flase negative reactions.

Molecular characterization of Histoplasma capsulatum isolated from an outbreak in treasure hunters Histoplasma capsulatum in treasure hunters

Background

In Mexico, primary pulmonary histoplasmosis is the most relevant clinical form of the disease. The geographical distribution of specific strains of Histoplasma capsulatum circulating in Mexico has not been fully established. Outbreaks must be reported in order to have current, updated information on this disease, identifying new endemic areas, manner of exposure to the fungi, and molecular characterization of the causative agents. We report a recent outbreak of histoplasmosis in treasure hunters and the molecular characterization of two isolates obtained from these patients.

Methods

Six patients admitted to the National Institute of Respiratory Diseases (INER) in Mexico City presented severe respiratory symptoms suggestive of histoplasmosis. They acquired the infection in the Veracruz (VZ) endemic zone. Diagnosis was made by X-ray and Computed tomography (CT), liver function, immunological techniques, and culture. Identification of H. capsulatum isolates was confirmed by using Polymerase chain reaction (PCR) was conducted with a probe from the M antigen, and the isolates were characterized by means of Random amplification of polymorphic DNA (RAPD)-PCR employed the 1253 oligonucleotide and a mixture of oligonucleotides 1281 and 1283. These were compared to eight reference strain isolates from neighboring areas.

Results

X-ray and CT revealed disseminated micronodular images throughout lung parenchyma, as well as bilateral retrocaval, prevascular, subcarinal, and hilar adenopathies, hepatosplenomegaly, and altered liver function tests. Five of the six patients developed disseminated histoplasmosis. Two H. capsulatum strains were isolated. The same band profile was detected in both strains, indicating that both isolates corresponded to the sole H. capsulatum strain. Molecular characterization of the isolates was similar in 100% with the EH-53 Hidalgo human (HG) strain (reference strain integrated into the LAm A clade described for Latin America).

Conclusions

The two isolates appeared to possess the same polymorphic pattern; they are indistinguishable from each other and from EH-53. It is important to remain updated on recent outbreaks of histoplasmosis, the manner of exposure to the fungi, as well as the molecular characterization of the isolates. The severity of cases indicates that this strain is highly virulent and that it is probably prevalent in Hidalgo and Veracruz states.

Comparison of different DNA-based methods for molecular typing of Histoplasma capsulatum

Histoplasma capsulatum is very prevalent in the environment and is one of the most common causes of mycoses in humans and diverse animals in Brazil. Multiple typing methods have been developed to study H. capsulatum epidemiology; however, there is limited information concerning comparisons of results obtained with different methods using the same set of isolates. To explore the diversity of H. capsulatum in Brazil and to determine correlations between the results of three different molecular typing techniques, we examined 51 environmental, animal, and human isolates by M13 PCR fingerprinting, PCR-restriction fragment length polymorphism (RFLP) analysis of the internal transcribed region 1 (ITS1)-5.8S-ITS2 region of the rDNA locus, and DNA sequencing and phylogenetic analysis of parts of four protein-encoding genes, the Arf (ADP ribosylation factor), H-anti (H antigen precursor), Ole (delta-9 fatty acid desaturase), and Tub1 (alpha-tubulin) genes. Each method identified three major genetic clusters, and there was a high level of concordance between the results of the typing techniques. The M13 PCR fingerprinting and PCR-RFLP analyses produced very similar results and separated the H. capsulatum isolates included in this study into three major groups. An additional approach used was comparison of our Brazilian ITS1-5.8S-ITS2 sequences with the sequences deposited previously in NCBI data banks. Our analyses suggest that H. capsulatum can be divided into different molecular types that are dispersed around the world. Our results indicate that the three methods used in this study are reliable and reproducible and that they have similar sensitivities. However, M13 PCR fingerprinting has some advantages over the other two methods as it is faster, cheaper, and more user friendly, which especially increases its utility for molecular typing of Histoplasma in situations where laboratory facilities are relatively limited.

Guedes HL, Nosanchuk JD, Zancopé-Oliveira RM. Biological function and molecular mapping of M antigen in yeast phase of Histoplasma capsulatum

Histoplasmosis, due to the intracellular fungus Histoplasma capsulatum, can be diagnosed by demonstrating the presence of antibodies specific to the immunodominant M antigen. However, the role of this protein in the pathogenesis of histoplasmosis has not been elucidated. We sought to structurally and immunologically characterize the protein, determine yeast cell surface expression, and confirm catalase activity. A 3D-rendering of the M antigen by homology modeling revealed that the structures and domains closely resemble characterized fungal catalases. We generated monoclonal antibodies (mAbs) to the protein and determined that the M antigen is present on the yeast cell surface and in cell wall/cell membrane preparations. Similarly, we found that the majority of catalase activity was in extracts containing fungal surface antigens and that the M antigen is not significantly secreted by live yeast cells. The mAbs also identified unique epitopes on the M antigen. The localization of the M antigen to the cell surface of H. capsulatum yeast and the characterization of the protein's major epitopes have important implications since it demonstrates that although the protein may participate in protecting the fungus against oxidative stress it is also accessible to host immune cells and antibody.

Epidemiology of equine histoplasmosis (epizootic lymphangitis) in carthorses in Ethiopia

A study was conducted between January 2003 and June 2004 on 19,082 carthorses in 28 towns in Ethiopia to investigate the epidemiology of equine histoplasmosis (EH). Clinical and microscopic examinations were used and an overall prevalence of 18.8% (3579/19082) was recorded. Statistically significant (P<0.001) differences was observed in the average prevalence with high, medium, and low prevalence categories. The highest prevalence (39%) was recorded at Mojo while the lowest (0.0%) was recorded at five towns, namely, Agaro, Bokoji, Debre Berhan, Dinsho, and Sagure. The prevalence of EH was not associated (R=0.08, F=0.15, P=0.71) with the mean annual rainfall but was associated (R=0.64, F=11.5, P<0.01) with the average annual temperature. Statistically significant (R=0.57, F=12.34, P<0.01) association was observed between the altitude of the study towns and the prevalence of EH. Moreover, the number of cases of EH increased significantly (R=0.88, F=90.9, P<0.001) with the horse population in the towns. In general, EH was prevalent in hot and humid towns with an altitude ranging from 1500m above sea level (asl) to 2300masl but was nil or low in cold and in dry and windy towns. It was concluded that EH is prevalent in Ethiopia and warrants the initiation of a control strategy.

Electrophoresis karyotype and chromosome-length polymorphism ofHistoplasma capsulatumclinical isolates from Latin America

Intact chromosomes of 19 clinical isolates of Histoplasma capsulatum recently obtained in Argentina, Mexico and Guatemala and the laboratory reference strain G186B from Panama were analyzed using pulsed-field gel electrophoresis. Chromosomal banding patterns of the human isolates revealed 5-7 bands, ranging from 1.3 to 10 Mbp in size. Strain G186B showed five bands of approximately 1.1, 2.8, 3.3, 5.4 and 9.7 Mbp. Thirteen different electrokaryotypes were identified, indicating that the genome of H. capsulatum varies widely in nature, as observed previously in laboratory strains. No definite association was found between electrokaryotype and geographical or clinical source.

Histoplasmosis: presentaciones clínicas y pruebas de laboratorio en un centro brasileño

Histoplasmosis, caused by the dimorphic fungus Histoplasma capsulatum, is endemic in many regions of the Americas, Asia and Africa. It has a wide spectrum of clinical manifestations, from asymptomatic infection to severe disseminated disease. A retrospective study was carried out to describe the clinical forms and assess the clinical significance of the laboratory diagnostic tests of patients with histoplasmosis during the period of July 1987 to December 2003 at Instituto de Pesquisa Clínica Evandro Chagas/ FIOCRUZ, RJ, Brazil. Seventy-four patients were included. Forty-nine percent of the cases (n = 36) occurred in HIV positive patients who presented with disseminated disease. The remaining 38 cases were classified in different clinical forms. Histoplasma capsulatum was isolated from 69.5% of the clinical specimens sent to culture. Immunodiffusion and immunoblot were positive in 72.6% and 100% of the performed tests, respectively. Histopathologic findings suggestive of H. capsulatum were found in 63.2% of the performed exams. Serology had a lower proportion of positivity amongst AIDS patients, when compared with HIV negative patients (X2 = 6.65; p lower than 0.008). Statistical differences between AIDS and non-AIDS patients were not observed with culture and histopathology. The specific role of each test varies according to the clinical form. Physicians need to know the value and limitations of the available diagnostic tests, but before that, they have to think about histoplasmosis and consider this clinical entity in their differential diagnosis.

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.

ELISA for early diagnosis of histoplasmosis

An ELISA was developed and evaluated as a method for detecting antibodies against glycosylated and deglycosylated histoplasmin (HMIN). Sera from patients with histoplasmosis, paracoccidioidomycosis, sporotrichosis, coccidioidomycosis, aspergillosis, cryptococcosis and healthy donors were tested by ELISA against purified, deglycosylated histoplasmin (ptHMIN) and compared with purified, native (i.e. glycosylated) histoplasmin (pHMIN). Although cross-reactivity was not abolished when ptHMIN was used in the test, it was reduced (pHMIN ELISA 93 % versus ptHMIN ELISA 96 %). However, there were statistically significant differences between the sensitivities of these two methods for the detection of antibodies (pHMIN ELISA 57 % versus ptHMIN ELISA 92 %; P < 0.001) and between the efficiency of the methods (pHMIN ELISA 83 % versus ptHMIN ELISA 95 %; P < 0.001). These parameters compare better than previously published data relating to the use of treated HMIN in diagnostic ELISAs. Some of the reactivities of serum samples were compared by immunoblotting using deglycosylated HMIN and by immunodiffusion using the crude antigen. The results demonstrated that cross-reactions with heterologous sera in both ELISAs could also be observed in immunoblotting and arose from shared protein epitopes. These data suggest that ELISA using deglycosylated HMIN is a very sensitive diagnostic method and, by using commercially available antigen, it can be easily standardized and performed faster than previous Western blot-based tests using the same antigen. It provides a useful adjunct to existing methods of diagnosis that could be applied even in situations where laboratory facilities were relatively limited.

Phenotyping and genotyping of Sporothrix schenckii isolates according to geographic origin and clinical form of Sporotrichosis

Sporothrix schenckii isolates of fixed and lymphocutaneous clinical forms from Mexico (MX), Guatemala (GT), and Colombia (CO) as well as environmental isolates from MX were studied by analyzing their phenotypic characteristics (conidial length, thermotolerance by percent growth inhibition [GI] at 35 and 37 degrees C, median lethal dose [LD(50)]) and genotypic characteristics (by random amplified polymorphic DNA [RAPD] analysis-PCR). A significant difference (P < 0.01) in the mean conidial length of S. schenckii clinical isolates from CO ( = 4.03 +/- 1.04 microm) compared with those of clinical isolates from MX ( = 2.06 +/- 0.53 microm) and GT ( = 2.68 +/- 0.83 microm) was observed. The lowest thermotolerance, as determined by measurement of percent GI, was exhibited by isolates from CO at 35 degrees C ( = 50.1% +/- 15.9%) and 37 degrees C ( = 72.7% +/- 10.9%). In general, the highest virulence, as determined by measurement of the LD(50) for mice, was observed for the MX environmental isolates. RAPD analysis-PCR with 10-mer primers OPBG-01, OPBG-14, and OPBG-19 generated 52 reproducible bands. The 44 Sporothrix isolates fell into four major groups by hierarchical cluster analysis. The first group (group I), formed by 25 (of 27) isolates from MX, had two subgroups: subgroup Ia with 10 environmental isolates and subgroup Ib with 14 clinical isolates. The second group (group II) had two subgroups: subgroup IIa, formed by isolates from CO, and subgroup IIb, formed by isolates from GT. Groups III and IV each had only one clinical isolate from MX. A principal-component analysis of the same data yielded three distinct groups, depending on the geographical origins of the isolates, including the isolates in groups III and IV from MX, which were grouped with the isolates from MX by principal-component analysis. This study revealed that isolates from CO had low thermotolerances at 35 and 37 degrees C and could be associated with superficial skin lesions in patients with fixed clinical forms of sporotrichosis, the most frequent form of the disease in CO. Distinct patterns dependent on geographical origins were also revealed by RAPD analysis-PCR, but these had no relation to the clinical form of the disease.

Genetic diversity of Histoplasma capsulatum strains isolated from soil, animals, and clinical specimens in Rio de Janeiro State, Brazil, by a PCR-based random amplified polymorphic DNA assay

Little is known about the genetic strain diversity and geographical range of Histoplasma capsulatum isolated in Rio de Janeiro State, Brazil. We characterized 13 environmental, 7 animal, and 28 clinical H. capsulatum isolates by using a PCR-based random amplified polymorphic DNA (RAPD) assay. DNA fingerprinting of these soil, animal, and clinical specimens was performed with four primers (1253, 1281, D-9355, and D-10513) and generated amplicons with considerable polymorphism. Although all of the isolates exhibited more than 80% genetic relatedness, they could be clustered into four to six genotypes for each primer. The RAPD profiles of H. capsulatum isolated from Rio de Janeiro State could be distinguished from those of the U.S. strains included in this study (Downs, G222B, G-186B, and FLS1) by showing less than 70% similarity to each primer. The genetic polymorphisms between H. capsulatum strains isolated from animals and soil obtained in the same geographic areas were 100% similar, suggesting that an environmental microniche could be acting as a source of infection for animals and the local human population.

Atypical disseminated cutaneous histoplasmosis in an immunocompetent child, caused by an "aberrant" variant of histoplasma capsulatum var. capsulatum

A case of atypical disseminated cutaneous histoplasmosis in a five-year old, otherwise healthy child, native and resident in Sao Paulo metropolitan area is reported. Cutaneous lesions were clinically atypical. Histologic examination disclosed a granulomatous reaction but no fungal structures could be demonstrated by specific staining nor by immunohistochemical reaction. The fungus was isolated from biopsy material on two different occasions, confirming diagnosis of an unusual fungal infection. The fungus, originally thought to be a Sepedonium sp. due to the large sized, hyaline or brownish colored tuberculated macroconidia and to lack of dimorphism (yeast form at 37 degrees C) produce H and M antigens, visualized by the immunodiffusion with rabbit anti-Histoplasma capsulatum hyperimmune serum. Patient's serum sample was non reactive with H. capsulatum antigen by immunodiffusion, counterimmunoelectrophoresis and complement fixation tests, and immunoenzymatic assay failed to detect the specific circulating antigen. This serum was tested negative by double immunodiffusion when antigen obtained from one of the isolated samples was used. Both cultures were sent to Dr. Leo Kaufman, Ph.D. (Mycoses Immunodiagnostic Laboratory, CDC-Atlanta/USA), who identified them as H. capsulatum by the exoantigen and gen-probe tests. Both clinic and mycologic characteristics of the present case were atypical, suggesting the fungus isolated is an "aberrant variant" of H. capsulatum var. capsulatum, as described by SUTTON et al. in 1997. Treatment with itraconazole 100 mg/day led to cure within 90 days

Relatedness analyses of Histoplasma capsulatum isolates from Mexican patients with AIDS-associated histoplasmosis by using histoplasmin electrophoretic profiles and randomly amplified polymorphic DNA patterns

The present paper analyzes the histoplasmin electrophoretic profiles and the randomly amplified polymorphic DNA (RAPD) patterns of the fungus Histoplasma capsulatum isolated from Mexican patients with AIDS-associated histoplasmosis. Clinical isolates from Guatemala, Colombia, and Panama, as well as H. capsulatum isolates from different sources in nature, were also processed. All histoplasmin samples shared four antigenic fractions of 200, 49, 10.5, and 8.5 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). According to their percentage of relatedness, based on SDS-PAGE histoplasmin electrophoretic image analysis, H. capsulatum isolates were divided in two groups: group A contained all AIDS-associated isolates studied and two human reference strains from Mexican histoplasmosis patients without AIDS; group B included bat guano, infected bat, and cock excreta isolates from the State of Guerrero, Mexico, plus three human histoplasmosis strains from Guatemala, Panama, and Colombia. Polymorphic DNA patterns evaluated by RAPD-PCR showed three major bands of 4.4, 3.2, and 2.3 kb in most H. capsulatum isolates studied. Four groups were related by DNA polymorphisms: group I was formed by most of the AIDS-associated H. capsulatum isolates studied, one human histoplasmosis strain from Colombia, two human reference strains from Mexican patients without AIDS, and one human histoplasmosis strain from Guatemala. Group II consisted of only a single strain from Panama. Group III included three strains: one from a Mexican patient with AIDS and two isolated from nature in Guerrero (cock excreta and bat guano). The last, group IV, consisted of only one strain isolated from an infected bat, captured in Guerrero. A tight relationship between phenotypic and genotypic characterization was observed, and both analyses could be useful tools for typing H. capsulatum from different sources and geographic origins.

Phylogenetic relationships of varieties and geographical groups of the human pathogenic fungus Histoplasma capsulatum Darling

The phylogeny of 46 geographically diverse Histoplasma capsulatum isolates representing the three varieties capsulatum, duboisii, and farciminosum was evaluated using partial DNA sequences of four protein coding genes. Parsimony and distance analysis of the separate genes were generally congruent and analysis of the combined data identified six clades: (i) class 1 North American H. capsulatum var. capsulatum, (ii) class 2 North American H. capsulatum var. capsulatum, (iii) Central American H. capsulatum var. capsulatum, (iv) South American H. capsulatum var. capsulatum group A, (v) South American H. capsulatum var. capsulatum group B, and (vi) H. capsulatum var. duboisii. Although the clades were generally well supported, the relationships among them were not resolved and the nearest outgroups (Blastomyces and Paracoccidioides) were too distant to unequivocally root the H. capsulatum tree. H. capsulatum var. farciminosum was found within the South American H. capsulatum var. capsulatum group A clade. With the exception of the South American H. capsulatum var. capsulatum group A clade, genetic distances within clades were an order of magnitude lower than those between clades, and each clade was supported by a number of shared derived nucleotide substitutions, leading to the conclusion that each clade was genetically isolated from the others. Under a phylogenetic species concept based on possession of multiple shared derived characters, as well as concordance of four gene genealogies, H. capsulatum could be considered to harbor six species instead of three varieties.

Aberrant Histoplasma capsulatum. Confirmation of identity by a chemiluminescence-labeled DNA probe

A cottony, light tan, filamentous fungus with pear-shaped microconidia and lacking tuberculated macroconidia was isolated from a bronchial lavage specimen. Subculture on several media at 37 degrees C failed to convert the fungus to a yeast form after several weeks; attempts at in vivo conversion in mice were also unsuccessful. Sera obtained several months apart showed M bands with Histoplasma capsulatum (HC) antigen by immunodiffusion and an increase in complement fixation titers with mycelial and yeast phase antigens of HC. Parallel identity was obtained on two occasions with exoantigen culture confirmation reagents for HC from Immuno-Mycologics as well as one of identity with Nolan reagents. Extracts from four Chrysosporium spp. strains had no identity reactions with HC with either kit. The fungus was identified as HC by the Accuprobe Histoplasma chemiluminescence-labeled DNA probe directed at ribosomal RNA, whereas all four Chrysosporium spp. isolates tested negative. DNA probes are a fast and accurate method to confirm the identity of aberrant fungal isolates.

Comparative evaluation of a chemiluminescent DNA probe and an exoantigen test for rapid identification of Histoplasma capsulatum

A chemiluminescent DNA probe (Accuprobe) assay developed by Gen Probe, Inc., for the rapid identification of Histoplasma capsulatum was evaluated and compared with the exoantigen test by using 162 coded cultures including Histoplasma capsulatum var. capsulatum, Histoplasma capsulatum var. duboisii, Histoplasma capsulatum var. farciminosum, Blastomyces dermatitidis, Coccidioides immitis, Paracoccidioides brasiliensis, and morphologically related saprobic fungi. Each test uses a chemiluminescent, acridinium ester-labeled, single-stranded DNA probe that is complementary to the rRNA of the target organism. Lysates of the test cultures were prepared by sonication with glass beads and heat treated. After the rRNA was released from the target organism, the labeled DNA probe combined with the target H. capsulatum rRNA to form a stable DNA-RNA hybrid. A hybridization protection assay was used, and the chemiluminescence of hybrids was measured initially with a Leader 1 luminometer as relative light units and later during the investigation with a probe assay luminometer as probe light units. Of the 162 coded mycelial cultures tested by the Accuprobe assay, 105 were identified as H. capsulatum. The test could be performed with an inoculum of a few square millimeters (1 to 2 mm2) of growth. In the primary evaluation, the Accuprobe identified 103 of the 105 cultures as H. capsulatum within 2 h. The remaining two cultures, contaminated with bacteria, had to be purified before the Accuprobe assay identified them correctly as H. capsulatum. Since each coded culture was concurrently tested for H. capsulatum, B. dermatitidis, and C. immitis exoantigens, the identification of all three dimorphic pathogens was provided simultaneously. Of the 162 coded cultures tested, 105 were identified by the exoantigen test as H. capsulatum, 12 were identified as B. dermatitidis, 13 were identified as C. immitis, and 32 were negative for H. capsulatum, B. dermatitidis, and C. immitis. The bacterial contamination in two isolates did not interfere with the exoantigen testing. The exoantigen test required 7- to 10-day-old colonies and required 48 to 72 h of incubation before definitive identification was obtained.

Histoplasma capsulatum infection associated with continuous ambulatory peritoneal dialysis

Fungal infection has become increasingly more important in patients undergoing continuous ambulatory peritoneal dialysis. We report here a case of Histoplasma capsulatum infection in such a Hong Kong Chinese patient who presented with fever and peritonitis. Histoplasma capsulatum was isolated from the dialysis fluid and histoplasma antibody was detected in the serum. The patient responded to the combined treatment of fluconazole, 5-flurocytosine and amphotericin B. This is the first reported case of histoplasmosis in Hong Kong.

[Obtention of Histoplasma capsulatum exoantigens in neopeptone, glucose, thiamine and asparagine (NGTA) media]

The purpose of this work is obtaining exocellular antigens H and M from 4 H. capsulatum strains using NGTA medium (neopeptone, glucose, thiamine and asparagine) for periods of 1, 2 and 3 months, at 36 degrees C and continuously shaken. The exocellular antigens were evaluated by double immunodiffusion test against H. capsulatum rabbit antiserum, 7 histoplasmosis sera, 4 paracoccidioidomycosis sera and a reference antigen and antibody furnished by C.D.C. (Atlanta--USA). Except for the exocellular antigen from strain B.679 with 1 month of culture, all exocellular antigens obtained from the strains B.679, 58 and O187 showed the H and M bands. The A.811 strain demonstrated only the fraction H. All the exocellular antigens reacted positively with sera from histoplasmosis patients, except those obtained from strains 58 and B.679 with 1 month of culture. With regard to paracoccidioidomycosis patients sera, the exocellular antigens from strains 58 and O187 did not cross-react with them.

DNA probe for the identification of Histoplasma capsulatum

A 1.85-kilobase HindIII nuclear DNA probe from Histoplasma capsulatum G217B detected polymorphic restriction fragments within whole-cell DNA from different clinical isolates of H. capsulatum, consistent with the previous system of classification. The probe failed to hybridize to DNA from Blastomyces dermatitidis, Candida spp., Saccharomyces cerevisiae, Sepedonium chrysospermum, and Chrysosporium keratinophilum under low-stringency conditions and therefore may have value as a diagnostic reagent to identify H. capsulatum.

Immunological separation of Entomophthorales genera

Exoantigens from Erynia neoaphidis, Conidiobolus major, C. thromboides, C. obscurus, Zoophthora radicans, and Basidiobolus ranarum were obtained from culture filtrates of fungal material grown in a yeast extract, peptone dialysate, dextrose medium and were tested against specific hyperimmune antisera prepared from E. neoaphidis, C. major, C. thromboides, and B. ranarum by the immunodiffusion technique. Specific precipitins were observed for E. neoaphidis and B. ranarum, while cross-reactions were detected among C. major, C. thromboides, and C. obscurus. The results suggest that genera of Entomophthorales can be easily separated by this simple immunological procedure.

Use of mitochondrial and ribosomal DNA polymorphisms to classify clinical and soil isolates of Histoplasma capsulatum

We have developed an improved scheme for the classification of environmental and clinical isolates of Histoplasma capsulatum that is based on analysis of mitochondrial DNA (mtDNA) and ribosomal DNA (rDNA). Strains were initially divided into mtDNA groups according to restriction digests of whole-cell DNA and Southern hybridization with cloned mtDNA probes. Strains within a mtDNA class could be further grouped by polymorphisms in rDNA. The majority of soil and clinical isolates from the United States had identical mtDNA patterns; however, rDNA polymorphisms were common in both types of isolates. The combination of mtDNA and rDNA typing described in this report will be useful in resolving questions concerning the epidemiology of H. capsulatum infections.

Electrophoretic and immunoblot analyses of Rhizopus arrhizus antigens

Four antigen preparations from Rhizopus arrhizus were made and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and column chromatography. Electrophoretic analyses of these antigens indicated that there are 18 to 28 component bands with a molecular mass range of approximately 10,500 to 83,000 daltons. Seven of these bands appear to be components common to three antigen preparations. Several of the bands identified by SDS-PAGE were composed of glycoproteins or carbohydrates as determined by their affinity for concanavalin A. Western blots, using sera from five patients with mucormycosis, consistently identified five different determinants in the R. arrhizus antigens separated by SDS-PAGE. This suggests that several of the Rhizopus antigens are present during mucormycosis. Four of the antigenic determinants recognized by patient sera reacted with the concanavalin A-peroxidase stain, indicating that they are composed of glycoproteins or carbohydrate. Enzyme-linked immunosorbent assays of sera from five patients with mucormycosis and with rabbit antisera resulted in antibody titers ranging from 1:64 to 1:32,000 for the R. arrhizus antigens.

Circulating antibodies and antigenic cross-reactivity in Hendersonula toruloidea and Scytalidium hyalinum infections

Twelve (34%) of thirty-five patients with an active infection on the palms or soles caused by Hendersonula toruloidea or Scytalidium hyalinum were found to have circulating antibodies to these organisms by counter immunoelectrophoresis or immunodiffusion, compared with 9% of uninfected controls. In every instance there was cross-reactivity between the positive patients' sera and the heterologous non-dermatophyte antigen. Using crossed and intermediate gel immunoelectrophoresis it was found that cytoplasmic extracts of H. toruloidea and S. hyalinum showed 34 and 41 precipitin peaks respectively, most of which were shared by both organisms. No cross-reactions were observed between the non-dermatophyte cytoplasmic extracts and hyperimmune animal antisera raised to Trichophyton rubrum, Trichophyton interdigitale, Aspergillus fumigatus or Candida albicans. Exoantigens prepared from the two non-dermatophytes showed similar cross-reactivity between the two species. It appears that H. toruloidea and S. hyalinum are very similar in antigenic structure, a finding which lends support to the view that they may be closely related. They are also antigenically distinct from other pathogenic fungi which commonly infect skin, a fact which may be useful in their cultural identification as well as their recognition in tissue specimens.

Comparative antigenic studies of species of Basidiobolus and other medically important fungi

An immunodiffusion technique was used to evaluate the antigenic relationship of various pathogenic and saprobic Basidiobolus spp., Conidiobolus spp., isolates of the order Mucorales, and several other medically important nonzygomycetous fungi. The antiserum to Basidiobolus haptosporus shared two lines of identity, designated inner (N) and outer (Y), when tested against exoantigens of known strains of B. haptosporus and Basidiobolus ranarum as well as exoantigens of a human Nigerian isolate and several wild isolates tentatively identified in B. ranarum. Both bands were heat stable at 56 degrees C for 30 min. Exoantigens of strains of Basidiobolus meristosporus, Basidiobolus microsporus, Conidiobolus incongruus, Conidiobolus coronatus, and other wild isolates of Basidiobolus spp. tested formed only the N immunoprecipitin band. Exoantigens of 10 isolates from other taxa did not produce any cross-reactive precipitin line. B. meristosporus antiserum that was tested against exoantigens of Basidiobolus spp. and of Conidiobolus spp. developed only an N band without a Y band. These data suggest that B. haptosporus and B. ranarum are antigenically similar to each other and distinct from B. meristosporus. Basidiobolus spp. and Conidiobolus spp. share a common N immunoprecipitin band, which implies a taxonomic relationship between these two genera. The absence of lines of identity between Basidiobolus spp. and other fungi tested suggests that, antigenically, Basidiobolus is a distinct genus.

Classification of Histoplasma capsulatum isolates by restriction fragment polymorphisms

Twenty isolates of the dimorphic, pathogenic fungus Histoplasma capsulatum were divided into three classes based on comparisons of restriction enzyme digests of their mitochondrial DNA and rDNA. The majority of isolates, including most North American strains and the African H. capsulatum var. duboisii variants, belong to class 2. Isolates from Central America and South America make up class 3. The attenuated Downs strain is the only member of class 1.

Reliability of exoantigens for differentiating Blastomyces dermatitidis and Histoplasma capsulatum from Chrysosporium and geomyces species

A recent study suggested that Chrysosporium species have the same diagnostic antigens as Histoplasma capsulatum and Blastomyces dermatitidis and, thus, compromise the antigenic identification of these pathogens. In light of these findings, studies were undertaken to determine the reliability of the exoantigen tests for identifying B. dermatitidis and H. capsulatum organisms from cultures. Sixty-three slant or shake culture extracts, or both, were derived from C. asperatum, C. keratinophilum, C. parvum, C. pruinosum, C. parvum var. crescens, Geomyces (Chrysosporium) pannorus, B. dermatitidis, and H. capsulatum. These were analyzed by use of a commercial exoantigen kit and exoantigen test reagents obtained from a commercial source. The results of these analyses were compared with those obtained with Centers for Disease Control reagents. Many of the extracts derived from nonpathogenic fungi produced nonspecific precipitin bands when reacted with the kit and reference antisera, particularly the B. dermatitidis antisera. None, however, produced antigens identical to the specific B. dermatitidis A and H. capsulatum H and M antigens. Our findings indicate that the properly controlled immunoidentification procedure is 100% specific for B. dermatitidis and H. capsulatum, and that cross-reacting antigens derived from morphologically similar saparophytic fungi do not pose identification problems.

Exoantigen test for Cladosporium bantianum, Fonsecaea pedrosoi, and Phialophora verrucosa

Exoantigens from 10-day-old cultures of 100 isolates of pathogenic and saprophytic dematiaceous fungi were analyzed by the exoantigen test. Antisera to Cladosporium bantianum ATCC 10958, Fonsecaea pedrosoi CDC AMO-B06, and Phialophora verrucosa CDC AMO-C12 were prepared in New Zealand rabbits immunized with soluble antigens from 1-month-old cultures. Absorbed and nonabsorbed antisera and exoantigens from the same organisms were used as reference reagents. Serologic reactions were analyzed in terms of the presence or absence of lines of identity or nonidentity. These reactions allowed presumptive differentiation of C. bantianum, F. pedrosoi, and Phialophora verrucosa from other dematiaceous fungi, including Cladosporium spp. (28 isolates), Exophiala spp. (18 isolates), Fonsecaea spp. (17 isolates). Lecythophora hoffmannii (4 isolates), Phaeoannellomyces werneckii (3 isolates), Phialophora spp. (17 isolates), Wangiella dermatitidis (9 isolates), and Rhinocladiella spp. (4 isolates).

Endemic canine and feline histoplasmosis in El Paso, Texas

Seventeen cases of histoplasmosis involving 2 dogs and 15 cats have occurred in the Upper Rio Grande Valley of El Paso since 1978. The diagnosis, based on clinical signs and radiographic findings, was confirmed by one or more of the following laboratory procedures: demonstration of intracellular Histoplasma capsulatum yeast cells in tissue, positive serology, or isolation of H. capsulatum from various organs of necropsied animals. H. capsulatum was isolated also from a bat cave and soil in the vicinity of some of the houses where the affected animals had resided. Skin-tests of 97 persons for histoplasmosis indicated a 14% positive prevalance in this locale.

Exoantigen test for differentiation of Exophiala jeanselmei and Wangiella dermatitidis isolates from other dematiaceous fungi

Concentrated (25X) exoantigens of 105 isolates of pathogenic and saprophytic dematiaceous fungi and 3 isolates of Sporothrix schenckii were analyzed by the microimmunodiffusion method. The reagents used were nonadsorbed and adsorbed sera produced in New Zealand rabbits. One set of rabbits was immunized with soluble antigens of a 1-month-old culture of Exophiala jeanselmei (ATCC 34123), and the other set was immunized with soluble antigens from a culture of Wangiella dermatitidis (ATCC 28869). The reference antigens were 25X-concentrated exoantigens of the above cultures. This exoantigen test permitted the differentiation of E. jeanselmei and W. dermatitidis from one another as well as from other Exophiala species, Fonsecaea species, Phialophora species, Cladosporium species, Rhinocladiella species, and Sporothrix schenckii by presence or absence of lines of identity or of partial identity, or lines of nonidentity. Using adsorbed serum eliminated the problems with cross-reactivity seen with nonadsorbed serum. Thus, with an adsorbed serum as the reagent, it was possible to presumptively differentiate E. jeanselmei and W. dermatitidis from one another and from other dematiaceous fungi.