Molecular typing of Histoplasma capsulatum isolated from infected bats, captured in Mexico

Tracing histoplasmosis genomic epidemiology and species occurrence across the USA

ABSTRACTHistoplasmosis is an endemic mycosis in North America frequently reported along the Ohio and Mississippi River Valleys, although autochthonous cases occur in non-endemic areas. In the United States, the disease is provoked by two genetically distinct clades of Histoplasma capsulatum sensu lato, Histoplasma mississippiense (Nam1) and H. ohiense (Nam2). To bridge the molecular epidemiological gap, we genotyped 93 Histoplasma isolates (62 novel genomes) including clinical, environmental, and veterinarian samples from a broader geographical range by whole-genome sequencing, followed by evolutionary and species niche modelling analyses. We show that histoplasmosis is caused by two major lineages, H. ohiense and H. mississippiense; with sporadic cases caused by H. suramericanum in California and Texas. While H. ohiense is prevalent in eastern states, H. mississipiense was found to be prevalent in the central and western portions of the United States, but also geographically overlapping in some areas suggesting that these species might co-occur. Species Niche Modelling revealed that H. ohiense thrives in places with warmer and drier conditions, while H. mississippiense is endemic to areas with cooler temperatures and more precipitation. In addition, we predicted multiple areas of secondary contact zones where the two species co-occur, potentially facilitating gene exchange and hybridization. This study provides the most comprehensive understanding of the genomic epidemiology of histoplasmosis in the USA and lays a blueprint for the study of invasive fungal diseases.

Epidemiological, clinical, diagnostic, and therapeutic features of histoplasmosis: A systematic review

Histoplasmosis is a mycosis due to a dimorphic fungus Histoplasma capsulatum. This study aimed at providing an overview of histoplasmosis epidemiological, clinical, diagnostic, and therapeutic aspects from the last 30 years. This review was carried out using a systematic literature search on histoplasmosis from 1992 to 2021. We describe the clinical features, diagnostic methods and treatment. Empirical searches were conducted via the databases PubMed, Google Scholar and Science Direct. Between 1992 and 2021, 190 manuscripts were published and reported 212 cases of histoplasmosis. These publications included 115 and 97 cases of American and African histoplasmosis respectively. The number of publications increased over the last ten years with a maximum in 2020 (12.34 % of the cases reported). The disseminated forms of histoplasmosis were the most frequently reported cases as compared to the localized forms. This was the case with the American histoplasmosis (75.65 %) as well as with the African histoplasmosis (55.67 %). Itraconazole (31.17 %) and Amphotericin B (26.62 %) were the most used drugs in the management of these cases. American histoplasmosis is distributed worldwide whereas African histoplasmosis is mainly present in intertropical Africa. There is a critical need for setting up a global surveillance system, towards a better understanding of the disease.

Molecular detection of Histoplasma capsulatum in organ samples from bats randomly captured in urban areas of Araraquara, São Paulo state, Brazil

The mycosis histoplasmosis is also considered a zoonosis that affects humans and other mammalian species worldwide. Among the wild mammals predisposed to be infected with the etiologic agent of histoplasmosis, bats are relevant because they are reservoir of Histoplasma species, and they play a fundamental role in maintaining and spreading fungal propagules in the environments since the infective mycelial phase of Histoplasma grows in their accumulated guano. In this study, we detected the fungal presence in organ samples of bats randomly captured in urban areas of Araraquara City, São Paulo, Brazil. Fungal detection was performed using a nested polymerase chain reaction to amplify a molecular marker (Hcp100) unique to H. capsulatum, which revealed the pathogen presence in organ samples from 15 out of 37 captured bats, indicating 40.5% of infection. Out of 22 Hcp100-amplicons generated, 41% corresponded to lung and trachea samples and 59% to spleen, liver, and kidney samples. Data from these last three organs suggest that bats develop disseminated infections. Considering that infected bats create environments with a high risk of infection, it is important to register the percentage of infected bats living in urban areas to avoid risks of infection to humans, domestic animals, and wildlife.

A Phylogeographic Description of Histoplasma capsulatum in the United States

Histoplasmosis is one of the most under-diagnosed and under-reported endemic mycoses in the United States. Histoplasma capsulatum is the causative agent of this disease. To date, molecular epidemiologic studies detailing the phylogeographic structure of H. capsulatum in the United States have been limited. We conducted genomic sequencing using isolates from histoplasmosis cases reported in the United States. We identified North American Clade 2 (NAm2) as the most prevalent clade in the country. Despite high intra-clade diversity, isolates from Minnesota and Michigan cases were predominately clustered by state. Future work incorporating environmental sampling and veterinary surveillance may further elucidate the molecular epidemiology of H. capsulatum in the United States and how genomic sequencing can be applied to the surveillance and outbreak investigation of histoplasmosis.

Histoplasma capsulatum Isolated from Tadarida brasiliensis Bats Captured in Mexico Form a Sister Group to North American Class 2 Clade

Histoplasma capsulatum is a dimorphic fungus associated with respiratory and systemic infections in mammalian hosts that have inhaled infective mycelial propagules. A phylogenetic reconstruction of this pathogen, using partial sequences of arf, H-anti, ole1, and tub1 protein-coding genes, proposed that H. capsulatum has at least 11 phylogenetic species, highlighting a clade (BAC1) comprising three H. capsulatum isolates from infected bats captured in Mexico. Here, relationships for each individual locus and the concatenated coding regions of these genes were inferred using parsimony, maximum likelihood, and Bayesian inference methods. Coalescent-based analyses, a concatenated sequence-types (CSTs) network, and nucleotide diversities were also evaluated. The results suggest that six H. capsulatum isolates from the migratory bat Tadarida brasiliensis together with one isolate from a Mormoops megalophylla bat support a NAm 3 clade, replacing the formerly reported BAC1 clade. In addition, three H. capsulatum isolates from T. brasiliensis were classified as lineages. The concatenated sequence analyses and the CSTs network validate these findings, suggesting that NAm 3 is related to the North American class 2 clade and that both clades could share a recent common ancestor. Our results provide original information on the geographic distribution, genetic diversity, and host specificity of H. capsulatum.

Analyses of the genetic diversity and population structures of Histoplasma capsulatum clinical isolates from Mexico, Guatemala, Colombia and Argentina, using a randomly amplified polymorphic DNA-PCR assay

We studied the genetic diversity and the population structure of human isolates of Histoplasma capsulatum, the causative agent of histoplasmosis, using a randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) assay to identify associations with the geographic distribution of isolates from Mexico, Guatemala, Colombia and Argentina. The RAPD-PCR pattern analyses revealed the genetic diversity by estimating the percentage of polymorphic loci, effective number of alleles, Shannon's index and heterozygosity. Population structure was identified by the index of association (I_A) test. Thirty-seven isolates were studied and clustered into three groups by the unweighted pair-group method with arithmetic mean (UPGMA). Group I contained five subgroups based on geographic origin. The consistency of the UPGMA dendrogram was estimated by the cophenetic correlation coefficient (CCCr = 0.94, P = 0.001). Isolates from Mexico and Colombia presented higher genetic diversity than isolates from Argentina. Isolates from Guatemala grouped together with the reference strains from the United States of America and Panama. The I_A values suggest the presence of a clonal population structure in the Argentinian H. capsulatum isolates and also validate the presence of recombining populations in the Colombian and Mexican isolates. These data contribute to the knowledge on the molecular epidemiology of histoplasmosis in Latin America.

Dimorphism and Dissemination of Histoplasma capsulatum in the Upper Respiratory Tract after Intranasal Infection of Bats and Mice with Mycelial Propagules

This article describes, for the first time, the role of the nasal mucosa (NM) as the initial site for the Histoplasma capsulatum mycelial-to-yeast transition. The results highlight that yeasts may arrive to the cervical lymph nodes (CLN) via phagocytes. Bats and mice were intranasally infected with H. capsulatum mycelial propagules and they were killed 10, 20, and 40 minutes and 1, 2, and 3 hours after infection. The NM and the CLN were monitored for fungal presence. Yeasts compatible with H. capsulatum were detected within the NM and the CLN dendritic cells (DCs) 2–3 hours postinfection, using immunohistochemistry. Histoplasma capsulatum was re-isolated by culturing at 28°C from the CLN of both mammalian hosts 2–3 hours postinfection. Reverse transcription-polymerase chain reaction assays were designed to identify fungal dimorphism, using mycelial-specific (MS8) and yeast-specific (YPS3) gene expression. This strategy supported fast fungal dimorphism in vivo, which began in the NM 1 hour postinfection (a time point when MS8 and YPS3 genes were expressed) and it was completed at 3 hours (a time point when only the YPS3 transcripts were detected) in both bats and mice. The presence of intracellular yeasts in the nasal-associated lymphoid tissue (NALT), in the NM nonassociated with the NALT, and within the interdigitating DCs of the CLN suggests early fungal dissemination via the lymph vessels.

Molecular detection of Histoplasma capsulatum in insectivorous and frugivorous bats in Southeastern Brazil

Bats are considered to play a significant role in the epidemiology of histoplasmosis, worldwide. We investigated the occurrence of H. capsulatum in lung samples from 89 bats, from urban areas in Southeastern Brazil, using nested PCR based on ribosomal DNA. Fungal DNA was detected in 31/89 samples (34.8%), of which 13/31 were Molossids (41.9%), 4/31 Eumops spp. (12.9%), 2/31 Artibeus lituratus (6.5%), and 12/31 others (38.7%). This is the first report of natural infection by H. capsulatum in A. lituratus in Southeastern Brazil, which reinforces the importance of these synanthropic animals in the epidemiology of histoplasmosis in urban areas.

The use of genetic markers in the molecular epidemiology of histoplasmosis: a systematic review

Histoplasmosis is a systemic mycosis caused by Histoplasma capsulatum, a dimorphic fungal pathogen that can infect both humans and animals. This disease has worldwide distribution and affects mainly immunocompromised individuals. In the environment, H. capsulatum grows as mold but undergoes a morphologic transition to the yeast morphotype under special conditions. Molecular techniques are important tools to conduct epidemiologic investigations for fungal detection, identification of infection sources, and determination of different fungal genotypes associated to a particular disease symptom. In this study, we performed a systematic review in the PubMed database to improve the understanding about the molecular epidemiology of histoplasmosis. This search was restricted to English and Spanish articles. We included a combination of specific keywords: molecular typing [OR] genetic diversity [OR] polymorphism [AND] H. capsulatum; molecular epidemiology [AND] histoplasmosis; and molecular epidemiology [AND] Histoplasma. In addition, we used the specific terms: histoplasmosis [AND] outbreaks. Non-English or non-Spanish articles, dead links, and duplicate results were excluded from the review. The results reached show that the main methods used for molecular typing of H. capsulatum were: restriction fragment length polymorphism, random amplified polymorphic DNA, microsatellites polymorphism, sequencing of internal transcribed spacers region, and multilocus sequence typing. Different genetic profiles were identified among H. capsulatum isolates, which can be grouped according to their source, geographical origin, and clinical manifestations.

Morphological and comparative genomic analyses of pathogenic and non-pathogenic Fusarium solani isolated from Dalbergia sissoo

Sissoo or shisham (Dalbergia sissoo Roxb.) is one of the finest wood of South Asia. Fusarium solani is a causal organism of sissoo wilt, decline, or dieback. It is also a potential causal organism associated with other valuable tree species. Thirty-eight Fusarium isolates including 24 F. solani and 14 Fusarium sp., were obtained in 2005 from different geographical locations in India. All 38 (18 pathogenic and 20 non-pathogenic) isolates were characterized for genomic analysis, growth behaviour, pigmentation and sensitivity to carbendazim. Based on growth pattern, growth rate, pigmentation and sensitivity to carbendazim, all 38 isolates showed a wide range of variability, but no correlation with pathogenicity or geographical distribution. Three techniques were used for comparative genomic analysis: random amplified polymorphic DNA (RAPD); inter simple sequence repeats (ISSR); and simple sequence repeats (SSR). A total of 90 primers targeting different genome regions resulted a total of 1159 loci with an average of 12.88 loci per primer. These primers showed high genomic variability among the isolates. The maximum loci (14.64) per primer were obtained with RAPD. The total variation of the first five principal components for RAPD, ISSR, SSR and combined analysis were estimated as 47.42, 48.21, 46.30 and 46.78 %, respectively. Among the molecular markers, highest Pearson correlation value (r = 0.957) was recorded with combination of RAPD and SSR followed by RAPD and ISSR (r = 0.952), and SSR and ISSR (r = 0.942). The combination of these markers would be similarly effective as single marker system i.e. RAPD, ISSR and SSR. Based on polymorphic information content (PIC = 0.619) and highest coefficient (r = 0.995), RAPD was found to be the most efficient marker system compared to ISSR and SSR. This study will assist in understanding the population biology of wilt causing phytopathogen, F. solani, and in assisting with integrated disease management measures.

The importance of molecular analyses for understanding the genetic diversity of Histoplasma capsulatum: an overview

Advances in the classification of the human pathogen Histoplasma capsulatum (H. capsulatum) (ascomycete) are sustained by the results of several genetic analyses that support the high diversity of this dimorphic fungus. The present mini-review highlights the great genetic plasticity of H. capsulatum. Important records with different molecular tools, mainly single- or multi-locus sequence analyses developed with this fungus, are discussed. Recent phylogenetic data with a multi-locus sequence analysis using 5 polymorphic loci support a new clade and/or phylogenetic species of H. capsulatum for the Americas, which was associated with fungal isolates obtained from the migratory bat Tadarida brasiliensis. This manuscript is part of the series of works presented at the "V International Workshop: Molecular genetic approaches to the study of human pathogenic fungi" (Oaxaca, Mexico, 2012).

Frequency and genetic diversity of the MAT1 locus of Histoplasma capsulatum isolates in Mexico and Brazil

The MAT1-1 and MAT1-2 idiomorphs associated with the MAT1 locus of Histoplasma capsulatum were identified by PCR. A total of 28 fungal isolates, 6 isolates from human clinical samples and 22 isolates from environmental (infected bat and contaminated soil) samples, were studied. Among the 14 isolates from Mexico, 71.4% (95% confidence interval [95% CI], 48.3% to 94.5%) were of the MAT1-2 genotype, whereas 100% of the isolates from Brazil were of the MAT1-1 genotype. Each MAT1 idiomorphic region was sequenced and aligned, using the sequences of the G-217B (+ mating type) and G-186AR (- mating type) strains as references. BLASTn analyses of the MAT1-1 and MAT1-2 sequences studied correlated with their respective + and - mating type genotypes. Trees were generated by the maximum likelihood (ML) method to search for similarity among isolates of each MAT1 idiomorph. All MAT1-1 isolates originated from Brazilian bats formed a well-defined group; three isolates from Mexico, the G-217B strain, and a subgroup encompassing all soil-derived isolates and two clinical isolates from Brazil formed a second group; last, one isolate (EH-696P) from a migratory bat captured in Mexico formed a third group of the MAT1-1 genotype. The MAT1-2 idiomorph formed two groups, one of which included two H. capsulatum isolates from infected bats that were closely related to the G-186AR strain. The other group was formed by two human isolates and six isolates from infected bats. Concatenated ML trees, with internal transcribed spacer 1 (ITS1) -5.8S-ITS2 and MAT1-1 or MAT1-2 sequences, support the relatedness of MAT1-1 or MAT1-2 isolates. H. capsulatum mating types were associated with the geographical origin of the isolates, and all isolates from Brazil correlated with their environmental sources.

Evaluation of the genetic diversity of Histoplasma capsulatum var. capsulatum isolates from north-eastern Brazil

Since the beginning of the HIV epidemic, there has been a significant increase in the number of histoplasmosis cases in Ceará, a state in north-east Brazil. The lack of epidemiological data on the genotypes circulating in the north-east region shows the importance of more detailed studies on the molecular epidemiology of Histoplasma capsulatum var. capsulatum in this region. Different molecular techniques have been used to better characterize the genetic profile of H. capsulatum var. capsulatum strains. The aim of this study was to analyse the genetic diversity of H. capsulatum var. capsulatum isolates in Fortaleza, the capital of Ceará, through the sequencing of the internal transcribed spacer (ITS)1-5.8S-ITS2 region, and establish the molecular profile of these isolates, along with strains from south-east Brazil, by RAPD analysis, featuring the different clusters in those regions. The isolates were grouped into two clusters. Cluster 1 included strains from the south-east and north-east regions with separation of isolates into three distinct subgroups (subgroups 1a, 1b and 1c). Cluster 2 included only samples from north-east Brazil. Sequencing of the ITS1-5.8S-ITS2 region allowed the detection of two major clades, which showed geographical correlation between them and their subgroups. Therefore, it can be concluded that the H. capsulatum var. capsulatum isolates from Ceará have a high degree of genetic polymorphism. The molecular data also confirm that populations of this fungus are composed of different genotypes in Brazil and worldwide.

Development of specific sequence-characterized amplified region markers for detecting Histoplasma capsulatum in clinical and environmental samples

Sequence-characterized amplified region (SCAR) markers, generated by randomly amplified polymorphic DNA (RAPD)-PCR, were developed to detect Histoplasma capsulatum selectively in clinical and environmental samples. A 1,200-bp RAPD-PCR-specific band produced with the 1281-1283 primers was cloned, sequenced, and used to design two SCAR markers, 1281-1283(220) and 1281-1283(230). The specificity of these markers was confirmed by Southern hybridization. To evaluate the relevance of the SCAR markers for the diagnosis of histoplasmosis, another molecular marker (M antigen probe) was used for comparison. To validate 1281-1283(220) and 1281-1283(230) as new tools for the identification of H. capsulatum, the specificity and sensitivity of these markers were assessed for the detection of the pathogen in 36 clinical (17 humans, as well as 9 experimentally and 10 naturally infected nonhuman mammals) and 20 environmental (10 contaminated soil and 10 guano) samples. Although the two SCAR markers and the M antigen probe identified H. capsulatum isolates from different geographic origins in America, the 1281-1283(220) SCAR marker was the most specific and detected the pathogen in all samples tested. In contrast, the 1281-1283(230) SCAR marker and the M antigen probe also amplified DNA from Aspergillus niger and Cryptococcus neoformans, respectively. Both SCAR markers detected as little as 0.001 ng of H. capsulatum DNA, while the M antigen probe detected 0.5 ng of fungal DNA. The SCAR markers revealed the fungal presence better than the M antigen probe in contaminated soil and guano samples. Based on our results, the 1281-1283(220) marker can be used to detect and identify H. capsulatum in samples from different sources.

Genetic diversity of Histoplasma capsulatum isolated from infected bats randomly captured in Mexico, Brazil, and Argentina, using the polymorphism of (GA)(n) microsatellite and its flanking regions

The genetic diversity of 47 Histoplasma capsulatum isolates from infected bats captured in Mexico, Brazil, and Argentina was studied, using sequence polymorphism of a 240-nucleotides (nt) fragment, which includes the (GA)(n) length microsatellite and its flanking regions within the HSP60 gene. Three human clinical strains were used as geographic references. Based on phylogenetic analyses of 240-nt fragments achieved, the relationships among H. capsulatum isolates were resolved using neighbour-joining and maximum parsimony methods. The tree topologies obtained by both methods were identical and highlighted two major clusters of isolates. Cluster I had three sub-clusters (Ia, Ib, and Ic), all of which contained Mexican H. capsulatum samples, while cluster II consisted of samples from Brazil and Argentina. Sub-cluster Ia included only fungal isolates from the migratory bat Tadarida brasiliensis. An average DNA mutation rate of 2.39 × 10(-9) substitutions per site per year was estimated for the 240-nt fragment for all H. capsulatum isolates. Nucleotide diversity analysis of the (GA)(n) and flanking regions from fungal isolates of each cluster and sub-cluster underscored the high similarity of cluster II (Brazil and Argentina), sub-clusters Ib, and Ic (Mexico). According to the genetic distances among isolates, a network of the 240-nt fragment was graphically represented by (GA)(n) length haplotype. This network showed an association between genetic variation and both the geographic distribution and the ecotype dispersion of H. capsulatum, which are related to the migratory behaviour of the infected bats studied.

An Hcp100 gene fragment reveals Histoplasma capsulatum presence in lungs of Tadarida brasiliensis migratory bats

Histoplasma capsulatum was sampled in lungs from 87 migratory Tadarida brasiliensis bats captured in Mexico (n=66) and Argentina (n=21). The fungus was screened by nested-PCR using a sensitive and specific Hcp100 gene fragment. This molecular marker was detected in 81·6% [95% confidence interval (CI) 73·4-89·7] of all bats, representing 71 amplified bat lung DNA samples. Data showed a T. brasiliensis infection rate of 78·8% (95% CI 68·9-88·7) in bats captured in Mexico and of 90·4% (95% CI 75·2-100) in those captured in Argentina. Similarity with the H. capsulatum sequence of a reference strain (G-217B) was observed in 71 Hcp100 sequences, which supports the fungal findings. Based on the neighbour-joining and maximum parsimony Hcp100 sequence analyses, a high level of similarity was found in most Mexican and all Argentinean bat lung samples. Despite the fact that 81·6% of the infections were molecularly evidenced, only three H. capsulatum isolates were cultured from all samples tested, suggesting a low fungal burden in lung tissues that did not favour fungal isolation. This study also highlighted the importance of using different tools for the understanding of histoplasmosis epidemiology, since it supports the presence of H. capsulatum in T. brasiliensis migratory bats from Mexico and Argentina, thus contributing new evidence to the knowledge of the environmental distribution of this fungus in the Americas.

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.

Adherence patterns of Histoplasma capsulatum yeasts to bat tissue sections

The adherence of Histoplasma capsulatum yeasts to lung, spleen, liver, gut, and trachea cryosections of Artibeus hirsutus bats and inbred BALB/c mice (control) was studied after in vitro yeast-tissue incubations. Candida albicans yeasts were used as a well-known adherent fungal model in the mice host, and latex beads were used as a negative adherence control. Adhered yeast cells were identified by using crystal violet staining and the immunoperoxidase method with specific antibodies. H. capsulatum yeasts adhered to all tissues tested, mainly in the lung. Moreover, H. capsulatum yeasts adhered preferentially to white and red spleen pulp, in contrast to the dispersed distribution of C. albicans yeasts. H. capsulatum yeasts were mostly found on the sinusoidal face of hepatocytes. In general, the gut showed a higher number of adhered H. capsulatum yeasts than the trachea in both bats and mice. H. capsulatum and C. albicans yeasts developed high selectivity for the lamina propria of the gut. In addition, H. capsulatum yeasts interacted better with the lamina propria and adventitia of the trachea. The number of H. capsulatum yeast cells that adhered to each tissue section type was always greater than the corresponding number of C. albicans yeast cells, and latex beads never adhered to the tissue sections. Controls with anti-H. capsulatum and normal rabbit sera showed a significant blockage of H. capsulatum yeast adherence to lung tissue. This is the first study describing the patterns of H. capsulatum yeast adherence to different bat and mouse tissues.

Bat-associated histoplasmosis can be transmitted at entrances of bat caves and not only inside the caves

Our observation of histoplasmosis cases augments the current knowledge on transmission by bats. In the presented cases, the only contact happened in the proximity of a bat cave but not inside the cave. We wish to communicate and stress that even outside of caves, bats may disperse the organism.

Typing of Histoplasma capsulatum strains by fatty acid profile analysis

The performance of fatty acid profiling for strain differentiation of Histoplasma capsulatum was assessed. Total fatty acids were isolated from the yeast-phase cells of seven stock and two previously unreported clinical strains of H. capsulatum var. capsulatum, as well as from one unreported clinical strain and one stock strain of H. capsulatum var. duboisii, and one strain of each of three other dimorphic zoopathogenic fungal species, Blastomyces dermatitidis, Paracoccidioides brasiliensis and Sporothrix schenckii. Different colony morphology and pigmentation types of the H. capsulatum strains were also included. The most frequently occurring fatty acids were oleic, palmitic, stearic and linoleic acids. There were variations in the relative percentage fatty acid contents of H. capsulatum strains that could be used for strain identification and discrimination. Differentiation between H. capsulatum strains was achieved by the comparison of detected fatty acids accompanied by principal component analysis using calculated Varimax-rotated principal component loadings. Statistical analysis yielded three major principal components that explained over 94 % of total variance in the data. All the strains of H. capsulatum var. capsulatum RFLP classes II and III were grouped into two distinct clusters: the heterogenic RFLP class I formed a large, but also well-defined group, whereas the outgroup strains of H. capsulatum var. duboisii, B. dermatitidis, P. brasiliensis and S. schenckii were shifted away. These data suggest that fatty acid profiling can be used in H. capsulatum strain classification and epidemiological studies that require strain differentiation at the intraspecies level.

Geographical distribution of genetic polymorphism of the pathogen Histoplasma capsulatum isolated from infected bats, captured in a central zone of Mexico

Fourteen Histoplasma capsulatum isolates recovered from infected bats captured in Mexican caves and two human H. capsulatum reference strains were analyzed using random amplification of polymorphic DNA PCR-based and partial DNA sequences of four genes. Cluster analysis of random amplification of polymorphic DNA-patterns revealed differences for two H. capsulatum isolates of one migratory bat Tadarida brasiliensis. Three groups were identified by distance and maximum-parsimony analyses of arf, H-anti, ole, and tub1 H. capsulatum genes. Group I included most isolates from infected bats and one clinical strain from central Mexico; group II included the two isolates from T. brasiliensis; the human G-217B reference strain from USA formed an independent group III. Isolates from group II showed diversity in relation to groups I and III, suggesting a different H. capsulatum population.

Application of Isotope Coded Affinity Tag (ICAT) Analysis for the Identification of Differentially Expressed Proteins Following Infection of Atlantic Salmon (Salmo salar) with Infectious Hematopoietic Necrosis Virus (IHNV) or Renibacterium salmoninarum (BKD)

Aquaculture and commercial fisheries worldwide suffer from significant economic loss due to diseases of net-pen reared fish. In British Columbia, infectious hematopoietic necrosis (IHN) and bacterial kidney disease (BKD) epidemics occur because there are currently no commercially available drugs or fully licensed vaccines to treat these diseases. With a better understanding of the molecular mechanisms underlying these diseases, this circumstance might be significantly improved. In the present study, we have used a proteomics approach in an effort to identify and quantitate differentially expressed proteins in the liver and kidneys of diseased and healthy Atlantic salmon (Salmo salar). Isotope coded affinity tagging (ICAT), 2D gel electrophoresis, and multidimensional liquid chromatography coupled to tandem mass spectrometry (2D-LC MS/MS) were used to identify hundreds of differentially expressed proteins. While the direct significance of changes in expression levels of many proteins remains to be elucidated, others appear to be more clearly related to the infectious process. Examples of the latter are discussed here and include, a natural killer cell enhancement factor (NKEF), procathepsin L, superoxide-producing NADPH oxidase and interferon-induced viral resistance protein Mx (IFI-Mx).

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.