Comparative evaluation of chemiluminescent DNA probe assays and exoantigen tests for rapid identification of Blastomyces dermatitidis and Coccidioides immitis

Diagnostic Approach to Coccidioidomycosis in Solid Organ Transplant Recipients

Coccidioidomycosis is a fungal infection endemic in the southwestern United States, Mexico, and parts of Central and South America. While coccidioidomycosis is associated with mostly mild infections in the general population, it can lead to devastating infections in immunocompromised patients, including solid organ transplant (SOT) recipients. Early and accurate diagnosis is important in achieving better clinical outcomes in immunocompromised patients. However, the diagnosis of coccidioidomycosis in SOT recipients can be challenging due to the limitations of diagnostic methods including cultures, serology, and other tests in providing a timely and accurate diagnosis. In this review, we will discuss the available diagnostic modalities and approaches when evaluating SOT recipients with coccidioidomycosis, from the use of conventional culture methods to serologic and molecular testing. Additionally, we will discuss the role of early diagnosis in assisting with the administration of effective antifungal therapy to reduce infectious complications. Finally, we will discuss ways to improve the performance of coccidioidomycosis diagnostic methods in SOT recipients with an option for a combined testing approach.

Blastomycosis: A Review of Mycological and Clinical Aspects

Blastomycosis is caused by a thermally dimorphic fungus that thrives in moist acidic soil. Blastomyces dermatitidis is the species responsible for most infections in North America and is especially common in areas around the Great Lakes, the St. Lawrence Seaway, and in several south-central and southeastern United States. Other Blastomyces species have more recently been discovered to cause disease in distinct geographic regions around the world. Infection almost always occurs following inhalation of conidia produced in the mold phase. Acute pulmonary infection ranges from asymptomatic to typical community-acquired pneumonia; more chronic forms of pulmonary infection can present as mass-like lesions or cavitary pneumonia. Infrequently, pulmonary infection can progress to acute respiratory distress syndrome that is associated with a high mortality rate. After initial pulmonary infection, hematogenous dissemination of the yeast form of Blastomyces is common. Most often this is manifested by cutaneous lesions, but osteoarticular, genitourinary, and central nervous system (CNS) involvement also occurs. The diagnosis of blastomycosis can be made by growth of the mold phase of Blastomyces spp. in culture or by histopathological identification of the distinctive features of the yeast form in tissues. Detection of cell wall antigens of Blastomyces in urine or serum provides a rapid method for a probable diagnosis of blastomycosis, but cross-reactivity with other endemic mycoses commonly occurs. Treatment of severe pulmonary or disseminated blastomycosis and CNS blastomycosis initially is with a lipid formulation of amphotericin B. After improvement, therapy can be changed to an oral azole, almost always itraconazole. With mild to moderate pulmonary or disseminated blastomycosis, oral itraconazole treatment is recommended.

Coccidioidomycosis: A Contemporary Review

Coccidioidomycosis, colloquially known as Valley Fever, is an invasive dimorphic fungal infection caused by Coccidioides immitis and C. posadasii. The fungi are found in the arid desert soils of the southwestern US, as well as in parts of Mexico and Central and South America. Acquisition is typically via inhalation of arthroconidia which become airborne after both natural (e.g., earthquakes, dust storms, and fires) and human-related events (e.g., military maneuvers, recreational activities, agriculture, and construction). The incidence of infection in increasing likely a result of both climatic and populational changes. Further, the recognized geographic distribution of Coccidioides spp. is expanding, as cases are being diagnosed in new areas (e.g., eastern Washington, Oregon, and Utah). Most coccidioidal infections are asymptomatic (60%); however, approximately one-third develop a pulmonary illness which is a leading cause of community-acquired pneumonia in highly endemic areas. Uncommonly (0.5–2% of cases), the infection disseminates to extrapulmonary locations (e.g., skin, bones/joints, and the central nervous system), and is most commonly seen among persons with cellular immunodeficiencies (e.g., transplant recipients, HIV, and pregnancy) and non-Caucasian races (especially African Americans and Filipinos). The diagnosis of coccidioidomycosis requires astute clinical suspicion and laboratory findings, including positive serology, cultures, and/or histopathology results. Treatment is warranted among persons with pneumonia who have risk factors for complicated disease and among those with extrapulmonary disease. Novel antifungals with improved fungicidal activity and rapidity of action with fewer side effects and drug interactions are needed. Preventive strategies (e.g., education regarding the disease, dust avoidance, mask wearing, including among select groups, antifungal prophylaxis, and surveillance laboratory testing) are advised for residents and travelers to endemic areas. Currently, no preventive vaccine is available. Coccidioidomycosis has been recognized for over a century, and an expanding wealth of knowledge has been gained regarding this emerging infectious disease which will be reviewed here.

Real-time PCR assay for detection and differentiation of Coccidioides immitis and Coccidioides posadasii from culture and clinical specimens

Coccidioidomycosis (Valley fever) is a pulmonary and systemic fungal disease with increasing incidence and expanding endemic areas. The differentiation of etiologic agents Coccidioides immitis and C. posadasii remains problematic in the clinical laboratories as conventional PCR and satellite typing schemes are not facile. Therefore, we developed Cy5- and FAM-labeled TaqMan-probes for duplex real-time PCR assay for rapid differentiation of C. immitis and C. posadasii from culture and clinical specimens. The RRA2 gene encoding proline-rich antigen 2, specific for Coccidioides genus, was the source for the first set of primers and probe. Coccidioides immitis contig 2.2 (GenBank: AAEC02000002.1) was used to design the second set of primers and probe. The second primers/probe did not amplify the corresponding C. posadasii DNA, because of an 86-bp deletion in the contig. The assay was highly sensitive with limit of detection of 0.1 pg gDNA/PCR reaction, which was equivalent to approximately ten genome copies of C. immitis or C. posadasii. The assay was highly specific with no cross-reactivity to the wide range of fungal and bacterial pathogens. Retrospective analysis of fungal isolates and primary specimens submitted from 1995 to 2020 confirmed 168 isolates and four primary specimens as C. posadasii and 30 isolates as C. immitis from human coccidioidomycosis cases, while all eight primary samples from two animals (rhesus monkey and rhinoceros) were confirmed as C. posadasii. A preliminary analysis of cerebrospinal fluid (CSF) and pleural fluid samples showed positive correlation between serology tests and real-time PCR for two of the 15 samples. The Coccidioides spp. duplex real-time PCR will allow rapid differentiation of C. immitis and C. posadasii from clinical specimens and further augment the treatment and surveillance of coccidioidomycosis.

Current and New Perspectives in the Diagnosis of Blastomycosis and Histoplasmosis

The diagnosis of blastomycosis and histoplasmosis can be difficult for clinicians who rarely see infections caused by these environmentally restricted dimorphic fungi. Historically, the diagnosis of blastomycosis has been established by culture and sometimes by histopathologic identification. Currently, antigen detection in urine and serum has been shown to aid in the rapid diagnosis of blastomycosis, and newer antibody assays are likely to contribute to our diagnostic capability in the near future. The gold standard for the diagnosis of histoplasmosis has been culture of the organism from involved tissues, aided in some patients by histopathological verification of the typical yeast forms in tissues. Antigen detection has contributed greatly to the ability of clinicians to rapidly establish the diagnosis of histoplasmosis, especially in severely ill and immunocompromised patients, and antibody testing for Histoplasma capsulatum provides important adjunctive diagnostic capability for several forms of both acute and chronic histoplasmosis. For both of these endemic mycoses, novel molecular tests are under active investigation, but remain available in only a few reference laboratories. In this review, we provide a synopsis of diagnostic test options that aid in establishing whether a patient has blastomycosis or histoplasmosis.

Spiromastigoides asexualis: Phylogenetic Analysis and Evaluation as a Cause of False-Positive Blastomyces DNA Probe Test Results

This is the first case of Spiromastigoides asexualis human infection, and it notably gave a false-positive Blastomyces DNA probe laboratory result. We further investigated other Spiromastigoides isolates as a cause of false-positive testing results, their phylogenetic relationship, and their susceptibility profiles to clinically available antifungal agents. Other S. asexualis isolates also resulted in positive Blastomyces DNA probe results, while Spiromastigoides species other than S. asexualis did not.

The utility of real-time polymerase chain reaction in detecting Coccidioides immitis among clinical specimens in the Central California San Joaquin Valley

Coccidioidomycosis, the fungal infection caused by dimorphic Coccidioides species, is typically diagnosed by histopathologic identification of spherules, by culture, or by serology. These tests are reliable but time-intensive, delaying diagnosis and treatment. Rapid real-time polymerase chain reaction (RT-PCR) can be performed and was validated to identify Coccidioides immitis using an in-house developed assay for the Becton Dickinson molecular instrument (BD MAXTM). These studies were performed using patient samples that had been shown to be positive on previously set up fungal cultures. To evaluate this new RT-PCR test in the clinical setting, we conducted a retrospective chart review of patients (N = 1160) who underwent Coccidioides PCR (Cocci PCR) on clinical samples between March 1, 2014, and Dec 31, 2016. We abstracted clinical, microbiologic, serologic, radiographic, treatment, and follow-up data. Specimens of cerebrospinal fluid (CSF), bronchioalveolar lavage fluid (BAL), lung tissue biopsy (LTB), sputum, and pleural fluid were evaluated to determine sensitivity and specificity. Of the 113 specimens that tested positive for Cocci PCR, all had clinical disease defined by traditional clinical criteria, yielding 100% specificity. Overall sensitivity was 74% versus 46% for fungal culture and was available in 4 hours rather than 1-2 weeks. Sensitivities varied by source material and clinical setting. CSF had a sensitivity of 59%, BAL for acute pneumonia 91%, sputum for acute pneumonia 94%, pleural fluid 86%, but LTB for lung nodules only 44%. Overall positive predictive value (PPV) was 100%, while negative predictive value (NPV) was 96%, but again this varied by specimen and clinical setting. Our experience with clinical testing of >1160 specimens over 2-3 years shows we can utilize this technology to improve our ability to diagnose disease but that the sensitivity varies by specimen source and clinical setting.

Impacts and Challenges of Advanced Diagnostic Assays for Transplant Infectious Diseases

The advanced technologies described in this chapter should allow for full inventories to be made of bacterial genes, their time- and place-dependent expression, and the resulting proteins as well as their outcome metabolites. The evolution of these molecular technologies will continue, not only in the microbial pathogens but also in the context of host-pathogen interactions targeting human genomics and transcriptomics. Their performance characteristics and limitations must be clearly understood by both laboratory personnel and clinicians to ensure proper utilization and interpretation.

Combined Endosonography Reduces Time to Diagnose Pulmonary Coccidioidomycosis

Coccidioidomycosis causes significant morbidity in endemic areas. In the absence of sensitive diagnostic serologic testing, clinicians have increasingly relied on lung and lymph node biopsies for diagnosis. Recently, endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA) has been shown to be an excellent sampling method for the diagnosis and staging of lung cancers, especially when combined with endoscopic ultrasound guided fine needle aspiration (EUS-FNA). We present 13 consecutive cases where EBUS-TBNA and/or EUS-FNA of pulmonary lymph nodes were performed as part of the workup for pulmonary coccidioidomycosis. EBUS-TBNA+EUS-FNA led to diagnosis in all nine cases in which they were performed concurrently, and in the remaining 4 in which either was performed individually. BAL was performed in all cases with positive results in 5 (38%). The mean time to diagnose by EBUS/EUS (1.6 d) was significantly shorter than by bronchoalveolar lavage (6.3 d) (P=0.003). The findings indicate that combined EBUS-TBNA+EUS-FNA for lymph node biopsy facilitates early and accurate diagnosis of pulmonary coccidioidomycosis.

Laboratory Diagnostics for Fungal Infections: A Review of Current and Future Diagnostic Assays

This article reviews the current diagnostic approaches, both serologic and molecular, for the detection of fungi associated with pulmonary disease. Classic serologic techniques, including immunodiffusion and complement fixation, both of which remain a cornerstone for fungal diagnostic testing, are reviewed and their performance characteristics presented. More recent advances in this field, including novel lateral-flow assays for fungal antigen detection, are also described. Molecular techniques for fungal identification both from culture and directly from patient specimens, including nucleic acid probes, mass spectrometry-based methods, nucleic acid amplification testing, and traditional and broad-range sequencing, are discussed and their performance evaluated.

Blastomycosis during pregnancy: a case report and review of the literature

The diagnosis of blastomycosis during pregnancy is rare, but can carry significant clinical questions for both the infected mother and developing fetus. Furthermore, given its rarity, providers have little available data to help manage and counsel patients in this uncommon, yet serious, scenario. We present a case of blastomycosis in a woman at 38weeks' gestation and review all published cases of blastomycosis during pregnancy. It is our hope to provide a multidisciplinary understanding of the current knowledge surrounding the presentation, diagnosis, management, and outcome of this unusual infection.

Molecular markers in the epidemiology and diagnosis of coccidioidomycosis

The prevalence of coccidioidomycosis in endemic areas has been observed to increase daily. To understand the causes of the spread of the disease and design strategies for fungal detection in clinical and environmental samples, scientists have resorted to molecular tools that allow fungal detection in a natural environment, reliable identification in clinical cases and the study of biological characteristics, such as reproductive and genetic structure, demographic history and diversification. We conducted a review of the most important molecular markers in the epidemiology of Coccidioides spp. and the diagnosis of coccidioidomycosis. A literature search was performed for scientific publications concerning the application of molecular tools for the epidemiology and diagnosis of coccidioidomycosis. The use of molecular markers in the epidemiological study and diagnosis of coccidioidomycosis has allowed for the typing of Coccidioides spp. isolates, improved understanding of their mode of reproduction, genetic variation and speciation and resulted in the development specific, rapid and sensitive strategies for detecting the fungus in environmental and clinical samples. Molecular markers have revealed genetic variability in Coccidioides spp. This finding influences changes in the epidemiology of coccidioidomycosis, such as the emergence of more virulent or antifungal resistant genotypes. Furthermore, the molecular markers currently used to identify Coccidioides immitis and Coccidioides posadasii are specific and sensitive. However, they must be validated to determine their application in diagnosis. 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).

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.

Detection of Blastomyces dermatitidis and Histoplasma capsulatum from culture isolates and clinical specimens by use of real-time PCR

Blastomyces dermatitidis and Histoplasma capsulatum are dimorphic fungi that often cause self-limited respiratory infections. However, they may also cause severe disseminated disease, depending on the level of the exposure to the organism and the host immune status. In addition, patients with infections caused by these fungi may have very similar clinical presentations. Although microbiologic culture is a standard method for detecting these pathogens, their recovery may require days to weeks, and the manipulation of cultures presents a significant safety hazard to laboratory personnel. Therefore, the goal of this study was to design a rapid, real-time PCR assay to detect and differentiate B. dermatitidis and H. capsulatum from culture isolates and directly from clinical specimens. Primers and fluorescence resonance energy transfer hybridization probes were designed to target the histidine kinase and glyceraldehyde-3-phosphate dehydrogenase genes of B. dermatitidis and H. capsulatum, respectively. The analytical sensitivity of the assay was determined to be 100 copies/μl for both fungi. From culture isolates, the assay demonstrated 100% specificity and 100% sensitivity for B. dermatitidis and 100% specificity and 94% sensitivity for H. capsulatum. Detection directly from 797 clinical specimens demonstrated specificities and sensitivities of 99% and 86% for B. dermatitidis and 100% and 73% for H. capsulatum compared with the results for culture. This real-time PCR assay provides a rapid method for the detection of B. dermatitidis and H. capsulatum from culture isolates and directly from clinical specimens.

The diagnosis of coccidioidomycosis

Until recently, culture, microscopy, and serology have been the available methods for the diagnosis of coccidioidomycosis. While Coccidioides is frequently isolated by culture, special precautions must be taken because of the risk of laboratory infection and because Coccidioides is on the Select Agent list. Serology is useful but the sensitivity remains lower than desired. A commercially available test for coccidioidal galactomannan antigenuria now exists and appears useful for immunocompromised hosts with severe disease. Polymerase chain reaction assays targeting specific coccidioidal genes have demonstrated utility but are not commercially available. Moreover, their sensitivity and the best sample type remain unestablished.

Persistent pulmonary infection with an azole-resistant Coccidioides species

We report a case of a life-threatening, recurrent, and azole-resistant pulmonary coccidioidomycosis in a patient receiving long-term fluconazole therapy for a history of coccidioidal meningitis. Since this diagnosis, the patient has received weekly amphotericin B for more than four years and remains in remission with a stable serum Coccidioides complement fixation antibody titer.

Diagnosis of Coccidioidomycosis by Culture: Safety Considerations, Traditional Methods, and Susceptibility Testing

The recovery of Coccidioides spp. by culture and confirmation utilizing the AccuProbe nucleic acid hybridization method by GenProbe remain the definitive diagnostic method. Biosafety considerations from specimen collection through culture confirmation in the mycology laboratory are critical, as acquisition of coccidioidomycosis by laboratory workers is well documented. The designation of Coccidioides spp. as select agents of potential bioterrorism has mandated strict regulation of their transport and inventory. The genus appears generally susceptible, in vitro, although no defined breakpoints exist. Susceptibility testing may assist in documenting treatment failures.

Use of the Coccidioides posadasii Deltachs5 strain for quality control in the ACCUPROBE culture identification test for Coccidioides immitis

Coccidioides posadasii Deltachs5 is a strain that is excluded from the select agent list. Sixteen assays using test reagents from three different ACCUPROBE Coccidioides immitis culture identification test lots had an average of 132,998 relative light units (RLU), which is well beyond the 50,000-RLU positive cutoff value for the test. Coccidioides posadasii Deltachs5 is a satisfactory quality control isolate in the ACCUPROBE culture identification test for Coccidioides immitis.

Coccidioidomycosis: a review and update

Coccidioidomycosis occurs in arid and semi-arid regions of the New World from the western United States to Argentina. Highly endemic areas are present in the southwest United States. Coccidioides species live in the soil and produce pulmonary infection via airborne arthroconidia. The skin may be involved by dissemination of the infection, or by reactive eruptions, such as a generalized exanthem or erythema nodosum. Interstitial granulomatous dermatitis and Sweet's syndrome have recently been recognized as additional reactive signs of the infection. Coccidioidomycosis is a "great imitator" with protean manifestations. Cutaneous findings may be helpful clues in the diagnosis of this increasingly important disease.

Detection of Coccidioides species in clinical specimens by real-time PCR

Coccidioides spp. are dimorphic fungal pathogens endemic to the semiarid regions of North, Central, and South America. Currently, direct smear and culture are the most common means of identifying Coccidioides spp. While these methods offer relatively sensitive and specific means of detecting Coccidioides spp., growth in culture may take up to 3 weeks, potentially delaying the diagnosis and initiation of appropriate antifungal therapy. In addition, growth of the organism represents a significant safety risk to laboratory personnel. The need for a rapid and safe means of diagnosing coccidioidomycosis prompted us to develop a real-time PCR assay to detect Coccidioides spp. directly from clinical specimens. Primers and fluorescent resonance energy transfer (FRET) probes were designed to target the internal transcribed spacer 2 region of Coccidioides. The assay's limit of detection is below 50 targets per reaction. An analysis of 40 Coccidioides sp. clinical isolates grown in culture demonstrated 100% sensitivity of the assay. A cross-reactivity panel containing fungi, bacteria, mycobacteria, and viruses was tested and demonstrated 100% specificity for Coccidioides spp. An analysis of 266 respiratory specimens by LightCycler PCR demonstrated 100% sensitivity and 98.4% specificity for Coccidioides spp. compared with culture. Analysis of 66 fresh tissue specimens yielded 92.9% sensitivity and 98.1% specificity versus those of the culture method. The sensitivity of the assay testing 148 paraffin-embedded tissue samples is 73.4%. A rapid method for the detection of Coccidioides spp. directly from clinical material will greatly assist in the timely diagnosis and treatment of patients, while at the same time decreasing the risk of accidental exposure to laboratory personnel.

Identification of Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides species by repetitive-sequence-based PCR

The performance of repetitive-sequence-based PCR (rep-PCR) using the DiversiLab system for identification of Coccidioides species, Blastomyces dermatitidis, and Histoplasma capsulatum was assessed by comparing data obtained to colony morphology and microscopic characteristics and to nucleic acid probe results. DNA from cultures of 23 Coccidioides, 24 B. dermatitidis, 24 H. capsulatum, 3 Arthrographis, and 2 Malbranchea isolates was extracted using a microbial DNA isolation kit as recommended by Bacterial Barcodes, Inc. Rep-PCR and probe results agreed for 97.2% of the dimorphic fungi when > or =85% similarity was used as the criterion for identification. Two H. capsulatum isolates were not identified, but no isolates were misidentified. From 43 of those cultures (15 Coccidioides, 14 B. dermatitidis, 14 H. capsulatum, 3 Arthrographis, and 2 Malbranchea), DNA also was extracted using an IDI lysis kit, a simpler method. Rep-PCR and probe results agreed for 97.7% of the dimorphic fungi when a criterion of > or =90% similarity was used for identification. One H. capsulatum isolate could not be identified; no isolates were misidentified. Using > or =85% similarity for identification resulted in one misidentification. These data suggest that the DiversiLab system can be used to identify Coccidioides and B. dermatitidis and, possibly, H. capsulatum isolates.

Kokzidioidomykose

Coccidioidomycosis is a systemic mycosis that is acquired by inhalation. It is endemic in desert-like areas of the southwest USA and neighboring regions, but is becoming increasingly prevalent in other regions of the world as a result of widespread travel. The clinical spectrum is broad, ranging from inapparent infections or symptoms of acute respiratory infection with spontaneous recovery to various manifestations of disseminated coccidioidomycosis. Since the majority of patients with disseminated coccidioidomycosis present with cutaneous manifestations, early diagnosis of this potentially life-threatening disease by dermatologists is important. Atypical skin changes, pulmonary infiltrates and a history of travel to areas where the disease is endemic are indicative of coccidioidomycosis. For conclusive diagnosis, identification of the fungus by histopathologic examination or culture is desirable. Serological tests can be helpful for establishing the diagnosis and monitoring the course of the disease. The treatment of choice for cutaneous coccidioidomycosis is currently oral azole antifungal agents, such as itraconazole 400 mg daily, continued for 6 months after clinical response. Since relapses are frequent after discontinuation of the treatment, close clinical, serological and radiological follow-up is required for years.

Molecular detection and typing of fungal pathogens

A major goal of molecular testing is to develop a cost-effective as well as sensitive and specific assay that can detect microbial DNA in clinical samples early in the course of disease. Additionally, the ability to analyze the genetic relatedness of fungi on a timelier basis using molecular methods will have a positive impact on epidemiologic investigating. As technology advances, it seems apparent that commercially available molecular assays will become available in the near future for the management of patients with suspected fungal infections.

Small subunit ribosomal DNA sequence shows Paracoccidioides brasiliensis closely related to Blastomyces dermatitidis

The similarities of paracoccidioidomycosis and blastomycosis are highly suggestive of a close relation of the two etiological agents. Whereas the agent of the first disease is exclusively endemic in Latin America, the agent of the latter one is endemic in North America and Africa. In symptomatic travelers visiting both areas of endemicity, differentiation of the diseases might be impossible, even though therapy and prognosis for these two diseases differ significantly. In order to identify differences in the 18S rRNA gene (rDNA) for use as molecular diagnostic tools, we sequenced this gene from five isolates of Paracoccidioides brasiliensis and compared them to known sequences of other fungi. Neighbor-joining, maximum parsimony, and maximum likelihood analyses and, finally, the Kishino-Hasegawa test revealed that P. brasiliensis, Blastomyces dermatitidis, and Emmonsia parva are more closely related than Histoplasma capsulatum and B. dermatitidis, whose teleomorphic forms belong to one genus, Ajellomyces. In accordance with the work of other investigators who have used internal transcribed spacer and large subunit rDNA sequences, our small subunit rDNA data show that the dimorphic fungus P. brasiliensis must be grouped within the order Onygenales and is closely related to members of the family Onygenaceae. There are hints in the molecular phylogenetic analysis that the family Onygenaceae might be further divided into two families. The subgroup that includes P. brasiliensis comprises all zoopathogenic species. The differences in the 18S rDNAs appear to be too small to allow species identification of the members of the family Onygenaceae pathogenic for humans by use of target sequences within this gene.

Limitation of the AccuProbe Coccidioides immitis culture identification test: false-negative results with formaldehyde-killed cultures

The AccuProbe Coccidioides immitis culture identification test (CI test) yielded false-negative results with formaldehyde-killed C. immitis submitted to a reference laboratory. Further evaluation with pure or mixed cultures or stored, heat-killed cultures revealed the CI test to be highly sensitive and specific for C. immitis except when the cultures were pretreated with formaldehyde.

Pulmonary infection caused by Gymnascella hyalinospora in a patient with acute myelogenous leukemia

We report the first case of invasive pulmonary infection caused by the thermotolerant ascomycetous fungus Gymnascella hyalinospora in a 43-year-old female from the rural midwestern United States. The patient was diagnosed with acute myelogenous leukemia and treated with induction chemotherapy. She was discharged in stable condition with an absolute neutrophil count of 100 cells per microliter. Four days after discharge, she presented to the Cancer Clinic with fever and pancytopenia. A solitary pulmonary nodule was found in the right middle lobe which was resected by video-assisted thoracoscopy (VATHS). Histopathological examination revealed septate branching hyphae, suggesting a diagnosis of invasive aspergillosis; however, occasional yeast-like cells were also present. The culture grew a mold that appeared dull white with a slight brownish tint that failed to sporulate on standard media. The mold was found to be positive by the AccuProbe Blastomyces dermatitidis Culture ID Test (Gen-Probe Inc., San Diego, Calif.), but this result appeared to be incompatible with the morphology of the structures in tissue. The patient was removed from consideration for stem cell transplant and was treated for 6 weeks with amphotericin B (AmB), followed by itraconazole (Itr). A VATHS with biopsy performed 6 months later showed no evidence of mold infection. In vitro, the isolate appeared to be susceptible to AmB and resistant to fluconazole and 5-fluorocytosine. Results for Itr could not be obtained for the case isolate due to its failure to grow in polyethylene glycol used to solubilize the drug; however, MICs for a second isolate appeared to be elevated. The case isolate was subsequently identified as G. hyalinospora based on its formation of oblate, smooth-walled ascospores within yellow or yellow-green tufts of aerial hyphae on sporulation media. Repeat testing with the Blastomyces probe demonstrated false-positive results with the case isolate and a reference isolate of G. hyalinospora. This case demonstrates that both histopathologic and cultural features should be considered for the proper interpretation of this molecular test and extends the list of fungi recognized as a cause of human mycosis in immunocompromised patients.

Developments in fungal taxonomy

Fungal infections, especially those caused by opportunistic species, have become substantially more common in recent decades. Numerous species cause human infections, and several new human pathogens are discovered yearly. This situation has created an increasing interest in fungal taxonomy and has led to the development of new methods and approaches to fungal biosystematics which have promoted important practical advances in identification procedures. However, the significance of some data provided by the new approaches is still unclear, and results drawn from such studies may even increase nomenclatural confusion. Analyses of rRNA and rDNA sequences constitute an important complement of the morphological criteria needed to allow clinical fungi to be more easily identified and placed on a single phylogenetic tree. Most of the pathogenic fungi so far described belong to the kingdom Fungi; two belong to the kingdom Chromista. Within the Fungi, they are distributed in three phyla and in 15 orders (Pneumocystidales, Saccharomycetales, Dothideales, Sordariales, Onygenales, Eurotiales, Hypocreales, Ophiostomatales, Microascales, Tremellales, Poriales, Stereales, Agaricales, Schizophyllales, and Ustilaginales).

Molecular and biochemical characterization of a Coccidioides immitis-specific antigen

Results of earlier investigations have indicated that the saprobic phase of Coccidioides immitis produces a heat-stable, 19-kDa antigen with serine proteinase activity which has been suggested to be specific for this pathogenic fungus. In the present study we have determined the N-terminal and partial internal amino acid sequences of the purified, 19-kDa antigen, cloned the gene which encodes this polypeptide, and confirmed that the secreted proteinase is a Coccidioides-specific antigen (CS-Ag). Both the genomic and cDNA sequences are reported and reveal that the csa gene which encodes this antigen has no introns. A 543-bp open reading frame encodes a 181-amino-acid-containing protein with a predicted molecular mass of 19.8 kDa and an isoelectric point of 8.3. The csa gene was localized on chromosome I of three representative C. immitis clinical isolates on the basis of Southern hybridizations. Expression of the csa gene in Escherichia coli using the pET21a plasmid vector yielded a recombinant protein that was recognized in immunoblot assays by antibody raised to the purified 19-kDa CS-Ag. Secretion of the native antigen is suggested to occur by cleavage of a putative 23-residue signal peptide. The native CS-Ag showed a low degree of glycosylation. Analysis of the carbohydrate composition of the CS-Ag revealed xylose, mannose, galactose, and glucose. However, the purified antigen showed no affinity for concanavalin A. A PCR method with specificity and high sensitivity for detection of C. immitis genomic DNA, using a pair of synthetic oligonucleotide primers whose sequences were based on that of the csa gene, was developed. A 520-bp product was amplified only when C. immitis genomic DNA was used as the template. The lower limits of DNA detection using this PCR method were 1 pg of C. immitis genomic DNA by ethidium bromide staining and 100 fg after Southern hybridization. The csa gene-based PCR method for detection of C. immitis DNA is useful for culture identification and may have clinical applications for the diagnosis of coccidioidal infections.

Chemiluminescent immunoassays: discrimination between the reactivities of natural and human patient antibodies with antigens from eukaryotic pathogens, Trypanosoma cruzi and Paracoccidioides brasiliensis

Quantitative chemiluminescent enzyme-linked immunosorbent assay (ELISA) and dot-blotting procedures were developed to evaluate the reactivity of human antibodies with crude antigens and purified molecules of parasites and fungi, mainly Trypanosoma cruzi and Paracoccidioides brasiliensis. Reproducible, highly sensitive, and strictly dose-responding results were obtained, with the specificity depending on the kind of antigen used. Mixed antigens (epimastigote membrane and HIV-1 heptapeptide) applied in dots could be independently recognized by specific sera. Purified antigens (T. cruzi F2/3 and P. brasiliensis gp43) at very small concentrations gave specific reactions with patients' sera diluted > or = 1:1,000 and were very poorly reactive or unreactive with natural antibodies using the chemiluminescent immunoassays. P. brasiliensis crude antigen Fava Netto polysaccharide antigen (FNPA) contained peptide epitopes recognized by natural antibodies and carbohydrate epitopes reactive with sera from histoplasmosis patients. It is very important that sensitive chemiluminescence immunoassays be used with purified antigenic molecules to ensure specificity for the diagnosis and follow-up of parasitic and fungal infections.