Blastomyces helicus, a New Dimorphic Fungus Causing Fatal Pulmonary and Systemic Disease in Humans and Animals in Western Canada and the United States

Lung infections due to emerging fungal pathogens

PURPOSE OF REVIEW

This review highlights the epidemiology, pathogenesis and clinical management of pulmonary infections caused by emerging fungal organisms.

RECENT FINDINGS

Emerging fungal infections have arisen as a result of population and environmental changes. An enlarging pool of immunocompromised hosts on triazole antifungal prophylaxis has led to an increased incidence of non- Aspergillus molds, such as Fusarium , Scedosporium and Lomentospora spp. Advances in diagnostic capabilities led to the identification of the Emergomyces genus and non- dermatitidis Blastomyces species, which have a significant disease burden in Africa and the Middle East. Climate change has contributed to changing the distribution of previously confined endemic mycoses, like coccidioidomycosis and talaromycosis. These emerging organisms pose important diagnostic and therapeutic challenges.

SUMMARY

Newly recognized pathogenic fungi and established endemic mycoses with expanding geographic boundaries have become important agents of pulmonary disease. There is a dearth of clinical evidence on the appropriate management of these infections.

Endemic Fungal Infective Endocarditis Caused by Coccidioides, Blastomyces and Histoplasma Species in the United States

We describe a recent case of Coccidioides bioprosthetic aortic valve infective endocarditis successfully managed at our institution. This led us to perform a literature review of endemic fungal infective endocarditis in the United States caused by Coccidioides, Blastomyces, and Histoplasma. Symptoms preceded infective endocarditis diagnosis by several months. Patients with Coccidioides and Blastomyces infective endocarditis were younger with fewer comorbid conditions. Valvular involvement was relatively uncommon in Blastomyces infective endocarditis (27%). Fungemia was noted in patients with infective endocarditis due to Histoplasma (30%) and Coccidioides (18%). Mortality rates for infective endocarditis were high (Histoplasma, 46%; Coccidioides, 58%; Blastomyces, 80%); infective endocarditis was commonly diagnosed post-mortem (Coccidioides, 58%; Blastomyces, 89%). Most surviving patients with infective endocarditis (Histoplasma, 79%; Coccidioides, 80%) underwent valve surgery along with prolonged antifungal therapy. The two surviving patients with Blastomyces infective endocarditis received antifungal therapy without surgery.

Blastomycosis-Associated Hospitalizations, United States, 2010-2020

BACKGROUND

Blastomycosis is an environmentally acquired fungal disease that can cause severe illness, with approximately 65% of reported cases requiring hospitalization. Recent trends in blastomycosis-associated hospitalizations in the United States have not been described.

METHODS

We analyzed hospital discharge data from the Healthcare Cost and Utilization Project (HCUP) National (Nationwide) Inpatient Sample. We calculated hospitalization rates per 100,000 population using U.S. census data and examined factors associated with in-hospital mortality.

RESULTS

An estimated 11,776 blastomycosis-associated hospitalizations occurred during 2010-2020 (average yearly rate 0.3 per 100,000 persons), with no apparent temporal trend. Rates were consistently highest among persons ≥65 years old and males. In-hospital death occurred in 7.9% and approximately doubled from 3.9% in 2010 to 8.5% in 2020. Older age, chronic obstructive pulmonary disease, and malignancy were associated with mortality.

CONCLUSIONS

Blastomycosis-associated hospitalizations can result in poor outcomes, underscoring the continued need for attention to early detection and treatment of blastomycosis and monitoring of disease trends.

Endemic Systemic Mycoses in Italy: A Systematic Review of Literature and a Practical Update

Endemic systemic mycoses such as blastomycosis, coccidioidomycosis, histoplasmosis, talaromycosis, paracoccidioidomycosis are emerging as an important cause of morbidity and mortality worldwide. We conducted a systematic review on endemic systemic mycoses reported in Italy from 1914 to nowadays. We found out: 105 cases of histoplasmosis, 15 of paracoccidioidomycosis, 10 of coccidioidomycosis, 10 of blastomycosis and 3 of talaromycosis. Most cases have been reported in returning travelers and expatriates or immigrants. Thirtytwo patients did not have a story of traveling to an endemic area. Fortysix subjects had HIV/AIDS. Immunosuppression was the major risk factor for getting these infections and for severe outcomes. We provided an overview on microbiological characteristics and clinical management principles of systemic endemic mycoses with a focus on the cases reported in Italy.

What Is New in Fungal Infections?

Invasive fungal infections are an increasingly important cause of morbidity and mortality. We provide a summary of important changes in the epidemiology of invasive fungal infections, citing examples of new emerging pathogens, expanding populations who are at-risk, and increasing antifungal resistance. We review how human activity and climate change may play a role in some of these changes. Finally, we discuss how these changes create the need for advances in fungal diagnostics. The limitations of existing fungal diagnostic testing emphasize the critically important role of histopathology in the early recognition of fungal disease.

Blastomycosis of the Central Nervous System

The reported incidence of blastomycosis is increasing in certain regions of the United States. The diagnosis is primarily made via urine antigen testing, culture, or cytology smear. The differential diagnosis for blastomycosis includes pneumonia, tuberculosis, and non-infectious pulmonary disease. Clinical context and epidemiologic exposure play a crucial role in diagnosis. However, the differential can expand significantly if there is disseminated central nervous system involvement, especially if pulmonary manifestations are not seen. Imaging begins to play a vital role when differentiating disseminated blastomycosis from other etiologies such as malignancy. Herein we present a case of a 58-year-old male who presented with seizures and right sided gaze preference found to have disseminated central nervous system blastomycosis. In this article, we will discuss symptoms and imaging findings of disseminated blastomycosis to help guide diagnosis and management.

The Geographic Distribution of Dimorphic Mycoses in the United States for the Modern Era

BACKGROUND

The dimorphic mycoses (DMs) of the United States-Histoplasma, Coccidioides, and Blastomyces-commonly known as endemic mycoses of North America (in addition to Paracoccidioides) are increasingly being diagnosed outside their historical areas of endemicity. Despite this trend, the maps outlining their geographic distributions have not been updated in more than half a century using a large, nationwide database containing individual-patient-level data.

METHODS

This was a retrospective analysis of >45 million Medicare fee-for-service beneficiaries from 1 January 2007 through 31 December 2016. Diagnoses of histoplasmosis, coccidioidomycosis, and blastomycosis were defined by International Classification of Diseases, Ninth/10th Revision, codes. The primary outcome was the incidence of histoplasmosis, coccidioidomycosis, and blastomycosis for each US county. Clinically meaningful thresholds for incidence were defined as 100 cases/100 000 person-years for histoplasmosis and coccidioidomycosis and 50 cases/100 000 person-years for blastomycosis.

RESULTS

There were 79 749 histoplasmosis, 37 726 coccidioidomycosis, and 6109 blastomycosis diagnoses in unique persons from 2007-2016 across 3143 US counties. Considering all US states plus Washington, DC, 94% (48/51) had ≥1 county above the clinically relevant threshold for histoplasmosis, 69% (35/51) for coccidioidomycosis, and 78% (40/51) for blastomycosis.

CONCLUSIONS

Persons with histoplasmosis, coccidioidomycosis, and blastomycosis are diagnosed in significant numbers outside their historical geographic distributions established >50 years ago. Clinicians should consider DM diagnoses based on compatible clinical syndromes with less emphasis placed on patients' geographic exposure. Increased clinical suspicion leading to a subsequent increase in DM diagnostic testing would likely result in fewer missed diagnoses, fewer diagnostic delays, and improved patient outcomes.

Molecular Phylogenetic Analysis of Paracoccidioides Species Complex Present in Paracoccidioidomycosis Patient Tissue Samples

Paracoccidioidomycosis (PCM) is the main and most prevalent systemic mycosis in Latin America, that until recently, it was believed to be caused only by Paracoccidioides brasiliensis (P. brasiliensis). In 2006, researchers described three cryptic species: S1, PS2, PS3, and later, another one, PS4. In 2009, Paracoccidioides lutzii (Pb01-like) was described, and in 2017, a new nomenclature was proposed for the different agents: P. brasiliensis (S1), P. americana (PS2), P. restrepiensis (PS3), and P. venezuelensis (PS4). These species are not uniformly distributed throughout Latin America and, knowing that more than one cryptic species could coexist in some regions, we aimed to identify those species in patients’ biopsy samples for a better understanding of the distribution and occurrence of these recently described species in Botucatu region. The Hospital of Medical School of Botucatu—UNESP, which is a PCM study pole, is located in São Paulo State mid-west region and is classified as a PCM endemic area. Genotyping analyses of clinical specimens from these patients that have been diagnosed and treated in our Hospital could favor a possible correlation between genetic groups and mycological and clinical characteristics. For this, molecular techniques to differentiate Paracoccidioides species in these biopsies, such as DNA extraction, PCR, and sequencing of three target genes (ITS, CHS2, and ARF) were conducted. All the sequences were analyzed at BLAST to testify the presence of P. brasiliensis. The phylogenetic trees were constructed using Mega 7.0 software and showed that 100% of our positive samples were from S1 cryptic species, therefore P. brasiliensis. This is important data, demonstrating the predominance of this species in the São Paulo State region.

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.

Fungal Nomenclature: Managing Change is the Name of the Game

Fungal species have undergone and continue to undergo significant nomenclatural change, primarily due to the abandonment of dual species nomenclature in 2013 and the widespread application of molecular technologies in taxonomy allowing correction of past classification errors. These have effected numerous name changes concerning medically important species, but by far the group causing most concern are the Candida yeasts. Among common species, Candida krusei, Candida glabrata, Candida guilliermondii, Candida lusitaniae, and Candida rugosa have been changed to Pichia kudriavzevii, Nakaseomyces glabrata, Meyerozyma guilliermondii, Clavispora lusitaniae, and Diutina rugosa, respectively. There are currently no guidelines for microbiology laboratories on implementing changes, and there is ongoing concern that clinicians will dismiss or misinterpret laboratory reports using unfamiliar species names. Here, we have outlined the rationale for name changes across the major groups of clinically important fungi and have provided practical recommendations for managing change.

Molecular Epidemiology of Blastomyces gilchristii Clusters, Minnesota, USA

We characterized 2 clusters of blastomycosis cases in Minnesota, USA, using whole-genome sequencing and single-nucleotide polymorphism analyses. Blastomyces gilchristii was confirmed as the cause of infection. Genomic analyses corresponded with epidemiologic findings for cases of B. gilchristii infections, demonstrating the utility of genomic methods for future blastomycosis outbreak investigations.

Surveillance for Coccidioidomycosis, Histoplasmosis, and Blastomycosis - United States, 2019

PROBLEM/CONDITION

Coccidioidomycosis, histoplasmosis, and blastomycosis are underdiagnosed fungal diseases that often mimic bacterial or viral pneumonia and can cause disseminated disease and death. These diseases are caused by inhalation of fungal spores that have distinct geographic niches in the environment (e.g., soil or dust), and distribution is highly susceptible to climate changes such as expanding arid regions for coccidioidomycosis, the northward expansion of histoplasmosis, and areas like New York reporting cases of blastomycosis previously thought to be nonendemic. The national incidence of coccidioidomycosis, histoplasmosis, and blastomycosis is poorly characterized.

REPORTING PERIOD

2019.

DESCRIPTION OF SYSTEM

The National Notifiable Diseases Surveillance System (NNDSS) tracks cases of coccidioidomycosis, a nationally notifiable condition reported to CDC by 26 states and the District of Columbia. Neither histoplasmosis nor blastomycosis is a nationally notifiable condition; however, histoplasmosis is voluntarily reported in 13 states and blastomycosis in five states. Health departments classify cases based on the definitions established by the Council of State and Territorial Epidemiologists.

RESULTS

In 2019, a total of 20,061 confirmed coccidioidomycosis, 1,124 confirmed and probable histoplasmosis, and 240 confirmed and probable blastomycosis cases were reported to CDC. Arizona and California reported 97% of coccidioidomycosis cases, and Minnesota and Wisconsin reported 75% of blastomycosis cases. Illinois reported the greatest percentage (26%) of histoplasmosis cases. All three diseases were more common among males, and the proportion for blastomycosis (70%) was substantially higher than for histoplasmosis (56%) or coccidioidomycosis (52%). Coccidioidomycosis incidence was approximately four times higher for non-Hispanic American Indian or Alaska Native (AI/AN) persons (17.3 per 100,000 population) and almost three times higher for Hispanic or Latino persons (11.2) compared with non-Hispanic White (White) persons (4.1). Histoplasmosis incidence was similar across racial and ethnic categories (range: 0.9-1.3). Blastomycosis incidence was approximately six times as high among AI/AN persons (4.5) and approximately twice as high among non-Hispanic Asian and Native Hawaiian or other Pacific Islander persons (1.6) compared with White persons (0.7). More than one half of histoplasmosis (54%) and blastomycosis (65%) patients were hospitalized, and 5% of histoplasmosis and 9% of blastomycosis patients died. States in which coccidioidomycosis is not known to be endemic had more cases in spring (March, April, and May) than during other seasons, whereas the number of cases peaked slightly in autumn (September, October, and November) for histoplasmosis and in winter (December, January, and February) for blastomycosis.

INTERPRETATION

Coccidioidomycosis, histoplasmosis, and blastomycosis are diseases occurring in geographical niches within the United States. These diseases cause substantial illness, with approximately 20,000 coccidioidomycosis cases reported in 2019. Although substantially fewer histoplasmosis and blastomycosis cases were reported, surveillance was much more limited and underdiagnosis was likely, as evidenced by high hospitalization and death rates. This suggests that persons with milder symptoms might not seek medical evaluation and the symptoms self-resolve or the illnesses are misdiagnosed as other, more common respiratory diseases.

PUBLIC HEALTH ACTION

Improved surveillance is necessary to better characterize coccidioidomycosis severity and to improve detection of histoplasmosis and blastomycosis. These findings might guide improvements in testing practices that enable timely diagnosis and treatment of fungal diseases. Clinicians and health care professionals should consider coccidioidomycosis, histoplasmosis, and blastomycosis in patients with community-acquired pneumonia or other acute infections of the lower respiratory tract who live in or have traveled to areas where the causative fungi are known to be present in the environment. Culturally appropriate tailored educational messages might help improve diagnosis and treatment. Public health response to these three diseases is hindered because information gathered from states' routine surveillance does not include data on populations at risk and sources of exposure. Broader surveillance that includes expansion to other states, and more detail about potential exposures and relevant host factors can describe epidemiologic trends, populations at risk, and disease prevention strategies.

Blastomycosis-Some Progress but Still Much to Learn

Blastomycosis, caused by Blastomyces spp., is an endemic mycosis capable of causing significant disease throughout the body. Higher rates of infection are seen in the Mississippi and Ohio River valleys, the Great Lakes region of the United States and Canada, much of Africa, and, to a lesser extent, in India and the Middle East. Limited reporting inhibits our true understanding of the geographic distribution of blastomycosis. An estimated 50% of those infected remain asymptomatic. Of those who present with symptomatic disease, pulmonary involvement is most common, while the most common extrapulmonary sites are the skin, bones, genitourinary system, and central nervous system. Itraconazole is the standard therapy for mild-moderate disease. Data for other azoles are limited. Amphotericin is used for severe disease, and corticosteroids are occasionally used in severe disease, but evidence for this practice is limited. Despite increasing incidence and geographic reach in recent years, there are still significant knowledge gaps in our understanding of blastomycosis. Here, we provide an updated review of the epidemiology, clinical presentations, and diagnostic and therapeutic approaches for this infection. We also discuss areas needing further research.

Phylogenetic and ecological reevaluation of the order Onygenales

The order Onygenales is classified in the class Eurotiomycetes of the subphylum Pezizomycotina. Families in this order have classically been isolated from soil and dung, and two lineages contain causative agents of superficial, cutaneous and systemic infections in mammals. The ecology and habitat choices of the species are driven mainly by the keratin and cellulose degradation abilities. The present study aimed to investigate whether the ecological trends of the members of Onygenales can be interpreted in an evolutionary sense, linking phylogenetic parameters with habitat preferences, to achieve polyphasic definitions of the main taxonomic groups. Evolutionary processes were estimated by multiple gene genealogies and divergence time analysis. Previously described families, namely, Arthrodermataceae, Ajellomycetaceae, Ascosphaeraceae, Eremascaceae, Gymnoascaceae, Onygenaceae and Spiromastigoidaceae, were accepted in Onygenales, and two new families, Malbrancheaceae and Neogymnomycetaceae, were introduced. A number of species could not be assigned to any of the defined families. Our study provides a revised overview of the main lines of taxonomy of Onygenales, supported by multilocus analyses of ITS, LSU, TUB, TEF1, TEF3, RPB1, RPB2, and ribosomal protein 60S L10 (L1) (RP60S) sequences, combined with available data on ecology, physiology, morphology, and genomics.

Emerging Fungal Infections: New Species, New Names, and Antifungal Resistance

BACKGROUND

Infections caused by fungi can be important causes of morbidity and mortality in certain patient populations, including those who are highly immunocompromised or critically ill. Invasive mycoses can be caused by well-known species, as well as emerging pathogens, including those that are resistant to clinically available antifungals.

CONTENT

This review highlights emerging fungal infections, including newly described species, such as Candida auris, and those that having undergone taxonomic classification and were previously known by other names, including Blastomyces and Emergomyces species, members of the Rasamsonia argillacea species complex, Sporothrix brasiliensis, and Trichophyton indotinae. Antifungal resistance also is highlighted in several of these emerging species, as well as in the well-known opportunistic pathogen Aspergillus fumigatus. Finally, the increased recognition and importance of fungal co-infections with respiratory pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is discussed.

SUMMARY

Both clinicians and clinical microbiology laboratories should remain vigilant regarding emerging fungal infections. These may be difficult both to diagnose and treat due to the lack of experience of clinicians and laboratory personnel with these organisms and the infections they may cause. Many of these fungal infections have been associated with poor clinical outcomes, either due to inappropriate therapy or the development of antifungal resistance.

Global guideline for the diagnosis and management of the endemic mycoses: an initiative of the European Confederation of Medical Mycology in cooperation with the International Society for Human and Animal Mycology

The global burden of the endemic mycoses (blastomycosis, coccidioidomycosis, emergomycosis, histoplasmosis, paracoccidioidomycosis, sporotrichosis, and talaromycosis) continues to rise yearly and these infectious diseases remain a leading cause of patient morbidity and mortality worldwide. Management of the associated pathogens requires a thorough understanding of the epidemiology, risk factors, diagnostic methods and performance characteristics in different patient populations, and treatment options unique to each infection. Guidance on the management of these infections has the potential to improve prognosis. The recommendations outlined in this Review are part of the "One World, One Guideline" initiative of the European Confederation of Medical Mycology. Experts from 23 countries contributed to the development of these guidelines. The aim of this Review is to provide an up-to-date consensus and practical guidance in clinical decision making, by engaging physicians and scientists involved in various aspects of clinical management.

Diagnostic Methods and Risk Factors for Severe Disease and Mortality in Blastomycosis: A Retrospective Cohort Study

Background: Blastomycosis can cause severe disease with progressive respiratory failure and dissemination even in immunocompetent individuals. We sought to evaluate risk factors for severe disease and mortality using clinical and laboratory data within a large health system in an endemic area. Methods: We performed a retrospective cohort study of patients diagnosed with blastomycosis at all Mayo Clinic sites from 1 January 2004 through 31 March 2020. Diagnosis was established by culture, histopathology/cytopathology, serology, antigen testing, or PCR. Disease was categorized as mild for patients treated in the outpatient setting, moderate for hospitalized patients who did not require intensive care, and severe for patients admitted to the intensive care unit. Logistic regression was used to evaluate risk factors for severe disease. A Cox proportional hazards model was constructed to evaluate mortality. Findings: We identified 210 patients diagnosed with blastomycosis. Mean age was 51 years (range, 6–84). Most subjects were male (71.0%). Extrapulmonary disease was confirmed in 24.8%. In this cohort, 40.5% of patients had mild disease, 37.6% had moderate disease, and 21.9% had severe disease. Independent risk factors for severe disease were neutrophilia (odds ratio (OR) 3.35 (95% CI 1.53–7.35), p = 0.002) and lymphopenia (OR 3.34 (95% CI 1.59–7.03), p = 0.001). Mortality at 90 days was 11.9%. Median time from diagnosis to death was 23 days (interquartile range 8–31 days). Independent risk factors for mortality were age (OR 1.04 (95% CI 1.01–1.08), p = 0.009), neutrophilia (OR 2.84 (95% CI 1.04–7.76), p = 0.041), and lymphopenia (OR 4.50 (95% CI 1.67–12.11), p = 0.003). Blastomyces immunodiffusion had an overall sensitivity of 39.6% (95% CI 30.1–49.8). Sensitivity was higher among those who were tested 4 weeks or longer after the onset of symptoms. Urine Blastomyces antigen had a significantly higher sensitivity of 80.8% (95% CI 68.1–89.2) compared to serology. There was a trend towards higher antigen concentration in patients with severe disease. The sensitivity of PCR from respiratory specimens was 67.6% (95% CI 50.1–85.5). Conclusion: In this cohort, we did not find an association between pharmacologic immunosuppression and disease severity. Lymphopenia at diagnosis was an independent risk factor for mortality. This simple marker may aid clinicians in determining disease prognosis.

Blastomycosis in Africa and the Middle East: A Comprehensive Review of Reported Cases and Reanalysis of Historical Isolates Based on Molecular Data

BACKGROUND

Blastomycosis has been reported from countries in Africa and the Middle East, but a decades-long debate has persisted regarding whether this is the same disease known in North America and caused by Blastomyces dermatitidis and Blastomyces gilchristii.

METHODS

We reviewed published cases of human and veterinary blastomycosis from Africa and the Middle East. We abstracted epidemiological and clinical features of cases, including sites of disease, diagnosis, management, outcomes, and, where available, genetic and antigenic typing of case isolates. In addition, we sequenced nucleic acids from 9 clinical isolates from Africa deposited in global collections as B. dermatitidis; for 5, we sequenced the internal transcribed spacer regions, and for the other 4 we sequenced the whole genomes.

RESULTS

We identified 172 unique human patients with blastomycosis, including 159 patients from 25 African countries and 12 patients from 5 Middle Eastern countries, and also identified 7 reports of veterinary blastomycosis. In humans, cutaneous disease predominated (n = 100/137, 73%), followed by pulmonary (n = 73/129, 57%) and osteoarticular involvement (n = 61/128, 48%). Unusual direct microscopy/histopathological presentations included short hyphal fragments in tissues (n = 23/129, 18%). There were 34 genotyped case isolates that comprised 4 species: Blastomyces percursus (n = 22, 65%), from 8 countries throughout all regions; Blastomyces emzantsi (n = 9, 26%), from South Africa; B. dermatitidis (n = 1, 3%), from the Democratic Republic of Congo; and B. gilchristii (n = 2, 6%), from South Africa and Zimbabwe.

CONCLUSIONS

Blastomycosis occurs throughout Africa and the Middle East and is caused predominantly by B. percursus and, at least in South Africa, B. emzantsi, resulting in distinct clinical and pathological patterns of disease.

Blastomycosis in Minnesota, USA, 1999-2018

Blastomycosis is a systemic disease caused by Blastomyces spp. fungi. To determine its epidemiology in blastomycosis-endemic Minnesota, USA, we evaluated all cases reported to public health officials during 1999-2018. We focused on time to diagnosis, exposure activities, and exposure location. A total of 671 cases and a median of 34 cases/year were reported. Median time to diagnosis was 31 days; 61% of patients were not tested for blastomycosis until they were hospitalized. The case-fatality rate was 10%, and patients who died were 5.3 times more likely to have a concurrent medical condition. Outdoor activities and soil exposure were reported by many patients, but no specific activity or exposure was common to most. Almost one third of patients were probably exposed in geographic areas other than their home county. Providers should consider alternative etiologies for patients with pneumonia not responding to antibacterial treatment, and public health officials should increase awareness in blastomycosis-endemic areas.

Immunology of Fungal Infections

Complex processes mediate immunity to fungal infections. Responses vary depending on the organism, morphogenic state, and infection site. Innate immune effectors such as epithelia, phagocytes, and soluble molecules detect pathogens, kill fungi, release cytokines, and prime the adaptive response. Adaptive responses to mucocutaneous or invasive disease are markedly different but intersect at certain pathways (molecules required for IL-23 and IL-12 signaling). Many of these pathways have been elucidated from the study of inborn errors of immunity. This review explores the general aspects of antifungal immunity and delves into the mechanisms that mediate protection from frequently encountered fungi.

Emerging Fungal Infections

Various uncommon fungal pathogens have been increasingly identified as causes of disseminated and invasive fungal disease (IFD) worldwide. Growing recognition and clinical knowledge of these emerging fungal pathogens has occurred through improved molecular diagnostics, nucleic sequence databases, and taxonomic reclassification of medically significant fungi. However, emerging fungal diseases carry significant morbidity and mortality and, due to a paucity of published literature, the collective clinical experience with these fungi is often limited. In this review, we focus on unusual emerging fungal pathogens not extensively covered elsewhere in this issue of Infectious Diseases Clinics of North America.

Blastomycosis

Blastomycosis is the fungal disease caused by thermally dimorphic fungi in the genus Blastomyces, with B dermatitidis complex causing most cases. It is considered hyperendemic in areas adjacent to the Great Lakes and along the St. Lawrence, Mississippi, and Ohio rivers, but definitive geographic distribution of blastomycoses remains obscure. Clinical presentation is variable. Disseminated blastomycosis with extrapulmonary manifestations is more common in immunosuppressed individuals. Culture positivity is required for definitive diagnosis, but compatible histology is often sufficient for presumptive diagnosis and initiation of treatment. Treatment should be provided to all symptomatic cases to prevent progression or recurrence.

Direct Tissue PCR and Genotyping for Species Identification in a Case of Laryngeal Blastomycosis

Otolaryngologic manifestations of infection with Blastomyces species are extremely rare and restricted geographically to recognized endemic regions. Here, we describe a case of laryngeal blastomycosis that presented as slowly progressive dysphonia. While a preliminary diagnosis was made using routine histopathology, a species identification of Blastomyces dermatitidis was made using polymerase chain reaction amplification and rapid genotyping without the need for fungal culture. All symptoms resolved following 1 month of antifungal therapy. Rapid molecular differentiation of B dermatitidis from Blastomyces gilchristii provides important insights into pathogenesis given recent recognition of differences in clinical spectra.

Endemic and Other Dimorphic Mycoses in The Americas

Endemic fungi are thermally dimorphic fungi that have a limited geographic range and can cause both primary disease and opportunistic infections. The Americas are home to more genera of endemic fungi than anywhere else on earth. These include Coccidioides, Histoplasma, Blastomyces, Paracoccidioides, and Sporothrix. Endemic fungi are found across the Americas and the Caribbean, from Blastomyces gilchristi, which extends into the northeast corners of North America, to Histoplasma capsulatum, which occurs all the way down in the southern regions of South America and into the Caribbean Islands. Symptoms of endemic fungal infection, when present, mimic those of many other diseases and are often diagnosed only after initial treatment for a bacterial or viral disease has failed. Endemic fungi place a significant medical burden on the populations they affect, especially in immunocompromised individuals and in resource-limited settings. This review summarizes the ecology, geographical range, epidemiology, and disease forms of the endemic fungi found in the Americas. An emphasis is placed on new and proposed taxonomic changes, including the assignment of new species names in Histoplasma, Blastomyces, and Paracoccidioides.

Analysis and modeling of Blastomyces dermatitidis environmental prevalence in Minnesota using soil collected to compare basal and outbreak levels

Outbreaks of blastomycosis, caused by the fungus Blastomyces dermatitidis, occur in endemic areas of the United States and Canada but the geographic range of blastomycosis is expanding. Previous studies inferred the location of B. dermatitidis through epidemiologic data associated with outbreaks because culture of B. dermatitidis from the environment is often unsuccessful. In this study, we used a culture-independent, PCR-based method to identify B. dermatitidis DNA in environmental samples using the BAD1 promoter region. We tested 250 environmental samples collected in Minnesota, either associated with blastomycosis outbreaks or environmental samples collected from high- and low-endemic regions to determine basal prevalence of B. dermatitidis in the environment. We identified a fifth BAD1 promoter haplotype of B. dermatitidis prevalent in Minnesota. Ecological niche analysis identified latitude, longitude, elevation, and site classification as environmental parameters associated with the presence of B. dermatitidis Using this analysis, a Random Forest model predicted B. dermatitidis presence in basal environmental samples with 75% accuracy. These data support use of culture-independent, PCR-based environmental sampling to track spread into new regions and to characterize the unknown B. dermatitidis environmental niche.Importance Upon inhalation of spores from the fungus Blastomyces dermatitidis from the environment, humans and animals can develop the disease blastomycosis. Based on disease epidemiology, B. dermatitidis is known to be endemic in the United States and Canada around the Great Lakes and in the Ohio and Mississippi River Valleys but is starting to emerge in other areas. B. dermatitidis is extremely difficult to culture from the environment so little is known about the environmental reservoirs for this pathogen. We used a culture-independent PCR-based assay to identify the presence of B. dermatitidis DNA in soil samples from Minnesota. By combining molecular data with ecological niche modeling, we were able to predict the presence of B. dermatitidis in environmental samples with 75% accuracy and to define characteristics of the B. dermatitidis environmental niche. Importantly, we showed the effectiveness of using a PCR-based assay to identify B. dermatitidis in environmental samples.

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.

Spontaneous resolution of blastomycosis symptoms caused by B. dermatitidis

Given the propensity of blastomycosis to disseminate or reoccur and the inability to predict which infections will experience severe manifestations, nearly all cases of blastomycosis are treated. Although, spontaneous resolution of symptoms is referred to generally in the literature, to our knowledge an individual case of this has not been previously reported. We report the spontaneous resolution of blastomycosis symptoms in a 40 year-old Caucasian male.

Onygenalean Fungi as Major Human and Animal Pathogens

During the last two decades, many onygenalean pathogens were discovered, redefined, or re-classified from existing taxa into clusters of micro-species, among which the original genotypes often appeared to be uncommon and exceptional. The impact of these developments on the diagnosis and treatment of fungal diseases remains to be determined in most instances. This exciting collection of invited articles provides a full flavor of ongoing changes in the knowledge about taxonomy, genetics, ecology, epidemiology, and clinical spectra of human and animal pathogens classified in the order Onygenales. Recent developments have set the stage for an ambitious translational research agenda. Diagnostic mycology laboratories now need MALDI-TOF-MS spectra, PCR probes, and other specific tools to assist them in the rapid diagnosis of new species. Similarly, an educational set of type materials of new species needs to be readily available for enhanced expertise among the wider medical mycology community. As several new species were discovered retrospectively, it is crucial to expand the re-sampling to other fungal culture collections and archived paraffin tissues. Finally, clinical and laboratory investigations are needed to get an accurate assessment of the prevalence and impact of new pathogens as the cause of major fungal diseases.

Revision and Update of the Consensus Definitions of Invasive Fungal Disease From the European Organization for Research and Treatment of Cancer and the Mycoses Study Group Education and Research Consortium

BACKGROUND

Invasive fungal diseases (IFDs) remain important causes of morbidity and mortality. The consensus definitions of the Infectious Diseases Group of the European Organization for Research and Treatment of Cancer and the Mycoses Study Group have been of immense value to researchers who conduct clinical trials of antifungals, assess diagnostic tests, and undertake epidemiologic studies. However, their utility has not extended beyond patients with cancer or recipients of stem cell or solid organ transplants. With newer diagnostic techniques available, it was clear that an update of these definitions was essential.

METHODS

To achieve this, 10 working groups looked closely at imaging, laboratory diagnosis, and special populations at risk of IFD. A final version of the manuscript was agreed upon after the groups' findings were presented at a scientific symposium and after a 3-month period for public comment. There were several rounds of discussion before a final version of the manuscript was approved.

RESULTS

There is no change in the classifications of "proven," "probable," and "possible" IFD, although the definition of "probable" has been expanded and the scope of the category "possible" has been diminished. The category of proven IFD can apply to any patient, regardless of whether the patient is immunocompromised. The probable and possible categories are proposed for immunocompromised patients only, except for endemic mycoses.

CONCLUSIONS

These updated definitions of IFDs should prove applicable in clinical, diagnostic, and epidemiologic research of a broader range of patients at high-risk.

Endemic mycoses: epidemiology and diagnostic strategies

INTRODUCTION

The global frequency of endemic mycoses has considerably increased, mainly due to environmental changes, population growth in endemic areas, and the increase in HIV-related immunosuppressed status. Among the most frequent endemic mycoses are coccidioidomycosis in semi-desert climates, and paracoccidioidomycosis, and histoplasmosis in tropical climates. The inoculum can enter the host through the airway or directly through the skin. Lymphatic and hematogenous spread may involve the skin.

AREAS COVERED

In this article, we provide up-to-date epidemiological and diagnostic data on major (histoplasmosis, paracoccidioidomycosis, coccidioidomycosis, blastomycosis) and minor (talaromycosis, adiaspiromycosis, emergomycosis) endemic mycoses.

EXPERT OPINION

Endemic mycoses include diseases with a localized endemic area, and a few of them converge. These mycoses all have in common the airway involvement and can cause pulmonary symptoms following initial asymptomatic infection. Among the risk groups to acquire these mycoses are travelers from endemic areas, archeologists, speleologists, and immigrants. Promising and useful diagnostic tools have been developed in endemic mycoses; however, most of them are not standardized or available in low-income countries.

Human Blastomycosis in South Africa Caused by Blastomyces percursus and Blastomyces emzantsi sp. nov., 1967 to 2014

We reevaluated 20 cases of blastomycosis diagnosed in South Africa between 1967 and 2014, with Blastomyces dermatitidis considered to be the etiological agent, in light of newly described species and the use of more advanced technologies. In addition to histopathological and/or culture-based methods, all 20 isolates were phenotypically and genotypically characterized, including multilocus typing of five genes and whole-genome sequencing. Antifungal susceptibility testing was performed as outlined by Clinical and Laboratory Standards Institute documents M27-A3 and M38-A2. We merged laboratory and corresponding clinical case data, where available. Morphological characteristics and phylogenetic analyses of five-gene and whole-genome sequences revealed two groups, both of which were closely related to but distinct from B. dermatitidis, Blastomyces gilchristii, and Blastomyces parvus The first group (n = 12) corresponded to the recently described species Blastomyces percursus, and the other (n = 8) is described here as Blastomyces emzantsi sp. nov. Both species exhibited incomplete conversion to the yeast phase at 37°C and were heterothallic for mating types. All eight B. emzantsi isolates belonged to the α mating type. Whole-genome sequencing confirmed distinct species identities as well as the absence of a full orthologue of the BAD-1 gene. Extrapulmonary (skin or bone) disease, probably resulting from hematogenous spread from a primary lung infection, was more common than pulmonary disease alone. Voriconazole, posaconazole, itraconazole, amphotericin B, and micafungin had the most potent in vitro activity. Over the 5 decades, South African cases of blastomycosis were caused by species that are distinct from B. dermatitidis Increasing clinical awareness and access to simple rapid diagnostics may improve the diagnosis of blastomycosis in resource-limited countries.

Re-drawing the Maps for Endemic Mycoses

Endemic mycoses such as histoplasmosis, coccidioidomycosis, blastomycosis, paracoccidioidomycosis, and talaromycosis are well-known causes of focal and systemic disease within specific geographic areas of known endemicity. However, over the past few decades, there have been increasingly frequent reports of infections due to endemic fungi in areas previously thought to be “non-endemic.” There are numerous potential reasons for this shift such as increased use of immune suppressive medications, improved diagnostic tests, increased disease recognition, and global factors such as migration, increased travel, and climate change. Regardless of the causes, it has become evident that our previous understanding of endemic regions for these fungal diseases needs to evolve. The epidemiology of the newly described Emergomyces is incomplete; our understanding of it continues to evolve. This review will focus on the evidence underlying the established areas of endemicity for these mycoses as well as new data and reports from medical literature that support the re-thinking these geographic boundaries. Updating the endemic fungi maps would inform clinical practice and global surveillance of these diseases.

Fantastic yeasts and where to find them: the hidden diversity of dimorphic fungal pathogens

Dimorphic fungal pathogens are a significant cause of human disease worldwide. Notably, the dimorphic fungal pathogens within the order Onygenales are considered primary pathogens, causing disease in healthy hosts. Current changes in taxonomy are underway due to advances in molecular phylogenetics, population genetics, and new emerging dimorphic fungal pathogens causing human disease. In this review, we highlight evolutionary relationships of dimorphic fungal pathogens that cause human disease within the order Onygenales and provide rationale to support increased investment in studies understanding the evolutionary relationships of these pathogens to improve rapid diagnostics, help identify mechanisms of antifungal resistance, understand adaptation to human host, and factors associated with virulence.

Racial Differences in Clinical Phenotype and Hospitalization of Blastomycosis Patients

Background

Dimorphic fungal infections, such as blastomycosis, cause significant morbidity and mortality. Historically, blastomycosis studies have focused on non-Hispanic whites, which limits our understanding of the clinical presentation and outcomes for patients of other races and ethnicities. We evaluated whether clinical presentation and disease severity varied across racial and ethnic groups.

Methods

Blastomycosis patients were identified from Marshfield Clinic Health System and data were abstracted from electronic medical records. Blastomyces genotyping was performed for cases with available isolates. Bivariate analyses (χ ² tests/analysis of variance) assessed associations of race and/or ethnicity, Blastomyces spp, and hospitalization status with demographics and clinical presentation. Multivariable logistic regression was used to evaluate the association of race and/or ethnicity and hospitalization.

Results

In total, 477 patients were included. Age differences were observed across race and ethnicity categories (P < .0001). Non-Hispanic whites were oldest (median, 48 years; interquartile range [IQR], 31–62) and Asians were youngest (26 years; IQR, 19–41). Non-Hispanic whites (55%) and African Americans (52%) had underlying medical conditions more frequently than Hispanic whites (27%) and Asians (29%). Odds of hospitalization were 2 to 3 times higher for Hispanic whites (adjusted odds ratio [aOR], 2.9; 95% confidence interval [CI], 1.2–1.7), American Indian or Alaska Native (AIAN) (aOR, 2.4; 95% CI, 1.0–5.5), and Asian (aOR, 1.9; 95% CI, 1.0–3.6) patients compared with non-Hispanic white patients. Ninety percent of Blastomyces dermatitidis infections occurred in non-Hispanic whites, whereas blastomycosis in Hispanic whites, AIAN, and Asian patients was frequently caused by Blastomyces gilchristii (P < .0001).

Conclusions

Hispanic whites, AIAN, and Asian blastomycosis patients were younger and healthier but more frequently hospitalized. Patients in these racial and ethnic groups may need more aggressive treatment and closer therapeutic monitoring.

[Climate change and systemic fungal infections]

BACKGROUND

Climate change may cause profound and complex changes in the prevalence of infectious diseases. Obligate pathogenic fungi causing endemic mycoses and the agents of cryptococcosis are environmental pathogens adapted to environmental niches. They may be exposed to changing climatic conditions, which may change the epidemiology of human infections.

OBJECTIVES

To review documented changes in the epidemiology of endemic fungal infections and cryptococcosis. To review evidence that changing climate is a potential mechanism for changes in the epidemiology of these infections.

METHODS

A selective literature review focusing on endemic mycoses and cryptococcosis.

RESULTS

Changes in endemic regions of infections caused by C. gattii and selected endemic mycoses have been well documented. Significant increases in the incidence of infections have been demonstrated for some areas. Climatic factors (temperature, precipitation, and extreme weather events), changes in land use, distribution of potential host animals, and global trade routes are discussed as contributory factors.

CONCLUSIONS

Improved surveillance of fungal infections of humans and animals including molecular typing of clinical and environmental isolates is necessary to understand the epidemiology of these infections. The characterization of environmental niches, mechanisms of distribution of fungi, and fungal adaptation mechanisms are needed to guide prevention strategies.

How Environmental Fungi Cause a Range of Clinical Outcomes in Susceptible Hosts

Environmental fungi are globally ubiquitous and human exposure is near universal. However, relatively few fungal species are capable of infecting humans, and among fungi, few exposure events lead to severe systemic infections. Systemic infections have mortality rates of up to 90%, cost the US healthcare system $7.2 billion annually, and are typically associated with immunocompromised patients. Despite this reputation, exposure to environmental fungi results in a range of outcomes, from asymptomatic latent infections to severe systemic infection. Here we discuss different exposure outcomes for five major fungal pathogens: Aspergillus, Blastomyces, Coccidioides, Cryptococcus, and Histoplasma species. These fungi include a mold, a budding yeast, and thermal dimorphic fungi. All of these species must adapt to dramatically changing environments over the course of disease. These dynamic environments include the human lung, which is the first exposure site for these organisms. Fungi must defend themselves against host immune cells while germinating and growing, which risks further exposing microbe-associated molecular patterns to the host. We discuss immune evasion strategies during early infection, from disruption of host immune cells to major changes in fungal cell morphology.

Emerging Fungal Infections: New Patients, New Patterns, and New Pathogens

The landscape of clinical mycology is constantly changing. New therapies for malignant and autoimmune diseases have led to new risk factors for unusual mycoses. Invasive candidiasis is increasingly caused by non-albicans Candida spp., including C. auris, a multidrug-resistant yeast with the potential for nosocomial transmission that has rapidly spread globally. The use of mould-active antifungal prophylaxis in patients with cancer or transplantation has decreased the incidence of invasive fungal disease, but shifted the balance of mould disease in these patients to those from non-fumigatus Aspergillus species, Mucorales, and Scedosporium/Lomentospora spp. The agricultural application of triazole pesticides has driven an emergence of azole-resistant A. fumigatus in environmental and clinical isolates. The widespread use of topical antifungals with corticosteroids in India has resulted in Trichophyton mentagrophytes causing recalcitrant dermatophytosis. New dimorphic fungal pathogens have emerged, including Emergomyces, which cause disseminated mycoses globally, primarily in HIV infected patients, and Blastomyceshelicus and B. percursus, causes of atypical blastomycosis in western parts of North America and in Africa, respectively. In North America, regions of geographic risk for coccidioidomycosis, histoplasmosis, and blastomycosis have expanded, possibly related to climate change. In Brazil, zoonotic sporotrichosis caused by Sporothrix brasiliensis has emerged as an important disease of felines and people.

Central Nervous System Infection with Other Endemic Mycoses: Rare Manifestation of Blastomycosis, Paracoccidioidomycosis, Talaromycosis, and Sporotrichosis

The central nervous system (CNS) is not a major organ involved with infections caused by the endemic mycoses, with the possible exception of meningitis caused by Coccidioides species. When CNS infection does occur, the manifestations vary among the different endemic mycoses; mass-like lesions or diffuse meningeal involvement can occur, and isolated chronic meningitis, as well as widely disseminated acute infection that includes the CNS, are described. This review includes CNS infection caused by Blastomyces dermatitidis, Paracoccidioides brasiliensis, Talaromyces marneffei, and the Sporothrix species complex. The latter is not geographically restricted, in contrast to the classic endemic mycoses, but it is similar in that it is a dimorphic fungus. CNS infection with B. dermatitidis can present as isolated chronic meningitis or a space-occupying lesion usually in immunocompetent hosts, or as one manifestation of widespread disseminated infection in patients who are immunosuppressed. P. brasiliensis more frequently causes mass-like intracerebral lesions than meningitis, and most often CNS disease is part of disseminated infection found primarily in older patients with the chronic form of paracoccidioidomycosis. T. marneffei is the least likely of the endemic mycoses to cause CNS infection. Almost all reported cases have been in patients with advanced HIV infection and almost all have had widespread disseminated infection. Sporotrichosis is known to cause isolated chronic meningitis, primarily in immunocompetent individuals who do not have Sporothrix involvement of other organs. In contrast, CNS infection in patients with advanced HIV infection occurs as part of widespread disseminated infection.

Peripheral blood smear findings in a kidney transplant recipient with disseminated histoplasmosis and elevated Aspergillus galactomannan

We report a case of disseminated histoplasmosis in a renal transplant recipient who presented with a nodular pulmonary lesion and elevated serum and bronchoalveolar lavage (BAL) Aspergillus galatomannan. This almost led to an erroneous diagnosis of invasive aspergillosis since the donor respiratory tract was known to be colonized with Aspergillus terreus. However, distinctive intracelluar Histoplasma yeasts on peripheral blood smear led to early diagnosis and appropriate treatment. The cross-reactivity between Aspergillus galactomannan and Histoplasma antigen is discussed further.