Evidence of subclinical blastomycosis in forestry workers in northern Minnesota and northern Wisconsin

Social determinants of health as drivers of fungal disease

Disparities in social determinants of health (SDOH) play a significant role in causing health inequities globally. The physical environment, including housing and workplace environment, can increase the prevalence and spread of fungal infections. A number of professions are associated with increased fungal infection risk and are associated with low pay, which may be linked to crowded and sub-optimal living conditions, exposure to fungal organisms, lack of access to quality health care, and risk for fungal infection. Those involved and displaced from areas of armed conflict have an increased risk of invasive fungal infections. Lastly, a number of fungal plant pathogens already threaten food security, which will become more problematic with global climate change. Taken together, disparities in SDOH are associated with increased risk for contracting fungal infections. More emphasis needs to be placed on systematic approaches to better understand the impact and reducing the health inequities associated with these disparities.

An update on current and novel molecular diagnostics for the diagnosis of invasive fungal infections

BACKGROUND

Invasive fungal infections cause millions of infections annually, but diagnosis remains challenging. There is an increased need for low-cost, easy to use, highly sensitive and specific molecular assays that can differentiate between colonized and pathogenic organisms from different clinical specimens.

AREAS COVERED

We reviewed the literature evaluating the current state of molecular diagnostics for invasive fungal infections, focusing on current and novel molecular tests such as polymerase chain reaction (PCR), digital PCR, high-resolution melt (HRM), and metagenomics/next generation sequencing (mNGS).

EXPERT OPINION

PCR is highly sensitive and specific, although performance can be impacted by prior/concurrent antifungal use. PCR assays can identify mutations associated with antifungal resistance, non-Aspergillus mold infections, and infections from endemic fungi. HRM is a rapid and highly sensitive diagnostic modality that can identify a wide range of fungal pathogens, including down to the species level, but multiplex assays are limited and HRM is currently unavailable in most healthcare settings, although universal HRM is working to overcome this limitation. mNGS offers a promising approach for rapid and hypothesis-free diagnosis of a wide range of fungal pathogens, although some drawbacks include limited access, variable performance across platforms, the expertise and costs associated with this method, and long turnaround times in real-world settings.

A case of tracheal and pulmonary blastomycosis presenting as asymptomatic pulmonary nodules

Blastomyces is an endemic fungal pathogen found in regions of North America. It is endemic in the Ohio and Mississippi river valleys, New York, Wisconsin, Colorado, Texas, Kansas, Nebraska, and other regions of the United States. It is common in Canada, mainly Ontario and Manitoba. Here, we report a case of tracheal and pulmonary blastomycosis. Interestingly, this case presented as an unexpected diagnosis as part of a malignancy workup. To our knowledge, this is only the second case of tracheal blastomycosis reported in the literature.

Outcomes With Severe Blastomycosis and Respiratory Failure in the United States

BACKGROUND

Outcomes of patients with severe pulmonary blastomycosis requiring mechanical ventilation (MV) are not well understood in the modern era. Limited historical case series reported 50-90% mortality in patients with acute respiratory distress syndrome caused by blastomycosis. The objective of this large retrospective cohort study was to describe the risk factors and outcomes of patients with severe pulmonary blastomycosis.

METHODS

We performed a retrospective cohort analysis utilizing the Nationwide Inpatient Sample from 2006-2014. Patients aged >18 years with a diagnosis of blastomycosis who received MV were included.

RESULTS

There were 1848 patients with a diagnosis of blastomycosis included in the study. Of these, 219 (11.9%) underwent MV with a mortality rate of 39.7% compared with 2.5% in patients not requiring ventilatory support (P < .01). The median (IQR) time to death for patients requiring MV was 12 (8-16) days. The median length of hospital stay for survivors of MV was 22 (14-37) days. The rate of MV was higher for patients treated in teaching hospitals (63.4% vs 57.2%, P = .05) and lower for those receiving care at a rural hospital (12.3% vs 17.2%, P = .04). In a multivariate model, female gender was associated with increased risk of mortality (OR, 1.84; 95% CI, 1.06-3.20; P = .03) as was increasing patient age (10-year age increase OR, 1.64; 95% CI, 1.33-2.02; P < .01).

CONCLUSIONS

In the largest published cohort of patients with blastomycosis, mortality for patients on MV is high at ~40%, 16-fold higher than those without MV.

Advances in Understanding Human Genetic Variations That Influence Innate Immunity to Fungi

Fungi are ubiquitous. Yet, despite our frequent exposure to commensal fungi of the normal mammalian microbiota and environmental fungi, serious, systemic fungal infections are rare in the general population. Few, if any, fungi are obligate pathogens that rely on infection of mammalian hosts to complete their lifecycle; however, many fungal species are able to cause disease under select conditions. The distinction between fungal saprophyte, commensal, and pathogen is artificial and heavily determined by the ability of an individual host's immune system to limit infection. Dramatic examples of commensal fungi acting as opportunistic pathogens are seen in hosts that are immune compromised due to congenital or acquired immune deficiency. Genetic variants that lead to immunological susceptibility to fungi have long been sought and recognized. Decreased myeloperoxidase activity in neutrophils was first reported as a mechanism for susceptibility to Candida infection in 1969. The ability to detect genetic variants and mutations that lead to rare or subtle susceptibilities has improved with techniques such as single nucleotide polymorphism (SNP) microarrays, whole exome sequencing (WES), and whole genome sequencing (WGS). Still, these approaches have been limited by logistical considerations and cost, and they have been applied primarily to Mendelian impairments in anti-fungal responses. For example, loss-of-function mutations in CARD9 were discovered by studying an extended family with a history of fungal infection. While discovery of such mutations furthers the understanding of human antifungal immunity, major Mendelian susceptibility loci are unlikely to explain genetic disparities in the rate or severity of fungal infection on the population level. Recent work using unbiased techniques has revealed, for example, polygenic mechanisms contributing to candidiasis. Understanding the genetic underpinnings of susceptibility to fungal infections will be a powerful tool in the age of personalized medicine. Future application of this knowledge may enable targeted health interventions for susceptible individuals, and guide clinical decision making based on a patient's individual susceptibility profile.

Blastomycosis in Southern Saskatchewan 2000-2015: Unique presentations and disease characteristics

In the literature, cases of blastomycosis in Canada have been documented in provinces bordering the Great Lakes, including Ontario and Quebec, as well as Manitoba. This is the first study to our knowledge reporting cases of mycosis seen in southern Saskatchewan suggesting a broader area of endemicity. We searched the Regina Qu'Appelle Health Region (RQHR) Microbiology Laboratory for all culture-confirmed cases of Blastomyces from January 2000 to December 2015 and identified 15 cases. Thirteen cases were reviewed, identifying common presenting symptoms, misdiagnosis, comorbidities, travel history, time from presentation to diagnosis, diagnostic specimen, treatment, and clinical outcome. Nine patients had no travel to areas known to be endemic to environmental blastomycosis. Eight patients presented with respiratory symptoms, four with skin lesions, four with constitutional symptoms, and one presented with chest pain after a fall. Initial misdiagnosis occurred in nine (69%) of the 13 cases, and all six patients that died of the disease were misdiagnosed. These six patients (46%) were acutely ill with refractory disseminated disease, leading to respiratory failure. It is probable that Blastomyces is present as an endemic fungus in the soil of southern Saskatchewan. Possibly due to a lack of awareness of this pathogen in the area, initial misdiagnoses were common and likely contributed to significant morbidity and mortality.

Cerebral Epidural Abscess Secondary to Blastomyces Masquerading as an Epidermoid Tumor

There have been infrequent reports of isolated central nervous system blastomycosis. We report a case of intracranial epidural abscess secondary to Blastomyces dermatitidis in a patient residing in Rhode Island with a history of remote travel to an endemic area. The clinical, radiographic, and pathologic features of this unique case are reviewed.

Risk factors for acquisition of endemic blastomycosis

BACKGROUND

Blastomycosis is potentially fatal, but environmental risk factors for acquiring blastomycosis are not well established.

METHOD

Matched cross-sectional questionnaire of 112 patients with history of blastomycosis and 118 control subjects in Manitoba and northwestern Ontario.

RESULTS

The most common tissues involved with blastomycosis were pulmonary, skin and soft tissues, and bone. A significantly greater proportion of patients with blastomycosis than control subjects were involved in outdoor occupations. A significantly greater percentage of patients with blastomycosis were immunosuppressed either from collagen vascular disease or immunosuppressive therapy, or had hypothyroidism. A significant association between canine and human blastomycosis was not observed.

CONCLUSIONS

Independent risk factors for development of blastomycosis included immunosuppression for any reason (including drugs or disease), collagen vascular disease, being an outdoor worker, and having a coworker with blastomycosis. Canine blastomycosis was not a risk factor for human disease in dog owners.

Clinical and laboratory update on blastomycosis

Blastomycosis is endemic in regions of North America that border the Great Lakes and the St. Lawrence River, as well as in the Mississippi River and Ohio River basins. Men are affected more often than women and children because men are more likely to participate in activities that put them at risk for exposure to Blastomyces dermatitidis. Human infection occurs when soil containing microfoci of mycelia is disturbed and airborne conidia are inhaled. If natural defenses in the alveoli fail to contain the infection, lymphohematogenous dissemination ensues. Normal host responses generate a characteristic pyogranulomatous reaction. The most common sites of clinical disease are the lung and skin; osseous, genitourinary, and central nervous system manifestations follow in decreasing order of frequency. Blastomycosis is one of the great mimickers in medicine; verrucous cutaneous blastomycosis resembles malignancy, and mass-like lung opacities due to B. dermatitidis often are confused with cancer. Blastomycosis may be clinically indistinguishable from tuberculosis. Diagnosis is based on culture and direct visualization of round, multinucleated yeast forms that produce daughter cells from a single broad-based bud. Although a long course of amphotericin B is usually curative, itraconazole is also highly effective and is the mainstay of therapy for most patients with blastomycosis.

Treatment of endemic mycoses

The endemic mycoses are a diverse group of diseases caused by thermally dimorphic fungi. While they share many characteristics, each has unique aspects with regards to their clinical course, diagnosis and management. Diagnosis may be difficult and delayed owing to the varied manifestations and wide differential diagnosis. Historically, treatment has been with amphotericin B, which has been limited by its significant toxicity. The advent of the azole class of medications has allowed for safer alternatives to amphotericin B. The azoles have become the mainstay of treatment for many, if not most, forms of these diseases. Guidelines have been released for the management of each of the North American endemic mycoses; however, many questions remain as to the best strategies for the diagnosis and management of various manifestations of these diseases.

Blastomycosis of Bones and Joints

A retrospective study of 45 patients hospitalized with blastomycosis of bones or joints revealed 41 cases of osteomyelitis and 12 cases of septic arthritis. The majority were men (35 [78%] patients) and non-Aboriginal (32 [71%] patients). Median time from the onset of symptoms to hospitalization was shorter in women than men (male, 48 d; female, 14 d; P < 0.02), and shorter for Aboriginals than non-Aboriginals (non-Aboriginal, 50 d; Aboriginal, 19 d; P < 0.04). Cutaneous disease was present in 33 (73%) patients, and lung involvement was present in 29 (64%) patients. The most common osseous sites of involvement were the lower limb and axial skeleton. Common orthopaedic symptoms of bone lesions included bone pain in 42 (78%) patients, swelling in 32 (59%) patients, and soft tissue abscesses in 21 (39%) patients. Joint infection (12 patients) manifested as a monoarticular arthropathy presenting with effusion in 9 (75%) patients, pain in 8 (67%) patients, and decreased range of motion in 5 (42%) patients. Osseous blastomycosis can mimic bacterial infection and should be included in the differential diagnosis of bone and joint infection in patients who have visited or who live in geographic regions where B dermatitidis is endemic.

Infectious disease occurrence in forestry workers: a systematic review

Forestry workers are a classic example of how environmental exposures put workers in some occupation at higher risk for infectious disease. Foresters are exposed to wild animals, arthropods, vegetation, and soil, all of which may harbor bacteria, viruses, fungi, or other eukaryotic parasites that are harmful to humans. Common routes of exposure to these pathogens include inhalation, direct contact, and vector-borne inoculation through the skin in injuries. A variety of vectors can transmit diseases of importance to foresters. They include ticks, flies, mosquitoes, and Reduviidae bugs. This is a systematic review of the scientific literature that details the risk of forestry workers face.

Blastomycosis of the Vocal folds with Life-Threatening upper Airway Obstruction: A Case Report

Blastomycosis is a chronic fungal disease that primarily affects the lower respiratory tract. The acute inflammatory phase of the primary pulmonary infection is characterized by a lymphohematogenous spread to extrapulmonary sites, especially the skin. The presence of disseminated infection with Blastomyces dermatitidis in the larynx is unusual. In areas of the United States where this fungus is endemic, failure to consider laryngeal involvement might lead to inappropriate therapy and thus worsening inflammation and airway compromise.

Cluster of pulmonary blastomycosis in a rural community: evidence for multiple high-risk environmental foci following a sustained period of diminished precipitation

Much of our understanding of the epidemiologic features of infection with Blastomyces dermatitidis has come from cluster and outbreak investigations which have established the association of human disease with recreational pursuits and the presence of infectious microfoci in areas of moist soil with high organic content. This report describes the clustering of eight cases of pulmonary blastomycosis without an apparent common source exposure which occurred during a 90 day period in a 96 square mile area (population 4,450) within Oconto County, Wisconsin. We conclude that multiple high-risk environmental foci may have existed following a sustained five-year period of diminished precipitation in the cluster area. A case-control study which included family and community controls concluded that multiple earth-disturbing activities engaged in by case-patients was statistically associated with illness. Lymphocyte-proliferation assays of whole blood samples detected previously unrecognized infection with B. dermatititidis among five of 32 family controls.

Blastomycosis of the epididymis and prostate

We report a case of blastomycosis presenting as epididymitis and prostatitis. The diagnosis was suggested by pathologic findings in the prostate and epididymis and was further supported by serology. The diagnosis was confirmed by culture and special staining. Long-term cure was accomplished after a 12-month course of oral ketoconazole (400 mg/day). Therapy was monitored by culture and serology. Blastomycosis is an unusual but significant pathogen which occasionally presents with genitourinary tract involvement. Effective diagnostic and oral treatment regimens are now available but are dependent on a high degree of suspicion in cases of chronic prostatitis or epididymitis.

Immunological and chemical characterization of glycoproteins in IEF fractions of Blastomyces dermatitidis yeast lysate antigen

After isoelectric focusing (IEF), fractions of a Blastomyces dermatitidis yeast lysate antigen were analysed for the presence of glycoproteins that may lead to cross-reactivity in immunoassays for the diagnosis of blastomycosis. Five major glycoproteins were apparent, two of which showed cross-reactivity when used in Western blots with sera obtained from dogs with histoplasmosis and coccidioidomycosis. These five glycoproteins were characterized for linkage to the proteins using N-glycosidase F (NGF) and for their lectin binding properties. The cross-reactive 235- and 160-kDa glycoproteins were found to possess mainly O-linked, high-mannose-type carbohydrates, and periodate-mediated oxidation of these molecules eliminated cross-reactivity observed with heterologous sera. Thus, the periodate-treated IEF antigens described here may be useful in solid-phase enzyme immunoassays for the diagnosis of blastomycosis.

Cutaneous manifestations of systemic mycoses

Systemic fungal diseases are primary pulmonary diseases caused by the dimorphic fungal pathogens, Blastomyces dermatitides, Coccidioides immitis. Histoplasma capsulatum, or Paracoccidioides brasiliensis. Infection occurs after inhalation of the infectious form of the fungus and may be acute, self-limited, or subclinical. Primary cutaneous infection occurs only after traumatic implantation of the fungus and is unusual. Erythema nodosum or erythema multiforme may accompany the acute form of the disease. Other cutaneous manifestations represent disseminated disease and, as such, require systemic antifungal therapy. Because cutaneous lesions have occurred coincidentally with other cutaneous pathologies, emphasis should be placed on a complete clinical history, physical examination, and diagnosis by histopathology and culture.