Epidemiology, Modern Diagnostics, and the Management of Mucorales Infections

Molecular mechanisms that govern infection and antifungal resistance in Mucorales

SUMMARYThe World Health Organization has established a fungal priority pathogens list that includes species critical or highly important to human health. Among them is the order Mucorales, a fungal group comprising at least 39 species responsible for the life-threatening infection known as mucormycosis. Despite the continuous rise in cases and the poor prognosis due to innate resistance to most antifungal drugs used in the clinic, Mucorales has received limited attention, partly because of the difficulties in performing genetic manipulations. The COVID-19 pandemic has further escalated cases, with some patients experiencing the COVID-19-associated mucormycosis, highlighting the urgent need to increase knowledge about these fungi. This review addresses significant challenges in treating the disease, including delayed and poor diagnosis, the lack of accurate global incidence estimation, and the limited treatment options. Furthermore, it focuses on the most recent discoveries regarding the mechanisms and genes involved in the development of the disease, antifungal resistance, and the host defense response. Substantial advancements have been made in identifying key fungal genes responsible for invasion and tissue damage, host receptors exploited by the fungus to invade tissues, and mechanisms of antifungal resistance. This knowledge is expected to pave the way for the development of new antifungals to combat mucormycosis. In addition, we anticipate significant progress in characterizing Mucorales biology, particularly the mechanisms involved in pathogenesis and antifungal resistance, with the possibilities offered by CRISPR-Cas9 technology for genetic manipulation of the previously intractable Mucorales species.

From Spores to Solutions: A Comprehensive Narrative Review on Mucormycosis

Mucormycosis is an infrequent but fatal illness that mainly affects patients with uncontrolled diabetes mellitus, diabetic ketoacidosis, solid and hematologic neoplasms, organ transplantation, chronic steroid intake, prolonged neutropenia, iron overload states, neonatal prematurity, severe malnutrition, and HIV. Many cases were reported across the world recently following the COVID-19 pandemic. Recent research has led to a better understanding of the pathogenesis of the disease, and global guidelines are now available for managing this serious infection. Herein, we comprehensively review the etiological agents, pathogenesis, clinical presentations, diagnosis, and management of mucormycosis.

A Systematic Review of the Therapeutic Outcome of Mucormycosis

Background

Mucormycosis is a potentially lethal mycosis. We reviewed peer-reviewed publications on mucormycosis to assess therapeutic outcomes.

Methods

A systematic literature search using the Ovid MEDLINE and EMBASE databases identified manuscripts describing human mucormycosis diagnosed according to European Organization for Research and Treatment of Cancer and the Mycoses Study Group criteria with therapeutic outcomes published from 2000 to 2022.

Results

In 126 articles, 10 335 patients were described, most from Asia (n = 6632, 66%). Diabetes was the most frequent underlying disease (n = 6188, 60%); 222 (2.1%) patients had no underlying diseases. The dominant clinical form was rhino-orbitocerebral (n = 7159, 69.3%), followed by pulmonary (n = 1062, 10.3%). Of 5364 patients with outcome data, amphotericin B monotherapy (n = 3749, mortality 31.5%) was most frequent, followed by amphotericin B + azole (n = 843, mortality 6.6%; P < .0001), amphotericin B followed by azole (n = 357, mortality 13.7%; P < .0001), posaconazole only (n = 250, mortality 17.2%; P < .0001), and isavuconazole only (n = 65, mortality 24.6%; P = .24). Duration and dose of antifungals varied widely. Documented outcomes from surgical resections in 149 patients found that 47 of 125 died (37.6%), compared with 16 of 24 (66.7%) patients who did not undergo surgery (P = .008).

Conclusions

Mucormycosis is more frequently reported in Asia than in Europe and is often linked to diabetes. Antifungal therapy, usually with surgery, is frequently effective for mucormycosis.

Pulmonary Mucormycosis: Beyond Classic COVID-19-Associated Fungal Infections

Coronavirus disease 2019 (COVID-19) is often linked to a broad range of opportunistic bacterial and fungal infections. The second wave of the COVID-19 pandemic has witnessed an unprecedented surge in mucormycosis cases, predominantly in India, while the disease remained relatively rare in Europe. The authors describe the case of a 62-year-old female patient admitted to the hospital for consolidation therapy with chemotherapy as a part of the treatment protocol for acute myeloid leukemia. During hospitalization, she was diagnosed with nosocomial COVID-19, which later progressed to respiratory deterioration. COVID-19 with bacterial superinfection was presumed, leading to the initiation of empirical antibiotic therapy. A bronchoscopy was performed several days later due to a lack of improvement, revealing an infection by the Rhizopus microsporus complex. Despite antifungal treatment, the patient experienced an unfavorable clinical course and ultimately died. Given the high index of suspicion required to diagnose pulmonary mucormycosis, which can lead to delays in appropriate treatment and increase the burden of disease, the authors are aiming to enhance its awareness.

Development of a monoclonal antibody and a lateral-flow device for the rapid detection of a Mucorales-specific biomarker

Mucoromycosis is a highly aggressive angio-invasive disease of humans caused by fungi in the zygomycete order, Mucorales. While Rhizopus arrhizus is the principal agent of mucoromycosis, other Mucorales fungi including Apophysomyces, Cunninghamella, Lichtheimia, Mucor, Rhizomucor and Syncephalastrum are able to cause life-threatening rhino-orbital-cerebral, pulmonary, gastro-intestinal and necrotising cutaneous infections in humans. Diagnosis of the disease currently relies on non-specific CT, lengthy and insensitive culture from invasive biopsy, and time-consuming histopathology of tissue samples. At present, there are no rapid antigen tests that detect Mucorales-specific biomarkers of infection, and which allow point-of-care diagnosis of mucoromycosis. Here, we report the development of an IgG2b monoclonal antibody (mAb), TG11, which binds to extracellular polysaccharide (EPS) antigens of between 20 kDa and 250 kDa secreted during hyphal growth of Mucorales fungi. The mAb is Mucorales-specific and does not cross-react with other yeasts and molds of clinical importance including Aspergillus, Candida, Cryptococcus, Fusarium, Lomentospora and Scedosporium species. Using the mAb, we have developed a Competitive lateral-flow device that allows rapid (30 min) detection of the EPS biomarker in human serum and bronchoalveolar lavage (BAL), with a limit of detection (LOD) in human serum of ~100 ng/mL serum (~224.7 pmol/L serum). The LFD therefore provides a potential novel opportunity for detection of mucoromycosis caused by different Mucorales species.

Invasive splenic mucormycosis due to Rhizopus microsporus during chemotherapy for acute monocytic leukemia: a case report and literature review

Mucormycosis is a rare opportunistic fungal infection associated with high mortality that typically occurs in immunocompromised patients. It is difficult to diagnose owing to non-specific clinical manifestations, the serologic index, imaging features, and the limitations of diagnostic methods. The incidence of invasive splenic mucormycosis is extremely rare, with only a few cases documented in the literature. We report a survival case of invasive splenic mucormycosis involving the liver caused by Rhizopus microsporus in a patient during consolidation therapy for acute monocytic leukemia (AML-M5). The patient initially presented with recurrent fever and splenomegaly accompanied by multiple focal hypodensities unresponsive to empiric anti-infective treatment. Splenic mucormycosis was diagnosed by Contrast-Enhanced Ultrasonography (CEUS) and metagenomic next-generation sequencing (mNGS). However, surgical intervention carries a high risk due to the progressive involvement of the liver in invasive splenic mucormycosis. Fortunately, monotherapy with amphotericin B was effective, and the patient underwent allo-HSCT. This case aims to emphasize the importance of utilizing mNGS and CEUS for the timely diagnosis of mucormycosis to help clinicians identify splenic mucormycosis and initiate appropriate therapy as soon as possible to improve therapeutic efficacy and prognosis.