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.

Antifungal Activity of Isavuconazole and Comparator Agents against Contemporaneous Mucorales Isolates from USA, Europe, and Asia-Pacific

Isavuconazole is the only US FDA-approved antifungal for treating invasive mucormycosis. We evaluated isavuconazole activity against a global collection of Mucorales isolates. Fifty-two isolates were collected during 2017-2020 from hospitals located in the USA, Europe, and the Asia-Pacific. Isolates were identified by MALDI-TOF MS and/or DNA sequencing and susceptibility tested by the broth microdilution method following CLSI guidelines. Isavuconazole (MIC_50/90, 2/>8 mg/L) inhibited 59.6% and 71.2% of all Mucorales isolates at ≤2 mg/L and ≤4 mg/L, respectively. Among comparators, amphotericin B (MIC_50/90, 0.5/1 mg/L) displayed the highest activity, followed by posaconazole (MIC_50/90, 0.5/8 mg/L). Voriconazole (MIC_50/90, >8/>8 mg/L) and the echinocandins (MIC_50/90, >4/>4 mg/L) had limited activity against Mucorales isolates. Isavuconazole activity varied by species and this agent inhibited at ≤4 mg/L 85.2%, 72.7%, and 25% of Rhizopus spp. (n = 27; MIC_50/90, 1/>8 mg/L), Lichtheimia spp. (n = 11; MIC_50/90, 4/8 mg/L), and Mucor spp. (n = 8; MIC₅₀, >8 mg/L) isolates, respectively. Posaconazole MIC_50/90 values against Rhizopus, Lichtheimia, and Mucor species were 0.5/8 mg/L, 0.5/1 mg/L, and 2/- mg/L, respectively; amphotericin B MIC_50/90 values were 1/1 mg/L, 0.5/1 mg/L, and 0.5/- mg/L, respectively. As susceptibility profiles varied among Mucorales genera, species identification and antifungal susceptibility testing are advised whenever possible to manage and monitor mucormycosis.

Complement, but Not Platelets, Plays a Pivotal Role in the Outcome of Mucormycosis In Vivo

BACKGROUND

Mucormycetes, a heterogeneous group of fungi, induce a life-threatening disease called mucormycosis. Immune deficiencies represent a major risk factor; hence, we wanted to illuminate the role of complement and platelets in the defense against mucormycetes.

METHODS

Rhizopus arrhizus (Ra), Rhizopus microsporus (Rm), Lichtheimia ramosa (Lr), Lichtheimia corymbifera (Lc), Rhizomucor pusillus (Rmp), and Mucor circinelloides (Mc) spores were opsonized with human and mouse serum, and C1q, C3c, and terminal complement complex (C5b-9) deposition was measured. Additionally, thrombocytopenic, C3-deficient, or C6-deficient mice were intravenously infected with selected isolates. Survival and immunological parameters were monitored, and fungal burden was determined and compared to that of immunocompetent and neutropenic mice.

RESULTS

In vitro experiments showed significant differences in complement deposition between mucormycetes. Mc isolates bound up to threefold more human C5b-9 than other mucormycetes. Lr, Lc, and Mc bound high levels of murine C3c, whereas human C3c deposition was reduced on Mc compared to Lr and Lc. Murine C3c deposition negatively correlated with virulence. Complement deficiencies and neutropenia, but not thrombocytopenia, were shown to be a risk factor for a lethal outcome.

CONCLUSION

Complement deposition varies between mucormycetes. Additionally, we demonstrated that complement and neutrophilic granulocytes, but not platelets, play an important role in a murine model of disseminated mucormycosis.

Use of topical amphotericin in a case of refractory sino-orbital angioinvasive mucormycosis

The standard of care for treatment of sino-orbital mucormycosis involves aggressive surgical debridement and liposomal amphotericin, and the roles of adjunctive and topical therapies are less clear. Here we describe a case of severe refractory sino-orbital mucormycosis in an immunocompetent patient who responded to combination therapy with liposomal amphotericin, isavuconazole, micafungin, and topical amphotericin deoxycholate after failing to achieve negative surgical margins.

Rhizomucor hepatosplenic abscesses in a patient with renal and pancreatic transplantation

Fungal infections are generally observed in immunosuppressed patients only, with a diagnostic challenge due to non-specific symptoms. For this reason, appropriate management may be delayed. This case report concerns a 36-year-old man with history of pancreas and kidney transplantation. He had chemotherapy for post-transplant B-cell lymphoma and presented with left upper abdominal pain and fever. Multiple investigations led to a final diagnosis of disseminated abdominal mucormycosis with multiple Rhizomucor abscesses in the liver, spleen and kidney transplant. Treatment was antifungal therapy and laparotomy with splenectomy, wedge resection of two fungal abscesses in segments II and IVb, and segmental left colic resection.

Host Immune Defense upon Fungal Infections with Mucorales: Pathogen-Immune Cell Interactions as Drivers of Inflammatory Responses

During the last few decades, mucormycosis has emerged as one of the most common fungal infections, following candidiasis and aspergillosis. The fungal order responsible for causing mucormycosis is the Mucorales. The main hallmarks of this infection include the invasion of blood vessels, infarction, thrombosis, and tissue necrosis, which are exhibited at the latest stages of the infection. Therefore, the diagnosis is often delayed, and the rapid progression of the infection severely endangers the life of people suffering from diabetes mellitus, hematological malignancies, or organ transplantation. Given the fact that mortality rates for mucormycosis range from 40 to 80%, early diagnosis and novel therapeutic strategies are urgently needed to battle the infection. However, compared to other fungal infections, little is known about the host immune response against Mucorales and the influence of inflammatory processes on the resolution of the infection. Hence, in this review, we summarized our current understanding of the interplay among pro-inflammatory cytokines, chemokines, and the host-immune cells in response to mucoralean fungi, as well as their potential use for immunotherapies.

Invasive Fungal Disease, Isavuconazole Treatment Failure, and Death in Acute Myeloid Leukemia Patients

We present 2 fatal cases of invasive fungal disease with isavuconazole treatment failure in immunocompromised patients: one with a TR34-L98H azole–resistant Aspergillus fumigatus isolate and the other a Rhizomucor–A. fumigatus co-infection. Such patients probably require surveillance by galactomannan antigen detection and quantitative PCRs for A. fumigatus and Mucorales fungi.

Pulmonary Mucormycosis (Zygomycosis) Presenting as an Infective Exacerbation of Chronic Obstructive Pulmonary Disease

Mucormycosis is a life-threatening fungal infection whose incidence has been rising recently, mainly due to the increasing use of immunosuppressive and corticosteroid treatment. In previous decades, mucormycosis was associated with a very poor prognosis as mortality was approximately 100%. Mortality rates reported in recent literature have only slightly improved despite the availability of targeted therapy with amphotericin B. Pulmonary mucormycosis is characteristically encountered in severely immunocompromised hosts, while rhino-orbital disease is often seen in individuals with diabetes mellitus. We report a rare case of fulminant pulmonary mucormycosis as an exceptionally rare complication of corticosteroid treatment in a 76-year-old patient with chronic obstructive pulmonary disease (COPD) and diabetes. The patient had presented with typical symptoms of an infective COPD exacerbation. The interesting aspects of our case were the absence of malignancy or immunosuppression, the isolation of Rhizomucor species, and the fungal invasion of the pleura and pericardium. Unfortunately, our patient died on the 49th day of hospitalisation, despite appropriate treatment.

Identification of fungal pathogens in a patient with acute myelogenic leukemia using a pathogen detection array technology

Invasive zygomycosis in immunocompromised patients results in a high mortality rate, and early identification is crucial to optimize therapy and to reduce morbidity. However, diagnosing specific species of zygomycetes fungi possess challenge in the clinical laboratories. A need for a rapid and sensitive diagnostic tool for early recognition of a zygomycetes fungus in clinical samples to the species level will lead to prompt and accurate therapy and the PathoChip provides one such platform. We utilized a pathogen array technology referred to as PathoChip, comprised of oligonucleotide probes that can detect all the sequenced viruses as well as known pathogenic bacteria, fungi and parasites and family-specific conserved probes, thus providing a means for detecting previously uncharacterized members of a family. We rapidly identified a zygomycetous fungus, Rhizomucor pusillus, an otherwise challenge for the clinical laboratories, predominantly in a patient with acute myelogenous leukemia. This report highlights the value of PathoChip as a diagnostic tool to identify micro-organisms to the species level, especially for those difficult to identify in most clinical laboratories. It will also help clinicians to obtain a critical snapshot of the infection profile of a patient to plan treatment strategies.

Stimulation of Fengycin-Type Antifungal Lipopeptides in Bacillus amyloliquefaciens in the Presence of the Maize Fungal Pathogen Rhizomucor variabilis

Most isolates belonging to the Bacillus amyloliquefaciens subsp. plantarum clade retain the potential to produce a vast array of structurally diverse antimicrobial compounds that largely contribute to their efficacy as biocontrol agents against numerous plant fungal pathogens. In that context, the role of cyclic lipopeptides (CLPs) has been well-documented but still little is known about the impact of interactions with other soil-inhabiting microbes on the expression of these molecules. In this work, we wanted to investigate the antagonistic activity developed by this bacterium against Rhizomucor variabilis, a pathogen isolated from diseased maize cobs in Democratic Republic of Congo. Our data show that fengycins are the major compounds involved in the inhibitory activity but also that production of this type of CLP is significantly upregulated when co-cultured with the fungus compared to pure cultures. B. amyloliquefaciens is thus able to perceive fungal molecules that are emitted and, as a response, up-regulates the biosynthesis of some specific components of its antimicrobial arsenal.

Metagenomic analysis of fungal diversity in Korean traditional wheat-based fermentation starter nuruk

Nuruk, a traditional natural starter, is extensively used in the brewing of Makgeolli, one of Korea's most popular alcoholic beverages that has been recently gaining global popularity. Thus, the quality of traditional nuruk needs to be enhanced. The nuruk mycobiome greatly influences both fermentation process as well as palatability enhancement. Limitations of culture-dependent identification restrict an accurate analysis of fungal diversity and distribution in nuruks. 454 pyrosequencing of two traditional wheat-based nuruks, prepared at two representative temperature conditions revealed a total of 153 and 53 OTUs for nuruks A and B, respectively, from a total of 33,157 ITS sequences. Phylogenetic assignments indicated that nuruk A mycobiota was dominated by the genera Aspergillus and Mucorales, whereas nuruk B by Rhizomucor. Species-level identification indicated that Mucorales sp., Aspergillus candidus, and Aspergillus cibarius predominated in nuruk A mycoflora whereas Rhizomucor pusillus, Mucorales sp., and Thermoascus crustaceus in nuruk B. The alpha diversity indices suggest nuruk A mycobiota to be more diverse than that of nuruk B at almost all time points of fermentation. Resemblances of patterns of predominant species composition and succession between culture-dependent and -independent phylogenetic analysis creates the potential to reconstruct the nuruk mycobiome in vitro, which allows the establishment of a standard inoculum for scientific comparison.

Identification of Mucorales isolates from soil using morphological and molecular methods

Background and Purpose:

Soil is the main habitat of saprophytic and pathogenic fungi. Mucoromycotina constitutes a large group of soil fungi, with certain opportunistic members causing systemic infections in immunocompromised hosts. The majority of human and animal infections are caused by the members of the genera Rhizopus, Mucor, Rhizomucor, Lichtheimia (Absidia), Cunninghamella, and Mortierella. Accordingly, in the present study, we aimed to isolate and identify the main genera of the order Mucorales, using molecular assays and morphological features.

Materials and Methods:

In total, 340 soil samples were collected from seven public parks throughout the city and sidewalk gardens in 14 municipal districts in Isfahan, Iran. All the samples were cultured on the appropriate media, incubated at 27°C for 2- 4 days, and examined daily for visible fungal growth. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was applied and macroscopic, microscopic, and physiological characteristics were assessed to identify fungal colonies.

Results:

400 pure colonies, belonging to the orders Mucorales and Mortierellales, including the genera Lichtheimia, Rhizopus, Rhizomucor, Mucor, Cunninghamella, and Mortierella, were identified. The genus Rhizopus (35.5%) was the most frequent isolate, followed by Mucor (32.25%) and Rhizomucor (27.5%).

Conclusion:

The results emphasize the importance of opportunistic fungi in public areas and indicate the risk of exposure for immunocompromised individuals.

Mucormycosis in Iran: a systematic review

Fungi in the order Mucorales cause acute, invasive and frequently fatal infections in susceptible patients. This study aimed to perform a systematic review of all reported mucormycosis cases during the last 25 years in Iran. After a comprehensive literature search, we identified 98 cases in Iran from 1990-2015. The mean patient age was 39.8 ± 19.2 years. Diabetes was the most common underlying condition (47.9%), and 22.4% of the patients underwent solid organ or bone marrow transplantation. The most common clinical forms of mucormycosis were rhinocerebral (48.9%), pulmonary (9.2%) and cutaneous (9.2%). Eight cases of disseminated disease were identified. Overall mortality in the identified cases was 40.8%, with the highest mortality rate in patients diagnosed with disseminated infection (75%). The mortality rate in rhinocerebral infection patients was significantly lower (45.8%). Rhinocerebral infection was the most common clinical manifestation in diabetes patients (72.9%). Patients were diagnosed using various methods including histopathology (85.7%), microscopy (12.3%) and culture (2.0%). Rhizopus species were the most prevalent (51.7%), followed by Mucor species (17.2%). Sixty-nine patients were treated with a combination of surgery and antifungal therapy (resulting survival rate, 66.7%). Owing to the high mortality rate of advanced mucormycosis, early diagnosis and treatment may significantly improve survival rates. Therefore, increased monitoring and awareness of this life-threatening disease is critical.

Investigation and Management of a Rhizomucor Outbreak in a Pediatric Cancer Hospital in Egypt

We describe an outbreak of mucormycosis in a pediatric oncology hospital during December 2010 and the measures taken to stop it. The outbreak began with two consecutive cases of laboratory-documented mucormycosis infections within 1 week. Investigations to track the source were conducted immediately. Air plate cultures from machines and ducts supplying patients' rooms revealed the growth of Rhizomucor. Of five affected patients, all had acute leukemia and three were histopathologically proven. All patients were treated with liposomal amphotericin B after mucormycosis was diagnosed. Posaconazole was used as a secondary prophylaxis in one case. Three patients died.

First case report of bloodstream infection by Rhizomucor pusillus in a child with hemophagocytic lymphohistiocytosis

We describe an unusual presentation of fatal infection due to Rhizomucor pusillus bloodstream infection in a 12-year old pediatric patient recently diagnosed with hemophagocytic lymphohistiocytosis. R. pusillus was isolated from one blood culture drawn on Day 11 of hospitalization.

DNA barcoding in Mucorales: an inventory of biodiversity

The order Mucorales comprises predominantly fast-growing saprotrophic fungi, some of which are used for the fermentation of foodstuffs but it also includes species known to cause infections in patients with severe immune or metabolic impairments. To inventory biodiversity in Mucorales ITS barcodes of 668 strains in 203 taxa were generated covering more than two thirds of the recognised species. Using the ITS sequences, Molecular Operational Taxonomic Units were defined by a similarity threshold of 99 %. An LSU sequence was generated for each unit as well. Analysis of the LSU sequences revealed that conventional phenotypic classifications of the Mucoraceae are highly artificial. The LSU- and ITS-based trees suggest that characters, such as rhizoids and sporangiola, traditionally used in mucoralean taxonomy are plesiomorphic traits. The ITS region turned out to be an appropriate barcoding marker in Mucorales. It could be sequenced directly in 82 % of the strains and its variability was sufficient to resolve most of the morphospecies. Molecular identification turned out to be problematic only for the species complexes of Mucor circinelloides, M. flavus, M. piriformis and Zygorhynchus moelleri. As many as 12 possibly undescribed species were detected. Intraspecific variability differed widely among mucorealean species ranging from 0 % in Backusella circina to 13.3 % in Cunninghamella echinulata. A high proportion of clinical strains was included for molecular identification. Clinical isolates of Cunninghamella elegans were identified molecularly for the first time. As a result of the phylogenetic analyses several taxonomic and nomenclatural changes became necessary. The genus Backusella was emended to include all species with transitorily recurved sporangiophores. Since this matched molecular data all Mucor species possessing this character were transferred to Backusella. The genus Zygorhynchus was shown to be polyphyletic based on ITS and LSU data. Consequently, Zygorhynchus was abandoned and all species were reclassified in Mucor. Our phylogenetic analyses showed, furthermore, that all non-thermophilic Rhizomucor species belong to Mucor. Accordingly, Rhizomucor endophyticus was transferred to Mucor and Rhizomucor chlamydosporus was synonymised with Mucor indicus. Lecto-, epi- or neotypes were designated for several taxa.

Nosocomial post-traumatic Rhizomucor soft tissue and bone infection treated with liposomial amphotericin B: case report

Mucornycosis is a rare fungal infection most commonly occuring in patients with severe immunocompromise, diabetes, uremia or trauma. Only a few cases of non axial skeletal bone osteomyelitis have been reported. We report a case of nosocomial cellulitis and osteomyelitis complicating a posttraumatic bacterial infection, successfully treated with liposomial amphotericin B and surgical debridement. Traumatized patients with extensive tissue loss, receiving broad-spectrum antibiotics, can develop impaired immune responses and are at risk for fungal infections.