Virulence traits and novel drug delivery strategies for mucormycosis post-COVID-19: a comprehensive review

The outbreak of a fatal black fungus infection after the resurgence of the cadaverous COVID-19 has exhorted scientists worldwide to develop a nutshell by repurposing or designing new formulations to address the crisis. Patients expressing COVID-19 are more susceptible to Mucormycosis (MCR) and thus fall easy prey to decease accounting for this global threat. Their mortality rates range around 32-70% depending on the organs affected and grow even higher despite the treatment. The many contemporary recommendations strongly advise using liposomal amphotericin B and surgery as first-line therapy whenever practicable. MCR is a dangerous infection that requires an antifungal drug administration on appropriate prescription, typically one of the following: Amphotericin B, Posaconazole, or Isavuconazole since the fungi that cause MCR are resistant to other medications like fluconazole, voriconazole, and echinocandins. Amphotericin B and Posaconazole are administered through veins (intravenously), and isavuconazole by mouth (orally). From last several years so many compounds are developed against invasive fungal disease but only few of them are able to induce effective treatment against the micorals. Adjuvant medicines, more particularly, are difficult to assess without prospective randomized controlled investigations, which are challenging to conduct given the lower incidence and higher mortality from Mucormycosis. The present analysis provides insight into pathogenesis, epidemiology, clinical manifestations, underlying fungal virulence, and growth mechanisms. In addition, current therapy for MCR in Post Covid-19 individuals includes conventional and novel nano-based advanced management systems for procuring against deadly fungal infection. The study urges involving nanomedicine to prevent fungal growth at the commencement of infection, delay the progression, and mitigate fatality risk.

A peek behind the curtain in the diagnosis and management of COVID‑19‑Associated Mucormycosis (CAM)

Coronavirus disease 2019 (COVID-19)-associated mucormycosis (CAM) is responsible for a high mortality rate due to its unique and severe host-pathogen interactions. Critically ill or immunocompromised COVID-19 patients are more prone to suffer from aggressive mycoses. Probable victims include those with uncontrolled diabetes mellitus (DM), metabolic acidosis, prolonged neutropenia, increased ferritin levels, hypoxia, and prolonged hospitalization with/without mechanical ventilators and corticosteroids administration. The current review aims to outline the journey of patients with CAM as well as the advantages and disadvantages of the currently available diagnostic techniques. It also discussed the current status of treatment options and caveats in the management of mucormycosis. Multidisciplinary team, early diagnosis, controlling the predisposing condition(s), complete surgical debridement, effective antifungal therapies (e.g., amphotericin B, isavuconazole, and posaconazole), and implementing antifungal stewardship programs are imperative in CAM cases.

Mucormycosis Amid COVID-19 Crisis: Pathogenesis, Diagnosis, and Novel Treatment Strategies to Combat the Spread

The havoc unleashed by COVID-19 pandemic has paved way for secondary ominous fungal infections like Mucormycosis. It is caused by a class of opportunistic pathogens from the order Mucorales. Fatality rates due to this contagious infection are extremely high. Numerous clinical manifestations result in damage to multiple organs subject to the patient's underlying condition. Lack of a proper detection method and reliable treatment has made the management of this infection troublesome. Several reports studying the behavior pattern of Mucorales inside the host by modulation of its defense mechanisms have helped in understanding the pathogenesis of this angio-invasive infection. Many recent advances in diagnosis and treatment of this fungal infection have not been much beneficial. Therefore, there is a need to foster more viable strategies. This article summarizes current and imminent approaches that could aid effective management of these secondary infections in these times of global pandemic. It is foreseen that the development of newer antifungal drugs, antimicrobial peptides, and nanotechnology-based approaches for drug delivery would help combat this infection and curb its spread.

Rhino-orbital mucormycosis due to Apophysomyces ossiformis in a patient with diabetes mellitus: a case report

Background

The most common aetiological agents of mucormycosis are Rhizopus, Mucor, Apophysomyces and Lichtheimia. Apophysomyces is comparatively rare, as it has been reported in less than 3% of mucormycosis cases. The genus Apophysomyces includes six species, and only A. elegans, A. mexicanus, A. variabilis and A. ossiformis have been reported to cause infections in both immunocompetent and immunocompromised patients.

Case presentation

We present a case of a 46-year-old male patient with bilateral blepharoedema, corneal opacity in the left eye and poorly controlled diabetes mellitus. The patient was subjected to total maxillectomy, exenteration of the left orbit and treatment with liposomal amphotericin B. Direct mycological analysis with KOH 10% revealed hyaline, coenocytic, long and wide hyphae. Apophysomyces ossiformis was identified from maxillary biopsy using 18S-ITS1–5.8S-ITS2-28S rRNA gene amplification and sequencing. The patient requested to be transferred to another hospital to continue treatment, where he died on the ninth day after admittance.

Conclusion

To the best of our knowledge, this is the first case of rhino-orbital mucormycosis due to A. ossiformis with a fatal outcome. This case reveals the need to identify the fungus causing mucormycosis with molecular methods to identify adequate treatment therapies for patients with this infection.

Challenges in the diagnosis and treatment of mucormycosis

The diagnosis and treatment of mucormycosis are challenging. The incidence of the disease seems to be increasing. Hematological malignancies are the most common underlying disease in countries with high income and uncontrolled diabetes in developing countries. Clinical approach to diagnosis lacks sensitivity and specificity. Radiologically, multiple (≥10) nodules and pleural effusion are reportedly associated with pulmonary mucormycosis. Another finding on computerized tomography (CT) scan, which seems to indicate the presence of mucormycosis, is the reverse halo sign. Microscopy (direct and on histopathology) and culture are the cornerstones of diagnosis. Molecular assays can be used either for detection or identification of mucormycetes, and they can be recommended as valuable add-on tools that complement conventional diagnostic procedures. Successful management of mucormycosis is based on a multimodal approach, including reversal or discontinuation of underlying predisposing factors, early administration of active antifungal agents at optimal doses, complete removal of all infected tissues, and use of various adjunctive therapies. Our armamentarium of antifungals is slightly enriched by the addition of two newer azoles (posaconazole and isavuconazole) to liposomal amphotericin B, which remains the drug of choice for the initial antifungal treatment, according to the recently published guidelines by ECIL-6, as well as those published by ECMM/ESCMID. Despite the efforts for better understanding of the pathogenesis, early diagnosis and aggressive treatment of mucormycosis, the mortality rate of the disease remains high.

Necrotizing fasciitis caused by Apophysomyces variabilis in an immunocompetent patient

Mucormycosis caused by Apophysomyces variabilis is rarely reported in humans. A case of A. variabilis infection in an immunocompetent men after friction burns in a car accident is described. The infection presented as a rapidly progressive necrotizing infection of the skin and soft tissue, which required extensive surgical debridement and total colonic defunctioning colostomy associated with prolonged antifungal therapy. A. variabilis infection should be considered as a differential diagnosis of rapidly progressive necrotizing skin and soft tissue infections in immunocompetent individuals.

[Fungal sinusitis]

Although sinusitis affects about 20 % of the population, fungal sinusitis is rare. Aspergillus sp. are most frequently implicated. Fungal sinusitis represents a wide spectrum of disorders, including acute or chronic and invasive or non-invasive forms. Invasive fungal sinusitis may develop in an immunocompromised or diabetic patient, whereas non-invasive fungal sinusitis should be considered in a chronic situation, resistant to antibiotics in immunocompetent patients. Allergic fungal sinusitis is related to hypersensitivity of the host to the fungus. The diagnosis of these infections requires radiological examination and endoscopy with mucosal biopsies examined histologically and mycologically in order to distinguish the different types of sinusitis. In the non-invasive forms, surgical treatment is essential, sometimes combined with antifungal and anti-inflammatory treatment. The invasive forms require antifungal treatment, combined with surgery in some forms, particularly mucormycosis.

Blood and tissue distribution of posaconazole in a rat model of invasive pulmonary aspergillosis

Posaconazole is the recommended prophylactic agent in patients at high risk of invasive fungal infection, since adequate drug levels seem to be reached in target sites despite the relatively low levels detected in blood. The objective of this study is to obtain pharmacokinetic (PK) information associated to blood and tissue distribution of posaconazole in an animal model of invasive pulmonary aspergillosis. The PK parameters in lung samples were systematically higher than in serum. After multiple-dose administration of posaconazole, a significant accumulation of the drug was evident in lung tissue. The PK behavior of posaconazole in this particular experimental model is similar to that observed in humans. Thus, we believe this model could be a valid tool to evaluate posaconazole exposure-response relationship.

Efficacy of Posaconazole in a Murine Model of Systemic Infection by Saprochaete capitata

The fungus Saprochaete capitata causes opportunistic human infections, mainly in immunocompromised patients with hematological malignancies. The best therapy for this severe infection is still unknown. We evaluated the in vitro killing activity and the in vivo efficacy of posaconazole at 5, 10, or 20 mg/kg twice a day (BID) in a murine neutropenic model of systemic infection with S. capitata by testing a set of six clinical isolates. Posaconazole showed fungistatic activity against all of the isolates tested. The different doses of the drug, especially the highest one, showed good efficacy, measured by prolonged survival, reduction of (1-3)-β-D-glucan levels in serum, tissue burden reduction, and histopathology.

Multicenter evaluation of MIC distributions for epidemiologic cutoff value definition to detect amphotericin B, posaconazole, and itraconazole resistance among the most clinically relevant species of Mucorales

Clinical breakpoints (CBPs) have not been established for the Mucorales and any antifungal agent. In lieu of CBPs, epidemiologic cutoff values (ECVs) are proposed for amphotericin B, posaconazole, and itraconazole and four Mucorales species. Wild-type (WT) MIC distributions (organisms in a species-drug combination with no detectable acquired resistance mechanisms) were defined with available pooled CLSI MICs from 14 laboratories (Argentina, Australia, Canada, Europe, India, Mexico, and the United States) as follows: 10 Apophysomyces variabilis, 32 Cunninghamella bertholletiae, 136 Lichtheimia corymbifera, 10 Mucor indicus, 123 M. circinelloides, 19 M. ramosissimus, 349 Rhizopus arrhizus, 146 R. microsporus, 33 Rhizomucor pusillus, and 36 Syncephalastrum racemosum isolates. CLSI broth microdilution MICs were aggregated for the analyses. ECVs comprising ≥95% and ≥97.5% of the modeled populations were as follows: amphotericin B ECVs for L. corymbifera were 1 and 2 μg/ml, those for M. circinelloides were 1 and 2 μg/ml, those for R. arrhizus were 2 and 4 μg/ml, and those for R. microsporus were 2 and 2 μg/ml, respectively; posaconazole ECVs for L. corymbifera were 1 and 2, those for M. circinelloides were 4 and 4, those for R. arrhizus were 1 and 2, and those for R. microsporus were 1 and 2, respectively; both itraconazole ECVs for R. arrhizus were 2 μg/ml. ECVs may aid in detecting emerging resistance or isolates with reduced susceptibility (non-WT MICs) to the agents evaluated.

Fungal necrotizing fasciitis, an emerging infectious disease caused by Apophysomyces (Mucorales)

BACKGROUND

The mucoralean fungi are emerging causative agents of primary cutaneous infections presenting in the form of necrotizing fasciitis.

AIMS

The aim of this study was to investigate a series of suspected necrotizing fasciitis cases by Apophysomyces species over one-year period in a northern Indian hospital.

METHODS

The clinical details of those patients suspected to suffer from fungal necrotizing fasciitis were recorded. Skin biopsies from local wounds were microscopically examined and fungal culturing was carried out on standard media. The histopathology was evaluated using conventional methods and special stains. Apophysomyces isolates were identified by their morphology and by molecular sequencing of the internal transcribed spacer (ITS) region of the ribosomal genes. Antifungal susceptibility testing was carried out following EUCAST guidelines and treatment progress was monitored.

RESULTS

Seven patients were found to be suffering from necrotizing fasciitis caused by Apophysomyces spp. Six isolates were identified as Apophysomyces variabilis and one as Apophysomyces elegans. Five patients had previously received intramuscular injections in the affected area. Three patients recovered, two died and the other two left treatment against medical advice and are presumed to have died due to their terminal illnesses. Posaconazole and terbinafine were found to be the most active compounds against A. variabilis, while the isolate of A. elegans was resistant to all antifungals tested.

CONCLUSIONS

Apophysomyces is confirmed as an aggressive fungus able to cause fatal infections. All clinicians, microbiologists and pathologists need to be aware of these emerging mycoses as well as of the risks involved in medical practices, which may provoke serious fungal infections such as those produced by Apophysomyces.

Primary cutaneous mucormycosis produced by the new species Apophysomyces mexicanus

A case of fungal necrotizing fasciitis that appeared in an immunocompetent Mexican woman after a car accident is described. The patient did not respond to antifungal treatment and died 4 days later. The fungus was molecularly identified as a new species of Apophysomyces, namely, Apophysomyces mexicanus.

Efficacy of liposomal amphotericin B and posaconazole in intratracheal models of murine mucormycosis

Mucormycosis is a life-threatening fungal infection almost uniformly affecting diabetics in ketoacidosis or other forms of acidosis and/or immunocompromised patients. Inhalation of Mucorales spores provides the most common natural route of entry into the host. In this study, we developed an intratracheal instillation model of pulmonary mucormycosis that hematogenously disseminates into other organs using diabetic ketoacidotic (DKA) or cyclophosphamide-cortisone acetate-treated mice. Various degrees of lethality were achieved for the DKA or cyclophosphamide-cortisone acetate-treated mice when infected with different clinical isolates of Mucorales. In both DKA and cyclophosphamide-cortisone acetate models, liposomal amphotericin B (LAmB) or posaconazole (POS) treatments were effective in improving survival, reducing lungs and brain fungal burdens, and histologically resolving the infection compared with placebo. These models can be used to study mechanisms of infection, develop immunotherapeutic strategies, and evaluate drug efficacies against life-threatening Mucorales infections.