Rhizopus homothallicus Causing Invasive Infections: Series of Three Cases from a Single Centre in North India

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.

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.

Mucormycosis and Its Upsurge During COVID-19 Epidemic: An Updated Review

Although mucormycosis may have reached an epidemic situation during the COVID-19 pandemic, the term was much more familiar even before the COVID-19 period. The year 2020 showed an outbreak of novel coronavirus (SARS-CoV-2) which affected millions of people all over the world. One of the noticeable complications observed to be associated with this disease is mucormycosis. It is an opportunistic infection caused by members of the Order Mucorales existing worldwide and has been commonly reported as a laboratory contaminant for a long time. However, nowadays due to the changes in the host environment, they have been emerging as potent opportunistic pathogens responsible for causing primary infections or coinfections with other diseases eventually resulting in morbidity and even mortality in severe cases. Although immunocompromised patients are more susceptible to this infection, few cases have been reported in immunocompetent individuals. Various risk factors which are responsible for the acquisition of mucormycosis include diabetes mellitus type 2, ketoacidosis, hematological malignancies, organ transplants, and chemotherapy recipients. Among the various etiological agents, Rhizopus is found to be the most common, and rhino-cerebral to be the most frequent clinical presentation. As far as pathogenesis is concerned, host cell invasion, thrombosis, and necrosis are the main events in the progression of this disease. The aim of the present review is to address a complete spectrum of mucormycosis and COVID-19-associated mucormycosis (CAM) in a single article. Both global and Indian scenarios of mucormycosis are taken into account while framing this review.

Clinical and Mycologic Characteristics of Emerging Mucormycosis Agent Rhizopus homothallicus

We retrospectively reviewed consecutive cases of mucormycosis reported from a tertiary-care center in India to determine the clinical and mycologic characteristics of emerging Rhizopus homothallicus fungus. The objectives were ascertaining the proportion of R. homothallicus infection and the 30-day mortality rate in rhino-orbital mucormycosis attributable to R. homothallicus compared with R. arrhizus. R. homothallicus accounted for 43 (6.8%) of the 631 cases of mucormycosis. R. homothallicus infection was independently associated with better survival (odds ratio [OR] 0.08 [95% CI 0.02-0.36]; p = 0.001) than for R. arrhizus infection (4/41 [9.8%] vs. 104/266 [39.1%]) after adjusting for age, intracranial involvement, and surgery. We also performed antifungal-susceptibility testing, which indicated a low range of MICs for R. homothallicus against the commonly used antifungals (amphotericin B [0.03-16], itraconazole [0.03-16], posaconazole [0.03-8], and isavuconazole [0.03-16]). 18S gene sequencing and amplified length polymorphism analysis revealed distinct clustering of R. homothallicus.

Epidemiology, Modern Diagnostics, and the Management of Mucorales Infections

Mucormycosis is an uncommon, yet deadly invasive fungal infection caused by the Mucorales moulds. These pathogens are a WHO-assigned high-priority pathogen group, as mucormycosis incidence is increasing, and there is unacceptably high mortality with current antifungal therapies. Current diagnostic methods have inadequate sensitivity and specificity and may have issues with accessibility or turnaround time. Patients with diabetes mellitus and immune compromise are predisposed to infection with these environmental fungi, but COVID-19 has established itself as a new risk factor. Mucorales also cause healthcare-associated outbreaks, and clusters associated with natural disasters have also been identified. Robust epidemiological surveillance into burden of disease, at-risk populations, and emerging pathogens is required. Emerging serological and molecular techniques may offer a faster route to diagnosis, while newly developed antifungal agents show promise in preliminary studies. Equitable access to these emerging diagnostic techniques and antifungal therapies will be key in identifying and treating mucormycosis, as delayed initiation of therapy is associated with higher mortality.

Rhizopus homothallicus rhino-orbital-cerebral mucormycosis: Six cases from a tertiary care Centre, North India

OBJECTIVE

To report six cases of Rhizopus homothallicus rhino-orbital-cerebral mucormycosis in North India between April 2021 and July 2021.

CASE DETAILS

All six patients had diabetes, concomitant SARS-CoV-2 infection, a history of oxygen requirement and steroid intake. Among these six cases 4 were female. All patients presented with sinus pain and peri-orbital swelling. COVID-19-associated mucormycosis (CAM) was diagnosed based on microbiological examination of the biopsied tissue, and its staging was determined radiologically by CT and MRI. Three patients were in stage III-C, the others were in stage II-C, II-D and IV-A. A multidisciplinary team treated the patients with extensive surgical debridement of the affected tissue, correction of predisposing comorbidities and administration of an antifungal agents. Patients were followed up for 6 months with routine direct nasal endoscopy to check the sinonasal cavity for any recurrence. All the six patients survived at 6 months of follow-up.

CONCLUSION

A timely initiated multidisciplinary team-based approach can reduce the mortality in rhino-orbital-cerebral mucormycosis cases caused by R. homothallicus.

Evaluation of environmental Mucorales contamination in and around the residence of COVID-19-associated mucormycosis patients

Introduction

Recently, India witnessed an unprecedented surge of coronavirus disease 2019 (COVID-19)-associated mucormycosis (CAM) cases. In addition to patient management issues, environmental Mucorales contamination possibly contributed to the outbreak. A recent study evaluated environment contamination by Mucorales in the hospital setting. However, a considerable number of CAM patients were never admitted to a hospital before the development of the disease. The present study, therefore, planned to evaluate Mucorales contamination of patients’ residences.

Methods

The residential environment of 25 patients with CAM living in north India was surveyed. Air samples were collected from indoor and immediate outdoor vicinity of the patients’ residence and cultured on Dichloran Rose–Bengal Chloramphenicol (DRBC) agar with benomyl for selective isolation of Mucorales. Surface swab samples were also collected from the air coolers fitted in those residences and cultured on DRBC agar. The isolates were identified by phenotypic and genotypic methods. Amplified fragment length polymorphism (AFLP) was employed to evaluate the genetic relatedness of the environmental and patients’ clinical isolates.

Results

The median spore count (mean ± SD, cfu/m3) of Mucorales in the air of patients’ bedrooms was significantly higher than in the air in other rooms in those residences (3.55 versus 1.5, p = 0.003) or the air collected directly from the front of the air cooler (p < 0.0001). The Mucorales spore count in the environment did not correlate with either ventilation of the room or hygiene level of the patients’ residences. Rhizopus arrhizus was isolated from the environment of all patients’ residences (n = 25); other Mucorales species isolated were Cunninghamella bertholletiae (n = 14), Rhizopus microsporus (n = 6), Rhizopus delemar (n = 6), Syncephalastrum racemosum (n = 1), Lichtheimia corymbifera (n = 1), and Mucor racemosus (n = 1). Genetic relatedness was observed between 11 environmental isolates from the patients’ bedrooms and respective clinical isolates from patients.

Discussion

The study supported the view that the patients might have acquired Mucorales from the home environment during the post-COVID-19 convalescence period. Universal masking at home during patients’ convalescence period and environmental decontamination could minimize exposure in those susceptible patients.

COVID-19-Associated Mucormycosis: A Matter of Concern Amid the SARS-CoV-2 Pandemic

Mucormycosis is an invasive fungal infection caused by fungi belonging to order Mucorales. Recently, with the increase in COVID-19 infections, mucormycosis infections have become a matter of concern globally, because of the high morbidity and mortality rates associated with them. Due to the association of mucormycosis with COVID-19 disease, it has been termed COVID-19-associated mucormycosis (CAM). In the present review, we focus on mucormycosis incidence, pathophysiology, risk factors, immune dysfunction, interactions of Mucorales with endothelial cells, and the possible role of iron in Mucorales growth. We review the limitations associated with current diagnostic procedures and the requirement for more specific, cost-effective, convenient, and sensitive assays, such as PCR-based assays and monoclonal antibody-based assays for the effective diagnosis of mucormycosis. We discuss the current treatment options involving antifungal drug therapies, adjunctive therapy, surgical treatment, and their limitations. We also review the importance of nutraceuticals-based therapy for the prevention as well as treatment of mucormycosis. Our review also highlights the need to explore the potential of novel immunotherapeutics, which include antibody-based therapy, cytokine-based therapy, and combination/synergistic antifungal therapy, as treatment options for mucormycosis. In summary, this review provides a complete overview of COVID-19-associated mucormycosis, addressing the current research gaps and future developments required in the field.

Recent Developments in the Diagnosis of Mucormycosis

Mucormycosis is a potentially fatal infection that presents in different clinical forms and occurs in patients with various risk factors. Recently, the COVID-19 epidemic has been responsible for an increase in the incidence of mucormycosis, particularly in India. As with other invasive filamentous fungal infections, there are no specific clinical or radiological signs, and we have fewer diagnostic tools available than for other invasive fungal infections. Therefore, the diagnosis of Mucormycosis remains difficult. Nevertheless, for optimal management, early and accurate diagnosis is important. According to the latest recommendations, diagnosis is based on direct examination of clinical specimens, and/or histopathology, and culture. There are also molecular tools for direct detection from clinical specimens, but these techniques are moderately recommended. The main problems with these molecular techniques are that, until now, they were not very well standardized; there was a great heterogeneity of DNA targets and methods, which resulted in variable sensitivity. It is in this field that most advances have been made in the last two years. Indeed, recent studies have evaluated the performance and kinetics of Mucorales qPCR in serum and have shown good sensitivity and specificity. Large inter-laboratory evaluations of qPCR in serum have also been performed and have demonstrated good qualitative and quantitative reproducibility. These new results suggest the use of Mucorales qPCR as part of the diagnostic strategy for mucormycosis. One way to achieve better reproducibility could be to use commercial methods. Currently, there are at least three commercial qPCRs for Mucorales (MucorGenius from PathoNostics, MycoGenie from Ademtech, and Fungiplex from Bruker) that can be used to test serum, respiratory samples, or biopsies. However, to date, there has been little evaluation of these methods. Overall, Mucorales PCR in tissue samples, in respiratory samples, and in serum is promising and its addition as a diagnostic tool in the definitions of invasive mucormycosis should be discussed.

Epidemiology of Mucormycosis in India

Mucormycosis is an angioinvasive disease caused by saprophytic fungi of the order Mucorales. The exact incidence of mucormycosis in India is unknown due to the lack of population-based studies. The estimated prevalence of mucormycosis is around 70 times higher in India than that in global data. Diabetes mellitus is the most common risk factor, followed by haematological malignancy and solid-organ transplant. Patients with postpulmonary tuberculosis and chronic kidney disease are at additional risk of developing mucormycosis in this country. Trauma is a risk factor for cutaneous mucormycosis. Isolated renal mucormycosis in an immunocompetent host is a unique entity in India. Though Rhizopus arrhizus is the most common etiological agent of mucormycosis in this country, infections due to Rhizopus microsporus, Rhizopus homothallicus, and Apophysomyces variabilis are rising. Occasionally, Saksenaea erythrospora, Mucor irregularis, and Thamnostylum lucknowense are isolated. Though awareness of the disease has increased among treating physicians, disease-associated morbidity and mortality are still high, as patients seek medical attention late in the disease process and given the low affordability for therapy. In conclusion, the rise in the number of cases, the emergence of new risk factors and causative agents, and the challenges in managing the disease are important concerns with mucormycosis in India.

Updates on the Taxonomy of Mucorales with an Emphasis on Clinically Important Taxa

Fungi of the order Mucorales colonize all kinds of wet, organic materials and represent a permanent part of the human environment. They are economically important as fermenting agents of soybean products and producers of enzymes, but also as plant parasites and spoilage organisms. Several taxa cause life-threatening infections, predominantly in patients with impaired immunity. The order Mucorales has now been assigned to the phylum Mucoromycota and is comprised of 261 species in 55 genera. Of these accepted species, 38 have been reported to cause infections in humans, as a clinical entity known as mucormycosis. Due to molecular phylogenetic studies, the taxonomy of the order has changed widely during the last years. Characteristics such as homothallism, the shape of the suspensors, or the formation of sporangiola are shown to be not taxonomically relevant. Several genera including Absidia, Backusella, Circinella, Mucor, and Rhizomucor have been amended and their revisions are summarized in this review. Medically important species that have been affected by recent changes include Lichtheimia corymbifera, Mucor circinelloides, and Rhizopus microsporus. The species concept of Rhizopus arrhizus (syn. R. oryzae) is still a matter of debate. Currently, species identification of the Mucorales is best performed by sequencing of the internal transcribed spacer (ITS) region. Ecologically, the Mucorales represent a diverse group but for the majority of taxa, the ecological role and the geographic distribution remain unknown. Understanding the biology of these opportunistic fungal pathogens is a prerequisite for the prevention of infections, and, consequently, studies on the ecology of the Mucorales are urgently needed.

A prospective multicenter study on mucormycosis in India: Epidemiology, diagnosis, and treatment

Mucormycosis due to Mucorales is reported at large numbers in uncontrolled diabetics across India, but systematic multicenter epidemiological study has not been published yet. The present prospective study was conducted at four major tertiary care centers of India (two in north and two in south India) during 2013-2015 to compare the epidemiology, treatment strategies and outcome of mucormycosis between the two regions. Molecular techniques were employed to confirm the identity of the isolates or to identify the agent in biopsy samples. A total of 388 proven/probable mucormycosis cases were reported during the study period with overall mortality at 46.7%. Uncontrolled diabetes (n = 172, 56.8%) and trauma (n = 31, 10.2%) were the common risk factors. Overall, Rhizopus arrhizus (n = 124, 51.9%) was the predominant agent identified, followed by Rhizopus microsporus (n = 30, 12.6%), Apophysomyces variabilis (n = 22, 9.2%) and Rhizopus homothallicus (n = 6, 2.5%). On multivariate analysis, the mortality was significantly associated with gastrointestinal (OR: 18.70, P = .005) and pulmonary infections (OR: 3.03, P = .015). While comparing the two regions, majority (82.7%) cases were recorded from north India; uncontrolled diabetes (n = 157, P = .0001) and post-tubercular mucormycosis (n = 21, P = .006) were significantly associated with north Indian cases. No significant difference was noted among the species of Mucorales identified and treatment strategies between the two regions. The mortality rate was significantly higher in north Indian patients (50.5%) compared to 32.1% in south India (P = .016). The study highlights higher number of mucormycosis cases in uncontrolled diabetics of north India and emergence of R. microsporus and R. homothallicus across India causing the disease.

Global Epidemiology of Mucormycosis

Mucormycosis is an angio-invasive fungal infection, associated with high morbidity and mortality. A change in the epidemiology of mucormycosis has been observed in recent years with the rise in incidence, new causative agents and susceptible population. The rise has been perceived globally, but it is very high in the Asian continent. Though diabetes mellitus overshadow all other risk factors in Asia, post-tuberculosis and chronic renal failure have emerged as new risk groups. The rhino-cerebral form of mucormycosis is most commonly seen in patients with diabetes mellitus, whereas, pulmonary mucormycosis in patients with haematological malignancy and transplant recipients. In immunocompetent hosts, cutaneous mucormycosis is commonly seen following trauma. The intriguing clinical entity, isolated renal mucormycosis in immunocompetent patients is only reported from China and India. A new clinical entity, indolent mucormycosis in nasal sinuses, is recently recognized. The causative agents of mucormycosis vary across different geographic locations. Though Rhizopusarrhizus is the most common agent isolated worldwide, Apophysomycesvariabilis is predominant in Asia and Lichtheimia species in Europe. The new causative agents, Rhizopus homothallicus, Mucor irregularis, and Thamnostylum lucknowense are reported from Asia. In conclusion, with the change in epidemiology of mucormycosis country-wise studies are warranted to estimate disease burden in different risk groups, analyse the clinical disease pattern and identify the new etiological agents.

Mucormycosis: Battle with the Deadly Enemy over a Five-Year Period in India

Mucormycosis is an emerging opportunistic fungal infection. Increasing immunocompromization, widespread use of antibacterial and antifungal agents (such as voriconazole prophylaxis), carcinomas, transplantation and lifestyle diseases such as diabetes are the main contributors to this situation. The predominant clinical manifestations of mucormycosis vary from host to host, with rhino-orbital-cerebral, pulmonary, cutaneous, and gastrointestinal infections being the most common. In India, the prevalence of mucormycosis is approximately 0.14 cases/1000 population, which is about 70 times the worldwide-estimated rate for mucormycosis. The present study was undertaken over a period of five years (January 2009-December 2014) to determine the prevalence of mucormycosis. The samples suspected of mucormycosis were examined by direct KOH wet mount and cultured on Sabouraud's dextrose agar without actidione and on blood agar as per standard mycological techniques. Histopathological correlation was done for most of the cases. Antifungal susceptibility testing was performed by the EUCAST reference method. We identified a total of 82 cases of mucormycosis out of a total of 6365 samples received for mycological culture and examination during the said time period. Out of these, 56 were male patients and 27 were females. Most common presentation was rhino-orbito-cerebral (37), followed by cutaneous (25), pulmonary (14), oral cavity involvement (4) and gastrointestinal (2). The most common risk factors were diabetes and intramuscular injections. The fungi isolated were Rhizopus arrhizus (17), Apophysomyces variabilis (12), R. microsporus (9), Lichtheimia ramosa (8), Saksenaea erythrospora (5), Syncephalastrum racemosus (4), R. homothallicus (2), Rhizomucor pusillus (1), Mucor irregularis (1) and A. elegans (1). The mainstay of the treatment was amphotericin B, along with extensive surgical debridement whenever feasible. Most of the patients (50) recovered, but 25 died. The rest of the patients left against medical advice. "Nip in the Bud" should be the mantra for clinicians/surgeons for a favorable prognosis. Early diagnosis, prompt institution of appropriate antifungal therapy, surgical debridement whenever necessary, knowledge of risk factors and their timely reversal is the key for management.