Rapid and Robust Identification of the Agents of Black-Grain Mycetoma by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

An updated list of eumycetoma causative agents and their differences in grain formation and treatment response

SUMMARYIn 2023, the World Health Organization designated eumycetoma causative agents as high-priority pathogens on its list of fungal priority pathogens. Despite this recognition, a comprehensive understanding of these causative agents is lacking, and potential variations in clinical manifestations or therapeutic responses remain unclear. In this review, 12,379 eumycetoma cases were reviewed. In total, 69 different fungal species were identified as causative agents. However, some were only identified once, and there was no supporting evidence that they were indeed present in the grain. Madurella mycetomatis was by far the most commonly reported fungal causative agent. In most studies, identification of the fungus at the species level was based on culture or histology, which was prone to misidentifications. The newly used molecular identification tools identified new causative agents. Clinically, no differences were reported in the appearance of the lesion, but variations in mycetoma grain formation and antifungal susceptibility were observed. Although attempts were made to explore the differences in clinical outcomes based on antifungal susceptibility, the lack of large clinical trials and the inclusion of surgery as standard treatment posed challenges in drawing definitive conclusions. Limited case series suggested that eumycetoma cases caused by Fusarium species were less responsive to treatment than those caused by Madurella mycetomatis. However, further research is imperative for a comprehensive understanding.

Specific and sensitive loop-mediated isothermal amplification (LAMP) method for Madurella strains, eumycetoma filamentous fungi causative agent

BACKGROUND

Filamentous fungi of the genus Madurella are the primary causative agents of mycetoma, a disease observed in tropical and subtropical regions. Since early diagnostics based on a morphological approach are difficult and have many shortcomings, a molecular diagnostic method suitable for rural settings is required. In this study, we developed the loop-mediated isothermal amplification (LAMP) method to present a foundational technique of the diagnosis of Madurella spp. (M. mycetomatis, M. pseudomycetomatis, M. tropicana, and M. fahalii), the common causative organisms of eumycetoma.

PRINCIPAL FINDINGS

We successfully designed a primer pair targeting the rDNAs of three Madurella spp. excluding M. fahalii, and detected up to 100 fg of genomic DNA extracted from isolates of M. mycetomatis and 1 pg of M. pseudomycetomatis and M. tropicana, within one hour. Second, a primer pair specific to M. mycetomatis, the most common causative species, or M. fahalii, a drug-resistant species, was constructed, and the detection limit of both primer pairs was 1 pg. The designed primers accurately distinguished 16 strains of the genus Madurella from various fungal species known to cause mycetomas.

CONCLUSION

In summary, we established the first model of a LAMP detection method that rapidly and sensitively detects and identifies Madurella isolates for clinical diagnostics. Moreover, the combined designed primer sets could identify mycetoma-causing strains simultaneously.

An overview of mycetoma and its diagnostic dilemma: Time to move on to advanced techniques

The neglected tropical disease mycetoma can become extremely devastating, and can be caused both by fungi and bacteria; these are popularly known as eumycetoma and actinomycetoma respectively. The classical triad of the disease is subcutaneous swelling, multiple discharging sinuses and the presence of macroscopic granules. The present study aims to highlight the existing diagnostic modalities and the need to incorporate newer and more advanced laboratory techniques like pan fungal/pan bacterial 16S rRNA gene polymerase chain reaction (PCR) and sequencing, Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), rolling circle amplification (RCA), loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA). It is important for the medical team to be aware of the various diagnostic options (both existing and future), so that diagnosis of such a debilitating disease is never missed, both by clinicians and microbiologists/pathologists. The newer diagnostic methods discussed in this article will help in rapid, accurate diagnosis thus facilitating early treatment initiation, and decreasing the overall morbidity of the disease. In the Indian context, newer technologies need to be made available more widely. Making clinicians aware and promoting research and development in mycetoma diagnostics is the need of the hour.

Disseminated Medicopsis Romeroi Infection in a Kidney Transplant Recipient

Medicopsis romeroi is a rare, dematiaceous fungus that is difficult to identify using conventional fungal tests. Although uncommon, immunocompromised patients are particularly susceptible to this opportunistic fungus. Here, we report the case of a renal transplant recipient who presented with painful disseminated subcutaneous and soft tissue lesions. Sequencing of the Internal transcribed spacer (ITS) region of the ribosomal DNA identified the fungus as Medicopsis romeroi. Additionally, tissue samples from a non-healing wound on the left forearm grew Rhizopus spp. on Sabouraud dextrose agar, indicating a Mucormycosis superinfection. The patient's condition improved with surgical intervention and antifungal therapy with Posaconazole and Terbinafine. This case demonstrates the need for a high index of suspicion in order to facilitate early diagnosis and treatment and thus reduce the risk of dissemination.

Mycetoma: Development of Diagnosis and Treatment

Mycetoma describes a heterogeneous group of cutaneous and subcutaneous infections caused by either fungi (eumycetomas) or bacteria (actinomycetomas). It is characterized by a triad of clinical symptoms: painless subcutaneous tumor-like swelling, multiple sinuses and fistulas, and discharged grains in pus. This predominantly affects the feet in more than 70% of patients. It is endemic in the “mycetoma belt” regions, including Africa, South America, and South Asia. Autochthonous mycetoma is rare in the United States of America (USA). We recently reported a Latin American immigrant with eumycetoma in the State of Maryland, USA. With millions of immigrants from endemic regions, the true number of mycetomas in the USA is most likely higher than currently recognized. With the aim to raise the awareness of clinicians about mycetoma, especially dermatologists and podiatrists, we update the development of the epidemiology, etiology, clinical presentations, pathogenesis, diagnosis, differential diagnosis, and treatment of mycetoma.

Implantation subcutaneous phaeohyphomycosis caused by Rhytidhysteron rufulum: A case report

Subcutaneous phaeohyphomycosis is caused by traumatic implantation of melanized environmental fungi. The majority of cases occur in tropical areas of the world or are associated with travel from these regions. Herein, we describe a rare case of subcutaneous phaeohyphomycosis caused by Rhytidhysteron rufulum in an immunocompetent Somalia-born patient. The use of molecular diagnostics as an essential tool for identification of rare fungal pathogens is highlighted.

Mass spectrometry in research laboratories and clinical diagnostic: a new era in medical mycology

Diagnosis by clinical mycology laboratory plays a critical role in patient care by providing definitive knowledge of the cause of infection and antimicrobial susceptibility data to physicians. Rapid diagnostic methods are likely to improve patient. Aggressive resuscitation bundles, adequate source control, and appropriate antibiotic therapy are cornerstones for success in the treatment of patients. Routine methods for identifying clinical specimen fungal pathogen are based on the cultivation on different media with the subsequent examination of its phenotypic characteristics comprising a combination of microscopic and colony morphologies. As some fungi cannot be readily identified using these methods, molecular diagnostic methods may be required. These methods are fast, but it can cost a lot. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is suitable for high-throughput and rapid diagnostics at low costs. It can be considered an alternative for conventional biochemical and molecular identification systems in a microbiological laboratory. The reliability and accuracy of this method have been scrutinized in many surveys and have been compared with several methods including sequencing and molecular methods. According to these findings, the reliability and accuracy of this method are very high and can be trusted. With all the benefits of this technique, the libraries of MALDI-TOF MS need to be strengthened to enhance its performance. This review provides an overview of the most recent research literature that has investigated the applications and usage of MT-MS to the identification of microorganisms, mycotoxins, antifungal susceptibility examination, and mycobiome research.

The developed molecular biological identification tools for mycetoma causative agents: An update

Mycetoma is a chronic granulomatous inflammatory disease that is caused either by bacteria or fungi. Bacterial mycetoma (actinomycetoma) can be caused by various causative agents of the genera Nocardia, Streptomyces and Actinomadura. On the other hand, fungal mycetoma (eumycetoma) is most commonly caused by causative agents belonging to the genera Madurella, Scedosporium and Falciformispora. Early and accurate diagnosis of the causative organisms can guide proper patient management and treatment. To allow rapid and accurate species identification, different molecular techniques were developed over the past decades. These techniques can be protein based (MALDI-TOF MS) as well as DNA based (Sequencing, PCR and isothermal amplification methods). In this review, we provide an overview of the different molecular techniques currently in use and identify knowledge gaps, which need to be addressed before we can implement molecular diagnostics for mycetoma in different clinical settings.

A Short-Tandem-Repeat Assay (MmySTR) for Studying Genetic Variation in Madurella mycetomatis

Madurella mycetomatis is the major causative agent of eumycetoma, a neglected tropical infection characterized by painless subcutaneous lesions, inflammation, and grains draining from multiple sinuses. To study the epidemiology of mycetoma, a robust discriminatory typing technique is needed. We describe the use of a short-tandem-repeat assay (MmySTR) for genotyping of M. mycetomatis isolates predominantly from Sudan. Eleven microsatellite markers (3 dinucleotides, 4 trinucleotide repeats, and 4 tetranucleotide repeats) were selected from the M. mycetomatis MM55 genome using the Tandem Repeats Finder software. PCR amplification primers were designed for each microsatellite marker using primer3 software and amplified in a multicolor multiplex PCR approach. To establish the extent of genetic variation within the population, a collection of 120 clinical isolates from different regions was genotyped with this assay. The 11 selected MmySTR markers showed a large genotypic heterogeneity. From a collection of 120 isolates, 108 different genotypes were obtained. Simpson's diversity index (D) value for individual markers ranged from 0.081 to 0.881, and the combined panel displayed an overall D value of 0.997. The MmySTR assay demonstrated high stability, reproducibility, and specificity. The MmySTR assay is a promising new typing technique that can be used to genotype isolates of M. mycetomatis Apart from the possible contribution of host factors, the genetic diversity observed among this group of isolates might contribute to the different clinical manifestations of mycetoma. We recommend that the MmySTR assay be used to establish a global reference database for future study of M. mycetomatis isolates.

Morphology and Phylogeny of Two Novel Species within the Class Dothideomycetes Collected from Soil in Korea

Two fungal strains (KNU-JJ-1827 and KNU-JJ-1829) belonging to the class Dothideomycetes were discovered from Jeju Island, Korea during this investigation of soil microfungi. Strain KNU-JJ-1827 showed fewer conidial septations, larger conidiogenous cells, and smaller conidia compared to the previously identified closest species of Didymocyrtis. Strain KNU-JJ-1829 revealed the similar characteristics of the nearest certain species of the genus Parathyridaria with the production of conidiogenous cells and conidia, because no asexual morphs were detected from the closest type strain Parathyridaria rosae. The novelty of the strains was also confirmed by analyzing molecular data using internal transcribed spacer regions and 28S rDNA. The molecular phylogeny also strongly support the detailed description and illustration for each proposed species as Didymocyrtis septata sp. nov. (KNU-JJ-1827) and Parathyridaria ellipsoidea sp. nov. (KNU-JJ-1829) isolated from soil in Korea.

The genus Madurella: Molecular identification and epidemiology in Sudan

Eumycetoma (mycotic mycetoma) is the fungal form of mycetoma, a subcutaneous infection occurring in individuals living in endemic areas of the disease. The Sudan is hyperendemic for mycetoma, with the highest incidence being reported from Gezira State, Central Sudan. The present study was conducted at the Gezira Mycetoma Center and aimed to determine the cause of black-grain eumycetoma in the state and describe its epidemiology. Black-grain specimens were collected during the surgical operation and direct detection of the causative agent was performed using M. mycetomatis species-specific PCR and ITS PCR followed by sequencing. Black-grain was reported from 93.3% of all confirmed mycetoma cases (n = 111/119), with a prevalence in young males. Of the 91 samples subjected to direct PCR, 90.1% (n = 82) gave positive results. The predominant species (88.2%) was Madurella mycetomatis. One sample was identified as M. fahalii, one as M. tropicana, and one matched the phytopathogenic species Sphaerulina rhododendricola. The highest endemic zones were Southern Gezira (76.6%) and Northern Sinnar (23.4%). The study confirmed that direct molecular detection on grains provides rapid and specific diagnosis of agents of eumycetoma.

Eumycetoma is a neglected fungal disease endemic in Africa, India, and Latin America. Black-grain eumycetoma is the most common type in Africa and is mainly caused by Madurella spp. The Sudan, and in particular Gezira State, central Sudan is hyperendemic for black-grain eumycetoma. Patients with this type of mycetoma are treated with surgery in combination with antifungal therapy. In this study, we collected surgical biopsies from patients attending Gezira Mycetoma Center to directly identify the etiology of black-grain eumycetoma in this state. We also studied the epidemiology of the disease based on the demography of the patients’ population. Our result showed that the highest endemic regions were Southern Gezira (76.6%) and Northern Sinnar (23.4%). By applying direct PCR and sequencing we confirmed that the most common etiology of the disease is Madurella mycetomatis (88.2%). In addition, we found one case of M. fahalii and the first Sudanese case of M. tropicana and Sphaerulina rhododendricola.

Mycetoma and Chromoblastomycosis: Perspective for Diagnosis Improvement Using Biomarkers

Background: Mycetoma and chromoblastomycosis are both chronic subcutaneous infectious diseases that pose an obstacle to socioeconomic development. Besides the therapeutic issue, the diagnosis of most neglected tropical diseases (NTD) is challenging. Confirmation using direct microscopy and culture, recognized as WHO essential diagnostic tests, are limited to specialized facilities. In this context, there is a need for simple user-friendly diagnostic tests to be used in endemic villages. Methods: This review discuss the available biomarkers that could help to improve the diagnostic capacity for mycetoma and chromoblastomycosis in a theoretical and practical perspective. Results: A lack of research in this area has to be deplored, mainly for mycetoma. Biomarkers based on the immune response (pattern of leucocytes, antibody detection), the dermal involvement (extracellular matrix monitoring, protein expression), and the presence of the infectious agent (protein detection) are potential candidates for the detection or follow-up of infection. Conclusion: Confirmatory diagnosis based on specific diagnostic biomarkers will be the basis for the optimal treatment of mycetoma and chromoblastomycosis. It will be part of the global management of NTDs under the umbrella of stewardship activities.

Medicopsis romeroi nodular subcutaneous infection in a kidney transplant recipient

Phaeohyphomycosis is a set of fungal infections caused by various dematiaceous fungi such as coelomycetes. These infections can occur either in immunocompetent or immunocompromised patients like solid organ transplants. Here we describe a nodular lesion of the right hallux that occurred in a kidney transplant patient. Microscopic examination of the biopsy revealed fungal hyphae and culture was positive to a grey to black mould that lacked characteristic elements to be identified. Nucleic acid sequencing targeting the internal transcribed spacer of the ribosomal DNA identified this mould as Medicopsis romeroi. The patient benefited of an antifungal therapy with voriconazole associated with surgical excision of the lesion. No relapse of the lesion was observed during a six-month follow-up. In solid organ transplants, phaeohyphomycosis caused by Medicopsis romeroi are very rare with only 12 cases reported. The clinical history should be well assessed since the lesion can appear several years after a cutaneous trauma that happened in a tropical region. Therapy generally combines antifungals with surgical excision of the lesion in order to avoid any relapse or dissemination of the infection.

Madurella real-time PCR, a novel approach for eumycetoma diagnosis

The genus Madurella comprising four species, M. fahalii, M. mycetomatis, M. pseudomycetomatis, and M. tropicana, represents the prevalent cause of eumycetoma worldwide. The four species are phenotypically similar and cause an invariable clinical picture, but differ markedly in their susceptibility to antifungal drugs, and epidemiological pattern. Therefore, specific identification is required for optimal management of Madurella infection and to reveal proper epidemiology of the species. In this study, a novel multiplex real-time PCR targeting the four Madurella species was developed and standardized. Evaluation of the assay using reference strains of the target and non-target species resulted in 100% specificity, high analytical reproducibility (R2 values >0.99) and a lowest detection limit of 3 pg target DNA. The accuracy of the real-time PCR was further assessed using biopsies from eumycetoma suspected patients. Unlike culture and DNA sequencing as gold standard diagnostic methods, the real-time PCR yielded accurate diagnosis with specific identification of the causative species in three hours compared to one or two weeks required for culture. The novel method reduces turnaround time as well as labor intensity and high costs associated with current reference methods.

Mycetoma, a progressive and disfiguring disease, is one of the neglected tropical diseases, caused by both bacteria and fungi. Eumycetoma is the fungal type and mainly caused by species of the genus Madurella. Madurella mycetomatis is the most prevalent species worldwide. However, other species such as M. fahalii, M. pseudomycetomatis, and M. tropicana can also cause mycetoma and have a different susceptibility towards the drug used for treating mycetoma patients. Currently, we lack a rapid and non-culture-based technique that can readily identify these four species from clinical samples. Due to its sensitivity, and specificity, real-time PCR is re-recognized by European Organization for Research and Treatment of Cancer (EORTC) to directly identify fungal agents from clinical samples. We developed and validated a multiplex real-time PCR-based technique using the least expensive chemistry to identify Madurella species within 3–4 hours. Development of such a technique will allow rapid diagnosis of eumycetoma and timely initiation of appropriate antifungal therapy.

The Diagnosis of Fungal Neglected Tropical Diseases (Fungal NTDs) and the Role of Investigation and Laboratory Tests: An Expert Consensus Report

The diagnosis of fungal Neglected Tropical Diseases (NTD) is primarily based on initial visual recognition of a suspected case followed by confirmatory laboratory testing, which is often limited to specialized facilities. Although molecular and serodiagnostic tools have advanced, a substantial gap remains between the desirable and the practical in endemic settings. To explore this issue further, we conducted a survey of subject matter experts on the optimal diagnostic methods sufficient to initiate treatment in well-equipped versus basic healthcare settings, as well as optimal sampling methods, for three fungal NTDs: mycetoma, chromoblastomycosis, and sporotrichosis. A survey of 23 centres found consensus on the key role of semi-invasive sampling methods such as biopsy diagnosis as compared with swabs or impression smears, and on the importance of histopathology, direct microscopy, and culture for mycetoma and chromoblastomycosis confirmation in well-equipped laboratories. In basic healthcare settings, direct microscopy combined with clinical signs were reported to be the most useful diagnostic indicators to prompt referral for treatment. The survey identified that the diagnosis of sporotrichosis is the most problematic with poor sensitivity across the most widely available laboratory tests except fungal culture, highlighting the need to improve mycological diagnostic capacity and to develop innovative diagnostic solutions. Fungal microscopy and culture are now recognized as WHO essential diagnostic tests and better training in their application will help improve the situation. For mycetoma and sporotrichosis, in particular, advances in identifying specific marker antigens or genomic sequences may pave the way for new laboratory-based or point-of-care tests, although this is a formidable task given the large number of different organisms that can cause fungal NTDs.

Long-Term Carriage of Medicopsis romeroi, an Agent of Black-Grain Mycetoma, Presenting as Phaeohyphomycosis in a Renal Transplant Patient

Medicopsis species are rare fungal pathogens that frequently resist common antifungal therapies and are difficult to identify morphologically as conidia are produced in pycnidia, a key feature of coelomycetes. Immunocompromised patients are at risk of these infections, even after remote exposure, and typically present with phaeohyphomycoses without dissemination. We present the case of a renal transplant recipient 6.5 years post-transplant who developed a slowly progressive soft tissue infection mimicking a synovial cyst. A cultured isolate was identified as Medicopsis romeroi by sequencing of multiple ribosomal loci. The patient responded well to debridement and posaconazole therapy. Solid-organ transplant patients are at risk of opportunistic fungal infection long after transplant, and molecular methods are often required for definitive identification.

The Accuracy of Histopathological and Cytopathological Techniques in the Identification of the Mycetoma Causative Agents

Mycetoma is a devastating neglected tropical disease, caused by various fungal and bacterial pathogens. Correct diagnosis to the species level is mandatory for proper treatment. In endemic areas, various diagnostic tests and techniques are in use to achieve that, and that includes grain culture, surgical biopsy histopathological examination, fine needle aspiration cytological (FNAC) examination and in certain centres molecular diagnosis such as PCR. In this retrospective study, the sensitivity, specificity and diagnostic accuracy of grain culture, surgical biopsy histopathological examination and FNAC to identify the mycetoma causative organisms were determined. The histopathological examination appeared to have better sensitivity and specificity. The histological examination results were correct in 714 (97.5%) out of 750 patients infected with Madurella mycetomatis, in 133 (93.6%) out of 142 patients infected with Streptomyces somaliensis, in 53 (74.6%) out of 71 patients infected with Actinomadura madurae and in 12 (75%) out of 16 patients infected with Actinomadura pelletierii. FNAC results were correct in 604 (80.5%) out of 750 patients with Madurella mycetomatis eumycetoma, in 50 (37.5%) out of 133 Streptomyces somaliensis patients, 43 (60.5%) out of 71 Actinomadura madurae patients and 11 (68.7%) out of 16 Actinomadura pelletierii. The mean time required to obtain the FNAC result was one day, and for the histopathological examinations results it was 3.5 days, and for grain it was a mean of 16 days. In conclusion, histopathological examination and FNAC are more practical techniques for rapid species identification than grain culture in many endemic regions.

In mycetoma endemic regions, the medical and health settings are commonly suboptimal, and only a few diagnostic tests and techniques are available. That had badly affected the patients’ proper diagnosis and management and thus the late presentation of patients with advanced disease. In this retrospective study, the experience of the MRC on the common in use diagnostic tests in the period between 1991 and 2018 is presented. In this study, the sensitivity, specificity rates and diagnostic accuracy of grain culture, surgical biopsy histopathological examination and FNAC to identify the mycetoma causative organisms were determined. The histopathological examination appeared to have better sensitivity and specificity. Furthermore, the grain culture identification needs high experience, it is the tedious procedure, and cross-contamination is common hence misdiagnosis is frequent. It can be concluded that histopathological examination and FNAC are more practical techniques for rapid species identification than grain culture in many endemic regions with poor diagnostic setting.

A novel dermatophyte relative, Nannizzia perplicata sp. nov., isolated from a case of tinea corporis in the United Kingdom

A novel dermatophyte was isolated from skin scales of a female patient presenting with tinea corporis of the wrist and arm. Her principal risk factor was long-term corticosteroid use for underlying Lupus autoimmune syndrome. Microscopic examination of skin scales from lesions revealed hyphae consistent with dermatophyte infection, and a morphologically identical fungus grew in pure culture on all cultures of skin scales. Repeat isolation of the same organism from persistent lesions five months later confirmed the novel species as the causative agent. Microscopic examination revealed predominantly smooth, thin-walled macroconidia, with large numbers of unicellular aleuriospores of varied shapes and sizes. Since the isolate exhibited considerable microscopic pleomorphism, sharing morphological features consistent with several dermatophyte genera, it was subjected to multi-locus phylogenetic analyses employing a total of six different loci. Sequence analyses of all loci revealed that the isolate clustered with species within Nannizzia but diverged from all known members of the genus by 2 to 13% depending on locus analyzed. The isolate exhibited high minimum inhibitory concentrations for terbinafine in vitro, which might explain why the infection had failed to respond to two cycles of oral treatment with this antifungal agent. Interestingly, sequences in GenBank of an unnamed "Microsporum sp" isolated from leg skin of a patient in the Czech Republic showed greater than 99% identity across all of the loci analysed in common, indicating that this novel organism, which we describe here as Nannizzia perplicata sp. nov., is likely not restricted to the UK.

Chronic Madura foot: mycetoma and/or Actinomyces spp or actinomycosis

A 58-year-old agricultural worker from a remote Western province farming community in Saudi Arabia presented with a 2-year history of right plantar foot soft tissue mass. According to the patient, the swelling had gradually increased in size over a few years, but it was painless and thus had not restricted him from continuing to farm until the lesion started to affect mobility. An MRI, microbiology and histopathology reported a rare infectious agent—Actinomyces spp, otherwise referred to as Madura foot. Three-dimensional CT aided in a preoperative surgical plan which included mass excision/debulking for this challenging lesion. Full eradication was not possible, and the patient required prolonged anti-infective therapy (>6 months) along with close surveillance to map resolution of infective symptoms.

Nigrograna mackinnonii, Not Trematosphaeria grisea (syn., Madurella grisea), Is the Main Agent of Black Grain Eumycetoma in Latin America

Mycetoma, a chronic and mutilating subcutaneous infection recognized by the WHO as a neglected tropical disease, has been reported in >25 countries in Africa, Asia, and South America. In Latin America, Trematosphaeria grisea is assumed to be the prevalent fungal agent. Recent molecular studies have shown that this is an environmental saprobe in Europe, where it is rarely implicated in human diseases. The aim of the present paper is to establish the identity of Latin American cases ascribed to Trematosphaeria grisea Three cases analyzed were caused by Nigrograna mackinnonii Data on an additional 21 strains in the literature revealed that N. mackinnonii rather than T. grisea is responsible for most cases of black grain eumycetoma in Latin America.