Molecular detection and identification of agents of eumycetoma: detailed report of two cases

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.

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.

Mycetoma in West Africa

BACKGROUND

Mycetoma is a neglected disease, which is socioeconomically important, and with the possibility of permanent disability in infected persons if not treated early. This is especially true in resource-limited settings such as West Africa, where there is a lack of facilities and skilled personnel to make a definitive laboratory diagnosis. Countries in West Africa have similar climatic conditions to Sudan. The majority of patients seek medical care very late, when there is already bone involvement, resulting in amputations. This results in poor capture of the true burden of the problem in the literature.

METHODS

A review of the literature revealed about 2685 documented cases in West Africa from 1929 to 2020; from 15 out of 16 countries, Senegal accounted for 74.1% (1943) of cases in the subregion.

RESULTS

The majority of lesions were found on the foot; however, other body parts were also reported. Rural dwellers accounted for most cases. Only 547 (20.4%) cases had identified isolates reported. Actinomycetoma accounted for 47.9% of cases, eumycetoma 39.7% and unidentified pathogens 12.4%. Actinomadura pelletieri was the predominant pathogen isolated (21.4%; 117 isolates).

CONCLUSION

There is a dire need for capacity building, provision of facility and health education to raise awareness of this debilitating disease in West Africa.

Long term follow-up of Maduromycosis treatment: A case review

Maduromycosis is a rare deep fungal infection characterized by painless progressive destruction of limb caused by either fungal or filamentous bacteria. Its presentation is usually initiated by trivial penetration injury in farmers or laborers, worsen by immunocompromised status. Due to its painless course, this infection will severely destruct and deform hence leading to high morbidity of patient. We report a rare presentation of maduromycosis in 49-year-old housewife with no history of penetrating injury and no comorbid. Multi-disciplinary team was involved to establish the accurate diagnosis. The patient underwent surgical debridement and was given prolonged anti-fungal therapy. Combination of the treatments with patient's adherence lead to recovery without further recurrence and the patient was able to perform daily living activity.

Cystic form of Actinomycotic mycetoma: A new case with a diagnostic challenge

Mycetoma, commonly known as Madura foot, is a chronic granulomatous infection caused either by fungi (eumycetoma) known as actinomycete. This disease occurs preferentially in young adults, and it affects the foot in particular. We report a Tunisian case of mycetoma occurring in an old patient, particular by its cystic presentation.

Madurella mycetomatis infection of the foot: a case report of a neglected tropical disease in a non-endemic region

Background

Mycetoma is an uncommon chronic granulomatous infection of cutaneous and subcutaneous tissues that can be caused by filamentous bacteria (actinomycetoma) or fungi (eumycetoma). It is the prerogative of young men between the third and fourth decade and is transmitted through any trauma causing an inoculating point. The classic clinical triad associates a painless hard and swelling subcutaneous mass, multiple fistulas, and the pathognomonic discharge of grains. Although endemic in many tropical and subtropical countries, mycetoma can also be found in non-endemic areas as in Morocco, and causes then diagnosis problems leading to long lasting complications. Therefore, we should raise awareness of this neglected disease for an earlier management. Under medical treatment however, mycetoma has a slow healing and surgery is often needed, and relapses are possible.

Case presentation

Herein we report a case of a 64 years old patient, with a history of eumycetoma occurring ten years ago treated with oral terbinafine coupled with surgery. A complete remission was seen after 2 years. He presented a relapse on the previous scar 6 months ago. There wasn’t any bone involvement in the magnetic resonance imaging (MRI). The patient was put under oral terbinafine with a slow but positive outcome.

Conclusion

Through this case report, we perform a literature review and highlight the importance of increase awareness of mycetoma in clinical practice especially in non-endemic regions.

Recurrent eumycetoma caused by novel species Madurella pseudomycetomatis: A case report

Mycetoma is a chronic-granulomatous disease characterized by the inflammation, swollen organ, draining sinuses containing blood, pus, and grains. We present a case of madura foot with novel etiologic agent Madurella pseudomycetomatis. Diagnosis was based on morphologic, physiologic, histipathologic and molecular methods. In vitro antifungal susceptibility tests revealed that MIC values for itraconazole, amphotericin B, and posaconazole were 0.0313 μg/ml, 0.0313 μg/ml, and 0.004 μg/ml, respectively. The patient was treated and recovered by itraconazole(400 mg/day) after prolonged course.

Mycetoma: reviewing a neglected disease

Mycetoma caused by either filamentous fungi (eumycotic) or bacteria (actinomycotic) has recently been recognized by the World Health Organization as a neglected tropical disease. Although mycetoma is preventable and treatable, especially in the early stages, it carries high morbidity and a huge socioeconomic burden. Skin and subcutaneous tissue is affected, with a classic presentation of hard woody swellings, discharging sinuses and presence of grains (containing the causative organism). Variants with swelling without sinuses have also been described. Left untreated it may involve underlying bone and muscle, leading to permanent disability. Common actinomycotic species include Streptomyces somaliensis, Actinomadura madurae, Actinomadura pelletieri, Nocardia brasiliensis and Nocardia asteroides, while Madurella mycetomatis, Madurella grisea, Pseudoallescheria boydii and Leptosphaeria senegalensis are common eumycotic agents. Men are more commonly affected than women, and the leg is the most frequently affected site. Diagnosis in suspected lesions is made with the help of grain examination, microscopy, imaging (radiography, ultrasonography, magnetic resonance imaging) and culture, and more recently by molecular methods such as PCR and molecular sequencing. Molecular sequencing for both fungi and bacteria is important for rapid and correct diagnosis, especially in culture-negative cases. Treatment is long, more successful in actinomycetoma than eumycetoma, and may require a holistic approach comprising antimicrobials, surgery and rehabilitation. Mycetoma can be prevented by simple measures such as wearing protective garments and shoes, especially in rural areas and during outdoor activities.

Addressing the most neglected diseases through an open research model: The discovery of fenarimols as novel drug candidates for eumycetoma

Eumycetoma is a chronic infectious disease characterized by a large subcutaneous mass, often caused by the fungus Madurella mycetomatis. A combination of surgery and prolonged medication is needed to treat this infection with a success rate of only 30%. There is, therefore, an urgent need to find more effective drugs for the treatment of this disease. In this study, we screened 800 diverse drug-like molecules and identified 215 molecules that were active in vitro. Minimal inhibitory concentrations were determined for the 13 most active compounds. One of the most potent compounds, a fenarimol analogue for which a large analogue library is available, led to the screening of an additional 35 compounds for their in vitro activity against M. mycetomatis hyphae, rendering four further hit compounds. To assess the in vivo potency of these hit compounds, a Galleria mellonella larvae model infected with M. mycetomatis was used. Several of the compounds identified in vitro demonstrated promising efficacy in vivo in terms of prolonged larval survival and/or reduced fungal burden. The results presented in this paper are the starting point of an Open Source Mycetoma (MycetOS) approach in which members of the global scientific community are invited to participate and contribute as equal partners. We hope that this initiative, coupled with the promising new hits we have reported, will lead to progress in drug discovery for this most neglected of neglected tropical diseases.

Successful medical treatment of an Aspergillus terreus mycetoma of the nostril/lip in a 16-year-old Fjord pony gelding with pituitary pars intermedia dysfunction

BACKGROUND

Mycetoma is a chronic, proliferative lesion of cutaneous/subcutaneous tissue characterized by draining tracts and granules in the discharge caused by actinomycetes (actinomycetoma) or filamentous fungi (eumycotic mycetoma).

OBJECTIVES

This case report describes the unusual finding of a cutaneous mycetoma of the lateral wing of the right nostril in a gelding.

ANIMAL

A 16-year-old Fjord gelding with suspected pituitary pars intermedia dysfunction (PPID) was presented for evaluation of a nonpainful, firm and raised mass involving the lateral wing of the right nostril and the lip.

METHODS AND RESULTS

Cytological examination of the mass showed marked pyogranulomatous inflammation and histopathological examination revealed a fungal mycetoma. Fungal culture identified the causative organism as Aspergillus terreus, which is not known for its propensity to cause either dermal granulomas or mycetoma in domestic animals. Further investigation, including a TRH stimulation test, led to a diagnosis of PPID (Cushing's disease), which may have led to immunosuppression of the animal and increased susceptibility to infection.

CONCLUSIONS AND CLINICAL IMPORTANCE

The horse was treated medically with pergolide for the PPID and oral potassium iodide for the fungal infection, with good therapeutic response and no relapse after five months. Surgical debridement or excision was not performed. To the best of the authors' knowledge, this is the first case report of a cutaneous mycetoma caused by A. terreus in a horse.

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

Eumycetoma, a chronic fungal infection endemic in India, Indonesia, and parts of Africa and South and Central America, follows traumatic implantation of saprophytic fungi and frequently requires radical surgery or amputation in the absence of appropriate treatment. Fungal species that can cause black-grain mycetomas include Madurella spp., Falciformispora spp., Trematosphaeria grisea, Nigrograna mackinnonii, Pseudochaetosphaeronema larense, Medicopsis romeroi, and Emarellia spp. Rhytidhysteron rufulum and Parathyridaria percutanea cause similar subcutaneous infections, but these infections lack the draining sinuses and fungal grains characteristic of eumycetoma. Accurate identification of the agents of subcutaneous fungal infection is essential to guide appropriate antifungal therapy. Since phenotypic identification of the causative fungi is often difficult, time-consuming molecular approaches are currently required. In the study described here we evaluated whether matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry might allow the accurate identification of eumycetoma agents and related fungi. A panel of 57 organisms corresponding to 10 different species from confirmed cases of eumycetoma and subcutaneous pedal masses, previously formally identified by PCR amplification and sequencing of internal transcribed spacer 1 (ITS1), was employed. Representative isolates of each species were used to create reference MALDI-TOF spectra, which were then used for the identification of the remaining isolates in a user-blinded manner. Here, we demonstrate that MALDI-TOF mass spectrometry accurately identified all of the test isolates, with 100%, 90.4%, and 67.3% of isolates achieving log scores greater than 1.8, 1.9, and 2.0, respectively.

Novel Taxa Associated with Human Fungal Black-Grain Mycetomas: Emarellia grisea gen. nov., sp. nov., and Emarellia paragrisea sp. nov

Eumycetoma is a debilitating, chronic, fungal infection that is endemic in India, Indonesia, and parts of Africa and South and Central America. It remains a neglected tropical disease in need of international recognition. Infections follow traumatic implantation of saprophytic fungi and frequently require radical surgery or amputation in the absence of appropriate treatment. Several fungal species can cause black-grain mycetomas, including Madurella spp. (Sordariales), Falciformispora spp., Trematosphaeria grisea, Biatriospora mackinnonii, Pseudochaetosphaeronema larense, and Medicopsis romeroi (all Pleosporales). We performed phylogenetic analyses based on five loci on 31 isolates from two international culture collections to establish the taxonomic affiliations of fungi that had been isolated from cases of black-grain mycetoma and historically classified as Madurella grisea Although most strains were well resolved to species level and corresponded to known agents of eumycetoma, six independent isolates, which failed to produce conidia under any conditions tested, were only distantly related to existing members of the Pleosporales Five of the six isolates shared >99% identity with each other and are described as Emarellia grisea gen. nov. and sp. nov; the sixth isolate represents a sister species in this novel genus and is described as Emarellia paragrisea. Several E. grisea isolates were present in both United Kingdom and French culture collections and had been isolated independently over 6 decades from cases of imported eumycetoma. Four of the six isolates involved patients that had originated on the Indian subcontinent. All isolates were all susceptible in vitro to the azole antifungals, but had elevated MICs with caspofungin.

Application of Isothermal Amplification Techniques for Identification of Madurella mycetomatis, the Prevalent Agent of Human Mycetoma

Appropriate diagnosis and treatment of eumycetoma may vary significantly depending on the causative agent. To date, the most common fungus causing mycetoma worldwide is Madurella mycetomatis. This species fails to express any recognizable morphological characteristics, and reliable identification can therefore only be achieved with the application of molecular techniques. Recombinase polymerase amplification (RPA) and loop-mediated isothermal amplification (LAMP) are proposed as alternatives to phenotypic methods. Species-specific primers were developed to target the ribosomal DNA (rDNA) internal transcribed spacer (ITS) region of M. mycetomatis. Both isothermal amplification techniques showed high specificity and sufficient sensitivity to amplify fungal DNA and proved to be appropriate for detection of M. mycetomatis. Diagnostic performance of the techniques was assessed in comparison to conventional PCR using biopsy specimens from eumycetoma patients. RPA is reliable and easy to operate and has the potential to be implemented in areas where mycetoma is endemic. The techniques may be expanded to detect fungal DNA from environmental samples.

Rapid identification of black grain eumycetoma causative agents using rolling circle amplification

Accurate identification of mycetoma causative agent is a priority for treatment. However, current identification tools are far from being satisfactory for both reliable diagnosis and epidemiological investigations. A rapid, simple, and highly efficient molecular based method for identification of agents of black grain eumycetoma is introduced, aiming to improve diagnostic in endemic areas. Rolling Circle Amplification (RCA) uses species-specific padlock probes and isothermal DNA amplification. The tests were based on ITS sequences and developed for Falciformispora senegalensis, F. tompkinsii, Madurella fahalii, M. mycetomatis, M. pseudomycetomatis, M. tropicana, Medicopsis romeroi, and Trematosphaeria grisea. With the isothermal RCA assay, 62 isolates were successfully identified with 100% specificity and no cross reactivity or false results. The main advantage of this technique is the low-cost, high specificity, and simplicity. In addition, it is highly reproducible and can be performed within a single day.

Treatment of eumycetoma largely depends on the causative pathogen. Identification of mycetoma agent with phenotypic features is too limited, and physiological and biochemical techniques are laborious, time-consuming and nonspecific, whereas the currently available molecular methods based on DNA sequencing are specific but extremely expensive. We describe rolling circle amplification method for identification of black grain eumycetoma using species-specific padlock probes. Eight probes were designed and successfully used for species identification and the results were easily visualized in 1% agarose gel. RCA provides a simple, reproducible, and cost-effective method for rapid identification of mycetoma agent that can be used in low-resource clinical settings.

The "dot-in-circle" sign in musculoskeletal mycetoma on magnetic resonance imaging and ultrasonography

This study aimed to present the ‘dot-in-circle’ sign, which indicates the typical magnetic resonance imaging (MRI) and ultrasonographic (USG) findings for mycetoma involving soft tissue and bone. A total of 8 cases with histopathological proof of mycetoma affecting the musculoskeletal system, and that were examined via MRI and/or coexistent diagnostic ultrasonography between 2004 and 2013 in Songklanagarind Hospital were included in this study. The ‘dot-in-circle’ sign on the MRI and USG images of all the patients was reviewed by two radiologists. The analytic method was descriptive. All cases of musculoskeletal mycetoma revealed the ‘dot-in-circle’ sign on MRI, which was seen as multiple, small, round- to oval-shaped hyperintense lesions separated and surrounded by a low-signal intensity rim (circle), and a tiny, central, low-signal focus (dot). An USG study was available in four patients, and all USG findings demonstrated the ‘dot-in-circle’ sign as a central hyperechoic area (dot) surrounded by hypoechoic tissue (circle). In conclusion, the ‘dot-in-circle’ sign is a typical feature on MRI and USG findings for the diagnosis of musculoskeletal mycetoma.

Mapping the potential risk of mycetoma infection in Sudan and South Sudan using ecological niche modeling

In 2013, the World Health Organization (WHO) recognized mycetoma as one of the neglected tropical conditions due to the efforts of the mycetoma consortium. This same consortium formulated knowledge gaps that require further research. One of these gaps was that very few data are available on the epidemiology and transmission cycle of the causative agents. Previous work suggested a soil-borne or Acacia thorn-prick-mediated origin of mycetoma infections, but no studies have investigated effects of soil type and Acacia geographic distribution on mycetoma case distributions. Here, we map risk of mycetoma infection across Sudan and South Sudan using ecological niche modeling (ENM). For this study, records of mycetoma cases were obtained from the scientific literature and GIDEON; Acacia records were obtained from the Global Biodiversity Information Facility. We developed ENMs based on digital GIS data layers summarizing soil characteristics, land-surface temperature, and greenness indices to provide a rich picture of environmental variation across Sudan and South Sudan. ENMs were calibrated in known endemic districts and transferred countrywide; model results suggested that risk is greatest in an east-west belt across central Sudan. Visualizing ENMs in environmental dimensions, mycetoma occurs under diverse environmental conditions. We compared niches of mycetoma and Acacia trees, and could not reject the null hypothesis of niche similarity. This study revealed contributions of different environmental factors to mycetoma infection risk, identified suitable environments and regions for transmission, signaled a potential mycetoma-Acacia association, and provided steps towards a robust risk map for the disease.

WHO has recognized mycetoma as one of the neglected tropical diseases (NTDs) worldwide. Studies indicate infections from soil or possibly mediated by thorn pricks, but no detailed studies have investigated effects of soil type and Acacia distributions on mycetoma in Sudan. Here, we investigated risk factors associated with mycetoma infections in Sudan using ecological niche modeling (ENM), integrating mycetoma case records, Acacia records, and geospatial data summarizing soil, land-surface temperature, and greenness. ENMs calibrated in endemic districts were transferred across Sudan, and suggested that greatest risk was in a belt across central Sudan. Mycetoma infections occur under diverse environmental conditions; we found significant niche similarity between Acacia and mycetoma. Model predictions were amply corroborated by a preliminary assessment of a much larger mycetoma case-occurrence data base. Our results revealed contributions of different environmental factors to mycetoma risk, raised hypotheses of a causal mycetoma-Acacia association, and provide steps towards a robust predictive risk map for the disease in Sudan.

Roussoella percutanea, a novel opportunistic pathogen causing subcutaneous mycoses

We report the isolation of a novel agent of subcutaneous mycosis from a 45-year-old Indian male immigrant in the United States. Phylogenetic analysis of partial small ribosomal subunit and large ribosomal subunit, internal transcribed spacer, partial translation elongation factor (TEF1), and RNA polymerase second largest subunit (rPB2) loci revealed that the strain was identical to another isolate previously reported as "Madurella mycetomatis." Both strains clustered in the order Pleosporales, nested in the family Arthopyreniaceae/Roussoellaceae. The fungus differed from known species and hence a new taxon, Roussoella percutanea, is introduced, typified by a strain that showed delayed production of pycnidial conidiomata. Antifungal susceptibility testing suggested that the new species is resistant to echinocandins and flucytosine, with variable results with azoles and amphotericin B.

Mycetoma caused by Madurella mycetomatis: a completely neglected medico-social dilemma

Mycetoma is a debilitating disease with a highly particular geographical distribution. The mycetoma belt circles the entire world just above the equator and defines the region with the highest prevalence and incidence. Although the disease is seen in Central America, India and all across Africa, Sudan seems to be the homeland of mycetoma. Mycetoma is an infectious disease caused either by bacteria (actinomycetoma) or true fungi (eumycetoma). In Sudan most cases are caused by the fungal species Madurella mycetomatis. The precise natural habitat of this fungus is still an enigma, but its DNA can easily be found in soil and plant samples in endemic areas. Although the entire human population in these areas are in regular contact with the fungus, most individuals are unaffected. Thus mycetoma is an ideal clinical and experimental model system for the study of host-pathogen interactions. Also, given its relative importance locally, improvements in clinical and laboratory diagnostics and knowledge of the epidemiology of the disease are badly needed. This chapter describes the current state of affairs in the field of eumycetoma caused by M. mycetomatis. The value of laboratory research on this disease and future perspective for control and prevention of the infection are discussed.

New species of Madurella, causative agents of black-grain mycetoma

A new species of nonsporulating fungus, isolated in a case of black-grain mycetoma in Sudan, is described as Madurella fahalii. The species is characterized by phenotypic and molecular criteria. Multigene phylogenies based on the ribosomal DNA (rDNA) internal transcribed spacer (ITS), the partial β-tubulin gene (BT2), and the RNA polymerase II subunit 2 gene (RPB2) indicate that M. fahalii is closely related to Madurella mycetomatis and M. pseudomycetomatis; the latter name is validated according to the rules of botanical nomenclature. Madurella ikedae was found to be synonymous with M. mycetomatis. An isolate from Indonesia was found to be different from all known species based on multilocus analysis and is described as Madurella tropicana. Madurella is nested within the order Sordariales, with Chaetomium as its nearest neighbor. Madurella fahalii has a relatively low optimum growth temperature (30°C) and is less susceptible to the azoles than other Madurella species, with voriconazole and posaconazole MICs of 1 μg/ml, a ketoconazole MIC of 2 μg/ml, and an itraconazole MIC of >16 μg/ml. Since eumycetoma is still treated only with azoles, correct species identification is important for the optimal choice of antifungal therapy.

Phenotypic and molecular characterization of Madurella pseudomycetomatis sp. nov., a novel opportunistic fungus possibly causing black-grain mycetoma

A case of black-grain mycetoma occurring on the lower jaw with an odontogenic origin, which to our knowledge is the first case reported in China, is presented here. The clinical manifestation, histopathological morphology, and microbiological features are described. The new species, Madurella pseudomycetomatis, isolated from the black grains discharged by this patient, was analyzed using sequence data of the multiloci of ribosomal DNA (rDNA) and its ability to ferment carbohydrate as well as morphology. The analyses of the internal transcribed spacer (ITS) region and the D1/D2 hypervariable region of the 28S ribosomal gene sequences support a new species designation. Antifungal susceptibility testing was conducted, indicating that Madurella pseudomycetomatis was highly susceptible to itraconazole, voriconazole, and amphotericin B; moderately susceptible to terbinafine; and resistant to fluconazole and flucytosine.

Management of mycetoma: major challenge in tropical mycoses with limited international recognition

PURPOSE OF REVIEW

The present review highlights an orphan infectious disease in alarming need of international recognition. While money is being invested to develop new broad-spectrum antimicrobial drugs to treat infection in general, improvement in the management of complicated infections such as mycetoma receives little support.

RECENT FINDINGS

Many case presentations describe single-center experience in the management of mycetoma. Unfortunately, randomized and blinded clinical studies into the efficacy of antimicrobial treatment are desperately lacking. Response to medical treatment is usually better in actinomycetoma than eumycetoma. Eumycetoma is difficult to treat using current therapies. Surgery in combination with azole treatment is the recommended regimen for small eumycetoma lesions in the extremities. Bone involvement complicates clinical management, leaving surgical amputation as the only treatment option. Although clinical management has not received major attention recently, laboratory technology has improved in areas of molecular diagnosis and epidemiology.

SUMMARY

Management of mycetoma and laboratory diagnosis of its etiological agents need to be improved and better implemented in endemic regions. Optimized therapeutic approaches and more detailed epidemiological data are urgently needed. It is vital to initiate multicenter collaborations on national and international levels to develop consensus clinical score sheets and state-of-the-art treatment regimens for mycetoma patients.

Molecular identification ofPhialophora oxysporaas the cause of mycetoma in a horse

CASE DESCRIPTION

An 18-year-old mare was evaluated for an oral mass that developed after extraction of a broken incisor.

CLINICAL FINDINGS

An ulcerated, firm, darkly pigmented, approximately 5-cm-diameter spherical mass involved the gingiva lateral and dorsal to the right first to third maxillary incisors. Osteolysis of the roots of the first and second right maxillary incisors and periosteal proliferation of the adjacent premaxilla margins were apparent on radiographs. Histologic examination of the mass revealed multiple coalescing and ramifying foci of abscess formation, each containing a well-defined, discrete, black mass (2 to 7 mm in diameter). Myriad fungal hyphae enmeshed in a black, granular, cementlike material were within each of the black structures. Mycetoma was the histologic diagnosis. The causative agent could not be identified via culture because of lack of distinguishing characteristics. Fungal DNA was isolated from frozen fungal cultures and paraffin sections. The D1/D2 domains of the large subunit P gene rDNA were amplified and sequenced. The sequences of the D1/D2 domains of both isolates were 96% homologous with those of Phialophora oxyspora.

TREATMENT AND OUTCOME

The mass was surgically excised, the local area curetted, and the wound allowed to heal by second intention. Postoperative treatment consisted of administration of phenylbutazone and IV administration of sodium iodide followed by oral administration of potassium iodide. There was no evidence of recurrence 1 year later.

CLINICAL RELEVANCE

Mycetomata should be a differential diagnosis for equine gingival masses. Identification of the fungal agent can be critical for selection of optimal treatments. Molecular methods may permit definitive identification when standard phenotypic-based identification criteria are inconclusive.

Molecular identification of black-grain mycetoma agents

Black-grain mycetomas are subcutaneous devastating chronic infections due to several dematiaceous fungi. They are diagnosed mostly in tropical countries. Identification of these fungi with standard mycological procedures is difficult because of their poor or delayed sporulation. The aim of this study was thus to assess the accuracy of molecular identification of these fungi. A total of 54 strains, mostly of clinical origin, were used, including 15 Madurella mycetomatis, 6 Madurella grisea, 12 Leptosphaeria senegalensis, 4 Leptosphaeria tompkinsii, 6 Pyrenochaeta spp., 4 Curvularia lunata, and 7 Exophiala jeanselmei strains. The internal transcribed spacer 1 (ITS1)-5.8S-ITS2 DNA region was amplified by using universal fungal primers and sequenced. Both intra- and interspecies sequence similarities were assessed. Madurella mycetomatis appeared to be a homogeneous species. More intraspecies variations were found for C. lunata and E. jeanselmei, leading, in some instances, to changes in the initial identification. L. senegalensis and L. tompkinsii showed intraspecies similarities of >99%, but similarity between the two species was <88%. Intergenera and interspecies variations were important, with sequence homologies of <81% between genera. In contrast, Pyrenochaeta romeroi and M. grisea appeared to be heterogeneous, with intraspecies similarities of 40 to 100% and 53 to 100%, respectively, which suggest either erroneous identification or the need for taxonomic revision. Epidemiological and therapeutic studies could benefit from a precise identification of the fungi responsible for black-grain mycetoma based not only on phenotypical characteristics but also on ITS sequencing.

In vitro susceptibilities of Madurella mycetomatis to itraconazole and amphotericin B assessed by a modified NCCLS method and a viability-based 2,3-Bis(2-methoxy-4-nitro-5- sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) assay

Susceptibilities of Madurella mycetomatis against amphotericin B and itraconazole in vitro were determined by protocols based on NCCLS guidelines (visual reading) and a 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) assay for fungal viability. The XTT assay was reproducible and sensitive for both antifungals. Itraconazole (MIC at which 50% of the isolates tested are inhibited [MIC(50)]) of 0.06 to 0.13 mg/liter) was superior to amphotericin B (MIC(50) of 0.5 to 1.0 mg/liter).