Ahmed H. Fahal

Mycetoma caused by Madurella mycetomatis: a neglected infectious burden

Tropical eumycetoma is frequently caused by the fungus Madurella mycetomatis. The disease is characterised by extensive subcutaneous masses, usually with sinuses draining pus, blood, and fungal grains. The disease affects individuals of all ages, although disability is most severe in adults who work outdoors. Compared with major diseases such as tuberculosis, malaria, and HIV, disease from M mycetomatis is underestimated but socioeconomically important. Many scientific case reports on mycetoma exist, but fundamental research was lacking until recently. We present a review on developments in the clinical, epidemiological, and diagnostic management of M mycetomatis eumycetoma. We describe newly developed molecular diagnostic and gene typing procedures, and their application for management of patients and environmental research. Fungal susceptibility tests have been developed as well as a mouse model of infection. These advances should greatly further our understanding of the molecular basis of eumycetoma.

Mycetoma: a thorn in the flesh

Mycetoma is a chronic, granulomatous, subcutaneous, inflammatory disease caused by true fungi (eumycetoma) or filamentous bacteria (actinomycetoma). It occurs in the mycetoma belt stretching between the latitudes of 15 degrees South and 30 degrees North and is endemic in relatively arid areas. The organisms are present in the soil and may enter the subcutaneous tissue by traumatic inoculation. Mycetoma commonly affects adults aged 20 to 40 years, predominantly males. The foot is most commonly affected. Both forms of mycetoma present as a progressive, subcutaneous swelling, although actinomycetoma has a more rapid course. Multiple nodules develop which may suppurate and drain through sinuses, discharging grains during the active phase of the disease. Diagnosis may involve radiology, ultrasonic imaging, cytology, culture, histology or immunodiagnosis. Actinomycetoma is amenable to treatment by antibiotics, preferably by combined drug therapy for long periods. Eumycetoma is usually treated by aggressive surgical excision combined with medical treatment.

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.

Environmental Occurrence of Madurella mycetomatis, the Major Agent of Human Eumycetoma in Sudan

ABSTRACT Madurella mycetomatis is the main causative agent of human eumycetoma, a severe debilitating disease endemic in Sudan. It has been suggested that eumycetoma has a soil-borne or thorn prick-mediated origin. For this reason, efforts were undertaken to culture M. mycetomatis from soil samples (n = 43) and thorn collections (n = 35) derived from areas in which it is endemic. However, ribosomal sequencing data revealed that the black fungi obtained all belonged to other fungal species. In addition, we performed PCR-mediated detection followed by restriction fragment length polymorphism (RFLP) analysis for the identification of M. mycetomatis DNA from the environmental samples as well as biopsies from patients with mycetoma. In the case of the Sudanese soil samples, 17 out of 74 (23%) samples were positive for M. mycetomatis DNA. Among the thorn collections, 1 out of 22 (5%) was positive in the PCR. All PCR RFLP patterns clearly indicated the presence of M. mycetomatis. In contrast, 15 Dutch and English control soil samples were all negative. Clinically and environmentally obtained fungal PCR products share the same PCR RFLP patterns, suggesting identity, at least at the species level. These observations support the hypothesis that eumycetoma is primarily environmentally acquired and suggest that M. mycetomatis needs special conditions for growth, as direct isolation from the environment seems to be impossible.

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

ABSTRACT 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 [MIC50]) of 0.06 to 0.13 mg/liter) was superior to amphotericin B (MIC50 of 0.5 to 1.0 mg/liter).

The safety and efficacy of itraconazole for the treatment of patients with eumycetoma due to Madurella mycetomatis

This prospective study aimed to determine the safety and efficacy of itraconazole for the treatment of patients with mycetoma due to Madurella mycetomatis. The study consisted of 13 patients with confirmed disease; all were treated with oral itraconazole in a dose of 400mg daily for three months after which the dose was reduced to 200mg daily for nine months. All patients showed good clinical response to 400mg itraconazole daily, but when the dose was reduced to 200mg daily, the clinical response was gradual and slow. Post-treatment surgical exploration showed that, in all patients, the lesions were well localized, encapsulated with thick capsule and they were easily removed surgically. In all these lesions, grains colonies were encountered and they were viable on culture. Post-operative biopsies showed no significant changes in the morphology of the grains. A constant finding was the presence of between 5-7 grains in a single cavity walled by fibrous tissue. The reaction surrounding the grains was a Type I tissue reaction characterized by a neutrophil zone around grains. Patients were followed up post-operatively for variable periods (range 18-36 months) and only one patient had recurrence. Initial pre-operative treatment with itraconazole may be recommended for eumycetoma patients to enhance lesions encapsulation and localization which can facilitate wide local excision to avoid unnecessary massive mutilating surgery and recurrence.

Mycetoma: a unique neglected tropical disease

Mycetoma can be caused by bacteria (actinomycetoma) or fungi (eumycetoma) and typically affects poor communities in remote areas. It is an infection of subcutaneous tissues resulting in mass and sinus formation and a discharge that contains grains. The lesion is usually on the foot but all parts of the body can be affected. The causative microorganisms probably enter the body by a thorn prick or other lesions of the skin. Mycetoma has a worldwide distribution but is restricted to specific climate zones. Microbiological diagnosis and characterisation of the exact organism causing mycetoma is difficult; no reliable serological test exists but molecular techniques to identify relevant antigens have shown promise. Actinomycetoma is treated with courses of antibiotics, which usually include co-trimoxazole and amikacin. Eumycetoma has no acceptable treatment at present; antifungals such as ketoconazole and itraconazole have been used but are unable to eradicate the fungus, need to be given for long periods, and are expensive. Amputations and recurrences in patients with eumycetoma are common.

Mycetoma Medical Therapy

Medical treatment of mycetoma depends on its fungal or bacterial etiology. Clinically, these entities share similar features that can confuse diagnosis, causing a lack of therapeutic response due to inappropriate treatment. This review evaluates the response to available antimicrobial agents in actinomycetoma and the current status of antifungal drugs for treatment of eumycetoma.

Polymorphisms in Genes Involved in Innate Immunity Predispose Toward Mycetoma Susceptibility

Madurella mycetomatis is the main causative agent of mycetoma, a tumorous fungal infection characterized by the infiltration of large numbers of neutrophils at the site of infection. In endemic areas the majority of inhabitants have Abs to M. mycetomatis, although only a small proportion of individuals actually develop mycetomal disease. It therefore appears that neutrophils are unable to clear the infection in some individuals. To test this hypothesis, 11 single nucleotide polymorphisms involved in neutrophil function were studied in a population of Sudanese mycetoma patients vs geographically and ethnically matched controls. Significant differences in allele distribution for IL-8 (CXCL8), its receptor CXCR2, thrombospondin-4 (TSP-4), NO synthase 2 (NOS2), and complement receptor 1 (CR1) were found. Further, the NOS2Lambaréné polymorphism was clearly associated with lesion size. The genotypes obtained for CXCL8, its receptor CXCR2, and TSP-4 all predisposed to a higher CXCL8 expression in patients, which was supported by the detection of significantly elevated levels of CXCL8 in patient serum. The NOS2 genotype observed in healthy controls was correlated with an increase in NOS2 expression and higher concentrations of nitrate and nitrite in control serum. We present the first evidence of human genetic predisposition toward susceptibility to mycetoma, a neglected infection of the poor.

The host tissue reaction to Madurella mycetomatis: new classification

In this prospective study, three types of tissue reaction to mycetoma grains are described. Type I reaction is characterized by the adherence of neutrophils to the surface of the grain leading to its disintegration. In Type II reaction, the fragmented grain and the dead neutrophils are cleared by macrophages and multinucleated giant cells, while in Type III reaction there is a discrete well developed epithelioid granuloma with Langhanss giant cells. The three types of reaction are usually seen in different combinations in the same lesion.