Journalof Medicaland VeterinaryMycology(1992), 30, Supplement1, 41-49
Mycetoma
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R. J. HAY 1, E. S. MAHGOUB:, G. LEON 3, S. AL-SOGAIR 4 AND O. WELSH 5
1Institute of Dermatology, St. Thomas's Hospital, London, UK; 2World Health Organisation, Eastern Mediterranean Regional Office, Alexandria, Egypt; alnternational Clinical Epidemiology Resource and Training Centre, McMaster University, Hamilton, Canada; ~Ministry of Health, Dammam, Saudi Arabia, and 5University Hospital, Monterrey, Mexico Mycetoma is a chronic, localized, slowly progressive and often painless, subcutaneous disease. It usually involves the lower limbs and is characterized by tumefaction, subcutaneous nodules, destructive granuloma, deformity and discharging sinuses with intercommunicating channels which exude pus with granules of varying sizes and colours. Two main categories of this disease are recognized, namely actinomycotic mycetoma or actinomycetoma caused by actinomycetes and eumycotic mycetoma or eumycetoma which is produced by fungi. There are four main actinomycete causes of mycetoma, Actinomadura madurae, Streptomyces somaliensis, Actinomadura pelletieri and Nocardia brasiliensis. These show distinct geographical differences and these organisms are the chief causes of actinomycetoma in the USA, Africa, South America and Mexico, respectively. In Saudi Arabia most actinomycetomas are due to S. somaliensis and A. madurae. Eumycetoma accounts for about 40% of the reported mycetomas throughout the world. The main organisms responsible for this are Madurella mycetomatis (worldwide), Pseudallescheria boydii (USA), Leptosphaeria senegalensis (West Africa), Madurella grisea (South America) and certain species of Acremonium, Phoma and Pyrenochaeta. Fungi cause nearly half of all mycetomas in Saudi Arabia, the chief causative organism being M. mycetomatis.
Epidemiology of mycetoma The epidemiology of any disorder is generally concerned with the distribution and pathogenetic determinants (biological, physical or social) of the disease under study. Epidemiology of mycetoma can, therefore, be considered under several parameters; the climatic characteristics of the endemic areas (the latitude, temperature, humidity and rainfall), the prevalent vegetation (thorny trees and bushes), demographic features of susceptible population (age, sex, occupation and race) and any anatomical predilection to account for the localization of the disease. Mycetoma is commonly found in countries around the Tropic of Cancer, the main belt lying between 15 S to 30 N of the Equator. It is mainly endemic in North Africa, India and Pakistan, Indonesia, Mexico, and parts of Central and South America. It is seen less frequently in the USA, Europe, Yemen and Saudi Arabia. Mycetoma is more common in those countries which have an arid land and a short rainy season with a relative humidity of 60-80%, followed by a prolonged period of hot and dry weather, the temperature ranging from 45-60°C. In general actinomycetomas occur in hot, dry, semi-desert terrain with an annual rainfall of 50-500 ram, whereas eumycetomas require hotter and more humid climates with rainfall ranging from 500-2000 mm. There are several 41
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notable exceptions, however, to this generalization. Thus, eumycetoma due to M. mycetomatis is often found in hot and dry terrain with poor rainfall, whereas actinomycetoma due to N. brasiliensis and Nocardia asteroides are found both in hot and humid climates. It has been shown that the soil and/or vegetation in endemic areas harbours mycetoma-causing actinomycetes and fungi and these are presumably transferred to the susceptible host through pricks from thorns and bushes, such as Acacia species, commonly found in semi-desert terrains. It is estimated that the disease is about five times more common in males; patients are usually 20-40 years old and are often outdoor workers such as farm labourers and herdsmen. Blacks and coloured races are affected more commonly, probably reflecting the ethnic background of the local population. Mycetoma in Saudi Arabia. Over the years, 21 cases of mycetoma, identified by morphology and culture, have been seen in Dammam, Saudi Arabia. Another 50 cases have so far been reported from this country by others [2,29]. Pooled data from these 71 cases reveal that actinomycetoma represents 55% (39/71) and eumycetoma accounts for 45% (32/71) of all cases. Sixty-one patients were males and 10 females (M:F 6:1); their ages ranged from 14-80 years, the mean being 39 years. Of these, 51 were Saudis (73%), 14 Yemenis (20%), three were from Somalia (4.2%), one patient was Sudanese and the other an Ethiopian. Feet were involved in 83% of cases followed by legs (11.4%) and hands (2.8%). In one case the thigh was involved and in another the perineum. The organisms isolated from Saudi Arabian cases and their relative frequencies are shown in Table 1. The first figure within brackets represents cases seen by us. In Saudi Arabia, foot involvement is the commonest presentation followed by the leg. Infection of the hand is less common than in Sudan or West Africa and involvement of arms and head has not been observed. Similarly, unlike Mexico where mycetoma of the chest wall may account for about 20% of cases, no such patients have been seen in Saudi Arabia (Table 2). TABLE 1. Aetiologyof mycetomain Saudi Arabia Actinomycetoma Streptomyces somaliensis Actinomadura madurae Nocardia brasiliensis Actinomadura pelletieri Nocardia asteroides
(6 (7 (1 (1 (0
+ + + + +
18) 15) 0) 0) 1)
Maduretla mycetomatis Madurella grisea Pseudallescheria boydii Cladosporium species
(6 + 22) (0 + 2) (0 + 1) (0 + 1)
Eumycetoma
Total
24/71 12/71 1/71 1/71 1/71
(33.8%) (16.9%)
(1.4%) (1.4%)
(1.4%)
28/71 (39.4%) (2.8%) 2/71 (1.4%) 1/71 (1.4%) 1/71 (21+5o)=71
The pathogenesis of mycetoma The main characteristic of a mycetoma infection is the presence of large aggregates formed from filaments of the causative organisms which are the centre of inflamma-
MYCETOMA
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tory activity [5]. Two important considerations are implicit in the development of mycetomas as with other infective conditions. The first is the effect of alterations in host resistance in the emergence of infection and the second is the ability of the organism to resist or evade host defences.
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TABLE 2, Mycetoma: anatomical predilection in various parts of the world
Foot Leg Thigh Perineum Hand Arm Chest Head
Saudi Arabia*Sudan
*W. Africa
*Mexico
83% 11.4% 1.4% 1.4% 2.8% ----
68% 10% 3% 3% 5% 3% 1% 2%
35% 28% -8% 2% 8% 20% 3%
68.8% 3.2% 2% 2% 10.7% 3.8% 1% 3.1%
*Taken from [29].
Host predisposition. Are mycetomas more common in compromised patients? There is little evidence to support the idea that patients with mycetomas have clinically relevant underlying abnormalities. In a large review of patients for instance, Mahgoub & Murray [29] found no consistent predisposing diseases and this is supported by other clinically based studies. In the UK on the other hand, where mycetoma is an imported infection, nine of 26 patients with mycetoma diagnosed between 1982-1991 had underlying diabetes mellitus. While this figure is higher than the expected prevalence of diabetes in the general population it has not been reported elsewhere and at best might be a contributory factor in the development of mycetoma. If there is no clinical evidence to suggest that clinically apparent defective host responses have predisposed infection it is possible that some occult immunological abnormality might be involved. Conflicting results have been reported from two studies of the immunology of mycetoma. In the first, evidence was presented that some patients had defective T-cell mediated responses, for instance in skin test reactivity to dinitrochlorobenzene or in lymphocyte responses to PHA [28]. Those most severely affected were patients whose mycetomas were extensive or had failed to respond to treatment. In contrast, a study from Saudi Arabia suggested that there was no consistent immune dysfunction affecting T-lymphocytes in mycetoma patients [2]. These two findings are not necessarily mutually exclusive and it is possible that those with extensive disease had secondary immunological abnormalities. It has been virtually impossible to produce mycetomas due to M. mycetomatis in many laboratory animals except in congenitally athymic nu nu mice [25]. By contrast when these animals are infected with Nocardia species they develop a disseminated infection analogous to disseminated nocardiosis in man rather than actinomycetoma, the organisms forming into branching filaments rather than grains. The main reason for the accumulation of polymorphonuclear leucocytes around mycetoma grains, the centre of abscess and sinus formation, is the production of chemotactic substances by mycetoma agents [43].
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Adaptive changes. The critical event determining the development of pathological changes is survival of the organisms in subcutaneous tissue [14]. This appears to depend on the ability of fungi or actinomycetes to adapt to an in vivo existence. This is accomplished in a variety of different ways, notably the thickening of the cell wall, seen with most fungal causes of mycetoma, the production of intramural or extracellular melanins, the production of immunomodulatory antigens and, in the case of Nocardia species, loss of the cell wall. Electron-microscopic changes within a eumycetoma grain include the formation of concentric rings of cell wall thickening and the presence of coarse cell wall fibrils around cells [39]. The 'onion skin' thickening of the cell wall is due to intrahyphal growth of cells demonstrable in experimental infection. In S. somaliensis mycetoma grains a fibrillar extracellular matrix forms around viable bacteria [32]. In the case of M. mycetomatis this is complicated by the presence of a homogenous electron dense layer around the periphery of hyphae in grains. While this may result in cell death there is evidence to suggest that this organism produces a melanin precursor which polymerizes externally to the fungal cell, for instance in the presence of rat collagen [6], thus acting as a defensive shield against phagocytic attack. Cell wall deposition of melanin is seen with other organisms causing mycetoma such as L. senegalensis [41]. While there is some evidence for immunomodulatory activity by other fungi and actinomycetes S. somalienesis is the only mycetoma agent where this has been established. This organism produces an extracellular polypeptide which is toxic to human fibroblast cell lines and which, in low concentrations, can reduce macrophage killing of S. somaliensis in vitro (M. Nasher & R. J. Hay, unpublished data). The production of this substance may well explain the prolonged survival of this actinomycete in vivo. There is no evidence that mycetoma agents express different antigens in vivo compared with those expressed in vitro [40].
Immunodiagnosis of mycetoma There are numerous methods which have been applied to the detection of antibody or antigens in body fluids in infectious diseases; recently new procedures such as the application of monoclonal antibodies, nucleic acid hybridization and the polymerase chain reaction have been added to the list. In mycetoma the range of techniques applied to the diagnosis has been limited, perhaps reflecting the low priority accorded to this disease and the shortage of financial support. The immunological responses of individuals with mycetoma has been assessed by skin tests [33] and a number of different serological methods such as complement fixation [1], immunodiffusion [11], counterimmunoelectrophoresis (CIE) [11], enzyme linked-immunoassay (ELISA) [21], microimmunodiffusion [3] and Western blotting [40]. Of these, skin tests have not been diagnostically useful. By contrast serodiagnostic techniques have been of great clinical value. Most of the tests have used cell extracts rather than exoantigens and cross-reactivity has been a problem. However these tests are extremely helpful for monitoring therapy and can provide the earliest clues to reactivation of infection particularly with actinomycetomas. For these purposes CIE has proved to be the simplest approach, although new ELISA tests for Nocardia mycetomas have also proved helpful.
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Treatment of eumycetoma
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On seeing a patient with mycetoma, many doctors will immediately consider amputating the affected limb or, if this is not possible, perform radical surgery. Medical treatment is only considered when the lesion involves a site not readily accessible to surgery such as the head. Both of these attitudes are wrong [24]. The correct approach is a combination of surgery and chemotherapy. Through the former, the greater bulk of the lesion is removed and by the latter, control is obtained and recurrence, a common problem, prevented in the most common fungal cause of this infection.
Ketoconazole. In the case of eumycetoma due to M. mycetomatis, which constitutes the major causative agent in tropical and subtropical Africa and Asia, the drug of choice is ketoconazole. In a clinical trial in Sudan, where results have been monitored since 1980, 50 patients received ketoconazole in a dose of 200 mg twice daily. Regardless of the stage and extent of the lesion, cure or significant improvement, where all sinuses were closed and the swelling greatly reduced, were obtained in 72% of patients. Some improvement was obtained in 20% of cases, the remaining 8% of cases showed no response or deteriorated [27]. Clinical progress was followed by counting the number of active sinuses and measuring the circumference of the lesion at the site of maximal swelling over the nearest bony prominence such as the malleoli or either end of the knee cap. Blood was taken at each visit to the clinic for serological follow-up performed by CIE. Xrays were taken every 3 months. Before starting treatment the liver function and full blood picture were checked. No significant side effects or biochemical abnormalities were seen in these patients. The length of treatment varied from 9 months to 3 years and all patients have been regularly followed up at 3- to 6-month intervals. In a further report [13], ketoconazole was not effective in mycetoma caused by P. boydii or Acremonium species. Itraconazole has also been tried in patients with M. mycetomatis infection for the last 5 years in a dose of 100 mg twice daily [26]. Results were less encouraging than with ketoconazole and no patient achieved mycological and clinical remission; 42% greatly improved and 33% showed no response or deteriorated. This is in contrast to the treatment of paranasal Aspergillus granuloma caused by Aspergillus flavus in Sudan. This condition has responded very well to combined surgery and therapy with itraconazole. The drug has been well tolerated in both conditions. It is also worth noting that the lesions of eumycetoma, if diagnosed early, are well circumscribed and can therefore easily be enucleated surgically.
Liposomal amphotericin B. Three patients with mycetomas due to M. grisea (2) and Fusarium species (1) have been treated with the intravenous liposomal formulation of amphotericin B (Ambisome, Vestar Inc, USA). The total doses given were 3.4, 2.8, and 4.2 g, respectively, with maximum daily doses of 3 mg kg -1. The only adverse effects seen were a transient rise in creatinine (1) and local irritation at the infusion site (1). All three achieved temporary remissions with drying of sinuses and
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diminution of swelling, but all relapsed within 6 months after stopping therapy (R. J. Hay & A. Bryceson, personal observations). Treatment of actinomycetoma
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A number of different antibiotics and antimicrobials have been used in the treatment of actinomycetoma. Sulphonamides and sulphones. This group of antimicrobials has the common characteristic of interfering with the folate metabolic pathway of susceptible bacteria. Sulphanilamide, a sulphonamide, was first used in 1941 with good results in the treatment of mycetoma [4]. Another antimicrobial of the sulphone group is DDS, dapsone. The first case cured with this drug in Mexico was reported in 1950 [7]. Subsequently Latapi & Lavalle confirmed its therapeutic success in a group of actinomycetoma patients [19]. In 1952, Gonzalez Ochoa et al., were the first to report its efficacy in vitro [9]. At present dapsone is used alone and in combination with other antimicrobials in the treatment of actinomycetoma. Its daily dosage is between 200 to 300 mg for periods of 1 to 2 years after the disease is clinically cured [8, 16, 34, 35]. The most frequent side effects are: methaemoglobinemia and haemolytic anaemia, exfoliative dermatitis, cyanosis of fingertips and lips. When this happens medication should be stopped or changed [17]. Other sulphonamides have also been used with variable success in the treatment of actinomycetoma, such as sulphisoxazole and sulphamethoxipiridazine [34, 42]. In the past two decades, actinomycetoma has been treated mainly with sulphamethoxazole trimethoprim (cotrimoxazole). This compound is a combination of a diaminopiridimine and a sulphonamide. Both of these antimicrobials act synergistically interfering in the folate metabolic pathway of the bacteria [30]. In general, Nocardia and other actinomycetomas respond well to treatment with cotrimoxazole, which is given for periods ranging from 6 months to several years with an average of 60-70% success [10, 22, 23]. There are patients who do not respond to this therapy and in these cases, a combination of other antimicrobials is indicated [12, 23]. The therapeutic dosage of cotrimoxazole is 8 and 40 mg kg-1 day-k The adverse reactions are minor gastro-intestinal disturbances, skin rashes and haematological side effects [20]. Tetracyclines. These have been used with only variable success in the treatment of actinomycetoma caused by N. brasiliensis, N. asteroides, A. madurae and A. pelletieri. Two compounds have been used; one (short acting) is oxytetracycline, 1.5 to 2 g day-1 for periods of 1 to 2 years. The other, minocycline (long acting) 200 mg day-1 for the same length of time [15, 16]. Streptomycin. The therapeutic effects of this antibiotic on actinomycetomas were first reported in 1957 [44]. Later Mahgoub treated 144 patients with actinomycetoma with different combined treatments, all of them included streptomycin. These regimens were: streptomycin-DDS, streptomycin-trimethoprim sulphamethoxazole and streptomycin-rifampicin; he recorded excellent cure rates and a number of others. The antibody titre and radiological improvement as well as the clinical response were the
MYCETOMA
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parameters of evaluation used to assess the therapeutic response [24]. Antituberculous drugs such as isoniazid and rifampicin have also been used with some success in a few cases [24].
Amikacin. This antibiotic belongs to the aminoglycoside group and is bactericidal [31]. Amikacin acts mainly by inhibition of protein synthesis of bacteria by interfering with their ribosomal functions [18]; it is active in vitro and in vivo (in experimentally induced infections) against N. asteroides and N. brasiliensis. In 1982 our first patient with an actinomycetoma caused by N. brasiliensis with dissemination to the lungs was treated; he had an excellent therapeutic response after 5 weeks of combined treatment with cotrimoxazole and amikacin [37]. This result was later corroborated using amikacin alone (2 cases) and in combination with cotrimoxazole in another 26 patients [38]. This therapy is reserved for those actinomycetoma patients who have had no response to first line treatments or who have a potentially hazardous site of infection: it is contraindicated where there is hepatic, ear or renal disease. The therapy is given in cycles. A cycle is defined as the period of simultaneous administration of amikacin (15 mg k g -1 day -1) divided into two daily doses for 3 weeks and T-S (7-35 mg kg -1 day-1 for 5 weeks. Twenty-six patients have been treated with this therapy. Twentyone needed one or two cycles of treatment (5-10 weeks) and only five needed three cycles (15 weeks). After the treatment was completed, the patients were asymptomatic and remained without further medication. All have been evaluated for periods of between 6 months to 7 years. Only one of the treated patients had a small recurrence (one pustule) 2 months after the last cycle of therapy and a fourth period of treatment was given, the patient remaining asymptomatic thereafter. Side-effects were minimal, gastrointestinal disturbances in three patients and low creatinine clearance rates in two, this reverted to normal after adjusting the amikacin dosage. Audiometry detected minimal sensorineural hearing loss at high tones in six patients, and a moderate deficit in one patient. When using aminoglycosides in mycetoma it is mandatory to perform periodic audiometry, before each cycle, and to avoid other drugs that can induce deafness. Our therapeutic results can be explained by a possible synergistic effect of the antimicrobials. This is supported by the findings of synergy in vitro in 30 N. brasiliensis strains to cotrimoxazole and amikacin in the majority of the strains tested [36]. The surgical treatment for actinomycetoma is at present very rarely indicated due to the good to excellent therapeutic responses to antibiotic combinations. ACKNOWLEDGEMENTS The authors would like to thank M. K. Moore and D. Wethered (UK), M. Nasher (N. Yemen), F. Zaini (Iran), S. Gumaa (Sudan) and M. K. Mowad and Y. AI-Humaidan (Saudi Arabia) for contributing material for use in this symposium.
CONTRIBUTORS The contributors to this symposium were: S. M. AI Sogair, The epidemiology of mycetoma; R. J. Hay, The pathogenesis of mycetoma; G. Leon, Immunology of
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mycetoma; E. S. Mahgoub, Treatment of eumycetoma; O. Welsh, Treatment of actinomycetoma. The co-convenors were R. J. Hay and E. S. Mahgoub.
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26. MAHGOUB, E. S. 1989. Mycetoma. In: R. J. HAY (Ed.) Tropical Fungal infections. Bailli~res Clinical Tropical Medicine and Communicable Diseases, 4, 31-44, Bailli6re Tindall, London. 27. MAHGOUB, E. S. & GUMAA, S. A. 1984. Ketoconazole in the treatment of eumycetoma due to Madurella mycetomii. Transactions of the Royal Society of Tropical Medicine and Hygiene, 78, 376-369. 28. MAHGOUB, E. S., GUMAA, S. A. • El. HASSAN, A. M. 1977. Immunological status of mycetoma patients. Bulletin de la Socigtd de Pathologie Exotique, 70, 48-54. 29. MAHGOUa, E. S. & MURRAY, I. G. 1973. Mycetoma. William Heinemann, London. 30. MANDELL,G. L. & SANDE, M. A. 1985. Antimicrobial agents sulfonamides, trimethoprim sulfamethoxazole and agents for urinary tract infections. In: The Pharmacological Basis of Therapeutics. 7th edn., pp. 1095-1114. Macmillan, New York. 31. NAKAE, R. & NAKAE, T. 1982. Diffusion of aminoglycoside antibiotics across the outer membrane of Escherichia coli. Antimicrobial Agents and Chemotherapy, 22, 554-559. 32. NASHER, M., WETHERED, D., HAY, R. J., MAHGOUB, E. S. & GUMAA S. A. 1987. The ultrastructure of actinomycetoma grains caused by Streptomyces somaliensis. American Journal of Hygiene and Tropical Medicine, 37, 174--179. 33. OR~z-ORTIZ, L., BOJALIL, L. F. & CONTRERAS, M. F. 1972. Delayed hypersensitivity to polysaccharides from Nocardia. Journal of Immunology, 108, 1409-1413. 34. SAMPAIO,S. t~ SILVALACAZ,C. 1965. Acao de sulfixozazol na actinomicose provacada eplo Actinomyces brasiliensis. O'Hospital, 50, 795-802. 35' SAUL, A. 1983. Micosis profundas en Lecciones de Dermatologia. pp. 127-168. Editorial Francisco Mendez Cervantes. Mexico, D. F. 36. WELSH,O. 1989. Amikacina-Trimethoprim-Sulfamethoxazole en el Tratamiento de Micetomas Actinomicosicos. Tesis Doctoral. Facultad de Medicina de la Universidad Autonoma de Nuevo Leon, Monterrey, Mexico. 37. WELSH,O. & LOPEZ, R. 1985. Micetomas con diseminacion pulmonar. Medicina Cutanea ILA., 13, 517-523. 38. WELSH, O., SAUCEDA, E., GONZALEZ, J. & OCAMPO, J. 1987. Amikacin alone and in combination with trimethoprim-sulfamethoxazole in the treatment of actinomycotic mycetoma. Journal of the American Academy of Dermatology, 17, 443-448. 39. WETHERED,D. B., MARKEY,M. A., HAY, R. J., MAHGOUB,E. S. & GUMAA,S. A. 1987. Ultrastructural and immunogenic changes in the formation of mycetoma grains. Journal of Medical and Veterinary Mycology, 25, 39-46. 40. WETHE~ED, D. B., MARKEr, M. A., HAY, R. J., MAHGOUR, E. S. & GUMAA, S. A. 1988. Humoral immune responses to mycetoma organisms: characterization of specific antibodies by the use of enzyme-linked immunosorbent assay and immunoblotting. Transactions of the Royal Society of Tropical Medicine and Hygiene, 82, 918-923. 41. WHEELER,M. H. & B~LL, A. A. 1988. Melanins and their importance in pathogenic fungi. Current Topics in Medical Mycology, 2, 338-387. 42. VIPULYASEKHA,S. t~ VATHANABHUTI,S. 1960. Treatment of nocardial mycetoma with sulphamethoxypyridazine. British Journal of Dermatology, 72, 188--191. 43. YOUSIF, M. A. & HAY, R. J. 1987. Leucocyte chemotaxis to mycetoma agents - the effect of the antifungal drugs griseofulvin and ketoconazole. Transactions of the Royal Society of Tropical Medicine
and Hygiene, 81,319-321. 44. ZIPROKOWSKI,L., ALTMANN, G., DALITH, F. & SPITZ, U. 1957. Mycetoma pedis: four cases treated with streptomycin. Archives of Dermatology, 75, 855-863.
Mycetoma
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R. J. HAY 1, E. S. MAHGOUB:, G. LEON 3, S. AL-SOGAIR 4 AND O. WELSH 5
1Institute of Dermatology, St. Thomas's Hospital, London, UK; 2World Health Organisation, Eastern Mediterranean Regional Office, Alexandria, Egypt; alnternational Clinical Epidemiology Resource and Training Centre, McMaster University, Hamilton, Canada; ~Ministry of Health, Dammam, Saudi Arabia, and 5University Hospital, Monterrey, Mexico Mycetoma is a chronic, localized, slowly progressive and often painless, subcutaneous disease. It usually involves the lower limbs and is characterized by tumefaction, subcutaneous nodules, destructive granuloma, deformity and discharging sinuses with intercommunicating channels which exude pus with granules of varying sizes and colours. Two main categories of this disease are recognized, namely actinomycotic mycetoma or actinomycetoma caused by actinomycetes and eumycotic mycetoma or eumycetoma which is produced by fungi. There are four main actinomycete causes of mycetoma, Actinomadura madurae, Streptomyces somaliensis, Actinomadura pelletieri and Nocardia brasiliensis. These show distinct geographical differences and these organisms are the chief causes of actinomycetoma in the USA, Africa, South America and Mexico, respectively. In Saudi Arabia most actinomycetomas are due to S. somaliensis and A. madurae. Eumycetoma accounts for about 40% of the reported mycetomas throughout the world. The main organisms responsible for this are Madurella mycetomatis (worldwide), Pseudallescheria boydii (USA), Leptosphaeria senegalensis (West Africa), Madurella grisea (South America) and certain species of Acremonium, Phoma and Pyrenochaeta. Fungi cause nearly half of all mycetomas in Saudi Arabia, the chief causative organism being M. mycetomatis.
Epidemiology of mycetoma The epidemiology of any disorder is generally concerned with the distribution and pathogenetic determinants (biological, physical or social) of the disease under study. Epidemiology of mycetoma can, therefore, be considered under several parameters; the climatic characteristics of the endemic areas (the latitude, temperature, humidity and rainfall), the prevalent vegetation (thorny trees and bushes), demographic features of susceptible population (age, sex, occupation and race) and any anatomical predilection to account for the localization of the disease. Mycetoma is commonly found in countries around the Tropic of Cancer, the main belt lying between 15 S to 30 N of the Equator. It is mainly endemic in North Africa, India and Pakistan, Indonesia, Mexico, and parts of Central and South America. It is seen less frequently in the USA, Europe, Yemen and Saudi Arabia. Mycetoma is more common in those countries which have an arid land and a short rainy season with a relative humidity of 60-80%, followed by a prolonged period of hot and dry weather, the temperature ranging from 45-60°C. In general actinomycetomas occur in hot, dry, semi-desert terrain with an annual rainfall of 50-500 ram, whereas eumycetomas require hotter and more humid climates with rainfall ranging from 500-2000 mm. There are several 41
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notable exceptions, however, to this generalization. Thus, eumycetoma due to M. mycetomatis is often found in hot and dry terrain with poor rainfall, whereas actinomycetoma due to N. brasiliensis and Nocardia asteroides are found both in hot and humid climates. It has been shown that the soil and/or vegetation in endemic areas harbours mycetoma-causing actinomycetes and fungi and these are presumably transferred to the susceptible host through pricks from thorns and bushes, such as Acacia species, commonly found in semi-desert terrains. It is estimated that the disease is about five times more common in males; patients are usually 20-40 years old and are often outdoor workers such as farm labourers and herdsmen. Blacks and coloured races are affected more commonly, probably reflecting the ethnic background of the local population. Mycetoma in Saudi Arabia. Over the years, 21 cases of mycetoma, identified by morphology and culture, have been seen in Dammam, Saudi Arabia. Another 50 cases have so far been reported from this country by others [2,29]. Pooled data from these 71 cases reveal that actinomycetoma represents 55% (39/71) and eumycetoma accounts for 45% (32/71) of all cases. Sixty-one patients were males and 10 females (M:F 6:1); their ages ranged from 14-80 years, the mean being 39 years. Of these, 51 were Saudis (73%), 14 Yemenis (20%), three were from Somalia (4.2%), one patient was Sudanese and the other an Ethiopian. Feet were involved in 83% of cases followed by legs (11.4%) and hands (2.8%). In one case the thigh was involved and in another the perineum. The organisms isolated from Saudi Arabian cases and their relative frequencies are shown in Table 1. The first figure within brackets represents cases seen by us. In Saudi Arabia, foot involvement is the commonest presentation followed by the leg. Infection of the hand is less common than in Sudan or West Africa and involvement of arms and head has not been observed. Similarly, unlike Mexico where mycetoma of the chest wall may account for about 20% of cases, no such patients have been seen in Saudi Arabia (Table 2). TABLE 1. Aetiologyof mycetomain Saudi Arabia Actinomycetoma Streptomyces somaliensis Actinomadura madurae Nocardia brasiliensis Actinomadura pelletieri Nocardia asteroides
(6 (7 (1 (1 (0
+ + + + +
18) 15) 0) 0) 1)
Maduretla mycetomatis Madurella grisea Pseudallescheria boydii Cladosporium species
(6 + 22) (0 + 2) (0 + 1) (0 + 1)
Eumycetoma
Total
24/71 12/71 1/71 1/71 1/71
(33.8%) (16.9%)
(1.4%) (1.4%)
(1.4%)
28/71 (39.4%) (2.8%) 2/71 (1.4%) 1/71 (1.4%) 1/71 (21+5o)=71
The pathogenesis of mycetoma The main characteristic of a mycetoma infection is the presence of large aggregates formed from filaments of the causative organisms which are the centre of inflamma-
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tory activity [5]. Two important considerations are implicit in the development of mycetomas as with other infective conditions. The first is the effect of alterations in host resistance in the emergence of infection and the second is the ability of the organism to resist or evade host defences.
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TABLE 2, Mycetoma: anatomical predilection in various parts of the world
Foot Leg Thigh Perineum Hand Arm Chest Head
Saudi Arabia*Sudan
*W. Africa
*Mexico
83% 11.4% 1.4% 1.4% 2.8% ----
68% 10% 3% 3% 5% 3% 1% 2%
35% 28% -8% 2% 8% 20% 3%
68.8% 3.2% 2% 2% 10.7% 3.8% 1% 3.1%
*Taken from [29].
Host predisposition. Are mycetomas more common in compromised patients? There is little evidence to support the idea that patients with mycetomas have clinically relevant underlying abnormalities. In a large review of patients for instance, Mahgoub & Murray [29] found no consistent predisposing diseases and this is supported by other clinically based studies. In the UK on the other hand, where mycetoma is an imported infection, nine of 26 patients with mycetoma diagnosed between 1982-1991 had underlying diabetes mellitus. While this figure is higher than the expected prevalence of diabetes in the general population it has not been reported elsewhere and at best might be a contributory factor in the development of mycetoma. If there is no clinical evidence to suggest that clinically apparent defective host responses have predisposed infection it is possible that some occult immunological abnormality might be involved. Conflicting results have been reported from two studies of the immunology of mycetoma. In the first, evidence was presented that some patients had defective T-cell mediated responses, for instance in skin test reactivity to dinitrochlorobenzene or in lymphocyte responses to PHA [28]. Those most severely affected were patients whose mycetomas were extensive or had failed to respond to treatment. In contrast, a study from Saudi Arabia suggested that there was no consistent immune dysfunction affecting T-lymphocytes in mycetoma patients [2]. These two findings are not necessarily mutually exclusive and it is possible that those with extensive disease had secondary immunological abnormalities. It has been virtually impossible to produce mycetomas due to M. mycetomatis in many laboratory animals except in congenitally athymic nu nu mice [25]. By contrast when these animals are infected with Nocardia species they develop a disseminated infection analogous to disseminated nocardiosis in man rather than actinomycetoma, the organisms forming into branching filaments rather than grains. The main reason for the accumulation of polymorphonuclear leucocytes around mycetoma grains, the centre of abscess and sinus formation, is the production of chemotactic substances by mycetoma agents [43].
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Adaptive changes. The critical event determining the development of pathological changes is survival of the organisms in subcutaneous tissue [14]. This appears to depend on the ability of fungi or actinomycetes to adapt to an in vivo existence. This is accomplished in a variety of different ways, notably the thickening of the cell wall, seen with most fungal causes of mycetoma, the production of intramural or extracellular melanins, the production of immunomodulatory antigens and, in the case of Nocardia species, loss of the cell wall. Electron-microscopic changes within a eumycetoma grain include the formation of concentric rings of cell wall thickening and the presence of coarse cell wall fibrils around cells [39]. The 'onion skin' thickening of the cell wall is due to intrahyphal growth of cells demonstrable in experimental infection. In S. somaliensis mycetoma grains a fibrillar extracellular matrix forms around viable bacteria [32]. In the case of M. mycetomatis this is complicated by the presence of a homogenous electron dense layer around the periphery of hyphae in grains. While this may result in cell death there is evidence to suggest that this organism produces a melanin precursor which polymerizes externally to the fungal cell, for instance in the presence of rat collagen [6], thus acting as a defensive shield against phagocytic attack. Cell wall deposition of melanin is seen with other organisms causing mycetoma such as L. senegalensis [41]. While there is some evidence for immunomodulatory activity by other fungi and actinomycetes S. somalienesis is the only mycetoma agent where this has been established. This organism produces an extracellular polypeptide which is toxic to human fibroblast cell lines and which, in low concentrations, can reduce macrophage killing of S. somaliensis in vitro (M. Nasher & R. J. Hay, unpublished data). The production of this substance may well explain the prolonged survival of this actinomycete in vivo. There is no evidence that mycetoma agents express different antigens in vivo compared with those expressed in vitro [40].
Immunodiagnosis of mycetoma There are numerous methods which have been applied to the detection of antibody or antigens in body fluids in infectious diseases; recently new procedures such as the application of monoclonal antibodies, nucleic acid hybridization and the polymerase chain reaction have been added to the list. In mycetoma the range of techniques applied to the diagnosis has been limited, perhaps reflecting the low priority accorded to this disease and the shortage of financial support. The immunological responses of individuals with mycetoma has been assessed by skin tests [33] and a number of different serological methods such as complement fixation [1], immunodiffusion [11], counterimmunoelectrophoresis (CIE) [11], enzyme linked-immunoassay (ELISA) [21], microimmunodiffusion [3] and Western blotting [40]. Of these, skin tests have not been diagnostically useful. By contrast serodiagnostic techniques have been of great clinical value. Most of the tests have used cell extracts rather than exoantigens and cross-reactivity has been a problem. However these tests are extremely helpful for monitoring therapy and can provide the earliest clues to reactivation of infection particularly with actinomycetomas. For these purposes CIE has proved to be the simplest approach, although new ELISA tests for Nocardia mycetomas have also proved helpful.
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Treatment of eumycetoma
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On seeing a patient with mycetoma, many doctors will immediately consider amputating the affected limb or, if this is not possible, perform radical surgery. Medical treatment is only considered when the lesion involves a site not readily accessible to surgery such as the head. Both of these attitudes are wrong [24]. The correct approach is a combination of surgery and chemotherapy. Through the former, the greater bulk of the lesion is removed and by the latter, control is obtained and recurrence, a common problem, prevented in the most common fungal cause of this infection.
Ketoconazole. In the case of eumycetoma due to M. mycetomatis, which constitutes the major causative agent in tropical and subtropical Africa and Asia, the drug of choice is ketoconazole. In a clinical trial in Sudan, where results have been monitored since 1980, 50 patients received ketoconazole in a dose of 200 mg twice daily. Regardless of the stage and extent of the lesion, cure or significant improvement, where all sinuses were closed and the swelling greatly reduced, were obtained in 72% of patients. Some improvement was obtained in 20% of cases, the remaining 8% of cases showed no response or deteriorated [27]. Clinical progress was followed by counting the number of active sinuses and measuring the circumference of the lesion at the site of maximal swelling over the nearest bony prominence such as the malleoli or either end of the knee cap. Blood was taken at each visit to the clinic for serological follow-up performed by CIE. Xrays were taken every 3 months. Before starting treatment the liver function and full blood picture were checked. No significant side effects or biochemical abnormalities were seen in these patients. The length of treatment varied from 9 months to 3 years and all patients have been regularly followed up at 3- to 6-month intervals. In a further report [13], ketoconazole was not effective in mycetoma caused by P. boydii or Acremonium species. Itraconazole has also been tried in patients with M. mycetomatis infection for the last 5 years in a dose of 100 mg twice daily [26]. Results were less encouraging than with ketoconazole and no patient achieved mycological and clinical remission; 42% greatly improved and 33% showed no response or deteriorated. This is in contrast to the treatment of paranasal Aspergillus granuloma caused by Aspergillus flavus in Sudan. This condition has responded very well to combined surgery and therapy with itraconazole. The drug has been well tolerated in both conditions. It is also worth noting that the lesions of eumycetoma, if diagnosed early, are well circumscribed and can therefore easily be enucleated surgically.
Liposomal amphotericin B. Three patients with mycetomas due to M. grisea (2) and Fusarium species (1) have been treated with the intravenous liposomal formulation of amphotericin B (Ambisome, Vestar Inc, USA). The total doses given were 3.4, 2.8, and 4.2 g, respectively, with maximum daily doses of 3 mg kg -1. The only adverse effects seen were a transient rise in creatinine (1) and local irritation at the infusion site (1). All three achieved temporary remissions with drying of sinuses and
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diminution of swelling, but all relapsed within 6 months after stopping therapy (R. J. Hay & A. Bryceson, personal observations). Treatment of actinomycetoma
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A number of different antibiotics and antimicrobials have been used in the treatment of actinomycetoma. Sulphonamides and sulphones. This group of antimicrobials has the common characteristic of interfering with the folate metabolic pathway of susceptible bacteria. Sulphanilamide, a sulphonamide, was first used in 1941 with good results in the treatment of mycetoma [4]. Another antimicrobial of the sulphone group is DDS, dapsone. The first case cured with this drug in Mexico was reported in 1950 [7]. Subsequently Latapi & Lavalle confirmed its therapeutic success in a group of actinomycetoma patients [19]. In 1952, Gonzalez Ochoa et al., were the first to report its efficacy in vitro [9]. At present dapsone is used alone and in combination with other antimicrobials in the treatment of actinomycetoma. Its daily dosage is between 200 to 300 mg for periods of 1 to 2 years after the disease is clinically cured [8, 16, 34, 35]. The most frequent side effects are: methaemoglobinemia and haemolytic anaemia, exfoliative dermatitis, cyanosis of fingertips and lips. When this happens medication should be stopped or changed [17]. Other sulphonamides have also been used with variable success in the treatment of actinomycetoma, such as sulphisoxazole and sulphamethoxipiridazine [34, 42]. In the past two decades, actinomycetoma has been treated mainly with sulphamethoxazole trimethoprim (cotrimoxazole). This compound is a combination of a diaminopiridimine and a sulphonamide. Both of these antimicrobials act synergistically interfering in the folate metabolic pathway of the bacteria [30]. In general, Nocardia and other actinomycetomas respond well to treatment with cotrimoxazole, which is given for periods ranging from 6 months to several years with an average of 60-70% success [10, 22, 23]. There are patients who do not respond to this therapy and in these cases, a combination of other antimicrobials is indicated [12, 23]. The therapeutic dosage of cotrimoxazole is 8 and 40 mg kg-1 day-k The adverse reactions are minor gastro-intestinal disturbances, skin rashes and haematological side effects [20]. Tetracyclines. These have been used with only variable success in the treatment of actinomycetoma caused by N. brasiliensis, N. asteroides, A. madurae and A. pelletieri. Two compounds have been used; one (short acting) is oxytetracycline, 1.5 to 2 g day-1 for periods of 1 to 2 years. The other, minocycline (long acting) 200 mg day-1 for the same length of time [15, 16]. Streptomycin. The therapeutic effects of this antibiotic on actinomycetomas were first reported in 1957 [44]. Later Mahgoub treated 144 patients with actinomycetoma with different combined treatments, all of them included streptomycin. These regimens were: streptomycin-DDS, streptomycin-trimethoprim sulphamethoxazole and streptomycin-rifampicin; he recorded excellent cure rates and a number of others. The antibody titre and radiological improvement as well as the clinical response were the
MYCETOMA
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parameters of evaluation used to assess the therapeutic response [24]. Antituberculous drugs such as isoniazid and rifampicin have also been used with some success in a few cases [24].
Amikacin. This antibiotic belongs to the aminoglycoside group and is bactericidal [31]. Amikacin acts mainly by inhibition of protein synthesis of bacteria by interfering with their ribosomal functions [18]; it is active in vitro and in vivo (in experimentally induced infections) against N. asteroides and N. brasiliensis. In 1982 our first patient with an actinomycetoma caused by N. brasiliensis with dissemination to the lungs was treated; he had an excellent therapeutic response after 5 weeks of combined treatment with cotrimoxazole and amikacin [37]. This result was later corroborated using amikacin alone (2 cases) and in combination with cotrimoxazole in another 26 patients [38]. This therapy is reserved for those actinomycetoma patients who have had no response to first line treatments or who have a potentially hazardous site of infection: it is contraindicated where there is hepatic, ear or renal disease. The therapy is given in cycles. A cycle is defined as the period of simultaneous administration of amikacin (15 mg k g -1 day -1) divided into two daily doses for 3 weeks and T-S (7-35 mg kg -1 day-1 for 5 weeks. Twenty-six patients have been treated with this therapy. Twentyone needed one or two cycles of treatment (5-10 weeks) and only five needed three cycles (15 weeks). After the treatment was completed, the patients were asymptomatic and remained without further medication. All have been evaluated for periods of between 6 months to 7 years. Only one of the treated patients had a small recurrence (one pustule) 2 months after the last cycle of therapy and a fourth period of treatment was given, the patient remaining asymptomatic thereafter. Side-effects were minimal, gastrointestinal disturbances in three patients and low creatinine clearance rates in two, this reverted to normal after adjusting the amikacin dosage. Audiometry detected minimal sensorineural hearing loss at high tones in six patients, and a moderate deficit in one patient. When using aminoglycosides in mycetoma it is mandatory to perform periodic audiometry, before each cycle, and to avoid other drugs that can induce deafness. Our therapeutic results can be explained by a possible synergistic effect of the antimicrobials. This is supported by the findings of synergy in vitro in 30 N. brasiliensis strains to cotrimoxazole and amikacin in the majority of the strains tested [36]. The surgical treatment for actinomycetoma is at present very rarely indicated due to the good to excellent therapeutic responses to antibiotic combinations. ACKNOWLEDGEMENTS The authors would like to thank M. K. Moore and D. Wethered (UK), M. Nasher (N. Yemen), F. Zaini (Iran), S. Gumaa (Sudan) and M. K. Mowad and Y. AI-Humaidan (Saudi Arabia) for contributing material for use in this symposium.
CONTRIBUTORS The contributors to this symposium were: S. M. AI Sogair, The epidemiology of mycetoma; R. J. Hay, The pathogenesis of mycetoma; G. Leon, Immunology of
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mycetoma; E. S. Mahgoub, Treatment of eumycetoma; O. Welsh, Treatment of actinomycetoma. The co-convenors were R. J. Hay and E. S. Mahgoub.
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and Hygiene, 81,319-321. 44. ZIPROKOWSKI,L., ALTMANN, G., DALITH, F. & SPITZ, U. 1957. Mycetoma pedis: four cases treated with streptomycin. Archives of Dermatology, 75, 855-863.
