Madurella

About the author:

Michele Rehbein is a double masters student currently attending Western Illinois University in the programs of Biology and Health Sciences, specifically focusing on microbiology and public health. She has been conducting research in the immunology-virology lab at WIU on West Nile virus. She plans to get her PhD after she has graduated from WIU, but in the meantime has interests in continuing research and gaining experience. This blog was created as a class project through a medical mycology course she is currently in.

Madurella

General Description:

Madurella is a filamentous fungus found in the soil. It is described as dark-walled or phaeiod, called dematiaceous, which means they are brown-pigmented (9). It is commonly found in tropical and subtropical areas such as Africa, India, and South America. Madurella is a pathogenic fungus that causes infections in humans.

Grains of M. grisea.

www.mycology.adelaide.edu.au

The optimum temperature for growth of M. grisea is 30°C, M. grisea will not grow at 37°C (12, 15) and this is a distinguishing factor between itself and M. mycetomatis. Colonies of M. grisea look dark, leathery, and folded with grooves and a light brown-grey surface. Colonies grow slowly and as they age the color becomes darker brown to red-brown with a brown-black reverse. Grains of M. grisea are black, round to lobed, soft to firm, and a size of up to 1.0 nm (15). There are two distinctive zones: a hyaline to weakly pigmented central zone and a deeply pigmented periphery (15). Hyphae have been described as either thin of 1 to 3 μm in width or broader at 3 to 5 μm in width (15).

M. mycetomatis

www.mycology.adelaide.edu.au

M. mycetomatis is a slow growing fungus and often only produces sterile hyphae (12). The colonies will grow slowly and are flat and leathery at first, then turn white to yellow to yellowish-brown, and becoming brown, folded, and heaped with age (15). Formation of aerial mycelia will also be observed. Two types of development of conidia have been observed: flask shaped phialides (projection from the vesicle of the fungus) that bear rounded conidia, and simply or branched conidiophores with pyriform, or pear shaped, conidia with truncated bases, ranging from 3-5 μm (15). The optimal growth temperature of M. mycetomatis is 37°C (15).

Phialides of M.mycetomatis
www.mycology.adelaide.edu.au

Distribution:

Madurella mycetomatis causes eumycetoma in individuals living in arid climate zones of east and west regions of Africa, specifically Somalia, Djibouti, Sudan, Nigeria, Mali, and Senegal, and it occasionally is found in the Middle East, and in southern India (12). M. grisea is a common etiologic agent found in South America (12). Other cases have been reported in temperate regions, such as the Appalachians in the United States, but is rarely found in Europe (8). Although the highest incidence of eumycetoma is found in Sudan from June through October when the hot, rainy seasons occur, the disease can be frequently imported into Western countries and the United Kingdom due to an increase of immigrants and tourists (5, 8).

Main distribution regions.

www.cia.gov

Habitat:

M. mycetomatis and M. grisea have both been isolated from the soil, thorny plants, and splinters, and are major causative agents of mycetoma (12).

nilscordes.com

Risk factors:

Males, ages 20 to 45 years old, are more susceptible than females, with approximately a ratio of 4:1 (12). This higher number of infection rates in men is very likely related to their occupations. Men tend to hold more jobs outdoors such as farmers, herders, and agriculture. Individuals who work outdoors in rural areas without proper footwear or proper foot protection can get this fungal infection from traumatic implantation. Some areas also do not have the proper medical or health care services and resources to properly treat the infection even if an early diagnosis is made (2). In some instances, some individuals cannot afford treatment either. Commonly seen is that most patients who are admitted for this type of infection often lack any knowledge or education of it (2).

Eumycetoma has been associated with patients who have generally normal health and is not associated with those who are immunosuppressed. However in some cases, a decreased activity level resulting from having the disease can actually lead to economic depression within communities (12). The economy can be hurt due to the amount of diseased individuals not able to attend their jobs, therefore reducing workforce efficiency. Between the years of 1979 and 1985, there was a study of 27 patients in the United Kingdom and 12 (44%) of these patients had diabetes mellitus that also had infection of eumycetoma (12).

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Veterinary forms:

Madurella spp. have been found to cause disease in dogs. It can cause dermal or visceral focal phaeohyphomycosis (14). Dogs that are infected present symptoms of focal granulomas with viscera as well as fever and malaise, and there may also be intracranial infection (14). Eumycetoma has also been found in horses, cattle, occasionally cats, and sometimes exotic animals, such as squirrel monkeys and parrots (12).

Transmission:

The main route of transmission for this fungus is intracutaneous (within the skin) inoculation (12). Infection can follow traumatic implantation of fungal spores or hyphal fragments that are present in the soil or on plant material (5). Eumycetoma is not transmissible between humans, animals to humans, or humans to animals (12).

Other fungi that cause dark grain mycetoma is Pyrenochaeta romeroi, Pseudallescheria boydii, and Scedosporium apiospermum (12). However, there has not been much data existing that understands the genetic relationship between these organisms and the possibility of other fungi that might provoke mycetoma (5).

Eumycetoma on a patient's hand.

Belkum et al., 2013.

Madura foot.

www.lucianoschiazza.it

Histopathology/Pathogenesis:

M. mycetomatis is the most common causative agent of eumycetoma worldwide (10). Mycetoma is a chronic, subcutaneous granulomatous, progressive and destructive inflammatory disease cause by true fungi (10). A mycetoma caused by a true fungus is classified as eumycetoma (10). Pathogenesis of mycetoma is not completely understood or known (2). It has also been an ignored disease for many years by international health organizations, until recently when the World Health Organization (WHO) recognized it as a neglected tropical disease (1).

Infections of eumycetoma tend to be slow and progress over time (8). These infections could potentially spread to the skin and deep structures such as bone. This could lead to deformity and destruction, and loss of function/disability. Sometimes an infection can become fatal. The most commonly affected body part of eumycetoma is the foot, with approximately 70% of cases observed (8). However other exposed body parts can get this disease. Other body parts seen with infection are the hand, leg, knee, arm, thigh, and perineum (8). Craniofacial mycetoma is rare, and there have also been infections seen in the paranasal sinuses, mandible, intraspinal, bladder, brain, and lung (8).

Periodic acid-Schiff stained section showing grains with broad hyphae.

Arenas et al., 2009.

Eumycetoma is characterized by its formation of black grain in the tissue which consist of densely packed fungal mycelia within a hard and cemented material that is observed as brown-black (10). The grain will look rounded, oval or tri-lobed, with a medulla and compact cortex. There are two types of grains that can be found: filamentous and vesicular (10). The chemical composition of these grains is not fully understood. It is suspected that some components of the grains are organic materials such as carbohydrates, lipids, proteins, and nucleic acids. The previously mentioned organic components may actually play a major role in the fungi’s pathogenicity and its resistance to numerous antifungal agents due to these components having direct contact with the host.

Grains from infected specimen.

Arenas et al., 2009.

Detection and Identification:

Pus, exudates, or biopsy material with grains are the primary indicators of eumycetoma (12). Taking into account the size, shape, color, and consistency of the grains also help with identification of which fungus may be the cause, such as Madurella. The grains caused by hyaline molds with be white or yellow, and grains caused by melanized fungi will be black (12). KOH prep can be used and staining with lactophenol cotton blue or lactofuchsin can be used. Eumycetoma grains for culture can be washed with sterile water or saline containing antibacterial antibiotics and they can be crushed and cultured in duplicate (12). Media that is suggested is SDA and brain heart infusion (BHI) with choloramphenicol, or penicillin and streptomycin, but cyclohexamide is not used as it may inhibit some causative fungi (12). The incubation temperatures should be between 25-30°C, and also keeping in mind some species are slow growing fungi, the cultures should be kept for 6-8 weeks (12).

Therapy:

Eumycetoma is difficult to treat and a major challenge. Therapy failure is common and there is also a high rate of the fungal disease to recur (1). Surgical treatment may sometimes be the only option if the lesion is very well defined (2). If there are very advanced lesions present, treatment with antifungal agents may be very ineffective, especially when it has progressed to the point where the bone is involved (12). Surgery in combination with azole treatment in recommended for smaller eumycetomas on extremities (2). Some reports suggest that voriconazole is a good azole to use for treatment for black grain mycetoma, itraconazole also helps to stabilize lesions prior to surgery (2). There have been reports showing that M. mycetomatis is the most susceptible to the azole class of antifungal agents with ketoconazole and itraconazole being the most frequently used drugs for treatment of it (1). A study done by Ahmed et al. 2014 also showed M. mycetomatis to be susceptible to ravuconazole.

Early diagnosis is a must and intervention is needed immediately with antimycotics potentially accompanied by surgery to eliminate the need for more serious surgical treatment and amputation (2).

Clinical Case Examples:

1. A 39 year old man living in Mali presented signs of chronic swelling with sinuses that showed draining purulent fluid in his left ankle (12). He decided to go to a clinic for treatment in December of 2000 which was located in Paris, France. The man had past history of surgical removal of an abscess near the current affected ankle with black grains found. He had been treated with trimethoprim-sulfamethoxazole, but had little to no improvement. A lytic lesion was found from radiography in his distal fibula and one week after the man had sought treatment he was taken into surgery for massive excision of the soft tissue and the infected bone (12). Specimens taken from the surgery showed numerous black grains. The black grains were washed in sterile water and cultured on SDA and chocolate agar. The plates were incubated at 30°C and 37°C and after 4-5 days a slow growing mold appeared. After 8 weeks of incubation no conidia were seen, and no identification could be done by observing morphology. PCR and sequencing of rDNA using ITS1 and ITS4 were done and Madurella mycetomatis was identified. There was additional surgery completed and the man was also given treatment of amoxicillin and itraconazole twice a day for 20 weeks (12). After a 2 month follow up, there was no recurrence of the fungal infection seen, however two years following the admittance of this man, his wound was still found to be draining (12).

2. A 21 year old farmer had a four year history of a nodular plaque involving the arch of the plantar surface of the right (2). The nodular plaque had developed after trauma to the foot while the farmer was working in the fields. The patient had been surgically treated within their community but scarring had developed, and recurrence appeared after 6 months from the date of the surgery. The patient had a lesion which had bloody drainage with serous exudate and black charcoal-like granules or grains (2). Using Lugol’s iodine, the grains were observed, and a biopsy was taken from the deep dermis near one of the fistulas (2). The biopsy showed filaments at the periphery with suppurative granuloma containing neutrophils, fibrous stroma, and Langerhans-type giant cells (2). Gomori-Grocott and periodic acid-Schiff (PAS) stains were used and cultures of the grains of SDA and Mycosel agar were positive for M. mycetomatis (2). By using X-ray and computed topography scan it was shown that only soft tissue not bone was affected by the infection (2). The patient was treated with itraconazole for 300 mg daily for six months but only a mild decrease in the inflammation occurred. Surgical removal was needed since there was only partial closing of the fistulae. Topical negative pressure (TNP) therapy was given to the patient to stimulate granulation tissue formation followed by an autologous skin grafting (2). For an additional 3 months, the patient was given itraconazole and by 18 months the patients was disease free.

Monday, February 22, 2016

Madurella