FUNGI AND ACTINOMYCETES THAT CAUSE MYCETOMA.

Definition of Mycetoma:•Also known as "Maduromycosis.

•It usually involves the subcutaneous tissue after a traumatic inoculation of the causative organism.

•Mycetoma may be caused by true fungi or by higher bacteria and hence it is usually classified into eumycetoma and actinomycetoma respectively.

•Tumefaction and formation of sinus tracts characterize mycetoma. The sinuses usually discharge purulent and seropurulent exudate containing grains.

•It may spread to involve the skin and the deep structures resulting in destruction, deformity and loss of function, very occasionally it could be fatal. Found in plant materials, eg wood or thorns and soil

•Localized infections. No association with any underlying disease.

•Draining sinuses. Temporary, may be visible. Pain before rupture of sinus

•This infection is endemic in Africa, India, and Central and South America.

•Aetiological agents include Madurella, Acremonium, Pseudallescheria, Exophiala, Leptosphaeria, Curvularia, Fusarium, Aspergillus etc

Etiology:Mycetoma is caused by:

•Higher bacteria actinomycetoma

•True Fungi eumycetoma

1.Mycetoma is caused by both fungi and bacterial actinomycetes.

2.When caused by a fungus, the swelling is called a eumycetoma and when caused by actinomycetes, called actinomycetoma.

3.It is important to know whether the mycetoma is fungal or actinomycete origin, because actinomycetic infections usually respond to treatment with antibiotics and sulphonamides, whereas fungal infections are resistant to antimicrobials.

Affected area: •Foot, which is commonly affected (Madura foot).

•Knee, arm, scalp, leg, head, neck, and thigh, perineum and wall of the chest.

Complications: Osteomyltis, secondary infection, and deformity.

Pathogenesis•The disease is usually acquired while performing agricultural work, and it generally afflicts men between 20 and 40 years old.

•The disease is acquired by contacting grains of bacterial or fungal spores that have been discharged onto the soil.

•Infection usually involves an open area or break in the skin.

•The disease is characterized by a yogurt-like discharge upon maturation of the infection.

•Infections normally start in the foot or hand and travel up the leg or arm.

Diagnosis:Diagnosis of mycetoma is usually accomplished by radiology, ultrasound or by fine needle aspiration of the fluid within an afflicted area of the body. It depends upon isolating the causative organism along with a knowledge of local endemic infection.

1- Clinical diagnosisTypical Soft tissue massNodular and contains sinusesMucopus containing small granules (colonies) is discharged through sinuses which open on the surface of the skin.2- Radiological and laboratory investigations.

Laboratory diagnosis:•Direct examination of grains

•Culture

•Histopathology

•SerologyClinical Material:

Tissue biopsy or excised sinus, serosanguinous fluid containing the granules which vary in size, colour and degree of hardness, depending on the aetiologic species,.

Granules are very important to differentiate between spp that cause mycetoma.

Collection of mucopus and examination for granules:•Using a sterile hypodermal needle, lift up the crusty surface over a sinus opening.

•Transfer a sample of the draining mucopus to a slide.

•Add a drop of distilled water or saline, and examine for granules. •Note the color, size, and shape of granules, and whether they are hard or soft when held between forceps.

Direct macroscopic:

•Actinomycetoma:Thin branching filaments

Gram positiveAcid fast in case of Nocardia

•Eumycetoma:Broad septate hyphaeSome time with chlamydosopres

Direct microscopy: grains examination•Color•Shape•Size•Consistency

•Crush a few of the granules on a small amount of D.W. and spread the contents on two slides.

•To one preparation, add one or two drops of KOH solution and leave for 5-10 minutes. Allow the other preparation to dry, and fix by covering with methanol for 2-3 minutes (Gram stain after indicating by KOH).

•Examine the KOH preparation microscopically using 10X and 40X. Look for the branching and intertwining threads , and note whether there are thick fungal hyphae of 4-8µm in the diameter or thin actinomycete threads (may appear fragmented) or about 1 µm diameter. Chlamydospores are usually present with fungal hyphae.

•If thin branches are seen in KOH preparation, stain the second preparation by Gram stain and look for gram positive actinomycete threads.

Culture of fungal grains:Culture: Clinical specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar.

This is required for confirmation of the diagnosis.•Wash in saline with antibiotics

•Culture on SDA with antibiotics

•Incubate at 37° C aerobically for 4-6 weeks •In another sample, wash in saline without antibiotics

•Culture on LJ or BHIA

•Incubate at 37° C aerobically for 4-6 weeks

Serology:There is no commercially available serological test for the diagnosis of mycetoma

Summary•Mycetoma is a chronic infection.

•Subcutaneous mass, draining sinuses, and grains.

•Caused by bacteria (actinomycetoma) or fungi (eumycetoma).

•Treated with antimicrobials or/and surgery.