BABCOCK UNIVERSITY COURSE MLSM 507 TOPIC: SUBCUTANEOUS MYCOSES

1. BABCOCK UNIVERSITY COURSE MLSM 507 TOPIC: SUBCUTANEOUS MYCOSES

2. Subcutaneous mycoses are infections that involve the skin and underlying tissues. • Fungi causing subcutaneous mycoses grow in soil or on decaying vegetation. • This is a diverse group which belong to several fungal genera. • Man and animal are accidental hosts. • The fungal spores enter the cutaneous or subcutaneous tissue through a trauma e.g. a thorn

3. prick or contamination of an open wound by soil. • Mycetoma (Madurmycosis or Madura foot) • Mycetoma was first reported in Madura, southern India. • A slow progressive chronic granulamatous infection, usually of foot.

4. Causative agent • Caused by species of actinomycetes and other filamentous fungi. • Fungi commonly associated with the condition are: Madurellamycetomatis, Phialophorajeanselmi, M. griseaetc. - Mycetomacosis is also caused by Actinomycesmadura, A. pelletieri, Norcardiabrasiliesis, Streptomycessomaliensis.

5. Clinical Disease • On entering the tissue, the disease begins as a small subcutaneous swelling of the foot. • The swelling gets larger and burrows into the deeper tissue and finally erupts on the skin surface as multiple sinuses. • Sero-purulent fluid containing granules is discharged from the sinuses. • Macroscopic and microscopic examination of the granules are diagnostic.

6. Laboratory diagnosis • Specimen: Exudate from mycetoma or tissue 1. Macroscopic examination • Examine the specimen for presence of granules; colour, size and consistency of granules if present. 2. Microscopic examination - Direct KOH mount: Crush granules in a drop of 10% KOH.

7. between two slides. • Examine microscopically to detect branching inter-twinning hyphae. • If the hyphae are 4- 8 um in diameter, the causative agent is a filamentous fungus: the function is called eumycetoma. • If it is actinomycetoma, prepare smear and stain with Gram to reveal Gram positive filamentous bacteria. Identify bacteriologically.

8. Culture • Inoculate Sabouraud agar and brain heart infusion agar. • Incubate at 22 – 260C for up to 3 weeks. • If no growth after 4 weeks, discard as negative. • Isolated fungus is identified on the basis of colonial morphology, microscopy and growth rate.

9. Chromoblastomycosis Causative agent: a group of geophilic fungi. • The disease is common in the tropical and subtropical regions of the world. • Three genera are involved: Cladosporium, Phialophora and Fonsecaea.

10. Clinical Disease • Farm workers who do not wear protective clothing are most affected. • The spores of the fungi enter the subcutaneous tissue through thorn pricks or splinter puncture wounds. • The infection starts as a papule at the site of inoculation and form warty cutaneous nodules.

11. Disease usually confined to legs and arms though other parts of the body may be affected. • Laboratory Diagnosis • Specimen: Tissue from the lesion. • KOH mount: Prepare KOH mount. • Examine for sclerotic bodies which appear as round, irregular dark brown yeast like with septa, about 5 – 20 um in size.

12. Tissue section stained by H & E : Presence of sclerotic bodies indicate chromoblastomycosis. • Culture • Homogenise the tissue and inoculate Sabouraud medium. Inoculate yeast extract phosphate medium if Histoplasma capsulatum is suspected. • Incubate at 300C and examine every 2-3 days for up to 4 weeks.

13. Identify any isolated fungi based on colonial and microscopic morphology and other tests: • Colonial morphology: Chromoblastomycosis causing fungi produce darkly pigmented, slightly folded and heaped up colonies with greyish-velvety surface, and showing a black pigment on the reverse. • Microscopic morphology • Cladosporium species: Most species, e.g. Cladosporiumcarionii, show branching long chains of

14. dematiaceous conida, arising from an erect tall, branching conidophore. • Phialophora species: The species, e.g. Phialophora verrucosa, shows tube-like or cup shaped phialides from which conidia arise. Each conidium has a distinct, small collar-like projections. Conidia appear in clusters near the tip of the phialide. • Fonsecaea species: Primary conidia give rise to secondary conidia (sympodial arrangement). This

15. gives the appearance of short chains of primary and secondary conidia around a sympodialconidiophore, e.g. Fonsecaeapedrosoi. • Sporotrichosis • A subcutaneous infection caused by the dimorphic fungus, Sporothrixschenckii. • The fungus lives in living or dead vegetaion. An occupational hazard for farmers, gardners and miners.

16. Clinical Disease: Infection contratces through thorn-pricks or other minor wounds on hand, arm or leg. • Infection begins as non healing ulcer and later becomes a nodular lesion of the skin and subcutaneous tissues. • The nodular lesions eventually breaks down and ulcerate.

17. Laboratory diagnosis • Specimens: Exudate from draining lesions or from unopened nodular lesions. • Procedures • Direct microscopy - KOH mount: Sporothrixschenckii appears as isolated yeast cells, usually round or cigar shaped.