Dimorphic fungi
- 2. DEFINITION • Dimorphic fungi are fungi that can reproduce as either a mycelial or a yeast-like state. • Generally the mycelial saprotrophic form grows at 25° C, and the yeast-like pathogenic form at 37° C. • This dimorphism is important in the identification of mycoses, as it makes rapid identification of many pathogenic organisms possible. • Some diseases caused by dimorphic fungi are: • sporotrichosis • blastomycosis • histoplasmosis • coccidioidomycosis • paracoccidioidomycosis • penicillosis 6/20/2015DIMORPHICFUNGI 2
- 4. Dimorphicfungi and diseasecausedby them FUNGUS DISEASE TARGET ORGANS BLASTOMYCES DERMATITIDIS North american blastomycosis Lung, skin. PARACOCCIDIOIDES IMMITIS South american blastomycosis Buccal and nasal mucosa HISTOPLASMA CAPSULATUM Histoplasmosis Respiratory system, pulmonary disease SPOROTHRIX SCHENCKII Sporotrichosis Nodules in skin, lymph nodes 6/20/2015DIMORPHICFUNGI 4
- 5. CONTENTS • SPOROTRICHOSIS • INTRODUCTION • MYCOLOGY • EPIDEMIOLOGY • PATHOGENESIS AND PATHOLOGY • CLINICAL FEATURES • LAB DIAGNOSIS • TREATMENT 6/20/2015DIMORPHICFUNGI 5
- 6. SPOROTRICHOSIS • Primarily a chronic mycotic infection of the cutaneous or subcutaneous tissues and adjacent lymphatics characterized by nodular lesions which may suppurate and ulcerate. • Infections are caused by the traumatic implantation of a dimorphic saprotrophic fungus Sporothrix schenckii into the skin, or very rarely, by inhalation into the lungs. • The infection may also occasionally involve the central nervous system, lungs or genitourinary tract. • This disease is also called as Rose Gardener’s disease 6/20/2015DIMORPHICFUNGI 6
- 7. Mycology • Causative fungus- Sporothrix schenckii •Family- Ophiostomataceae •Order- Ophiostomatales •Class- Unitunicate Pyrenomycetes •Phylum- Ascomycota 6/20/2015DIMORPHICFUNGI 7
- 8. EPIDEMIOLOGY • S.schenckii is a saprophyte associated with plants and soil. • It is isolated from various natural sources and dead vegetation like wood, bark, leaves etc. • Predominantly occurs in young population due to frequent contact with natural sources of infection. • Males are affected 3 times more than that of females. 6/20/2015DIMORPHICFUNGI 8
- 9. PATHOGENESIS • S.schenckii produces 2 extracellular proteinases i.e. proteinase I and proteinase II. • The former is serine proteinase , inhibited by chymostatin whereas the latter is an aspartic proteinase inhibited by pepstatin. • They play an important role in fungal invasion and growth. • The 3 granulomatous patterns are; i. Sporotrichoid type ii. Tuberculoid type iii. Foreign body type. 6/20/2015DIMORPHICFUNGI 9
- 10. CLINICAL FEATURES • It causes lymphatic and sub cutaneous infection. • The disease is broadly classified into 5 clinical types. 1. Lymphocutaneous Sporotrichosis 2. Fixed Cutaneous Sporotrichosis 3. Mucocutaneous Sporotrichosis 4. Disseminated Sporotrichosis 5. Pulmonary Sporotrichosis 6/20/2015DIMORPHICFUNGI 10
- 11. 1. Lymphocutaneous Sporotrichosis • Commonest type that follows subcutaneous implantation of spores in a penetrating wound. • Incubation period varies from 8-30 days. • Initial manifestation is appearance of a small, firm, non- tender, mobile subcutaneous nodule which becomes violaceous and may ulcerate forming sporotrichotic chancre. • The disease is characterised by involvement of lymphatics and development of characteristic linear-nodulo-ulcerative secondary lesions along lymphatics. • This type of lesion is called “sporotrichoid” 6/20/2015DIMORPHICFUNGI 11
- 13. 2. Fixed Cutaneous Sporotrichosis • Cutaneous sporotrichosis where the lesions remain localised to inoculation site. • Commonly seen among individuals with higher degree of immunity because of prior exposure to organism. • Lesions commonly appear on neck, trunk, or face as ulcerative, verrucose, papular, acneform, gummatous or erythematoid. 6/20/2015DIMORPHICFUNGI 13
- 14. 6/20/2015 14 DIMORPHICFUNGI Fixed cutaneous verrucous-type sporotrichosis of the wrist and hand
- 15. 3. Mucocutaneous Sporotrichosis • Lesions develop in mouth, pharynx, vocal cords or nose. • Lesions are erythematous, ulcerative and suppurative at first and later granulomatous, vegetative or papillomatous. • Regional lymph nodes become enlarged and firm. 6/20/2015DIMORPHICFUNGI 15
- 16. 4. Disseminated Sporotrichosis • Occurs by the hematogenous spread from primary lesion or from suppurating lymph nodes. • Dissemination is manifested with the beginning of subcutaneous nodules and later become papules, pustules, gummata or confluent areas of folliculitis. • Mostly seen in AIDS patients. 6/20/2015DIMORPHICFUNGI 16
- 17. 5. Pulmonary Sporotrichosis • It occurs without the involvement of cutaneous or subcutaneous tissue. • Once the conidia of S.schenckii enter lungs, they may form nodules, cavities or diffuse reticulonodular infiltrates. • A single cavitary lesion of upper lobe is the most distinctive feature. • The solitary residual fibrocaseous nodule- sporotrichoma is an infrequent pathogenic manifestation of pulmonary sporitrichosis. 6/20/2015DIMORPHICFUNGI 17
- 18. LAB DIAGNOSIS i. Direct microscopy ii. Fungal culture iii. Immunodiagnosis SPECIMEN COLLECTED: Pus, exudate, aspirate from Nodules Curettage Swabbing from open lesions 6/20/2015DIMORPHICFUNGI 18
- 19. DIRECT MICROSCOPY • KOH wet mount preparation • Shows small, elongated yeast cells . cigar-shaped and budding S. schenckii yeast cells. Direct examination (10% KOH) of the pus from a lesion of a human patient with sporotrichosis, showing nonspecific budding yeast cells 6/20/2015DIMORPHICFUNGI 19
- 20. • GRAM STAIN • Shows GP irregularly stained yeast cells which are very few in number. • IN TISSUE SECTIONS • Organism appears as cigar shaped bodies yeast cells in H&E and PAS • Asteroid bodies may be seen in direct smear examination and on histopathological examination with H&E. • The fungi are surrounded by refractile, eosinophilic halo called Splendore-Hoeppli phenomenon. 6/20/2015DIMORPHICFUNGI 20
- 21. Section from a fixed cutaneous lesion on the face of a child with sporotrichosis showing round Periodic Acid-Schiff (PAS) positive yeast-like cells, one with an elongated bud. Sporothrix schenckii is a dimorphic fungus and this is the typical parasitic or yeast-like form seen in tissue. (Courtesy Professor D. Weedon, Brisbane, Qld.). 6/20/2015DIMORPHICFUNGI 21
- 22. FUNGAL CULTURE • Specimens inoculated on 2 sets of SDA, BHIA with actidione, BA, CA incubated at 25°C and 37°C. • Colonies at 25°C are initially moist, off-white to cream colored which appear within 3-5 days and turn gray, brown, or black leathery in abt 10-14 days. 6/20/2015DIMORPHICFUNGI 22
- 23. Microscopic morphology of the saprophytic or mycelial form of Sporothrix schenckii when grown on SDA at 25oC. Note clusters of ovoid conidia produced sympodially on short conidiophores arising at right angles from the thin septate hyphae. 6/20/2015DIMORPHICFUNGI 23
- 24. • 2 types of sporulation is seen. • Spore borne individually on delicate sterigma along hyphae • pyriform spores borne in small groups • Depending upon the pattern of orgin of conidiophore, 2 types of appearance seen; • Flower like pattern • Palm tree - like 6/20/2015DIMORPHICFUNGI 24
- 25. Sporothrix schenckii on Sabouraud's dextrose agar grown at 25oC colonies are moist and glabrous, with a wrinkled and folded surface. Pigmentation may vary from white to cream to black 6/20/2015DIMORPHICFUNGI 25
- 26. Microscopic morphology of the parasitic or yeast form of Sporothrix schenckii when grown on brain heart infusion agar containing blood and incubated at 370C. Note budding yeast cells. 6/20/2015DIMORPHICFUNGI 26
- 27. TREATMENT • Saturated Solution of Potassium Iodide(SSKI) is the drug of choice. • Oral ketoconazole or itraconazole • Terbinafine 6/20/2015DIMORPHICFUNGI 27
- 28. •HISTOPLASMOSIS • INTRODUCTION • MYCOLOGY • EPIDEMIOLOGY • PATHOGENESIS AND PATHOLOGY • CLINICAL FEATURES • LAB DIAGNOSIS • TREATMENT 6/20/2015DIMORPHICFUNGI 28
- 29. HISTOPLASMOSIS • An intracellular mycotic infection of the reticuloendothelial system caused by the inhalation of the fungus. • Approximately 95% of cases of histoplasmosis are inapparent, subclinical or benign. • 5% of the cases have chronic progressive lung disease, chronic cutaneous or systemic disease. • The infection is also known as Darling’s disease. 6/20/2015DIMORPHICFUNGI 29
- 30. MYCOLOGY • Causative organism is Histoplasma capsulatum, a thermally dimorphic fungus. • 3 varieties of this dimorphic fungi are; i. H.c.var.capsulatum ii. H.c.var.duboisii iii. H.c.var.farciminosum 6/20/2015DIMORPHICFUNGI 30
- 31. Mycelial colonies of H.capsulatum Culture of Histoplasma capsulatum on SDA showing a white suede-like colony-albino type Culture of Histoplasma capsulatum on SDA showing a white suede-like colony-brown type 6/20/2015DIMORPHICFUNGI 31
- 32. EPIDEMIOLOGY • Causative agent has been isolated from soil. • Soil with high nitrogen content ecspecially related to droppings of chickens and bats. • Adult men are more affected than women. • 3 types of histoplasmosis are; i. Histoplasmosis capsulati ii. Histoplasmosis duboisii iii. Histoplasmosis farciminosi 6/20/2015DIMORPHICFUNGI 32
- 33. HISTOPLASMOSIS CAPSULATI • Classic histoplasmosis • Highly infectious mycosis • PATHOGENESIS • Infection occurs when microconidia are inhaled and get converted to yeasts in alveolar macrophages in the lungs. • Characterized by localized granulomatous inflammation and dissemination to reticuloendothelial system. 6/20/2015DIMORPHICFUNGI 33
- 34. Clinical Features • Asymptomatic in 90-95% • Asymptomatic form is indicated by presence of positive histoplasmin skin test. • The clinical types are classified as; 1. Acute Pulmonary Histoplasmosis 2. Chronic Pulmonary Histoplasmosis 3. Cutaneous, Mucocutaneous Histoplasmosis 4. Disseminated Histoplasmosis 6/20/2015DIMORPHICFUNGI 34
- 35. 1.Acute Pulmonary Histoplasmosis • It is an acute influenza like self limited illness. • Characterized by general malaise with fever, headache, chills, profuse sweating, sore throat, dry cough, chest pain, and dyspnoea. • Calcification of lung seen in the later stage. 6/20/2015DIMORPHICFUNGI 35
- 36. 2.Chronic Pulmonary Histoplasmosis • Mostly found in adults with formation of cavities in the lung either due to primary lesions or reactivation of apparently healed old lesion. • Presented with hemoptysis, weight loss, ulcerative lesions over the lips, mouth, nose, larynx and intestine. • The lesions become calcified as concentric rings i.e. histoplasmoma 6/20/2015DIMORPHICFUNGI 36
- 37. 3.Cutaneous & Mucocutaneous Histoplasmosis • Skin and mucous membrane lesions. • There is petechial or ecchymotic purpura on the abdominal wall or thorax. 6/20/2015DIMORPHICFUNGI 37
- 38. 4.Disseminated Histoplasmosis • Manifested as fever, anorexia, weight loss, anemia, leucopenia, hepatosplenomegaly and lymphadenopathy. • Late sequelae of subclinical infection is called Presumed Ocular Histoplasmosis Syndrome (POHS) characterized by distinct features as atrophic histo spots 6/20/2015DIMORPHICFUNGI 38
- 39. LAB DIAGNOSIS • Specimens collected are; 1. Sputum 2. Bone marrow 3. Lymph nodes aspirate 4. Peripheral blood film 5. Biopsy of lesions from skin, mucous membrane. 6/20/2015DIMORPHICFUNGI 39
- 40. Direct Microscopy • Direct examination of H.capsulatum is best done with H&E stain. Tissue section stained with haematoxylin and eosin (H&E) from a biopsy of the mouth lesion , numerous yeast cells of Histoplasma capsulatum seen 6/20/2015DIMORPHICFUNGI 40
- 41. Tissue section stained by Grocott's methenamine silver (GMS) from a lung biopsy showing numerous yeast cells of Histoplasma capsulatum inside macrophages. 6/20/2015DIMORPHICFUNGI 41
- 42. KOH wet mount • The size of yeast cells being too small is invariably missed out. • Therefore thick and thin smears prepared out of perpheral blood, bone marrow etc are stained with calcofluor white, giemsa, or wright stains. • Fungus appear as small, oval yeast cells, within PMNC. 6/20/2015DIMORPHICFUNGI 42
- 44. FUNGAL CULTURE • Inoculated onto SDA with antibacterial antibiotics and actidione and is incubated at 25°C and 37°C. • Another set of culture on BHI agar with same antimicrobials is also inoculated and incubated as 25°C. • Special media: Kelley’s medium 6/20/2015DIMORPHICFUNGI 44
- 45. SEROLOGICAL TESTS • Serology for histoplasmosis is a little more complicated than for other mycoses, but it provides more information than blastomycosis serology. • There are 4 tests: •Latex agglutination •Complement Fixation •Immunodiffusion •EIA 6/20/2015DIMORPHICFUNGI 45
- 47. TREATMENT • The drug of choice (DOC) is Amphotericin B, with all its side effects. • Itraconazole and Voriconazole is now also being used. 6/20/2015DIMORPHICFUNGI 47
- 48. REFERENCES • Text book of MEDICAL MYCOLOGY • Jagdish Chander • A text book of microbiology • P.Chakraborty 6/20/2015DIMORPHICFUNGI 48