Dimorphic fungi

Dimorphic fungi

1. DIMORPHIC FUNGI Prabin Shah BScMLT , MSc (Biochemistry) 1/17/2015 DIMORPHIC FUNGI 1

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 1/17/2015 DIMORPHIC FUNGI 2

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4. Dimorphic fungi and disease caused by 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 1/17/2015 DIMORPHIC FUNGI 4

5. CONTENTS SPOROTRICHOSIS INTRODUCTION MYCOLOGY EPIDEMIOLOGY PATHOGENESIS AND PATHOLOGY CLINICAL FEATURES LAB DIAGNOSIS TREATMENT 1/17/2015 DIMORPHIC FUNGI 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 S porothrix schenckii into the skin, or very rarely, by inhalation into the lungs. T he infection may also occasionally involve the central nervous system, lungs or genitourinary tract . This disease is also called as Rose Gardener’s disease 1/17/2015 DIMORPHIC FUNGI 6

7. M ycology Causative fungus- Sporothrix schenckii Family- Ophiostomataceae Order- Ophiostomatales Class- Unitunicate Pyrenomycetes Phylum- Ascomycota 1/17/2015 DIMORPHIC FUNGI 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 . 1/17/2015 DIMORPHIC FUNGI 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; Sporotrichoid type Tuberculoid type Foreign body type. 1/17/2015 DIMORPHIC FUNGI 9

10. CLINICAL FEATURES It causes lymphatic and sub cutaneous infection. The disease is broadly classified into 5 clinical types. Lymphocutaneous Sporotrichosis Fixed Cutaneous Sporotrichosis Mucocutaneous Sporotrichosis Disseminated Sporotrichosis Pulmonary Sporotrichosis 1/17/2015 DIMORPHIC FUNGI 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 ” 1/17/2015 DIMORPHIC FUNGI 11

12. Lymphocutaneous sporotrichosis showing typical elevated subcutaneous nodules developing along the regional lymphatics of the forearm 1/17/2015 DIMORPHIC FUNGI 12

13. 2. Fixed C utaneous 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 . 1/17/2015 DIMORPHIC FUNGI 13

14. 1/17/2015 14 DIMORPHIC FUNGI 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 . 1/17/2015 DIMORPHIC FUNGI 15

16. 4. Disseminated S porotrichosis 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. 1/17/2015 DIMORPHIC FUNGI 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 . 1/17/2015 DIMORPHIC FUNGI 17

18. LAB DIAGNOSIS Direct microscopy Fungal culture Immunodiagnosis SPECIMEN COLLECTED: Pus, exudate, aspirate from Nodules Curettage Swabbing from open lesions 1/17/2015 DIMORPHIC FUNGI 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 1/17/2015 DIMORPHIC FUNGI 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. 1/17/2015 DIMORPHIC FUNGI 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.). 1/17/2015 DIMORPHIC FUNGI 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. 1/17/2015 DIMORPHIC FUNGI 22

23. Microscopic morphology of the saprophytic or mycelial form of Sporothrix schenckii when grown on SDA at 25 o C. Note clusters of ovoid conidia produced sympodially on short conidiophores arising at right angles from the thin septate hyphae. 1/17/2015 DIMORPHIC FUNGI 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 1/17/2015 DIMORPHIC FUNGI 24

25. Sporothrix schenckii on Sabouraud's dextrose agar grown at 25 o C colonies are moist and glabrous , with a wrinkled and folded surface. Pigmentation may vary from white to cream to black 1/17/2015 DIMORPHIC FUNGI 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 37 C. Note budding yeast cells. 1/17/2015 DIMORPHIC FUNGI 26

27. TREATMENT Saturated Solution of Potassium Iodide(SSKI) is the drug of choice. Oral ketoconazole or itraconazole T erbinafine 1/17/2015 DIMORPHIC FUNGI 27

28. HISTOPLASMOSIS INTRODUCTION MYCOLOGY EPIDEMIOLOGY PATHOGENESIS AND PATHOLOGY CLINICAL FEATURES LAB DIAGNOSIS TREATMENT 1/17/2015 DIMORPHIC FUNGI 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. 1/17/2015 DIMORPHIC FUNGI 29

30. MYCOLOGY Causative organism is Histoplasma capsulatum , a thermally dimorphic fungus. 3 varieties of this dimorphic fungi are; H.c.var.capsulatum H.c.var.duboisii H.c.var.farciminosum 1/17/2015 DIMORPHIC FUNGI 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 1/17/2015 DIMORPHIC FUNGI 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; Histoplasmosis capsulati Histoplasmosis duboisii Histoplasmosis farciminosi 1/17/2015 DIMORPHIC FUNGI 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. 1/17/2015 DIMORPHIC FUNGI 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; Acute Pulmonary Histoplasmosis Chronic Pulmonary Histoplasmosis Cutaneous, M ucocutaneous Histoplasmosis Disseminated Histoplasmosis 1/17/2015 DIMORPHIC FUNGI 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 o f lung seen in the later stage. 1/17/2015 DIMORPHIC FUNGI 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 1/17/2015 DIMORPHIC FUNGI 36

37. 3.Cutaneous & Mucocutaneous Histoplasmosis Skin and mucous membrane lesions. There is petechial or ecchymotic purpura on the abdominal wall or thorax. 1/17/2015 DIMORPHIC FUNGI 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 1/17/2015 DIMORPHIC FUNGI 38

39. LAB DIAGNOSIS Specimens collected are; Sputum Bone marrow Lymph nodes aspirate Peripheral blood film Biopsy of lesions from skin, mucous membrane. 1/17/2015 DIMORPHIC FUNGI 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 1/17/2015 DIMORPHIC FUNGI 40

41. Tissue section stained by Grocott's methenamine silver (GMS) from a lung biopsy showing numerous yeast cells of Histoplasma capsulatum inside macrophages. 1/17/2015 DIMORPHIC FUNGI 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. 1/17/2015 DIMORPHIC FUNGI 42

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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 1/17/2015 DIMORPHIC FUNGI 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 1/17/2015 DIMORPHIC FUNGI 45

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47. TREATMENT The drug of choice (DOC) is Amphotericin B , with all its side effects . Itraconazole and Voriconazole is now also being used. 1/17/2015 DIMORPHIC FUNGI 47

48. REFERENCES Text book of MEDICAL MYCOLOGY Jagdish Chander A text book of microbiology P.Chakraborty 1/17/2015 DIMORPHIC FUNGI 48

49. THANK YOU 1/17/2015 DIMORPHIC FUNGI 49