SYSTEMIC MYCOSES HISTOPLASMOSIS • Systemic granulomatous disease caused by a dimorphic fungus, Histoplasma capsulatum • Also known as Darling’s disease • Three varieties: 1. H. capsulatum var. capsulatum  classical histoplasmosis (commonest) 2. H. capsulatum var. duboisii  African histoplasmosis 3. H. capsulatum var. farciminosum  epizootic histoplasmosis H. capsulatum var. capsulatum • Epidemiology • Histoplasmosis occurs worldwide • Endemic in USA, particularly in states bordering the Ohio River valley and the lower Mississippi River • In India - reported frequently from the region of West Bengal along the Ganga River • The fungus inhabits humid and acidic soil that contains large amount of bird or bat droppings Histoplasmosis - Pathogenesis • Contaminated soil disturbed inhalation of spores (i.e. microconidia) Spores engulfed inside the alveolar macrophages and then transform into yeast forms yeasts survive within the phagolysosome carried to the lymph nodes spread to other parts of the body through bloodstream • Majority show strong cell-mediated immune response within 2 weeksGranulomas heal with fibrosis and calcification. rarely reactivates Clinical Manifestations • Classical histoplasmosis ranges from asymptomatic infection (in immunocompetent people) to lifethreatening illness seen in people with low CMI • Pulmonary histoplasmosis (MC) - Acute form - mild flu like illness, pulmonary infiltrates in chest X-ray with hilar or mediastinal lymphadenopathy - Chronic cavitary histoplasmosis - in smokers Clinical Manifestations • Mucocutaneous histoplasmosis: Skin and oral mucosal lesions secondary to pulmonary infection • Oral lesions - in Indian patients • Disseminated histoplasmosis: if CMI is very low - Common sites - bone marrow, spleen, liver, eyes and adrenal glands Laboratory Diagnosis • Specimens: sputum, aspirate from bone marrow and lymph node, blood and biopsies from skin and mucosa • Direct microscopy: • Histopathological staining (PAS, Giemsa or GMS stain)  tiny oval yeast cells (2–4 μm size) with narrowbased budding within the macrophages with an underlying granulomatous response Culture • Gold standard method of diagnosis • Media: SDA, blood agar and BHI agar in duplicate and incubated simultaneously at 25°C and 37°C • Histoplasma is a dimorphic fungus At 25°C: mycelial phase - white to buff brown colonies that • consist of two types of conidia or spores: 1. Tuberculate macroconidia, with typical thick walls and fingerlike projections which is a characteristic feature of this fungus 2. Microconidia are smaller, thin, and smooth-walled At 37°C: yeast form (creamy white colonies Histoplasma capsulatum Other Tests • Serology: Antibodies -CFT and immunodiffusion test - Antibodies appear after 1 month of infection more useful in chronic stage - False positive - past infection or cross infection with Blastomyces • Skin test: delayed type hypersensitivity response to histoplasmin antigen, which indicates prior exposure. • Molecular test: PCR targeting specific ITS D1/D2 gene Treatment Histoplasmosis • Liposomal amphotericin B - acute pulmonary and disseminated histoplasmosis • Itraconazole - chronic cavitary pulmonary histoplasmosis Histoplasma variants • - H. capsulatum var. duboisii Causes African histoplasmosis Frequent skin and bone involvement yeast form exists as large thick walled oval yeast cells (7– 15 μm) with prominent narrow based budding • H. capsulatum var. farciminosum - Causes epizootic histoplasmosis - A form of lymphangitis in horses and mules BLASTOMYCOSIS • Also known as North American blastomycosis or Gilchrist’s disease or Chicago disease • Caused by - Blastomyces dermatitidis, a dimorphic fungus, • Pathogenesis • Transmitted by inhalation of the conidia • Spores are engulfed by alveolar macrophages, where they get converted into yeast phase. • Expresses BAD-1 (B.dermatitidis adhesin-1) an essential virulence factor and also a major inducer of cellular and humoral immune responses Clinical Manifestations • Acute pulmonary blastomycosis - most common form • Extrapulmonary manifestations : - Skin involvement - most common extrapulmonary form: verrucous (more common) or ulcerative type of skin lesions - Osteomyelitis along with contiguous soft tissue - Abscesses and draining sinuses - Prostate and epididymis - Central nervous system in AIDS patients Blastomycosis • Epidemiology • Endemic in North America, particularly in states bordering the Ohio River and Mississippi River. Laboratory Diagnosis • H istopathological staining of the tissue biopsy specimens: thickwalled round yeast cells of 8–15 μm size with single broad-based budding (figure of 8 appearance) Laboratory Diagnosis • C ulture media - SDA, blood agar and BHI agar are inoculated - At 25°C, mycelial form - hyphae with small pear-shaped conidia - At 37°C mold to yeast conversion • Skin test: delayed type hypersensitivity to blastomycin antigen • Antibody detection: Immunodiffusion yeast phase antigens such as antigen—A, BAD-1 and ASWS antigen Blastomycosis • Antigen detection – in urine (more sensitive) and in serum • Molecular methods - DNA probe hybridization and real time PCR • Treatment Blastomycosis - Liposomal amphotericin B - drug of choice - Itraconazole - immunocompetent patients with mild pulmonary or non-CNS extrapulmonary blastomycosis COCCIDIOIDOMYCOSIS • • • • Also called desert rheumatism or Valley fever or California fever Coccidioides has two species - C. immitis and C. posadasii Pathogenesis Transmitted by inhalation of arthroconidia  lungs, they enlarge, become rounded, and develop internal septations to form large sac like structures of size up to 200 μm called spherules, that encompass numerous endospores rupture and release packets of endospores  disseminate and develop into new spherules Clinical Manifestations • Most patients are asymptomatic (60%) • Pulmonary coccidioidomycosis (most common) pneumonia, cavities, pleural effusion or nodule formation • Skin lesions - rashes or erythema nodosum and arthritis • Disseminated form: Males and persons with low CMI - skin, bone, joints, soft tissues, and meninges COCCIDIOIDOMYCOSIS • Epidemiology • It is endemic in certain parts of Arizona, California, Nevada, • New Mexico, Texas, Utah and northern Mexico. Laboratory Diagnosis • H istopathological staining sputum or tissue biopsy specimens • Spherules -large sac like structures (20–80 μm size), have thick, double refractile wall, and filled with endospores Culture • On SDA - Mycelial growth, described as fragmented hyphae consisting of barrel-shaped arthrospores with alternate cells distorted (empty cells) • Coccidioides differs from other dimorphic fungi as it grows as mold at both 25°C and 37°C in usual culture media • Forms spherules at 37°C in certain special culture media only Spherules and hyphal forms of Coccidioidis Other Tests • Serology: Antibodies - immunodiffusion test and CFT • Skin test: delayed hypersensitivity reaction indicates past infection • Treatment Coccidioidomycosis • Itraconazole - drug of choice • Diffuse pneumonia with pulmonary sequelae amphotericin B PARACOCCIDIOIDOMYCOSIS • Also known as South American blastomycosis, LutzSplendore-de Almeida disease • Systemic disease caused by the dimorphic fungus— Paracoccidioides brasiliensis • Paracoccidioidomycosis is endemic in Brazil and other South American countries Pathogenesis and Clinical Manifestations • Transmission is by inhalation of spores 1. Acute form (or juvenile type): - Under 30 years, less common but more severe form - Disseminated infection involving multiple viscera and is refractory to treatment 2. Chronic form (or adult form): 90% of cases - Results from reactivation of quiescent lung lesions - Less severe form, manifested as progressive pulmonary disease affecting lower lobes, with fibrosis • Skin, oral mucosal lesions and cervical lymphadenopathy Laboratory Diagnosis • Histopathological staining - pus, tissue biopsies or sputum - Round thick-walled yeasts, with multiple narrow-necked buds attached circumferentially  Mickey mouse or pilot wheel appearance • Culture on SDA yields mycelial form at 25°C which converts into yeast phase at 37°C when grown in BHI agar supplemented with blood and glutamine • Serology: Antibodies - immunodiffusion, ELISA using gp43 antigen of P. brasiliensis • Skin test Paracoccidioidomycosis Treatment • Itraconazole - drug of choice for • Seriously ill patients - amphotericin B • Sulfonamides are effective, but the response is slow with frequent relapses