Systemic Mycosis 06-07
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Caustive agents Histoplasma capsulatum Blastomyces dermatitidis Cryptococcus neoformans Coccidioides immitis Paracoccidioides brasillensis
HistoplasmosisCausative Agent Histoplasma capsulatum var capsulatum Histoplasma capsulatum var. duboisii o The organism is misnamed because: It infects macrophages NOT plasma cells & It is non-capsulated Morphology Dimorphic fungus Smallest yeast cells Reproduce by budding
HistoplasmosisSource of Infection Soil containing bird or bat excreta No case to case transmission Pathogenesis Spores are inhaled, engulfed by macrophages and develop into yeast forms Granulomas formed in the lung which may get calcified like TB Disseminate and may infect macrophages in RES (liver, spleen, LN & BM)
Histoplasma yeasts within macrophages
HistoplasmosisClinical Features In immunocompetent persons o Asymptomatic or flue-like symptoms o Chronic lesions in lungs give TB-like picture In immunosuppressed persons o Disseminated infection o Febrile illness o Enlargement of RE system, hepatosplenomagaly o Ulcerated lesions on tongue in AIDS patients
HistoplasmosisLab Diagnosis Direct examination of sputum Not helpful as few organisms in sputum Bone marrow aspirate histology : Oval yeast cells within macrophages by Giemsa stain Culture on Sabourauds Dextrose Agar incubate at 25oC & 37oC to show dimorphic forms Serology o An Ab titre of 1:32 with yeast phase Ags is considered diagnostic Histoplasmin skin test: Epidemiological value only Histopathology of BMA: to see parasitic yeast form
Oral lesions following hematogenous dissemination
Macroconidia and microconidia. Phase contrast microscopy, potato glucose agar, slide culture, 25C
Rough-walled macroconidia, Sabouraurd glucose agar, 25C, lactophenol cotton blue preparation.
Yeast form growing at 37C in the laboratory. Phase contrast microscopy, 37C, 630X
HistoplasmosisTreatment Oral itraconazole Disseminated disease o Amphotericin B o Fluconazole in meningitis May need surgical resection of pulmonary lesions
BLASTOMYCOSIS Pathogenesis Blastomyces dermatitidis Dimorphic fungus Pathogenesis Inhalation of infectious particles Cutaneous inoculation Infiltration of macrophages and neutrophils and granuloma formation
BLASTOMYCOSIS Clinical findings Asymptomatic Pulmonary infection Chronic skin infection Subcutaneous nodule & ulceration Disseminated infection Bone, GUT, CNS, spleen
Broad based budding yeast cells, KOH, from a lung
Broad based budding and thickened cell walls and globose shape are characteristic of the yeast form of Blastomyces dermatitidis.
Colony of Blastomyces dermatitidis on Mold Inhibitory Agar after14 days, 30C.
Skin lesion following dissemination from the lungs.
The cutaneous lesion developed following dissemination of the fungus from the lungs.
Treatment Amphotericin B Azoles are alternative in immuocompetent patients
CryptococcosisCausative agent Cryptococcus neoformans (5) o A typical yeast with a thick capsule (25) o Urease positive Source of infection Pigeon or birds droppings & contaminated soilIndia Ink Preparation
CryptococcosisPathogenesis Capsule is the virulence factor (antiphagocytic) Human infection by inhalation Most infections are asymptomatic May develop pneumonia Disseminate to CNS causing meningitis
CryptococcosisClinical Features Disease usually affects immunocompromised Lung infection usually asymptomatic Cryptococcal meningitis
Meningitis Intermittent headache & dizziness & vomiting Difficulty in thinking Slight fever Slowly progressing to weight loss, impairment of nerves May be difficult to diagnose in early stages
o Among top four life-threatening infections in AIDS
CryptococcosisLab Diagnosis o o o CSF Examination Turbid CSF Decreased glucose & increased protein Increased cell count >100 cells mostly lymphocytes o India Ink preparation o Periodic acid-Schiff (PAS), detect fungal elements o Culture on SDA (grows in 48-72 hrs) o Capsular Antigen in CSF by latex agglutination Yeast cell with a thick capsule
India Ink Preparation
Negative cryptococcal antigen latex test
Mixed culture of C. neoformans and C. albicans showing the distinctive brown colonies of C. neoformans, due to the selective absorption of pigment from the media, compared to the white colonies of C. albicans.
Encapsulated yeast in India ink preparation. The small round structure in the center of the white area is the yeast cell. 400X.
India ink preparation of CSF from a patient with cryptococcal meningitisshowing a budding yeast cell of C. neoformans surrounded by a characteristic wide gelatinous capsule.
Raised skin lesions resulting from dissemination of the yeast in an immunocompromised patient.
C. neoformans yeasts in lung tissue. Gram stain, 100X
CryptococcosisTreatment Systemic fungal agents that cross blood brain barrier (BBB) Fluconazole as prophylaxis in AIDS patients Combined Amphotericin B & flucytosine
COCCIDIOIDOMYCOSISCausative agent Coccidioides immitis Microscopy 37C: Spherules filled with endospores 25C: hyphae, barrel-shaped arthroconidia
COCCIDIOIDOMYCOSIS Pathogenesis Inhalation of the infectious particle, arthroconidia and spherule formation in vivo Engulfment within phagosomes by alveolar MQs Activation of macrophages (phagosomelysosome fusion) leads to killing Immune complex formation deposition leading to local inflammatory response
COCCIDIOIDOMYCOSIS Clinical findingsPRIMARY INFECTION Asymptomatic in most cases Fever, chest pain, cough, weight loss Nodular lesions in lungs SECONDARY (DISSEMINATED) INF. (1%) Chronic / fulminant Infection of lungs, meninges, bones and skin
COCCIDIOIDOMYCOSIS DiagnosisSamples: Sputum, tissue Direct examination (KOH; H&E) 2. Culture SDA: Mould colonies at 25 C Spherule production in vitro by incubation in an enriched medium at 37C, 20% CO2
Alternating arthroconidia. Note annular frill at both ends of the separated arthroconidia. Phase contrast microscopy, tease mount from colony, 25C
Sherules and endospores in lung tissue. 1000X.
Alternating arthroconidia and hyphae. Lactophenol blue mount, tease preparation of mould colony, 25C
The rash is a immunologic response to the fungus. It is most commonly seen in caucasion women.
COCCIDIOIDOMYCOSIS Treatment Amphotericin B Itraconazole Fluconazole (particularly for meningitis)
Features of systemic fungal pathogensOrganism Culture at 25 0C Culture at 370C Tissue Primary disease pneunonia Disseminate d disease C. meningitis
Mold, tuberculate macroconid
Small intracellular yeast
Pneumonia, hilar adenopthay pneunonia
Skin and bone lesions Pneumonia, meningitis Skin & bones
Skin and RES
Case presentationA 52 years-old male arrived at an emergency room in a disoriented and poorly responsive state with difficult breathing. The patients history included poorly controlled diabetes and chronic obstructive pulmonary disease secondary to cigarette smoking. Current medications included steroids his pulmonary disease. Physical examination showed that the patient was slightly febrile, lethargic, and in respiratory failure. He showed deteriorating mental status, and a diagnosis of meningitis was considered . A lumber tap produced a CSF sample that on direct smear using calcofluor reagent showed encapsulated budding yeast. Despite aggressive therapy with amphotericin B and 5flucytosine, the patients condition failed to improve. The patient died on the third day of hospitalization.