PRIMARY SYSTEMIC MYCOSES Flashcards
(27 cards)
Comparison between Primary and Opportunistic Systemic Infections
Primary systemic pathogens:
* geographic restriction
* Dimorphic
* Infection by inhalation
* Pyogenic/granulomatous host response
* Similar to TB
* Infection confers immunity
Opportunists
* Ubiquitous: found widely in the environment
* Yeasts or molds
* Infection by various routes
* Host response varies
* Widely variable
* No lasting immunity
What are Systemic Mycoses?
Systemic mycoses are fungal infections with potentials of a protean/multi-systemic manifestation
They can also spread haematogenously throughout the body.
What are Primary systemic mycoses?
infections result from the inhalation of the spores of dimorphic fungi that have their saprophytic mold forms in the soil (atmospheric temp.) Within the lungs (blood temp.), the spores differentiate into yeasts
Endemic mycoses
Most infections are asymptomatic or mild and resolve without treatment
What are some aetiologic agents of systemic mycoses?
- Histoplasma capsulatum et duboisii –Histoplasmosis
- Coccidioides immitis – Coccidioidomycosis
- Blastomyces dermatitidis – Blastomycosis
- Paracoccidioides brasiliensis –
- Paracoccidioidomycosis.
What is Histoplasmosis and it’s epidemiology?
Histoplasmosis is a systemic disease, primarily of the reticuloendothelial system
the most prevalent pulmonary fungal infection in humans
Affects the bone marrow, lungs, liver, and the spleen
Epidemiology
Distributed worldwide especially in warm humid environments
The incidence of H. capsulatum is high in soils that are enriched with birds and bats droppings
Also frequently occurs when soil is disrupted as occurs with excavation
Has a predilection for males (4:1)
Also occurs more frequently in people who smoke and have COPD
What is the causative organism of Histoplasmosis? How is it tranmitted?
Caused by Histoplasma capsulatum var. capsulatum
North and South America
A variety called Histoplasma capsulatum var. duboiisi is commonly seen in Africa
It is a dimorphic organism that exists as a mycelium at room temperature and yeast at 37°C
Can be sexually induced to give ascopores
Transmission
By inhalation of conidia (infective form is small enough to reach terminal bronchioles)
Histoplasmosis – Pathogenesis
Organism settles in terminal airways following inhalation and are phagocytosed by macrophages (intracellular)
Both caseating and non caseating granulomas are formed and fibrosis may follow
Organism may remain dormant for years and be reactivated when patient is immunosuppressed
Histoplasmosis – various Clinical manifestations and their features
What is the incubation period
Incubation period: - I week to a few months
Severity of disease depends on inoculum size, patient’s age and co-morbidities
Disease may be local (pulmonary) or disseminated
Acute primary pulmonary histoplasmosis
May be asymptomatic (majority) or self-limiting flu-like syndrome with fever, chills, myalgias, headaches, and nonproductive cough
most patients will have hilar lymphadenopathy and pulmonary infiltrates or nodules on CXR
granulomatous nodules in the lungs or other sites heal with calcification
Cavitary Pulmonary histoplasmosis
Reactivation process
Occurs mostly in men older than 50 years who have COPD. They have cavitary lesions in upper lobes and present with weight loss, night sweats, cough, fever and chest pain. Most cases resolve spontaneously
If the inflammatory process persists, chronic pulmonary disease results
This may present as a mass (Histoplasmoma) which enlarges, becomes calcified and may obstruct airways
Fibrosis may distort airways and cause bronchiectasis and emphysema
Disseminated Histoplasmosis may occur in two ways:
As progression of acute disease
Reactivation of a dormant infection.
In what individuals is the outcome of histoplasmosis most fatal ?
extremes of ages and immunosuppression
What is the primary sign of infection in children? In adults, histoplasmosis more commonly appears as what?
Hepatosplenomegaly is the primary sign of infection in children, while in adults, histoplasmosis more commonly appears as a pulmonary disease
Discuss African Histoplasmosis (causative organism and manifestation)
African Histoplasmosis
Caused by H.capsulatum var duboiisi
More cutaneous manifestations
Ulcers, nodules and rashes
Osteolytic lesions may develop in skull, ribs and vertebrae
May be disseminated to multiple organs
Treatment of Histoplasmosis
- Acute pulmonary histoplasmosis is managed with supportive therapy and rest
- Itraconazole
- Liposomal Amphotericin B: Maintenance itraconazole for immunosuppressed
- Surgical excision
- NOTE: Disease is not communicable from person to person
What is the Epidemiology Coccidiomycosis?
Endemic in USA, Mexico and central America. These areas have in common arid climates, alkaline soil and hot summers that favour organisms growth
What is the Aetiology of COCCIDIOIDOMYCOSIS?
Disease is caused by dimorphic fungus Coccidioides immitis and C. posadasii
Transmitted by inhalation of arthroconidia (arthrospores)
What is the Pathogenesis COCCIDIOIDOMYCOSIS?
Inhaled arthroconidia converts to spherule in the lungs and stimulates an inflammation
Granuloma formation may occur in chronic disease
Coccidioidomycosis is primarily a pulmonary disease which may present as what?
Acute disease
Pulmonary nodules/cavities
Chronic fibrocavity pneumonia
rapidly fatal diffuse reticulonodular pneumonitis Vs Pneumocystis pneumonia in AID
Clinical Presentation of Coccidioidomycosis
- About 60 % of the infections in the endemic area are asymptomatic
- About 25 % suffer a “flu-like” illness and recover without therapy-VALLEY fever
- After 1-2 weeks about 15% of these patients develop hypersensitivity reactions, which present as a rash, erythema nodosum, or erythema multiforme
- Pulmonary coccidioiodomycosis exhibits the typical symptoms of a pulmonary fungal disease and resembles pulmonary tuberculosis
Treatment of Coccidioidomycosis
Voriconazole
Fluconazole
Amphotericin B
Treatment for CNS infection is peculiar
Diagnosis of Coccidioidomycosis
Diagnosis
Direct microscopy with ?????
Culture of sputum and specimens from nodule biopsy with isolation of organisms on Cultures on IMA or brain–heart infusion blood agar slants (dimorphism is not temperature induced)
Arthroconidia infectious-biosafety cabinet
Confirmation with DNA probes
Spherules stain with PAS, H&E staining
Serology (ELISA and complement fixation)
Epidemiology, Aetiology and Pathogenesis of Blastomycosis
Epidemiology
Endemic in South eastern USA, Middle east, India and South America.
Outbreaks limked to rural river banks (natural habitat yet unknown)
Aetiology
Disease is caused by dimorphic fungus Blastomyces dermatitidis
Transmitted by inhalation of conidia in mycelial phase
Pathogenesis
Inhaled arthroconidia changes to yeast in the lungs and alveolar macrophages and cell mediated immunity mouth a response to contain infection
Non caseating granuloma is formed which may keep organism dormant with no evidence of respiratory disease
Organism may also be disseminated to other sites
Clinical Presentation of Blastomycosis,
Disseminated disease to the which organs?
Blastomycosis is may present as:
Acute Pulmonary infection ( flu-like symptoms, cough, arthralgia)
Chronic Pulmonary infection (mass lesions, cavities, diffuse pneumonitis). chronic infection with granulomatous and suppurative lesions that is initiated in the lungs
Disseminated disease to the following organs
Skin (ulcers, verrucae, subcutaneous nodules)
Bone and joint disease.
Genitourinary tract usually the prostate, testes
CNS (very rarely)
What is the Laboratory Diagnosis and Treatment of Blastomycosis?
Laboratory Diagnosis
Direct light microscopy (wet preparation) of BAL, sputum, pleural fluid, urine shows characteristic budding yeasts with broad base
Direct microscopy
Histology
Culture
Dimorphic in-vitro conversion
Serology-CF (not too useful) ??????
Treatment
Amphotericin B
Itraconazole
Voriconazole
Surgical resection of necrosed bones and tissues.
What is the most prevalence pulmonary fungal infection in humans?
Histoplasmosis
