Fungal Pneumonia Flashcards
endemic fungal pneumonia
histoplasmosis
blastomycosis
coccidioidomycosis
fungal pneumonia associated with immunosuppression
aspergillosis
pneumocystosis
What are some of the major characteristics of endemic mycoses?
thermally dimorphic fungi that exist in nature, soil
hyphal form in the environment, yeast form in tissue
inhalation leads to pulmonary infection and dissemination
no evidence of transmission among humans or animals
otherwise healthy individuals are infected
general characteristics of Histoplasma capsulatum
soil-based fungus associated with river valleyes and bird and bat guano
in the US, mostly endemic to Ohio and Mississippi river valleys
acquisition associated with disruption of the soil by excavation or construction, inhilation and pulmonary infection
dimorphic - mycelial (37 degrees C or higher) and yeast phase
hallmark of tissure response is caseating or noncaseating granulomas
clinical manifestations of H. capsulatum
> 90% go unrecognized, asymptomatic or mild influenza-like illness
Ghon complex and pulmonary calcifications are common in healed pulmonary histoplasmosis
complications of H. capsulatum infection
mediastinal lymphadenitis
mediastinal fibrosis
cavitary pulmonary histoplasmosis
progressive disseminated histoplasmosis (PDH)
diagnosis of Histoplasmosis
culture in brain heart infusion agar with blood, antibiotics, and cyclohexamide
cultures incubated for 30 degrees C for up to 6 weeks
majority cultures show grwoth within 7 days
sputum culture
histopathology
rapid diagnosis by polysaccharide antigen detection in urin, serum, BAL fluid
histopathology of Histoplasmosis
yeast visualized poorly by H and E stain
better seen with periodic acid-Schiff (PAS) and Gomorimethenamine silver (GMS) stains
treatnebt if Histoplasmosis
acute pulmonary disease
if symptoms less than 4 weeks no treatment
if symptoms greater than 4 weeks itraconazole for 6-12 weeks
chronic pulmonary disease, disseminated disease, granulomatous mediastinitis - Amphotericin B then Itraconazole for 6-24 months
general characteristics of Blastomyces dermatitidis
organism found in warm, moist soil of wooded areas rich in organic debris, such as decaying vegetation
dimorphic funcgus, mycelial form at room temeprature and yeast form at 37 degrees C
endemic to North America, including southeasterna nd south central states, especially those bordering the Mississippi and Ohio River basins and the Great Lakes
usualt portal of entry in humans is through the inhalation of conidia, which convert to the yeast phase in the lung
the typical inflammatory response consists of clusters of neutrophils and noncaseating granulomas with epithelioid and giant cells
Broad Based Budding yeast
clinical manifestation of Blastomycosis
pulmonary blastomycosis - acute or chronic, mimics infection with pyogenic bacteria, TB, other fungal infections, and malignancy
extrapulmonary manifestations - cutaneous disease and bone infection
diagnosis of Blastomycosis
definitive diagnosis requires recovery in culture
can also examine secretions
histopathological examination - pyogranuloma, GMS stain
antigen assay
serologic testing - complement fixation, immunodiffusion, radioimmunoassay, ezyme immunoassay
treatment of Blastomycosis
asymptomatic disease limited to the lungs - follow the patient closely for disease progression or dissemination
in immunocompromized, progressive pulmonary disease, or extrapulmonary disease - amphotericin B and itraconazole
What are the two species of Coccidioides?
- Coccidioides immitis* (CA)
- Coccidioides Posadasii* (other states and countries outside the US)
Where is Coccidioidomycosis endemic to?
southwestern US, especially in New Mexico, Arizona, and the San Joaquin Valley of California
general characteristics of Coccidioides spp.
dimorphic fungi that exists as either a mycelium or a spherule
found in the soil, grows by apical extension, true septa form along course
alternating mycelial cells undergo autolysis
remaining cells (arthroconidida) develop a hydrophobic outer layer and can remain viable for long periods
fragile attachments of arthroconidia to adjacent cell remnants make them prone to separation by physical disruption or mild air turbulence
arthroconidia become airborne and can be inhaled and deposited in the lungs
Coccidioides spp. development in the lungs
arthroconidia remodel into spherical cells, shedding outer wall
cell multiplication -> spherule divide into endospores
in tissue, spherules can develop to a size of 75 microns in diameter, containing 100 endospores
spherule matures, outer wall thins and ruptures
endospores are released to propagate in tissue or revert to mycelial growth if removed from tissue
clinical manifestations of Coccidioidomycosis
asymptomatic or subclinical
non-specific respiratory infection
pulmonary nodule - hard to distinguish form malignancy
chronic fibrotic pneumonia
disseminated disease - skin, bone and joints, meningitis (fatal if untreated)
diagnosis of Coccidioidomycosis
not detected by Gram staining
spherules visualized in tissue by H and E stains, silver or periodic acid-Schiff stains
grow well on most media after 5-7 days of incubation - highly infectious cultures
serologic testing - most frequent means of diagnosing primary infection, highly specific for active infection
urine antigen testing
treatment of Coccidioidomycosis
vast majority of early infections resolve without specific antifungal therapy
solitary pulmonary nodule - no treatment
cavitary disease - no treatment if asymptomatic
severe pneumonia and chronic progressive fibrocavitary pulmonary or disseminated disease - treat with amphotericin B, fluconazole, or itraconazole for 3-6 months
diffuse pneumonia needs one year or more of treatment
meningitis or ongoing immunosuppression is life-long
general characteristics of Aspergillus spp.
ubiquitous, found in soil, water, food, air, decaying vegetation
normal pulmonary host defenses - rarely develop disease
prolonged and profound neutropenia result in high risk for invasive aspergillosis
usually infect through inhaled conidia
infection progresses across tissue planes invades blood vessels leading to infarction of distal tissue
clinical manifestations of Aspergillosis
fever, chest pain, shortness of breath, cough, and/or hemoptysis
patients with severe neutropenia frequently present with fever and no localizing pulmonary symptoms
diagnosis of Aspergillosis
chest CT more sensitive than x-ray for detecting earliest stages of disease
- single or multiple nodules with or without caviation
- patchy consolidation or peribronchial infiltrates
“Halo sign”
infection may involve sinuses, CNS, heart, and skin
histopathology - septate hyphae with acute angle branching
antigen assays in serum or BAL - galactomannan and beta-d-glucan
Halo sign
in CXR for aspergillosis, nodule with surrounding ground glass infiltrate - hemorrhage into area surrounding fungal infection
treatment of Aspergillosis
voriconazole is the treatment of choice
alternatives include amphotericin B, the echinocandins, posaconazole, and itraconazole
recovery of neutrophils in patients with neutropenia is critical to recovery
general characteristics of Pneumocystic jiroveci
fungus, morphologic forms include cysts, sporozites, and trophozoites
worldwide distribution - mostly healthy children exposed by 3-4
airborne and person-to-person transmission
disease associated with defects in cellular and humoral immunity
Pneumocystis does not appear unless CD4 count is less than 200
clinical presentation of Pneumocystis
progressive exertional dyspnea, fever, non-productive cough, chest discomfort, worsens over days-weeks
diagnosis of Pneumocystis
laboratory findings include hypoxemia and elevated LDH
CXR findings include diffuse bilateral symmetrical intersittial infiltrates
chest CT shows patchy ground glass attenuation
diagnosis confirmed by identification of the organism by immunofluorescent antibody staining of induced sputum or BAL fluid with excellent sensitivity and specificity
treatment of Pneumocystis
trimethoprim-sulfamethoxazole or trimethroprim plus dapsone, clindamycin plus primaquine, atovaquone, and pentamidine
corticosteroids for severe disease, decreases inflammation with dying organisms
