Pulmonary Fungal Infection 1 Flashcards
When are Coccidioides most infectious and what do they form in order to become infection?
Dry summer form hyphae with alternating arthrospores
How are coccidioides spread
Formation of arthroconidia in the summer months–carried by wind and inhaled by humans
Who are the people most susceptible to coccidioides?
Snow birds moving to Southwest US
Where is coccidioides endemic?
Southwestern US
When coccidioides enters the terminal bronchiole of a patient what occurs
Changes form:
Spherules–highly resistant to eradication by immune sys
Thick, doubly-refractive wall
Filled with endospores
Wall ruptures to release endospores–new spherules
Are spherules and endospores seen with coccidioides pathogenesis infectious?
NO–no human to human spread
What is required in order for a patient to develop serious pneumonia or dangerous dissemination when infected by coccidioides?
Must be a high dose or the patient must be immunosuppressed
What occurs during the acute phase of a coccidioide infection?
Innate immunity–marcophages attempt to clear the infection and are often successful
When the innate immune system is inadequate for clearance of coccidioides, what occurs?
Chronic phase–lymphocytes and histiocytes initiate granuloma and giant cell formation
Many patient are asymptomatic or develop non-specific flu-like symptoms 60%
What are the symptomatic diseases that occur with coccidioides infection?
Valley fever or desert rheumatism
- Fever
- Arthralgias
- Erythema nodosum–shins (side effect of immune response–so its working)
- Erythema multiforme–rash on entire body
- Chest pain
What is most likely to occur if a patient is immunosuppressed and gets an coccidioides infection?
Disseminated infection–both intracellular travel in macrophages and hematogenous spread
What risk factors make pts more susceptible to disseminated infection from a coccidioides infection?
Advanced age Immunocompromise Late-stage pregnancy Occupational high-level exposure BLACK or FILIPINO race--this is an actual racial bias and not based on socioeconomic status
What are the primary sites of disseminated infection from a coccidioides infection?
Bones and meninges
When do most coccidioid infections occur?
Summer or autumn
Will a patient with a disseminated coccidioides infection (immunosuppressed) have a positive or negative PPD and what is used with the PPD test?
Negative
PPD with coccidioidin or spherulin
When erythema nudosum (adults)/ multiforme (peds) or arthralgias occurs with a coccidioides infection, what does this indicate
This is a HSR–meaning the immune system is working properly
Red, tender nodules on exterior surfaces –such as lower legs
Delayed cell-mediated HSR to the fungal antigens
RISK of dissemination is LOW
Where does a coccidioides infection disseminate to and what is found on PE?
Meninges–syms similar to bac meningitis but onset is slow
Bone–osteomyelitis
Skin or lymph nodes–soft tissue abscesses, hematogenously seeded
Syms:
- Night sweats
- Dyspnea
- Fever
- Weight loss
Biopsy of coccidioides
Exam for spherules
How should coccidiodes be cultured
On sabouraud’s agar at 25C
Its a cottony white mold composed of hyphae with arthrospores–INFECTIOUS
What is found within the CSF with a coccidiodes infection?
Lymphocytic pleocytosis Elevated protein Hypoglycorrhachia--low glucose Eosinophilia IgG
What a predisposed complications of coccidioides infection that must be treated even with mild disease
Severe immunosuppression DM Black/Fillipino Cardiopulmonary dz Pregnancy
Persisting lung lesions or disseminated coccidioides infection should be treated with?
Amphotericin B and long-term itraconazole
Minimum of 6 months therapy
Meningitis caused by coccidioides infection should be treated with?
Fluconazole–gets through BBB
Is histoplasma thermally dimorphic?
Yes–mold in soil, yeast in tissue–real budding yeast
What are the two types of asexual spores that are formed by histoplasma and which one is infectious?
Tuberculate macroconidia–thick walls with fingerlike projections
Microconidia–smaller, thin, smooth-walled–INFECTIOUS
Where is histoplasma endemic
Ohio, Missouri, and mississippi river valleys
Acidic damp soil with high organic content
What are the environmental factors that play a role in infection with histoplasma?
Soil
Bird droppings–starlings or bat guano
Excavation of contaminated soil for construction can set off an outbreak
How do histoplasma spores engulfed by alveolar macrophages survive endocytosis and lysosomal fusion?
Produce bicarbonate and ammonia–raising pH and inactivating hydrolytic enzymes
How does histoplasma get throughout the body?
Survives endocytosis and lysosomal fusion within macrophages by producing bicarb and ammonia, raising pH and inactivating hydrolytic enzymes
Convert to yeasts in macrophages and replicate there then spread throughout the body in macrophages
95% of patients are asymptomatic or get mild nonspecific syms then get better
What can be seen during inflammatory response with a histoplasma infection?
Erythema nodosum
High-dose exposure to histoplasma may cause?
Pneumonia with cavitary lung lesions on primary infection
What occur when very young, very old, or immunosuppressed pts become infected with histoplasma?
Pancytopenia
ULCERATED LESIONS ON THE TONGUE
Why isn’t PPD useful for histoplasma?
Too many false positives and negatives
What are seen with mild cases of histoplasma
Nonspecific flu-like syms with self-limited dz
May have EN or EM
What are some findings with spreading in lungs with histoplasma infection?
Cough Chest pain Hemoptysis ARDS Cavitary lesions--characteristic sound on auscultation
What are findings on PE with disseminated histoplasma infection?
Tongue lesions Granulomas in liver and spleen Weight loss Endocarditis, dysrhythmia GI-lesions, mass Ocular--scars in back CNS--mas lesions, meningismus, CN deficits Meningitis--fever, low CSF glucose, slow onset
What will be seen on biopsy or bone marrow aspirate histology of histoplasma infection?
Oval yeast cells within macrophages
How is histoplasma cultured?
Seaboard’s agar–thermally dimorphic
25C–tuberculate macroconidia–white and fuzzy
37C–yeast–slick and slimy
What is assessed using ELISA when testing for histoplasma?
Histoplasma polysaccharide antigen from urine and serum
What is the tx for histoplasma in healthy pt?
self-limited–monitor for 1 month
What is the tx for pt with histoplasma that has spread to the lungs?
Itraconazole 6-12 wks
What is the tx for disseminated histoplasma?
Amphotericin B followed with itraconazole for at least 1 year
What is the tx for a pt with histoplasma meningitis?
fluconazole–penetrates spinal fluid well
Where is Blastomyces endemic?
All over north america
Mostly eastern north America and great lakes region
What are the characteristics of the mold form of blastomyces?
Hyphae with small pear-shaped conidia
Conidia are infectious by inhalation
What are the characteristics of the yeast form of blastomyces?
Round with doubly refractive wall and single broad-based bud
What is the infectious agent of blastomyces?
Conidia–mold form
What are the virulence factors of blastomyces?
Yeast–produce immune-modulator BAD1 on cell surface
What predisposes pts to dissemination of blastomyces and if untreated what occurs?
Immunosuppression and preexisting pulmonary dz
Untreated symptomatic cases have significant mortality
What is found on exam with the mild form of blastomyces?
Nonspecific flu-like illness that is self-limiting
What is found on exam with pneumonia caused by blastomyces?
High fever Chills Cough with mucopurulent sputum pleuritic chest pain occasionally EN
What are specific findings on exam that allow for the differentiation of blastomyces from coccidioides or histoplasma?
Skin lesions where the organism can be cultured
What is used for dx of pneumonia caused by blastomyces?
Sputum microscopy–KOH mount
How should a biopsy of blastomyces be prepared and what are the findings?
Stain with PAS or Silver
Thick-walled yeast cells with single, broad-based buds, micro abscesses, suppurating granulomatous rxn, noncaseating
What is seen on culture of blastomyces?
Hyphae with small-pear shaped conidia
What is used for tx of pts who have symptomatic but not severe blastomyces infection
Itraconazole
What is used for severe blastomyces infections
Amphotericin B
Meningitis caused by blastomyces is treated with?
Fluconazole
What are the characteristics of the mold form of paracoccidioides
Thin, septate hyphae
What are the characteristics of yeast form of paracoccidioides?!!!
Thick-walled with MULTIPLE BUDS
What is seen with a more severe infection from paracoccidiodes?
Oral mucous membrane lesions and lymph node enlargement
How should pus or tissue samples of paracoccidiodes be examined and what is found?
KOH mount—yeast cells with MULTIPLE BUDS!!
What is the tx for paracoccidiodes?
Oral itraconazole for 6 months
What is tx for severe paracoccidiodes infection
IV amphotericin
