Respiratory Fungi Flashcards
1
Q
Systemic Mycoses
A
Histoplasma, Coccidiodes, Blastomyces, Paracoccidioides
- Primary pathogens
- Severe disease in immunocompromised hosts
-
Airborne/Environmental transmission
- No person-to-person transmission
- Starts in the lungs but frequently disseminates to viscera
- Endemic to certain geographic areas
-
Dimorphic
- Molds @ 25°C
- Yeast or spherules @ 37°C
2
Q
Histoplasma capsulatum
Characteristics
A
- Causes Histoplasmosis
-
Dimorphic
-
Mold grows in soil w/ high N2 content
- Bat and bird droppings promote growth
- Filamentous septate hyphae
- Produces spores ⇒ micro and macroconidia
- Macroconidia = tuberculate chlamydospores
- Yeast grows @ 37°C within Mφ
-
Mold grows in soil w/ high N2 content
3
Q
Histoplasma
Transmission
A
Inhalation of microconidia
(Asexual spores)
Causes histoplasmosis.
4
Q
Histoplasmosis
Epidemiology
A
Ohio and Mississippi Valleys
&
Central and South America
Outbreaks associated with bird roosts, caves, urban renal projects involving excavation.
5
Q
Histoplasmosis
Clinical Presentation
A
- Asymptomatic infection ⇒ 90%
-
Flu-like sx ⇒ 5%
- Fever, chills, malaise, HA, lymphadenopathy
- Some progress to pulmonary histoplasmosis ⇒ 1%
- Cough, SOB
- Resembles TB w/ caseating granulomas
-
Progressive disseminated disease ⇒ 1%
- Immunocompromised hosts
- Found in 10-25% of AIDS pts living in endemic areas
6
Q
Histoplasmosis
Pathogenesis
A
Disease manifestations depend on innoculum size & host immune status:
- Microconidia enter lung
- Converts to yeast form
- Phagocytosis by alveolar MΦ
- Replicate within MΦ
- Facultative intracellular parasites
- MΦ transport yeast to regional LN
-
Transient fungemia
- Skin, liver, spleen common sites
- Does not necessarily mean disseminated disease
- Can be seen even with mild cases
-
T-cell sensitization ⇒ fungicidal activity of Tc & MΦ
- Can take 6-8 weeks
- Subsequent granuloma formation
- Clinical picture frequently resembles TB
- Resolution or progression
- Possible reactivation when immunity wanes
7
Q
Histoplasmosis
Diagnosis
A
8
Q
Histoplasmosis
Treatment
A
-
Mild pulmonary disease
- Self-limiting
- No treatment
-
Severe acute pulmonary disease
- Itraconazole
-
Systemic disease
- Amphotericin B followed by oral itraconazole
9
Q
Histoplasma vs Tuberculosis
A
- Both histoplasmosis & TB
- Primary pathogen w/ severe disease in immunocompromised
- Facultative intracellular organisms
- Infection by respiratory route
- Pulmonary infection that can disseminate
- Can detect infection by skin testing
- Reactivation can occur
- Mtb only ⇒ person to person transfer
10
Q
Coccidioides immitis
Characteristics
A
- Causes Coccidiomycosis
- AKA Valley Fever or Desert Rheumatism
- Most virulent of the mycoses
-
Dimorphic
-
Arthrospores grow in warm, alkaline soil
- Barrel-shaped septate hyphae
- Growth enhanced by bird droppings
-
Spherules containing endospores grow @ 37°C
- Extracellular pathogens
-
Arthrospores grow in warm, alkaline soil
11
Q
Coccidioides
Epidemiology
A
- Prefers soil of arid regions
- San Joaquin Valley
- Southwest US
- Mexico and parts of Central and South America
- Conditions that favor aerosols promote outbreaks
- Cycles of heavy rain followed by draught
- Warming trends leading to dispersal
- 150k new infections/yr
- 80% of longterm residents infected
- Non-immune visitors/new residents at risk
12
Q
Coccidioides
Transmission
A
Inhalation of arthrospores (arthroconidia)
13
Q
Coccidioides
Risk Factors
A
High risk for chronic/disseminated disease:
- > 65 y/o
- HIV
- 1st trimester of pregnancy
- DM
- Native Americans, Filipinos, African Americans, Hispanics
14
Q
Coccidioides
Pathogenesis
A
- Most virulent of systemic mycosis ⇒ only need a few for infection
- Arthrospores (conidia) inhaled into mid-lung area
- Temperature causes conversion into a large spherule w/ many small endospores
- Extracellular pathogen
- Spherule rupture releasing endospores ⇒ ± dissemination
- Requires cell-mediated immunity to eradicate spherules
15
Q
Coccidioides
Clinical Presentation
A
- Asymptomatic ⇒ 50-60%
- Flu-like illness ⇒ called Desert Rheumatism, Valley Fever, or Primary coccidiomycosis
- Cough, CP, weight loss, arthralgia, skin rash
- Can last for weeks to months
-
Severe/chronic pulmonary disease ⇒ 5-10%
- Cavitary disease common
-
Disseminated disease ⇒ 1%
- Also called chronic meningitis
- Fatal if untreated
- Requires lifelong treatment
16
Q
Coccidioides
Diagnosis
A
-
Skin test ⇒ reactivity within 2 weeks
- Anergy in disseminated disease
- Indicates infection has occurred but not neccessarily responsible for present illness
- Biopsy ⇒ spherule forms
-
Culture ⇒ mold forms
- Sputum or tissue sample
- Grown on Sabouraud’s agar
- Takes 2-3 days
- Lab acquired infections a problem
-
Serology
- CSF ⊕ within 2-3 weeks
- Rising titers after 2-3 months suggest dissemination
17
Q
Coccidioides
Treatment
A
- Most difficult of systemic mycoses to treat
-
Recurrent/relapse disease is common
- Reinfection after successful treatment
- 12-24 months of azole depending on severity
- Amphotericin B for severe disease
- Chronic meningitis ⇒ amphotericin B then switch to azole for life
18
Q
Blastomyces dermatitidis
Characteristics
A
- Causes Blastomycosis
- Morphology ⇒ dimorphic
- Septate hyphae and asexual spores @ 25°C
- Broad-based budding yeast cells @ 37°C
19
Q
Blastomyces
Epidemiology
A
-
Endemic east of the Mississippi River
- Esp. Arkansas, Kentucky, Louisiana, North Carolina, Tennessee, Mississippi
- Spores grown in soil high in decaying organic matter
- E.g. wooded areas
- Outbreaks via occupational or recreational contact w/ soil
- See disease commonly in 20-50 y/o males
21
Q
Blastomyces
Pathogenesis
A
- Inhaled conidia (asexual spores)
- Yeast forms in lung within MΦ
- See a mixed granulomatous & pyogenic response (abscess)
- Similar to TB & bacterial PNA
-
Dissemination may involve skin and bone but is rare
- Not a common opportunist in immunocompromised but causes severe disease when it occurs
- Cell-mediated immunity critical but PMNs also play a role in clearing infection
- Reactivation possible
22
Q
Blastomyces
Clinical Presentation
A
- Asymptomatic to flu-like illness
-
Pulmonary form
- Similar to bacterial PNA ⇒ infiltrates but no calcification
- Cough and CP
-
Dissemination with or without pulmonary resolution
- Skin, joints, bone, CNS
- Ulcerative lesions of skin and bones
23
Q
Blastomyces
Diagnosis
A
- ID organism in tissue
- Culture - takes > 1 week
- Mold form
- Yeast form (broad-based budding yeast)
- Ag based tests
25
Q
Paracoccidioides brasiliensis
Characteristics
A
- Causes South American Blastomycosis
- Morphology ⇒ dimorphic
- Septate hyphae @ 25°C
-
Yeast form grow in vivo @ 37°C
- Multiple daughter cells off a single parent cell connected by a thin isthmus ⇒ blastoconidia
- Seen in tissue and can be grown in culture
- “Pilot wheel” morphology seen w/ GMS stain or H&E in tissue
26
Q
Paracoccidiodes brasiliensis
Epidemiology
A
- Major systemic mycoses in Latin America > Central America
- Highest incidence in Brazil
- Mold form grows in areas of high humidity, rich vegetation, and acidic soil
- Esp. along river banks in the Amazon
- Common in rural areas
- Children frequently infected but asymptomatic
- Disease common in men 30-50 y/o
28
Q
Paracoccidioides
Clinical Presentation
A
-
Primary disease
- Usually asymptomatic or self-limiting
-
Adults ⇒ primary or reactivation disease
-
Chronic pulmonary disease
- Productive cough, weight loss, fever
- Mucocutaneous forms
-
Chronic pulmonary disease
-
Juvenile form
- Flu-like, lymphadenopathy, hepatosplenomegaly
-
Disseminated form
- Young children and immunocompromised
29
Q
Paracoccidioides
Diagnosis
A
-
Demonstrate yeast form in tissue or sputum
- “Pilot wheel” ⇒ yeast
- Don’t confuse with tuberculate macroconidia of Histoplasma ⇒ spores
- These won’t be found in tissue or sputum samples
- Organisms grown in culture need biosafety cabinet
- Serology ⇒ evaluate response to treatment
32
Q
Zygomycetes
Characteristics
A
“Mucormycetes”
- Cause Mucormycosis
- Molds that grow rapidly
- Morphology
- Broad hyphae w/ few or no septa
- Asexual spores contained in sporangium ⇒ sporangiospores
- Root-like structure called rhizoids
35
Q
Zygomycetes
Clinical Presentation
A
-
Pulmonary zygomycosis
- Primary infection in neutropenic pts
- Pulmonary invasion, infarcts in pulmonary vessels, and hemorrhage
-
Rhinocerebral zygomycosis
- Invasive infection
- Starts in nasal cavity, sinuses, or orbit
- Extends into face and CNS
- Most common in DKA and hematologic malignancy
-
Cutaneous zygomycosis
- Primary or secondary
- Nodular with ecchymotic center
36
Q
Zygomycetes
Pathogenesis
A
-
Angioinvasive
- Similar to aspergillus infection
- Tissue and vessel infarction
-
Dissemination
- May cause disease in multiple organ systems
- Cutaneous manifestations from invasive infection or following traumatic injury
37
Q
Zygomycosis
Diagnosis
A
- Tissue biopsy for direct microscopy and culture
- Stain with KOH w/ calcofluor white
- See broad irregularly branched, twisted or folded hypae w/ few septa
- Culture is frequently negative
40
Q
Aspergillus
Morphology
A
- Exist as molds
- Composed of septate hyphae
- Branches @ 45° angles ⇒ dichotomous branching
- Characteristic of Aspergillus
- Reproduce asexually by conidiaphore formation
43
Q
Aspergilloma
A
-
Usually seen in those with underlying lung diease
- Particularly those with pre-existing cavities in the lung
- Non-allergic colonization
- Chronic process with development of pathological changes in the lung
- Formation of Aspergillus containing granulomas
- Causes “fungus ball” formations on CXR
- Granulomas must be surgically removed + antifulgal medications
44
Q
Systemic or Invasive
Aspergillosis
A
-
Only in immunocompromised individuals
- Risk factor ⇒ neutropenia
- May involve pulmonary, sinus, cerebral, or cutaneous sites
- Pathogenesis involves angioinvasion, thrombosis, and dissemination to other organs
- Damage caused by tissue infarcts, hemorrhage, and necrosis
