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Microbiology > Exam #4: Fungal Infections of the Respiratory Tract > Flashcards

Exam #4: Fungal Infections of the Respiratory Tract Flashcards

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Biology 101 flashcards
1
Q

What is Zygomycosis (Mucromycosis)?

A 
A class of diseases caused by infection of fungi belonging to the class, "Zygomycetes" 
- Found in: soil, decaying vegetation, and food
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2
Q

What species of Zygomycetes cause Zygomycosis?

A

1) Rhizopus
2) Absidia
3) Mucor

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3
Q

What are the predisposing factors to zygomyces infection?

A
  • Immunosuppression
  • DM
  • Burns

*Infection in a normal, healthy individual is rare

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4
Q

What are the characteristics of the zygomycetes?

A
  • Non-septate hyphae

- Reproduce sexually to produce spores

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5
Q

Describe the common clinical presentation & pathogenesis of rhinocerebral zygomycosis.

A
  • Primarily occurs in Diabetic patients
  • Infection originates in sinuses, following inhalation of spores
  • Spreads to neighboring tissues

Essentially, infection begins as a typical sinus infection but then progresses to facial/ periorbital edema, visual disturbances, altered mental status, coma, & death as the infection spread to tissues surrounding the sinuses.

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6
Q

Aside from the sinuses, where else can there be zygomycotic infections?

A
  • Skin via traumatic inoculation

- GI (neonates & premature infants)

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7
Q

How is zygomycosis diagnosed? Morphologically what is the key feature that you’re looking for?

A
  • Observation of hyphal elements
  • Culture confirmation

Broad aseptate hyphae in blood vessels frequently branching at 90 degree angles

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8
Q

How is zygomycosis treated?

A

Amphotericin B

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9
Q

What species of candidia causes most candidiasis infections?

A

C. albicans

Note that this is considered to be part of the normal flora

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10
Q

Candidia is dimorphic. Which form is present in the normal flora & which form is typically pathogenic?

A

Normal= yeast

Pathogenic= mold/ hyphae

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11
Q

What is Thrush? What are the symptoms/ presentation?

A
  • Oral Candidiasis infection

- Diffuse erythema with white patches (cheesy) on the surface of the buccal mucosa, throat, tongue, & gums

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12
Q

What patient populations are susceptible to Thrush?

A
  • Infants
  • Adults undergoing treatment with: steroids, antineoplastic drugs, antibiotics
  • AIDS patients
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13
Q

How is oral candidiasis diagnosed?

A

Direct observation of candidia in clinical material

*Note that culture is typically not necessary; candidia is part of the normal flora (yeast); therefore, it is difficult to distinguish between colonization & infection.

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14
Q

How is oral candidiasis treated?

A

Oral formulations of nystatin & azole compounds i.e. mouthwash or lozenges

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15
Q

What patient populations most frequently get an esophagitis?

A

AIDS/ HIV

*Extension of thrush/ oral candidiasis into the esophagus

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16
Q

What are systemic mycoses?

A
  • Diverse group of fungal infections that initally infect the lungs & then lead to systemic infection
  • All originate as an inhaled pathogen
  • Occur in BOTH healthy and immunosuppressed individuals
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17
Q

What five fungi are considered “systemic mycoses?”

A

1) Histoplasma capsulatum
2) Blastomyces dermatitidis
3) Paracoccidioides brasiliensis
4) Coccidioides immits
5) Crytococcus neoformans

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18
Q

Which of the systemic mycoses are dimorphic? What forms are they in in the enviornment & in human?

A

1) Histoplasma capsulatum
2) Blastomyces dermatitidis
3) Paracoccidioides brasiliensis
4) Coccidioides immits

*Exist as MOLD in environment, & YEAST in human infection, which is opposite of candidia

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19
Q

What is cryptococcus neoformans?

A

Crytococcus neoformans is an encapsulated yeast

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20
Q

Where is histoplasma capsulatum geographically most prevalent?

A
  • North & Central America

- In the U.S, specifically in the Mississippi & Ohio River Valley

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21
Q

What causes histoplasmosis?

A

Histoplasma capsulatum

Note that this disease is also known as “Darling’s Disease, Cave Dweller’s Disease, & Spelunker’s Disease”

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22
Q

What form of histoplasma capsulatum is present in the environment? What causes infection?

A
  • Mold that is commonly found in soil containing bird & bat droppings
  • Infection is acquired by inhalation of micro or macroconidia

*95% of exposed individuals are asymptomatic

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23
Q

Describe the pathogenesis of histoplasmosis.

A
  • Inhaled fungal spores are phagocytosed by pulmonary macrophages & convert into the YEAST form
  • Organism survives and replicates within macrophages causing “pulmonary histoplasmosis.”
  • Progression from that state can be to chronic pulmonary histoplasmosis or disseminated histoplasmosis, both of which are more common in immunosuppressed individuals
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24
Q

What are the symptoms of pulmonary histoplasmosis?

A

Dry cough
Fever
Fatigue

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25
Q

How is pulmonary histoplasmosis treated?

A
  • Most infections resolve without any intervention

- Calcification of pulmonary lesions due to cell mediated immunity & macrophage activation

26
Q

What are the symptoms of disseminated histoplasmosis?

A
  • Fever
  • Night sweats
  • Anorexia
  • Weight loss
  • Fatigue

+ Respiratory symptoms

27
Q

How is histoplasmosis diagnosed?

A

1) Direct observation of organisms in tissues or clinical samples
2) Cultivation of organisms from clinical samples
3) Serological testing

*A combination of these approaches is commonly employed

28
Q

How is histoplasmosis treated?

A

Amphotericin B

*AIDS patients and other immunosuppresssed individuals often require lifelong suppressive therapy to prevent relapse (with azoles)

29
Q

What organism causes Blastomycosis

A

Blastomyces Dermatitidis

30
Q

Where is Blastomyces Dermatitidis geographically most prevalent?

A

1) Ohio & Mississippi River Valley (like histoplasma capsulatum)
2) AND, to a lesser extend, the Arkansas River Basin

31
Q

How is Blastomyces dermatitidis differentiated from Histoplasma?

A

Larger size & very thick cell wall present in Blastomyces

32
Q

How does pulmonary blastomycosis present?

A

Like Histoplasmosis with a mild flu-like illness, as bacterial pneumoni, or as TB:

  • Cough, BUT with frank sputum production
  • Fever
  • Fatigue
33
Q

How does disseminated Blastomycosis present?

A

Ulcerative lesions of the skin, bone, and urogenital tract

  • Skin lesions are ulcerative & disfiguring (painless)
  • Bone necrosis & granuloma formation
  • Prostate involvement
34
Q

How is blastomycosis diagnosed?

A

Observation of distinct yeast form in sputum or biopsy

35
Q

How is blastomycosis treated?

A

Amphotericin B is the gold standard

Note that Fluconazole & other azole compounds have shown promise in uncomplicated pulmonary disease

36
Q

What organism causes Paracoccidioidomycosis?

A

Paracoccidioides barasiliensis

37
Q

Where is paracoccidioides barasiliensis geographically most prevalent? Is it more common in men or women?

A
  • Most prevalent in South America

- 90% of the disease occurs in men; appears estrogen may inhibit growth

38
Q

How does paracoccidiodomycosis present?

A
  • Most infections as asymptomatic
  • Primary pulmonary infection is similar to histoplasmosis & blastomycosis
  • Disseminated disease typically presents as chronic cutaneous & mucocutaneous ulcers
39
Q

How is paracoccidiodomycosis diagnosed?

A
  • Direct observation of morphology
  • Large yeast covered with multiple buds
  • Takes on a “ship’s wheel” or “Mickey mouse ears” appearance
40
Q

What is the most common systemic fungal infection seen in the US? Where is it most geographically prevalent?

A
  • Coccidiodomycosis
  • San Joaquin Valley

*Must be reported & typically
follows a drought-rain-drought cycle that results in large numbers of fungal elements in blowing dust

41
Q

What are the distinguishing features of coccidiodomycosis?

A

Spherule, which is a multinucleated structure that undergoes several internal divisions to produce hundreds of single nucleated spores

42
Q

What are the symptoms of coccidiodomycosis?

A
  • Most infected individuals are asymptomatic
  • Remainder develop flu-like symptoms
  • A small number of those will later develop progressive chronic pulmonary disease with cavity formation
43
Q

What is the presentation of disseminated coccidioiomycosis?

A
  • Desert rheumatism, which is a triad of symptoms including: fever, skin nodules, & joint pain
  • Coccidial meningitis (lesser of the two causes of fungal meningitis)
44
Q

What is the leading cause of fungal meningitis?

A

Cryptococcus neoformans

45
Q

How is crytococcus neoformans different from the other systemic fungi?

A

NOT Dimorphic; rather, it is an encapsulated yeast

46
Q

Where is cryptococcus present?

A

Bird droppings (mostly pigeon)

47
Q

How does fungal meningitis differ from bacterial meningitis?

A

Fungal= slow onset vs. bacterial fast onset

48
Q

How is cryptococcus diagnosed?

A

India Ink

49
Q

How is cryptococcus meningitis treated?

A
  • Long term Amphotericin B & 5-Fluorcytosine (6-10 weeks)

- AIDS patients may require suppressive therapy

50
Q

What is pneumocystis carinii pneumonia (PCP)?

A

The causative agent of a highly lethal form of pneumonia that develops in immunocompromised patients (AIDS)

51
Q

Describe the pathogenesis of PCP.

A
  • Single celled eukaryotic organism with simlarities to protozoa
  • Exists in a cyst and trophozoites form
  • Infection is initiated by inhalation of the cyst form
52
Q

What is the clinical presentation of PCP?

A
  • Dyspnea
  • Nonproductive cough
  • Fever
53
Q

How is PCP diagnosed?

A

Identification of organisms in clinical material through specialized staining techniques

54
Q

How is PCP treated?

A

Trimethoprim-sulfamethoxazole compounds that interfere with folate synthesis

55
Q

What species of aspergillus are most commonly associated with disease?

A

A. fumigatus & A. flavus

56
Q

Describe the pathogenesis of aspergillus.

A
  • Aspergillus exists in the environment as a mold that releases conidia that are aerosolized
  • Conidia are inhaled and infect existing lung lesions
  • Hyphal growth in tissue causes disease pathology
57
Q

What is an aspergilloma?

A
  • Fungus ball that infections a pre-existing lung lesion
58
Q

How do aspergillomas present on CXR?

A

Space-occupying lesions that move as the patient changes position

59
Q

How is aspergillus diagnosed?

A
  • Hyphae observed in clinical sample

- Appear as V-shaped branches at a 45 degree angle in blood vessels

60
Q

How is aspergillosis treated?

A
  • Newer classes of azoles
  • Echinocandin
  • Amphotericin B

*Surgical removal of aspergillomas is common

Microbiology (49 decks)

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