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*MHD Exam 6 > Opportunistic Fungal Infections > Flashcards

Opportunistic Fungal Infections Flashcards

1
Q

What is the predominant isolate of Candida from hospitals?

A

C. albicans

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2
Q

colonies resemble bacteria in culture

A

Candida species

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3
Q

What are the risk factors for candidemia in hospitalized patients?

A
  • hematologic malignancy
  • neutropenia
  • GI surgery
  • premature infant
  • patients >70 y/o
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4
Q

In which organs do the Candida species cause infection?

A

ANY organ system (superficial mucosal and cutaneous to widespread hematogenous)

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5
Q

Candida causes which skin and nail infections?

A

onychomycosis and paronychia

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6
Q

What are the mucosal infections caused by Candida species?

A
  • pseudomembranous candidiasis (thrush)
  • vulvovaginal candidiasis (yeast infection)
  • chronic mucocutaneous candidiasis
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7
Q

Thrush is usually seen in which type of patients?

A

patients with some level of immunosuppression (steroids, diabetes, HIV/AIDS, neonates)

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8
Q

Candida can overgrow in the vaginal mucosa due to:

A
  • stress, pregnancy, and illness affecting immune system
  • certain medications (birth control, steroids)
  • antibiotics (disrupt normal vaginal flora)
  • uncontrolled diabetes
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9
Q

How can Candida affect the eye?

A

endophthalmitis:

  • exogenous=trauma or surgical procedure on eye w/ direct inoculation of organism into AC
  • endogenous=candidemia with hematogenous seeding of retina and choroid
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10
Q

Describe the features of chronic mucocutaneous candidiasis.

A
  • Rare hereditary immunodeficiency disorder due to T-cell malfunction
  • Candida infections develop and persist, beginning in infancy
  • Severe, unremitting mucocutaneous lesions with disfiguring granulomatous apperance
  • Extensive nail involvement and vaginitis
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11
Q

What are the systemic Candida infections?

A
  • Fungemia (endogenous or exogenous)

- Hematogenous dissemination

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12
Q

How is endocarditis caused by fungus different from endocarditis caused by bacteria?

A

Embolic events are more common in fungal endocarditis. However, clinical presentation is the same (fever and heart murmur).

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13
Q

What is a better way of diagnosing Candida: microscopy or culture?

A

culture (microscopy is LESS sensitive)

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14
Q

When diagnosing Candida, you can test yeast for production of ________.

A

germ tube (a unique feature to yeast)

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15
Q

Which type of stain is needed to visualize Candida?

A

Calcofluor White (a fluorescent brightener that binds to chitin)

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16
Q

What are the features of Candida albicans on microscopy?

A
  • clusters of round structures (blastoconidia) along hyphae and at points of septa
  • pseudohyphae and true hyphae
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17
Q

Which Candida species produces a germ tube?

A

C. albicans

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18
Q

What is an important structural feature of Cryptococcus neoformans?

A

polysaccharide capsule

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19
Q

Cryptococcus neoformans is found ______ and associated with ____________.

A

worldwide; pigeon droppings and soil

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20
Q

What are the primary pathogens of cryptococcosis?

A
  • C. neoformans

- C. gattii

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21
Q

How are the yeast cells of Cryptococcus different from the yeast cells of Candida?

A

they are round (not oval) and larger than Candida

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22
Q

Where is C. gattii endemic to?

A

Southern California and Mexico; may be endemic to other regions of the US (endemic range is expanding)

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23
Q

C. neoformans and C. gattii cause disease in which type of host?

A

Both can cause disease in immunocompetent hosts. However, C. neoformans more commonly causes disease in immunocompromised hosts, while C. gatti more commonly causes disease in immunocompetent hosts.

24
Q

What are the clinical syndromes associated with Candida?

A
  • Primary pulmonary focus (via inhalation; ranges from asymptomatic to fulminant bilateral pneumonia)
  • CNS infection secondary to spread
  • Other (less common): skin lesions, ocular infection, osseous lesions, prostatic involvement
25
Q

presents with “soap bubble” lesions in brain

A

Cryptococcus CNS infection secondary to spread

26
Q

What has resulted in a decline in the incidence of C. neoformans?

A
  • anti-retrovirals

- fluconazole

27
Q

What are the risk factors for developing C. neoformans infection?

A
  • advanced HIV/AIDS
  • organ transplant
  • corticosteroid treatment
  • CD4+ count <200
28
Q

C. gattii most commonly causes which condition?

A

cryptococcoma (parencyhmal lesions)

29
Q

Overall, does C. neoformans or C. gattii have a higher mortality?

A

C. neoformans has a higher mortality. However, C. gattii causes more severe neurologic sequelae due to CNS granuloma formation.

30
Q

What does Cryptococcus look like on gram stain?

A

round, encapsulated, budding yeast (stain does NOT penetrate capsular material)

31
Q

India ink stain was a preparation used in the past to visualize which organism?

A

Cryptococcus

32
Q

a urease (+) fungus

A

cryptococcus

33
Q

What are the ways to detect cryptococcal antigens?

A
  • Latex Agglutination

- Later Flow Assay

34
Q

What is the method of choice for diagnosing patients with cryptococcal meningitis?

A

Lateral Flow Assay (highly sensitive and specific; detects antigens in CSF as well as serum)

35
Q

a staining procedure that DOES stain the capsule of Cryptococcus

A

mucicarmine

36
Q

What is a key feature of Aspergillus in tissue?

A

dichotomous brainching (Y-shaped, acute angle)

37
Q

How are species of Aspergillus identified?

A

according to color and structure

38
Q

What is the most important Aspergillus species?

A

Aspergillus fumigatus

39
Q

What are the clinical manifestations of Aspergillus infection?

A
  • Allergic Bronchopulmonary Aspergillosis (ABPA)
  • Obstructive Bronchial Aspergillosis
  • Aspergilloma (fungus ball)
40
Q

many “species” are actually complexes w/ indistinguishable cryptic species, thus having implications for antifungal resistance profiles

A

Aspergillus

41
Q

What are some of the characteristics of Aspergillus?

A
  • rapidly growing mold
  • found in air, soil, construction dust
  • septate hyphae
  • dichotomous branching
42
Q

Name some of the key features of invasive Aspergillosis.

A
  • Ranges from superficial to disseminated infection
  • High mortality (>70%) in invasive and pulmonary disease
  • Angioinvasive nature
  • Progression due to range of immunosuppression
43
Q

Aspergillus species are also known as ______.

A

conidia

44
Q

What are main things to remember about laboratory diagnosis of aspergillosis?

A
  • Recovery from sterile sites should be considered significant
  • Recovery from contaminated sites should be scrutinized
  • NOT recovered from blood culture
  • Culture is not 100% sensitive, therefore it is necessary to use multiple tools for diagnosis
45
Q

Mucormycosis refers to _______ infection produced by various fungi in these families.

A

angiotropic (blood vessel-invading)

46
Q

What are the risk factors for infection with mucomycetes?

A
  • diabetic ketoacidosis
  • renal failure
  • solid organ transplant
  • severely burned patients
  • immunosuppressive disorders
  • use of corticosteroids
  • hematologic malignancy
47
Q

Agents of mucormycosis are commonly found where?

A

on fruit, bread, and in soil; common components of organic debris

48
Q

Do mucomycetes cause infection more commonly in immunocompetent or immunocompromised hosts?

A

usually immunocompromised (esp. stem cell transplant recipients and patients w/ underlying hematologic malignancies)

49
Q

What are the most commonly identified etiologic agents of mucormycosis in humans?

A

Rhizopus species

50
Q

What is the main treatment strategy for mucormycosis?

A

surgical management via debridement of necrotic tissue

51
Q

What are the common manifestations of mucormycosis?

A
  • rhinocerebral
  • pulmonary
  • periorbital
  • cutaneous
  • disseminated
52
Q

What is the most frequent clinical presentation of mucormycosis?

A

rhinocerebral

53
Q

What is unique about Pneumocystis jirovecii?

A

It lacks ergosterol in its plasma membrane, therefore making it insensitive to antifungal drugs that target ergosterol biosynthesis.

54
Q

What is the major component of the cell wall of Pneumocystis jirovecii?

A

1,3-B-glucan (NOT chitin)

55
Q

What predisposes a patient to developing Pneumocystis jirovecii?

A

immunosuppression (primarily HIV/AIDS)

56
Q

What does CXR show with Pneumocystis jirovecii?

A

bilateral ground-glass opacity with pneumatoceles (thin-walled, air-filled cysts)

57
Q

What are the diagnostic stains for Pneumocystis jirovecii?

A
  • Cell wall stains (GMS)

- Direct Fluorescent Antibody stain (better for HIV+ patients)

*MHD Exam 6 (20 decks)

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