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MYCOVIRO > 8.1-OPPORTUNISTIC FUNGI INTRO + CANDIDIASIS > Flashcards

8.1-OPPORTUNISTIC FUNGI INTRO + CANDIDIASIS Flashcards

1
Q

Fungi that cause opportunistic infections in immunocompromised patients

A

opportunistic fungi

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2
Q

In what type of patients do opportunistic infections occur?

A

Immunocompromised or immunodeficient patients

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3
Q

Why do immunocompromised patients develop opportunistic fungal infections?

A

Their weakened immune system makes them susceptible to opportunistic fungal pathogens

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4
Q

What are subcutaneous mycoses typically caused by?

A

Dematiaceous fungi

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5
Q

What type of fungi primarily cause opportunistic infections?

A

Hyaline fungi (moniliaceous fungi)

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6
Q

What does “moniliaceous fungi” mean?

A

Fungi with non-pigmented hyphae

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7
Q

Name some opportunistic pathogens.

A

Sporothrix
Pseudallescheria boydii
Fusarium falciforme
Dermatophytes
Trichosporon
Malassezia

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8
Q

What are the common sources of opportunistic fungal infections?

A

Candida, related yeasts, and other exogenous fungi found in soil, water, and air

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9
Q

Is Candida part of the normal biota?

A

Yes

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10
Q

Name some common opportunistic fungal pathogens and the diseases they cause

A

Candidiasis → Candida albicans

Cryptococcosis → Cryptococcus neoformans

Aspergillosis (fungal ball) → Aspergillus niger

Pneumocystis pneumonia → Pneumocystis jirovecii (Pneumocystis carinii)

Penicilliosis → Talaromyces marneffei (Penicillium marneffei)

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11
Q

What is the significance of Talaromyces marneffei (Penicillium marneffei) in opportunistic mycoses?

A

It is a dimorphic fungus
Sometimes grouped with systemic mycoses because it can cause systemic infections
Considered opportunistic because it primarily affects immunocompromised patients

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12
Q

Which systemic fungi are sometimes grouped with T. marneffei?

A

Histoplasma
Coccidioides
Paracoccidioides
Blastomyces

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13
Q

What genus of yeast causes candidiasis?

A

Candida

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14
Q

Where is Candida normally found in the human body?

A

Skin, mucous membranes, and gastrointestinal tract (GIT)

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15
Q

When does Candida cause disease?

A

When the host is immunocompromised or has predisposing factors

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16
Q

What is the most prevalent systemic mycosis?

A

Candidiasis

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17
Q

Name the most common Candida species that cause candidiasis

A

Candida albicans
Candida parapsilosis
Candida glabrata
Candida tropicalis
Candida guilliermondii
Candida dubliniensis

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18
Q

What Candida species are resistant to azole antifungals?

A

Candida krusei
Candida lusitaniae

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19
Q

What is the most virulent fungus of all fungi?

A

Coccidioides

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20
Q

What is the most prevalent systemic mycosis?

A

Candidiasis

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21
Q

What fungus is most commonly associated with granulomatous infections?

A

Histoplasma capsulatum

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22
Q

Which Candida species are azole-resistant?

A

Candida krusei and Candida lusitaniae

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23
Q

What mucous membranes can candidiasis affect?

A

Mouth and vagina

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24
Q

What are the cutaneous infections caused by Candida?

A

Diaper rash → occurs when diapers are not frequently changed

Onychomycosis → nail infection (Tinea unguium)

Paronychomycosis (Paronychia) → infection of the nails and surrounding tissues

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25
What are systemic infections caused by Candida?
Endocarditis → heart infection Meningitis → brain infection Urinary Tract Infections (UTIs) Pulmonary infections → lung infection Fungemia → fungal infection spreading through the blood
26
What host factors increase susceptibility to candidiasis?
Altered skin barrier (allows Candida to invade tissues) Altered mucosal membranes Prolonged antibiotic therapy Chemotherapy Corticosteroid therapy Smoking Hormonal or nutritional imbalance Leukopenia (low WBC count) Defective leukocyte activity Defective cell-mediated immunity
27
What infections are associated with Candida tropicalis?
Vaginitis UTI Intestinal, pulmonary, and systemic infections
28
What infections are associated with Candida parapsilosis?
Endocarditis Otitis externa (outer ear infection) Nail infections
29
What infections are associated with Candida krusei?
Endocarditis (rare) UTIs Vaginitis
30
What is the microscopic appearance of Candida?
Budding yeast with blastoconidia Pseudohyphae with no constrictions
31
How does Candida stain?
Gram-positive
32
On what media does Candida grow readily?
Blood Agar Plate (BAP) Sabouraud Dextrose Agar (SDA)
33
What is the colonial appearance of Candida?
Soft, cream-colored colonies Yeasty odor Pseudohyphae grow submerged below the agar surface
34
What is the characteristic appearance of Candida on Eosin Methylene Blue (EMB) agar?
Spider-like projections
35
What test is used to distinguish C. albicans from other Candida species?
Germ Tube Test
36
How does C. albicans appear in the Germ Tube Test?
Produces true hyphae Forms budding yeast and pseudohyphae Has a lollipop-like structure with terminal conidia
37
What additional test helps confirm C. albicans?
Formation of large, spherical chlamydospores on nutritionally deficient media
38
What happens when C. albicans is incubated in serum at 37°C for 60-90 minutes?
Germ tubes form thinner and more uniform than pseudohyphae
39
What test can be used to speciate different Candida isolates?
Sugar fermentation and assimilation tests
40
What Candida species can be identified through sugar fermentation and assimilation tests?
C. tropicalis C. parapsilosis C. guilliermondii C. kefyr C. krusei C. lusitaniae C. glabrata
41
What is a distinguishing feature of C. glabrata?
Produces only yeast cells (no pseudohyphae) Appears as tiny yeast cells on cornmeal agar
42
What infections are associated with C. glabrata?
Fungemia Kidney infections Lung infections Genitourinary tract infections CNS infections
43
What sugars does C. glabrata assimilate?
Glucose and trehalose
44
What are the two serotypes of Candida albicans identified by adsorbed antisera?
Serotype A (includes C. tropicalis) and Serotype B
45
What host responses do Candida cell wall components and enzymes elicit?
Innate host defenses Th1 and Th2 immune responses
46
What antibodies are found in patients with systemic candidiasis?
Antibodies against: Candidal enolase Secretory proteases Heat shock proteins
47
What is the function of enzymes released by Candida?
They elicit immune host defenses
48
How does superficial candidiasis occur?
Increase in Candida population Damage to skin or epithelium, allowing invasion by yeasts and pseudohyphae
49
When Candida enters the bloodstream and phagocytic host defenses fail to contain its growth
systemic candidiasis
50
Adhesins that: Bind host receptors Mediate attachment to epithelial and endothelial cells Establish Candida infections
ALS (Agglutinin-Like Sequence) surface glycoproteins
51
What is an example of a pattern recognition receptor (PRR) that binds Candida?
Dectin-1, which binds β-1,3-glucan of C. albicans
52
What immune response is triggered by Candida?
Cytokine production Granulocyte colony-stimulating factors (G-CSF) Activation of neutrophils and monocytes
53
What are the risk factors for superficial candidiasis?
AIDS Pregnancy Diabetes (high glucose levels) Young or old age (weakened immune system) Birth control pills Trauma (burns, maceration of skin) Corticosteroid or antibiotic use High glucose levels Cellular immunodeficiency
54
whitish pseudomembranous lesion composed of: Epithelial cells Yeasts Pseudohyphae
Thrush (Oral Candidiasis)
55
How can thrush be differentiated from a milk deposit in infants?
Milk deposit → Easily scraped off Thrush → Scraping causes bleeding due to fungal invasion of epithelium
56
Candida infection of the vaginal mucosa, leading to: Irritation Pruritus (itching) Cheesy vaginal discharge
Vulvovaginitis
57
What factors predispose a person to vulvovaginitis?
Diabetes Pregnancy Antibacterial drugs (alter vaginal flora) Excessive use of feminine wash Imbalances in vaginal acidity and secretions
58
What are other forms of cutaneous candidiasis?
Skin invasion Intertriginous infection (moist skin folds) Interdigital infection (between fingers/toes) Onychomycosis (Tinea unguium) → nail infection
59
What areas are most commonly affected by cutaneous candidiasis?
Skin folds (e.g., under breasts, armpits, groin) Diaper area in infants Hands of individuals frequently exposed to water
60
Candida infection in the blood
candidemia
61
What are the causes of candidemia?
Indwelling catheters Surgery Intravenous drug use Aspiration Damage to skin or GIT
62
In immunocompromised patients, where can candidemia cause occult lesions?
Kidneys Skin (maculonodular lesions) Eyes Heart Meninges
63
What conditions are systemic candidiasis most often associated with?
Chronic corticosteroid use Immunosuppressive therapy Hematologic diseases Chronic granulomatous disease
64
What is candidal endocarditis associated with?
Prosthetic heart valves Fungal vegetations on heart valves
65
How do kidney infections occur in candidiasis?
As a systemic manifestation
66
What are the risk factors for Candida urinary tract infections (UTIs)?
Foley catheters Diabetes Pregnancy Antibacterial antibiotic use
67
When does chronic mucocutaneous candidiasis (CMC) typically begin?
Early childhood
68
What conditions are associated with CMC?
Cellular immunodeficiencies Endocrinopathies
69
What is the result of CMC?
Chronic, superficial, disfiguring infections of the skin or mucosa
70
What immune response is defective in CMC patients?
Th17 response to Candida
71
What specimens are collected for Candida diagnosis?
Swabs & scrapings (for superficial lesions) Blood, spinal fluid, tissue biopsies, urine, exudates (for systemic infections) Material from removed intravenous catheters
72
What are Candida cells examined for in Gram-stained smears or histopathological slides?
Pseudohyphae and budding cells
73
How is Candida identified in superficial or cutaneous infections?
By examining skin or nail scrapings, similar to dermatophytes
74
What stains and chemicals are used for skin or nail scrapings in Candida diagnosis?
10% KOH and Calcofluor white
75
At what temperatures are Candida specimens cultured?
Room temperature (RT) or 37°C
76
What structural features are examined in Candida yeast colonies?
Presence of pseudohyphae
77
How is Candida albicans identified?
By germ tube production or chlamydospore formation
78
How are other Candida species speciated?
Biochemical reactions
79
Why is a positive culture from normally sterile body sites considered significant?
Because it indicates that Candida is the cause of infection
80
What determines the diagnostic value of a quantitative urine culture for Candida?
The integrity of the specimen and the yeast census
81
What do positive blood cultures for Candida indicate?
Systemic candidiasis Transient candidemia (due to a contaminated IV line)
82
What is the best specimen for diagnosing systemic Candida infection?
Blood
83
Why do sputum cultures have no diagnostic value in Candida infections?
Because Candida can be part of the normal respiratory flora
84
Why should skin lesion cultures be done for Candida infections?
To confirm diagnosis and differentiate from dermatophyte infections
85
What immune responses to Candida are seen in most people?
Serum antibodies Cell-mediated immunity (due to lifelong exposure)
86
What specific serologic test detects Candida cell wall mannan?
Latex agglutination test or enzyme immunoassay
87
What serologic test detects β-glucan, and why is it not specific for Candida?
It detects β-glucan, a fungal cell wall component Not specific because other fungi also contain β-glucan
88
How can β-glucan tests still be useful in Candida diagnosis?
When interpreted with other lab and clinical data
89
What is the treatment for thrush and mucocutaneous candidiasis?
Topical nystatin Oral ketoconazole or fluconazole
90
What is the treatment for systemic candidiasis?
Amphotericin B (± oral flucytosine, fluconazole, or caspofungin)
91
What is the treatment for chronic mucocutaneous candidiasis?
Oral ketoconazole and other azoles
92
What treatment is used for immunocompromised patients with candidiasis who do not respond to antibacterial therapy?
Azoles or short-course low-dose Amphotericin B
93
How can cutaneous candidiasis be cleared?
Eliminate contributing factors, such as: Excessive moisture Use of antibacterial drugs
94
What is the most important preventive measure for candidiasis?
Maintain microbiota balance and intact host defenses
95
What factors can disrupt microbiota balance, leading to Candida overgrowth?
Prolonged antibiotic therapy Excessive use of feminine wash
96
Is candidiasis communicable?
No
97
How can Candida be nosocomially transmitted?
Particular strains may be transmitted to susceptible patients

MYCOVIRO (22 decks)

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