8.1-OPPORTUNISTIC FUNGI INTRO + CANDIDIASIS Flashcards
Fungi that cause opportunistic infections in immunocompromised patients
opportunistic fungi
In what type of patients do opportunistic infections occur?
Immunocompromised or immunodeficient patients
Why do immunocompromised patients develop opportunistic fungal infections?
Their weakened immune system makes them susceptible to opportunistic fungal pathogens
What are subcutaneous mycoses typically caused by?
Dematiaceous fungi
What type of fungi primarily cause opportunistic infections?
Hyaline fungi (moniliaceous fungi)
What does “moniliaceous fungi” mean?
Fungi with non-pigmented hyphae
Name some opportunistic pathogens.
Sporothrix
Pseudallescheria boydii
Fusarium falciforme
Dermatophytes
Trichosporon
Malassezia
What are the common sources of opportunistic fungal infections?
Candida, related yeasts, and other exogenous fungi found in soil, water, and air
Is Candida part of the normal biota?
Yes
Name some common opportunistic fungal pathogens and the diseases they cause
Candidiasis → Candida albicans
Cryptococcosis → Cryptococcus neoformans
Aspergillosis (fungal ball) → Aspergillus niger
Pneumocystis pneumonia → Pneumocystis jirovecii (Pneumocystis carinii)
Penicilliosis → Talaromyces marneffei (Penicillium marneffei)
What is the significance of Talaromyces marneffei (Penicillium marneffei) in opportunistic mycoses?
It is a dimorphic fungus
Sometimes grouped with systemic mycoses because it can cause systemic infections
Considered opportunistic because it primarily affects immunocompromised patients
Which systemic fungi are sometimes grouped with T. marneffei?
Histoplasma
Coccidioides
Paracoccidioides
Blastomyces
What genus of yeast causes candidiasis?
Candida
Where is Candida normally found in the human body?
Skin, mucous membranes, and gastrointestinal tract (GIT)
When does Candida cause disease?
When the host is immunocompromised or has predisposing factors
What is the most prevalent systemic mycosis?
Candidiasis
Name the most common Candida species that cause candidiasis
Candida albicans
Candida parapsilosis
Candida glabrata
Candida tropicalis
Candida guilliermondii
Candida dubliniensis
What Candida species are resistant to azole antifungals?
Candida krusei
Candida lusitaniae
What is the most virulent fungus of all fungi?
Coccidioides
What is the most prevalent systemic mycosis?
Candidiasis
What fungus is most commonly associated with granulomatous infections?
Histoplasma capsulatum
Which Candida species are azole-resistant?
Candida krusei and Candida lusitaniae
What mucous membranes can candidiasis affect?
Mouth and vagina
What are the cutaneous infections caused by Candida?
Diaper rash → occurs when diapers are not frequently changed
Onychomycosis → nail infection (Tinea unguium)
Paronychomycosis (Paronychia) → infection of the nails and surrounding tissues
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
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
What infections are associated with Candida tropicalis?
Vaginitis
UTI
Intestinal, pulmonary, and systemic infections
What infections are associated with Candida parapsilosis?
Endocarditis
Otitis externa (outer ear infection)
Nail infections
What infections are associated with Candida krusei?
Endocarditis (rare)
UTIs
Vaginitis
What is the microscopic appearance of Candida?
Budding yeast with blastoconidia
Pseudohyphae with no constrictions
How does Candida stain?
Gram-positive
On what media does Candida grow readily?
Blood Agar Plate (BAP)
Sabouraud Dextrose Agar (SDA)
What is the colonial appearance of Candida?
Soft, cream-colored colonies
Yeasty odor
Pseudohyphae grow submerged below the agar surface
What is the characteristic appearance of Candida on Eosin Methylene Blue (EMB) agar?
Spider-like projections
What test is used to distinguish C. albicans from other Candida species?
Germ Tube Test
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
What additional test helps confirm C. albicans?
Formation of large, spherical chlamydospores on nutritionally deficient media
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
What test can be used to speciate different Candida isolates?
Sugar fermentation and assimilation tests
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
What is a distinguishing feature of C. glabrata?
Produces only yeast cells (no pseudohyphae)
Appears as tiny yeast cells on cornmeal agar
What infections are associated with C. glabrata?
Fungemia
Kidney infections
Lung infections
Genitourinary tract infections
CNS infections
What sugars does C. glabrata assimilate?
Glucose and trehalose
What are the two serotypes of Candida albicans identified by adsorbed antisera?
Serotype A (includes C. tropicalis) and Serotype B
What host responses do Candida cell wall components and enzymes elicit?
Innate host defenses
Th1 and Th2 immune responses
What antibodies are found in patients with systemic candidiasis?
Antibodies against:
Candidal enolase
Secretory proteases
Heat shock proteins
What is the function of enzymes released by Candida?
They elicit immune host defenses
How does superficial candidiasis occur?
Increase in Candida population
Damage to skin or epithelium, allowing invasion by yeasts and pseudohyphae
When Candida enters the bloodstream and phagocytic host defenses fail to contain its growth
systemic candidiasis
Adhesins that:
Bind host receptors
Mediate attachment to epithelial and endothelial cells
Establish Candida infections
ALS (Agglutinin-Like Sequence) surface glycoproteins
What is an example of a pattern recognition receptor (PRR) that binds Candida?
Dectin-1, which binds β-1,3-glucan of C. albicans
What immune response is triggered by Candida?
Cytokine production
Granulocyte colony-stimulating factors (G-CSF)
Activation of neutrophils and monocytes
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
whitish pseudomembranous lesion composed of:
Epithelial cells
Yeasts
Pseudohyphae
Thrush (Oral Candidiasis)
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
Candida infection of the vaginal mucosa, leading to:
Irritation
Pruritus (itching)
Cheesy vaginal discharge
Vulvovaginitis
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
What are other forms of cutaneous candidiasis?
Skin invasion
Intertriginous infection (moist skin folds)
Interdigital infection (between fingers/toes)
Onychomycosis (Tinea unguium) → nail infection
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
Candida infection in the blood
candidemia
What are the causes of candidemia?
Indwelling catheters
Surgery
Intravenous drug use
Aspiration
Damage to skin or GIT
In immunocompromised patients, where can candidemia cause occult lesions?
Kidneys
Skin (maculonodular lesions)
Eyes
Heart
Meninges
What conditions are systemic candidiasis most often associated with?
Chronic corticosteroid use
Immunosuppressive therapy
Hematologic diseases
Chronic granulomatous disease
What is candidal endocarditis associated with?
Prosthetic heart valves
Fungal vegetations on heart valves
How do kidney infections occur in candidiasis?
As a systemic manifestation
What are the risk factors for Candida urinary tract infections (UTIs)?
Foley catheters
Diabetes
Pregnancy
Antibacterial antibiotic use
When does chronic mucocutaneous candidiasis (CMC) typically begin?
Early childhood
What conditions are associated with CMC?
Cellular immunodeficiencies
Endocrinopathies
What is the result of CMC?
Chronic, superficial, disfiguring infections of the skin or mucosa
What immune response is defective in CMC patients?
Th17 response to Candida
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
What are Candida cells examined for in Gram-stained smears or histopathological slides?
Pseudohyphae and budding cells
How is Candida identified in superficial or cutaneous infections?
By examining skin or nail scrapings, similar to dermatophytes
What stains and chemicals are used for skin or nail scrapings in Candida diagnosis?
10% KOH and Calcofluor white
At what temperatures are Candida specimens cultured?
Room temperature (RT) or 37°C
What structural features are examined in Candida yeast colonies?
Presence of pseudohyphae
How is Candida albicans identified?
By germ tube production or chlamydospore formation
How are other Candida species speciated?
Biochemical reactions
Why is a positive culture from normally sterile body sites considered significant?
Because it indicates that Candida is the cause of infection
What determines the diagnostic value of a quantitative urine culture for Candida?
The integrity of the specimen and the yeast census
What do positive blood cultures for Candida indicate?
Systemic candidiasis
Transient candidemia (due to a contaminated IV line)
What is the best specimen for diagnosing systemic Candida infection?
Blood
Why do sputum cultures have no diagnostic value in Candida infections?
Because Candida can be part of the normal respiratory flora
Why should skin lesion cultures be done for Candida infections?
To confirm diagnosis and differentiate from dermatophyte infections
What immune responses to Candida are seen in most people?
Serum antibodies
Cell-mediated immunity (due to lifelong exposure)
What specific serologic test detects Candida cell wall mannan?
Latex agglutination test or enzyme immunoassay
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
How can β-glucan tests still be useful in Candida diagnosis?
When interpreted with other lab and clinical data
What is the treatment for thrush and mucocutaneous candidiasis?
Topical nystatin
Oral ketoconazole or fluconazole
What is the treatment for systemic candidiasis?
Amphotericin B (± oral flucytosine, fluconazole, or caspofungin)
What is the treatment for chronic mucocutaneous candidiasis?
Oral ketoconazole and other azoles
What treatment is used for immunocompromised patients with candidiasis who do not respond to antibacterial therapy?
Azoles or short-course low-dose Amphotericin B
How can cutaneous candidiasis be cleared?
Eliminate contributing factors, such as:
Excessive moisture
Use of antibacterial drugs
What is the most important preventive measure for candidiasis?
Maintain microbiota balance and intact host defenses
What factors can disrupt microbiota balance, leading to Candida overgrowth?
Prolonged antibiotic therapy
Excessive use of feminine wash
Is candidiasis communicable?
No
How can Candida be nosocomially transmitted?
Particular strains may be transmitted to susceptible patients
