Micro2 X4: Ch 47 + 48

Who do opportunistic fungi primarily cause disease in? Exs?

-immunocompromised hosts

-such as those with neutropenia, AIDS, transplants, corticosteroids, or hematologic malignancies.

What are the major opportunistic fungal genera and what type of fungi are they?

-Candida( yeasts)

-Cryptococcus (encapsulated yeasts)

-Aspergillus (molds with septate hyphae)

What are other key opportunists?

-Mucorales (broad, non-septate molds)

-Pneumocystis jiroveci

What type of infections are Candida? What do they arise from and when?

-usually endogenous

-arising from normal microbiota when host defenses or microbiota balance are disrupted

risk factors for cadidiasis

broad-spectrum antibiotics, central venous catheters, T-cell defects, neutropenia, dialysis, ICU stay, and parenteral nutrition (intravenous deliver fo nutrients)

What is the form of candida albicans?

forms both yeasts and hyphae

What is a major virulence factor for invasive diseases?

hyphal transition

What are host defenses against Candida?

-T-cells prevent mucosal overgrowth

-neutrophils prevent invasion and dissemination

What does disseminated candidiasis target? What may be the only sign?

-targets eyes, kidneys, liver, spleen, brain, and heart

-candidemia--> blood stream infection that may result in fever and chills

What does Cryptococcus neoformans produce in vivo? What does it do/ why is it important?

-produces a large polysaccharide capsule in vivo

-it inhibits phagocytosis and is central to virulence.

What does Cryptococcosis typically presents as? Esp in whom?

-subacute-chronic meningitis

-especially in patients with T-cell deficiency (e.g., AIDS).

diagnosis of cryptococcal meningitis

-CSF India ink

-cryptococcal antigen testing (CSF + serum),

-culture

How does Aspergillus cause disease?

causes disease via inhaled conidia

How does Aspergillus spread in the body? What can they cause?

germinate into septate hyphae capable of angioinvasion → infarction, hemorrhage, necrosis.

What can Aspergillus cause?

Invasive pulmonary aspergillosis

How does invasive pulmonary aspergillosis present?

-fever

-pleuritic pain

-hemoptysis

-nodular lesions with "halo sign" or cavitation on imaging

What do Mucorales cause?

similar angioinvasive disease as aspergillus

What do mucorales form?

broad, non-septate hyphae

What groups are high-risk for Mucorales?

diabetics with ketoacidosis and neutropenic patients

categories of skin-related fungal infections and how they're defined

-ubcutaneous,cutaneous (dermatophytes), and superficial mycoses

-defined primarily by depth of tissue involvement

examples of subcutaneous mycoses

sporotrichosis, mycetoma, chromoblastomycosis

How do people subcutaneous mycoses infections?

enter through traumatic inoculation and may extend into deeper tissues or lymphatics

What is the most common subcutaneous mycosis in the US? What is it caused by?

-Sporotrichosis

-dimorphic Sporothrix schenckii complex

What is the classic hallmark of sporotrichosis?

Lymphangitic spread with nodules along draining lymphatics

What are environmental reservoirs for Sporothrix? Who is it most common in?

-soil, vegetation, sphagnum moss

-common in gardeners, landscapers, and outdoor workers.

What is an important epidemiologic concern for outbreaks (notably in Brazil)? Especially with what?

-zoonotic transmission from cats, especially with S. brasiliensis

diagnosis of sporotrichosis

culture; "cigar-shaped" yeasts are rarely seen on histopathology.

treatment of sporotrichosis

-Itraconazole is first-line

-severe disease requires amphotericin B followed by prolonged itraconazole.

Mycetoma presentation

odules, sinus tracts, and grains (colonies)

What body region does mycetoma usually affect and specifically in what geographic region?

-lower extremities

-tropical regions

features of Chromoblastomycosis

verrucous nodules and diagnostic sclerotic bodies (pigmented, septate)

What type of tissues do dermatophytes infect? Examples?

-keratinized tissues only--> skin, hair, nails

-Microsporum, Trichophyton, Epidermophyton

Characteristics of typical tinea lesions

centrifugal growth with active margins and central clearing ("ringworm").

dermatophytes diagnosis

KOH prep of scrapings from the active border reveals hyaline, septate hyphae; culture confirms species

What can superficial mycoses (Malassezia) cause?

cause seborrheic dermatitis and tinea versicolor

Where do Malassezia infections remain? What do they respond to?

-infections remain strictly in the stratum corneum

-respond to topical azoles or antifungal shampoos.