Opportunistic Fungal Infections (Medical Mycology) Flashcards
What are edible mushrooms?
They are fungi
What are fungi?
Fungi are eukaryotes that exist that exist as unicellular or multicellular
What is the cellular organization of fungi?
They have complex cellular organization but lack chlorophyll thus, they differ from plant cells
What are the organelles of the fungi?
Nucleus where DNA is wrapped around histones
Mitochondria
Ribosomes
Cell wall
Plasma Membrane
What does the cell wal of the fungi contain?
Chitin,
Glucans
Mannans
Polysaccharides
What does the fungal cell membrane contain?
Ergosterol
(Mammalian cells contain cholesterol)
How many fungi species have been identified?
More than 200 000 fungal species have been identified, however, less than 300 can cause disease in human
What are the different fungal morphologies?
- Yeast
- Yeast-like fungi
- Filamentous fungi
- Dimorphic fungi
What are the differences between bacteria and fungi?
Bacteria: prokaryotes, smaller, cell wall peptidoglycan, growth pH 6.5to 7, cell cycle 20 minutes, motile with flagella, 70S ribosomes, pili, no cytoskeleton
Fungi: eukaryotes, bigger, chitin cell wall, pH value 4 to 6, cell cycle 12 to 24 hours, immobile, 80S ribosomes, no pills, microtubules
What are the different types of medically important fungi?
Dimorphic
Opportunistic
What are the two kinds of dimorphic fungi?
Mold form at 25°C (environmental temperature)
Yeast form at 37°C (body temperature)
What are he examples of dimorphic fungi?
Bastomyces Dermatitis
Coccidiiodes Immitis
Histoplasma capsulatum
Paracoccidioides brasiliensis
What are examples of opportunistic fungi?
Candida albicans
Cryptococcus neoformans
Aspergillus fumigatus
What are the virulence factors of fungal pathogens (surface components)? (3)
- Cell wall glycoproteins: facilitate adherence.
- Capsule: prevent phagocytosis by immune cells
- Melanin pigment: antioxidant, detoxify, reactive oxygen radicals released by immune cells
What are the virulence factors of fungal pathogens (immune evasion)? (3)
- Thermo-tolerance: grow in different shapes at 37
- Resist killing by phagocytosis
- Cytocidal activity against epithelial and monocytic cells
What are the virulence factors of fungal pathogens (exoenzymes)?
- Elastase: degrades elastin and enhances invasion of lung, skin, and blood vessels
- Alkaline protease: degrades collagen and elastin, enhances invasion of lung tissues
- Acid proteases: cleaves IgA2 immunoglobulin
- Keratinase: degrades scleroprotein in the skin
What are the virulence factors of fungal pathogens (toxins and toxic metabolites)?
- Aflatoxin: causes liver toxcity and carcinogenic
What is candidiasis?
Caused by yeast candida
Candidiasis can occur in the mouth and throat, vagina, or the bloodstream (esophageal candidiasis, nail infection, thrush)
What is the C. neoformans infection?
Caused by cryptococcus neoformans, which can infect the brain (meningitis) in people with HIV/AIDS (cryptococcus meningitis and skin infections)
What is aspergillosis?
Caused by the fungus Aspergillus and usually occurs in people with lung diseases or weak immune systems (nail infections, lung infection and burn infection)
What is mucormycosis?
A rare infection that m(rhinocerebral mucormycosis and skin infections)
What is pneumocystis pneumonia? (PCP)
Caused by the fungus Pneumocystis jirovecii and mainly affects people with weakened immune systems (lung infections)
What is Blastomycosis?
Caused by the fungus Blastomyces, which lives in moist soil in parts of the US and Canada (skin infections)
What is Sprotrichosis?
Caused by the fungus Sporothrix, which lives throughout the world in soil and on plants (skin and subcutaneous infections)
What is histoplasmosis?
Caused by the fungus Histoplasma, which lives in the environment, often in association with large amounts of bird or bat droppings (skin and lung infections)
What is ringworm?
Infect immune-competent people, a common fungal skin infection that often looks like a circular rash (athlete’s foot, scalp infection, ringworm circle)
What fungus causes ringworm?
Tinea fungus
What are fungal eye infections?
Different types of fungi can cause eye infections, these are rare but can develop after an eye injury (fungal keratitis, infection of the cornea, periorbital fungal infection)
What are the opportunistic fungal infections in Cushing’s? (6)
- Candidiasis –> esophageal, endocarditis
- Cryptococcosis –> pulmonary, meningitis, disseminated disease
- Histoplasmosis –> pulmonary, adrenal
- Aspergillosis –> invasive pulmonary, endophthalmitis, disseminated disease
- Pneumocystosis –> pneumoniaa
- Scedosporiosis –> osteomyelitis, arthritis
What are the important clinical findings of candida?
Thrush in mouth and vagina, endocarditis in intravenous drug users
What are the important clinical findings of cryptococcus?
Meningitis
What are the important clinical findings of aspergillus?
Fungus ball in lung, wound and burn infections; indwelling catheter ingfection, sinusitis
What are the important clinical findings of mucor and rhizopus? What are the predisposing factors?
Necrotic lesion formed when mold invades blood vesself; predisposing factors are diabetic ketoacidosis, renal acidosis and cancer
What are the lab findings of candida?
Gram (+), culture grows yeast colonies, candida albicans form germ tubes
What are the lab findings of cryptococcus?
India ink stain shows yeast with a large capsule; the culture grows very mucoid colonies
What are the lab findings of aspergillus?
Culture grows mold with green spores and conidia in radiating chains
What are the lab findings of mucor and rhizopus?
Culture grows mold with black spores; conidia enclosed in a sac called sporangium
Which kind of species cause monilial thrush?
C. albicans and other candida
What else do candida species cause?
Bloodstream infections
What are the main candida species?
C. albicans
C. auris
C. tropicalis
C. glbrata
C. krusei
C. parapsilosis
What is the range of infections caused by the candida species?
Infections range from superficial mucosa and cutaneous candidiasis to widespread hematogenous dissemination involving target organs
What is candida auris?
A superbug!
An emerging fungal infection as hospital-acquired infection in immune-compromised patients
Why is candida auris considered a superbug?
Due to its antifungal resistance
What is mucor and rhizopus?
Mold
What does mucor and rhizopus cause (mucrmycosis)?
Extensive tissue damage in immune-suppressed people
Spreads from the nasal mucosa to paranasal sinuses orbital and brain
What is the prognosis of mucor and rhizopus?
Rapidly fatal if left untreated
What are the types of infections that are caused by mucor and rhizopus?
- Mucormycosis
- Rhinocerebral mucormycosis
- Cutaneous mucormycosis
- Periorbital fungal infection
What is the enzyme found in mucor and rhizopus? What is its function?
Ketone reductase, allows them to thrive in high glucose, acidic conditions. Serum from healthy individuals inhibits the growth of Rhizopus, whereas serum from individuals in diabetic ketoacidosis stimulates growth
What is cryptococcus neoformans?
A spherical to oval, encapsulated yeast-like organism, 2 to 20μM in diameter, which replicates by budding
What do the c. neoformans subspecies and the gatti subspecies cause?
Cryptococcosis in the lung and CNS thus manifests as pneumonia and/or fungal meningitis
What is the major virulence factor of cryptococcus neoformans?
The capsule
What is the function of the capsule of C. neoformans?
- Inhibits phagocytic function
- Downregulates cytokines
- Induces suppressive T cells
- Inhibits antigen presentation
What are the other virulence factors of C. noeformans?
Melanin production –> serves as an antioxidant
Exoenzymes –> facilitate tissue invasion
What temperatures do C. neoformans have the ability to grow in?
Ability to grow at 37oC
What are Aspergillus species?
They are abundant indoors and outdoors, spores are breathed and cause allergic reactions, infections, and invasive disease
What population do the Aspergillus species target?
Immune-compromised people and individuals who suffer from COPD
What is the target organ of the Asergillus species?
It mainly in the lungs but also infects sinuses and skin
What are the different types of Aspergillus? (6)
- Allergic bronchopulmonary aspergillosis (ABPA) –> symptoms similar to asthma
- Allergic aspergillus sinusitis
- Aspergilloma
- Chronic pulmonary Aspergillosis
- Invasive Aspergillosis
- Cutaneous Aspergillosis
What are the lab diagnoses of fungal infections?
- Potassium hydroxide wet mount
- Lactophenil cotton blue wet mouth
- Other staining methods: gram stain, papanicolau stain, PAS, immunofluorescence detection, antigen detection, histology
- Fungal culture on Sabouraud’s dextrose agar
What is the potassium hydroxide wet mount?
Skin scrapping mounted with 10% KOH solution, KOH increases rigidity of cell wall
What is the Lactophenol cotton blue wet mount?
LActic acid preserves fungal structures, phenol kills live fungus, cotton blue stain chitin in cell wall
What is fungal culture on Sabouraud’s dextrose agar?
pH 5.6 to prevent bacterial growth and antibiotics like cyclohexamide
