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Mycology
Fungi cause mycoses
Eukaryotic
Moulds (hypae in mycelium,…
Mycology
- Fungi cause mycoses
- Eukaryotic
- Moulds (hypae in mycelium, penetrative or aerial) or yeasts (spherical, unicellular) or dimorphic
Superficial and cutaneous mycoses
- limited to the outermost layer of the skin, the epidermis
- Hair shafts and nails may be involved
Cutaneous
Dermatophytosis
- Also known as tinea or ringworm.
---Tinea circinata: classical skin lesion, scaly, dry middle, slightly raised inflamed spreading margin.
---Tinea unguium: onychomycosis (nails). Nails peel off bed.
- Caused by 3 genera: Trichophyton spp., Microsporum spp., Epidermophyton floccosum
Candidiasis
- Skin, mucous membranes, nails
- Candida infection: Usually in yeast form, reproduce by budding, in humans can be yeast, hyphae or pseudohyphae.
---Most commonly Candida albicans, but 10 are pathogenic.
---opportunistic fungus
- Occurs when:
---Immunocompromised: diabetes, AIDS, drugs.
---Balance of normal bacterial flora altered (antibiotics)
---Damaged or moist skin: vagina, nappy area, under breasts.
- Candidiasis of mucous membranes produce discharge: White, cottage cheese, inflammation, painful, itchy.
- Can be systemic infection- fatal.
Superficial
White and black piedra
- Superficial infection of hair shafts, producing nodules
Pityriasis versicolor
- Malassezia furfur
- Patches of skin pigmentation differences.
Subcutaneous mycoses
- Soil fungi introduced by skin trauma
- Involve skin and tissues like fat/fascia/bone underneath
Sporotrichosis
- Features: small papule at trauma site, enlarging non healing ulcer, pus filled red swellings moving up limb (lymph channels), pus discharge, infection progresses for months, gradually heals.
- Sporothrix schenckii
- Sporotrichoid infections: other fungi, Nocardia, M. marinum
Chromoblastomycosis
Small scaly nodule at site of innoculation --> spread slowly as scaly thick plaque --> becomes raised and warty --> cauliflower-like lesion.
Fungal mycetoma
- Tumefaction: Tumour-like swelling
- Draining sinuses: pus or serosanguinous fluid
- Granules: small collections of mycelia in concrete matrix
- Genus Madurella are the most common
- Madura foot
Phaeohyphomycosis
- Cyst in normal host
- Involve paranasal sinuses of brain in the immunocompromised
Opportunistic mycoses
- Opportunistic mycoses occur in patients with impaired immunity – localised or generalised impairment
Candida
- Severe mucocutaneous lesions
---Oral, oesophageal/gastric candidiaisis
- Candidaemia
---In the blood stream
---Risk factors: debilitation, immunesuppression, surgery, IV cannula.
---Can settle into any tissue or organ --> nodules, abscesses, destruction
Pneumocysts jiroveci
- Pneumonia (AIDS and the severely malnourished)
---progressive interstitial pneumonia with fever and worsening shortness of breath
- Most common infection in AIDS
- Chest x-ray appearance is often described as “ground glass”
- Untreated mortality 100%, treated 40%
Filamentous saprophytic fungi
- environmental fungi
- absorb their nutrition as they grow on rotting vegetation
- colonise the nasal cavity, sinuses and airways of normal hosts
Zygomycosis (= mucormycosis)
- 5 Genera that we don't need to remember.
- Invade and destroying blood vessels --> necrosis
- facial sinuses and orbits with gross, rapid tissue destruction. Fatal.
Hyalohyphomycosis and pheohyphomycosis
- H has clear hyphae, P has pigmented hyphae
- Each has a bunch of genera
- Direct innoculation or inhalation
- Feet, kidney, arms...
Aspergillosis
- Aspergillus : ~ 900 species. 8 cause disease
- Conida: asexual spores
- Diseases: sinusitis, pulmonary and disseminated aspergillosis, aspergilloma
Deep seated mycoses
- Affect internal body organs
- Virulent enough to cause disease in hosts with normal immune systems
- Route of infection is usually inhalational
Endemic deep seated mycoses
- limited to particular geographical areas, mainly the Americas.
- Shared features: environmental, dimorphic, inhaled spores, most infections asymptomatic, flu-like illness before pneumonia, mucocutaneous lesions, may affect brain, genitourinary, bone.
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Cryptococcosis
- Cryptococcus neoformans
- Yeast with a large capsule. Visualized with India ink
- Disease:
---Pulmonary cryptococcosis
---CNS cryptococcsis: meningoencephalitis, acute or insidious
---Cutaneous cryptococcosis: nodular skin lesions