Microbiology of Fungal Infections Flashcards
What is an eukaryotic organism?
Cells that have membrane-bound nucleus which contain mitochondria, golgi bodies and other organelles
What is fungi?
Eukaryotic organism with plasma membrane and a rigid cell wall external to membrane
What are the two basic growth forms of fungi?
Yeasts = unicellular
Filamentous/Hyphal = multicellular structures
Describe the four main components making up the structure of fungi
Vacuoles
Organelles
Plasma Membrane
External Cell Wall
What does the plasma membrane in fungus consist of?
Phospholipid bilayer
Sterols - Ergosterol usually
Embedded proteins (channels etc.)
Synthases (specialised protein enzymes to build cell wall)
Describe the structure of the external cell wall
Consists of:
- carbohydrate polymers (beta-glucans, chitins, mannose)
- mannoproteins
What is a true pathogen?
A pathogen able to cause disease in all exposed individuals
- note: very few fungi are true pathogens
What is an opportunistic pathogen?
only able to cause disease in an immunocompromised host
State the regional classifications for fungal infections
Superficial and cutaneous
Subcutaneus
Systemic
List four travel-associated true fungal pathogens that cause systemic infection?
Histoplasmosis
Coccidiomycosis
Blastomycosis
Paracoccidioidomycosis
What is dermatophytosis (a.k.a. Tinea/Ringworm)?
Superficial, localised infection of keratinised tissue
- skin, hair, nails
Describe the transmission of dermatophytosis
Via direct or indirect contact
- sharing towels, bedsheets
Need moisture and trauma
What is pityriasis versicolor?
Superficial infection of the stratum corneum
- produces hyperpigmented/depigmented macules on trunk and proximal limbs
What causes pityriasis versicolor?
Malassezia furfur
What is superficial candidiasis?
Superficial infection most commonly of mucous membranes
- also skin and nails
What most commonly causes superficial candidiasis?
Candida albicans (90%) - normal commensal which canges to pseudohyphal form (yeast-like)
How can candidiasis become invasive?
Usually due to immunodeficiency (e.g. neurtopenia, ABX, indwelling lines)
- candida species invade bloodstream
What causes Cryptococcosis?
Caused by Cryptococcus neoformans - encapsulated yeast (commensal) in the environment, esp. in soil
Normally associated with immunodeficiency
Usually presents as a CNS infection
What causes Pneumocystosis?
Pneumocystis Jiroveci which causes infection of lungs
- very common in AIDS patients
What is the treatment for pneumocystosis?
Co-Trimoxazole (due to protazoan-like tendencies)
What do histoplasmosis and coccidiomycosis have in common?
They both usually cause asymptomatic pulmonary infection in most
What is the significance of using a wood’s lamp?
Useful since many fungi are fluorescent
- not all, also some bacteria are fluorescent
When would serology be used instead of culture?
In systemic infections when no time for full culturing and need rapid identification of fungi
