Fungal infection Flashcards
(23 cards)
Differences between fungi and bacteria other than just differences between eukaryotes and prokaryotes
Fungi = eukaryotic
Bacteria = prokaryotic
- Fungi are dimorphic hyphae or yeasts
- Fungi lack chloroplasts
- Fungi have membrane-bound organelles
- Fungi cell membranes contain ergosterol not cholesterol
- Fungi divide by budding, not binary fission
- Fungal cell walls contain glucans and chitins instead of peptidoglycan
The three types of illnesses caused by fungi
Allergies
Mycotoxicoses
Mycoses
Cause of allergies and types of allergies
- Fungal spores in the air upon inhalation or contact with the skin
- Rhinitis (inflammation of nasal mucosa)
- Dermatitis
- Asthma
- ABPA (allergic bronchopulmonary aspergillosis)
Symptoms of allergies
- Congestion
- Sneezing
- Itching
- Watery eyes
- Coughing
- Headache
Definition of mycotoxicosis
Toxic reaction caused by inhalation or ingestion of secondary metabolites of moulds that cause a negative effect on humans
Example of a myotoxicosis
Aflatoxin produced by aspergillum flavus
- Presence of aflatoxin and hepatitis B = increased risk of liver cancer
Symptoms of mycotoxicoses
- Breathing problems
- Dizziness
- Severe vomiting
- Diarrhoea
- Dehydration
- Hepatic failure then renal failure 6 days later
How are mycoses classified and what are the four classifications?
Classified by level of tissue affected
- Superficial
- Cutaneous
- Subcutaneous
- Systemic (deep)
Features of superficial mycoses
- Present on surface of skin
- Infection of skin or hair shaft
- No living tissue invaded
- No cellular response from host
Examples of superficial mycoses
Piedraia hortae
Trichosporon beigelli
Malassazia globosa
Phaeoannellomyces wenecki
Features of cutaneous mycoses
- Confined to epidermis
- Dermatophytes or keratinophilic fungi
- Produce extracellular enzymes that hydrolyse keratin (keratinases)
- Inflammation caused by host response to metabolic by-products
Examples of cutaneous mycoses
Epidermophyton
Trychopyton
Microsporum
Candida albicans
Definition of subcutaneous mycoses
Chronic, localised infections of the skin and subcutaneous tissue following traumatic implantation of the infective agent
Examples of subcutaneous mycoses
Sporotrichosis (sporothrix)
Chromoblastomycosis (several spp.)
Mycetoma (several spp.)
Mechanisms of action of anti fungal drugs targeting fungal cell membrane
- Inhibition of ergosterol synthesis by inhibiting fungal cytochrome p450 enzymes
- Polyene antifungals form pores in the membrane by binding to ergosterol and promoting leakiness
- Azole antifungals inhibit 14alpha-demethylase which produces ergosterol
Mechanisms of action of anti-fungal drugs targeting DNA synthesis
- Some compounds selectively activated by fungi, arresting DNA synthesis
- Pyrimidine analogues (molecules similar to pyrimidine bases) can target fungi-specific DNA synthesis pathways with not worry of host cells’ DNA synthesis being impaired
Mechanisms of action of antifungals targeting fungi cell walls
- Inhibition of beta 1,3 gluten synthase
- Prevents synthesis of glucan which makes up fungal cell wall with chitin
Superficial mycoses definition
Fungal infections limited to the outermost layers of the skin and hair
Systemic mycoses definition
Fungal infections infecting internal organs either by primary or opportunistic pathogens
Primary pathogen definition
Pathogen able to establish infection in a healthy host
Opportunistic pathogen definition
Pathogen requires compromised host to establish infection
Example of superficial mycoses and its features
Superficial candida infections
- Usually due to impaired epithelial barrier functions
- Occur in all age groups
- Most common in newborn and elderly
Examples of systemic mycoses and their features
Systemic candida infections
- Opportunistic
- Chemotherapy, gut-related surgery, catheters all increase risk of infection
Systemic invasive pulmonary aspergillosis
- Incidence caused by underlying condition
- Organ or stem cell transplant 15%
- Myeloid and lymphatic leukaemia 10%
- AIDS 3%
