Microbiology 9 - Fungal Infection Flashcards
Why are fungi saphrophytes?
Fungi digest food externally - they secrete proteases to break the food down, therefore they live suspended in their food source.
How do fungi replicate?
They replicate via spores.
What are the three types of diseases caused by fungi?
- Allergies
- Mycotoxicoses
- Mycoses
What allergic diseases are caused by inhalation of fungal spores?
- Rhinitis
- Dermatitis
- Asthma
- Allergic broncho-pulmonary aspergillosis (in asthmatics)
What is mycotoxicosis?
A toxic reaction caused by inhalation or ingestion of a mycotoxin. These are secondary metabolites of moulds which cause toxic effects in humans and animals. Therefore, they are poisons.
List the symptoms of mycotoxicosis.
Breathing problems, dizziness, vomiting, diarrhoea, dehydration, hepatic and renal failure.
What is aflatoxin?
The most carcinogenic natural compound known - a mycotoxin.
What are mycoses?
A disease caused by a fungus which results in superficial, cutanous, subcutaneous, or systemic disease. They are classified in those four categories.
What are superficial mycoses?
Superficial cosmetic infections of the skin/hair shaft, which infects dead cells so does not illicit an immune response.
Give some examples of superficial mycoses.
- Black piedra caused by Piedraia hortae
- Dandruff caused by Malassezia globosa.
How does Malassezia globosa cause dandruff?
Produces oleic acid, which causes inflammation of the stratum corneum.
What are cutaneous mycoses?
Ddermatophytes or keratinophilic fungi ehich produce keratinases capably of hydrolysing keratin. This causes inflammation in the host due to metabolic by-products.
What is tinea capitis?
Scalp ringworm - infects the scalp, eyebrows, and eyelashes. A type of cutaneous mycosis.
What is Tinea pedis?
Athletes foot - cutaneous mycosis.
What are subcutaneous mycoses?
Chronic, localised infections of the skin following traumatic implantation of the fungus. Seen in combat-relate blast wounds.
What is sporotrichosis?
Subcutanous mycosis caused by infected cat scratches.
What are the two types of fungus causingdeep mycoses?
Opportunistic, which require a weakened immune system, and primary which can establish infection in a normal host.
Give an example of an opportunistic commensal fungus.
Candida albicans. Risk factors include chemotherapy, gut related surgery and catheters.
How are fungal infections diagnosed?
Skin, soutum, bronchoalveolar lavate, blood, vagina, swab, spinal fluid, tissue biopsy, microscopy. Culture methods or non-culture methods (assays) can be used.
What do antifungal drugs target?
They target the:
- Membrane function
- Cell wall synthesis
- Nucleic acid synthesis
- Membrange ergosterol biosynthesis
List the main tyoes of antifungals.
Polyenes, azoles, and echinocandins.
What is a huge problem with antifungal treatment?
The development of resistant strains.
