34. Mycology Flashcards
What are fungi?
They are a distinct kingdom of eukaryotes with rigid cell walls.
What are the two types of fungi?
Yeast and moulds
What is the difference between yeast and moulds?
Yeasts = grow as SINGLE cells which reproduce by asexual BUDDING
Mould = grow as long filaments (hyphae) and form a mat (mycelium)
What morphology can fungi have?
They can be unicellular or grow as hyphae (filamentous structures)
Give examples of fungal diseases.
Athletes’ foot, thrush, ringworm.
Give examples of Yeasts.
Candida, Pneumocystis and Cryptococcus.
Describe the characteristics of Cryptococcus neoformans and the diseases it causes.
- It is a free-living encapsulated yeast
- Gives white mucoid colonies on Sabouraud dextrose plates after 48 hours
Diseases (usually in immuno-compromised):
- Self-limiting pneumonia
- Crytptococcoma (large fungal mass)
- Skin infections (crytotococcosis, rare but longlasting)
- Meningitis
How can Cryptococcus infection be diagnosed?
- Gives white mucoid colonies on Sabouraud dextrose plates after 48 hours
- Classic India ink stain exclusion -> When India ink is applied, the fungi do not take up the ink
When is treatment against Cryptococcus infection essential? How is treatment done?
- When the CNS is involved
- Oral and IV anti-fungals include Fluconazole, Nystatin, Amphotericin B
Describe the characteristics of Candida albicans and the diseases it causes.
- It is a fungus that is normally commensal in the mouth, gut and vagina
- However, it can result in local and systemic opportunistic infections when the patient is immunocompromised (e.g. in HIV) or when the microbiome is disrupted (e.g. antibiotics)
- Candidiasis can be in 3 main forms:
- Oropharyngeal (OPC)
- Oesophageal
- Vulvovaginal (thrush)
- OPC is very painful can seriously affect nutrition and taking oral meds.
How can Candida infection be diagnosed?
Clinical clues:
- Unexplained fever which is not responsive to antibiotics
- Multiple non painful cutaneous lesions
Laboratory tests:
- Neutropenia <100 PMNs/mm3
- Yeast in urine sample
- IV catheter culture grows yeast
Describe some treatment for Candida infection.
Systemic anti-fungal treatment is usually fluconazole.
Give an example of a filamentous fungi.
Aspergillus
Describe the characteristics of Aspergillus species and the diseases they cause.
- Filamentous fungi found ubiquitously in environment
- Infections typically in immunocompromised patients, although they can also happen where there is repeated tissue damage and scarring (e.g. COPD)
- Invasive aspergillosis has a high mortality rate (>25%) and is primarily a lung infection, but can spread to be systemic
How does aspergillus cause disease?
Travel to the lung
Germinates in epithelial cells and cavities caused by Tb
Causes neutropenia
Who does aspergillus infect?
Only in immunocompromised individuals or when there is repeated tissue damage and scarring eg COPD or Tb or bronchiectasis
Most people breathe in Aspergillus spores every day without getting sick.
Describe the characteristics of Pneumocystis jiroveci and the diseases it causes.
- It is a fungus that is found in the lungs of healthy individuals and is an opportunistic pathogen.
- Infection primarily affects the immunocompromised.
- Symptoms of infection include pneumonia, non-productive cough, weight loss and night sweats.
How can Pneumocystis jiroveci infection be diagnosed?
- Chest X-ray shows widespread infiltrates
- Definitive diagnosis from BAL – see characteristic cysts “crushed ping-pong balls’
Fungal diseases tend to be … infections.
Opportunistic
With which condition are fungal infections often associated with?
AIDS
Why is antifungal chemotherapy important for cancer patients?
*Vulnerable due to neutropenia/ cellular immune defects/ catheters -> fungal infections one of leading causes of morbidity/ mortality.
