34. Mycology (HT) Flashcards
Describe the features of the kingdom of fungi.
- All eukaryotes with rigid cell walls
- Unicellular or grow as hyphae (filamentous structures)
What are some fungi species that you need to know?
[IMPORTANT]
- Cryptococcus neoformans
- Candida albicans
- Pneumocystis jiroveci
- Aspergillus spp
Only the first part of the names are mentioned in the spec.
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 [IMPORTANT]
- 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.
Describe the characteristics of Aspergillus species and the diseases they cause.
- They are filamentous fungi that are found ubiquitously in the environment
- Infections are 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
Draw the progression of a Aspergillus infection.
- The infection is mostly pulmonary
- The fungi cross the basement membrane in areas where defences are insufficient
- In cases of immunosuppression, there will be some immune cell recruitment that leads to collateral tissue damage
- In cases of neutropenia, the infection can spread and become an uncontrolled systemic infection.
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
Give some examples of fungal infections that are mentioned in the spec.
- Thrush
- Athlete’s foot
- Ringworm
How would you diagnose immunodeficiency?
