Fungal Infections and Antifungals Flashcards
What are fungi
Eukaryotic organisms with chitinous cell walls and ergosterol containing plasma membranes
Difference between mould and yeast
Yeast is a unicellular type of fungi whereas mould is multicellular filaments of the fungi.
How Candida infections present
Can be deep seated in the immunocompromised
Candidaemia CNS Endocarditis UTI Bone
Diagnosing Candida Infection
Culture, Mannan, Antibodies, Serology for beta-D-glucan
RF for candida
– Malignancies, esp haematological
– Burns patients
– Complicated post-op courses (eg Tx or GIT Sx)
– Long lines
Types of cryptococcus and who they infect
Encapsulated yeast
– Serotypes A&D = C neoformans
(immunodeficient)
– Serotypes B&C = C gattii (immunocompetent)
What animal is cryptococcus associated with
Pigeons
How cryptococcus infections present
Presents as meningitis with insidious onset in HIV
Diagnosing Cryptococcus
Cryptococcal Antigen in serum/CSF + india ink staining
Treatment of Cryptococcus
Rx: 3/52 amphotericin B +/- flucytosine
Treatment of Candida
fluconazole for C. albicans, amphotericin-B for invasive disease
How Aspergillous infections presents
A spectrum from allergy to invasion
-Presents as pneumonia, esp. in immunocompromised. High mortality.
Diagnosis of Aspergillosis
Cultures of mould, ELISA, PCR, β-Glucan test, grows on Czapek dox agar
Treatment of Asper
voriconazole
How PCP presents
Pneumonia in immunodeficient, haemoptysis
Why do some antifungals not work on PCP
Lacks ergosterol in it’s cell wall
Investigations for PCP
– Microscopy
– PCR
– Beta-D-glucan
Treatment of PCP
High dose cotrimoxazole 2-3/52
What are Mucormycoses
Fungal species belonging to the order Mucorales favouring immunocompromised and diabetic patients.
Clinical features of Mucormycoses
Rhinocerebral => CNS
Pulmonary
Cutaneous
What are Dermatophytes
A group of fungi capable of ivading dead keratin of skin, hair and nails
Name each type of dermatophyte and the area affected
Tinea pedia- foot
Tines capitis- scalp
Tinea cruis- groin
Tinea corporis- abdo
Management of dermatophytes
Topical clotrimazole, ketoconazole
MOA of polyenes
Cell membrane integrity- transmembrane channel and leakage
MOA of azoles
Cell membrane synthesis- binds to lanosterol 14a demythlase- inhibiting ergosterol production
Side effect of polyenes
Nephrotoxicity
Echinocandins MOA
Interfere with fungal cell wall synthesis by inhibition of ß-(1,3) D-glucan synthase
• Loss of cell wall glucan results in osmotic fragility
Flucytosine MOA
DNA synthesis
Why does flucytosine have limited activity
Acquired Resistance
Due to:
– Decreased uptake (permease activity)
– Altered 5-FC metabolism
Examples of a polyene, its uses and side effects
Amphotericin B
Serious toxic side effects- vomiting, riggers, blood pressure
