Diagnosis and Manaement of Fungal Infections Flashcards
What can predispose to invasive mould infections
Immunocompromised High dose corticosteroids Trauma, Diabetes, COPD Haem malignancy bone marrow transpant HIV Organ translplant Malignancies
What can predispose to candidaemia
Immunocompromised High dose corticosteroids Abdo surgery, IV lines, Antibitoics, Diabetes, Lymphoma, Pregnancy Haem malignancy bone marrow transpant HIV Organ translplant Malignancies
Use of X ray in fungal diagnsois
Useful at giving hints but rearey diagnostic
GIve the Radiological signs of aspergillosis
CXR –> patchy changes. May see crecent -shaped lesions on a chest radiograph but this is a late sign following neutrophil recovery
CT –> Halo sign (early finding 1-10 days)
BUT AGAIN these are not diangostic only suspeicion
Diangosic methods
1) Direct microscopy
2) Culture ID Susceptbility
What is direct microscopy particularly good for
Can identify if fungus is present very quickly
But many cases where levels sare too small for funsu BUT hyphae may give clue about properties –> i.e. if its mucoraceous –> start antifungals immediately!!!!
What is the exception to fungi generally growing slowly
Candida will generalyl grow well witin 24 hours!
What can we use to culture yeasr
Chromagenic agar –> can hepl particualry for Candida
1) Dalmau culture
Firstly try to seperate C. ablicans –> if germ tubes present it is likely this
Then do biochemical tests –> test with assimilation studies
What can we use to identify mould culture
Generaly colous, morpholohical geatures and sporing upon microscopy can give us lots of information on diagnosis on culture alone and this is often clinically sufficient
What moudls are bad at being identified onculture
Agents of dark grey mycetoma –> these are often poor at sporing and form dark grey coloies –> under micscioe can only see huphae and hese samples need DNA identification tools
What Traditional sequencing method is a slow process for yeasts
Pyrosequencing –> used to give yeast ID in half a day
But MALDI-TOF Has superceded this
How does pyrosequecning work
Involved 4 enzymes and bases wer eindividually ingested
If base was incorprated it release a pyrophosphate which then gets converted to ATP
This drives a luciferase reaction producing a volt of light
The next base in then injjected
This conitinues until sequencing is complete
Quick but was limited to small gragments
What is MALDI-TOF
Matrix Associated Laser Desorption/Ionizaton - Time of FLight
It is a mass spectromoter –> initially almost too sensitive to give useful results but the MALDI-TOF matric means particles that are analysed and larger and the profile given realtes more to the organism and not where its grown.
It is much quicker and can be done in an hour but it very explensive
What do we used to test susceptibility of fungi
CLSI Borth dilution –> make diltions of antigungal agent and expose to suspencion of fungus to it
What serological methods can we use for fungal diagnosis
1) Examinaning Antiboides
2) examining antigens
