Microbiology 18: Fungal Infections Flashcards
Name 3 yeasts ?
Candida
Cryptococcus
Histoplasma
Name 2 Moulds ?
Aspergillus
Dermatophytes
What does it mean if a fungi is dimorphic?
It can change between yeasts and moulds depending on environmental conditions
Which groups of people are particularly at risk of systemic candidiasis ?
Very low birth weight infants
Immunocompromised
Patients on ITU
Patients receiving TPN
How do you differentiate Candida Albicans from other Candidas ?
They form Germ tubes
What is the candida infection that affects skin folds in children called ?
Intertrigo
Which yeast infection is particularly more common in HIV +ve patients ?
Cryptococcus
Which yeast shows capsules when stained on India ink ?
Cryptococcus
Name the Cryptococcus Neoformans variant which causes meningitis in immunosupressed people especially around SE asia and Australia where there are Eucalyptus trees ?
Cryptococcus Neoformans var. gatii
Which antigen if detected in serology can suggest aspergillus infection ?
Galactomannan
Name an aggressive disease caused by a mould which is considered a surgical emergency and requires debridement ?
Mucormycosis
Characterised by cellulitis of the orbit and face which progresses with discharge and black pus from the palate and nose
A hyper pigmented lesion on the back which has a “spaghetti and meatballs” appearance on microscopy and orange fluorescence under Wood’s light.
Most likely organism ?
M.furfur
This is pityriasis versicolour
A rose gardener gets pricked by a rose thorn on his arm. This leads to small nodular lesions on the surface which start to ulcerate.
Most likely organism ?
Sporothrix schenkii (rose gardener’s disease)
This fungus causes loss of hair and scaly red lesions on the scalp.
Most likely organism ?
Tinea capatis
List 3 types of infections caused by Tinea ?
Athletes foot (Tinea pedis)
Ringworm (Tinea Corporis)
Tinea capatis
What is the main treatment for Aspergillus infection ?
Voriconazle
Which anti fungal is used to treat Candida infection ?
Fluconazole (but losing sensitivity) Amphotericin B (for invasive disease)
Which anti fungal is used to treat Cryptococcus infection ?
Ampoterecin B
Which organism causes Pityriasis versicolour ?
Malassezia. FurFur
Which organism causes seborrheic dermatitis ?
Malassezia globosa
features of candida
form individual cells
replicate by budding
invasive candidiasis more common in people receiving TPN
types: candida albicans, candida galbrata, candida krusei, candida tropicalis
candida can affect the eyes - endopthalmitis
generalised candidiasis can be seen in babies - secondary to seborrheic dermatitis
how is candidiasis diagnosed
swabs
blood cultures for candidaemia
sabouraud agar
beta-D glucan assay
how is candidiasis managed
treat for at least 2 weeks with antifungals from first negative blood cultures
echinicandins
fluconazole
features of cryptococcus
acute pulmonary, systemic or meningitic disease cause by inhalation of a fungus
ambisome treatment
AIDS and T cell impaired patients more susceptible
cryptococcal meningitis can cause hydrocephalus
management of cryptococcus
3 weeks amphotericin B with or without flucytosine
secondary suppression with fluconazole
features of aspergillus spp.
causes: mycotoxicosis, allergy, invasive disease, systemic and fatal disseminated disease
aspergillus fumigatus, aspergillus favus, aspergillus niger
aspergillus balls may form in previous TB areas
invasive aspergillosis more common in IC patients
diagnosis of aspergillosis
bloods
serology - look for IgE
antigen detection - galactomannan
how is aspergillosis managed
amphoteracin
(fluconazole not very effective)
6 week therapy
list examples of dermatophyte infections
tinea pedis - trichophyton rubrum tinea cruris - trichophyton rubrum tinea corporis tinea capitis onychomycosis (thickened nails) pityriasis versicolor - malassezia furfur
what is mucormycosis
group of moulds causing severe and invasive disease
affects IC patients + those with poorly controlled diabetes
cellulitis of the orbit
black eschars
decreasing levels of consciousness - rhinocerebral mucormycosis
causes: rhizopum spp. ,rhizomucor spp, mucor spp.
SURGICAL EMERGENCY
name common antifungals
polyene antifungals - amphoteracin B
azole antifungals - ketoconazole, itraconazole
DNA/RNA synthesis antifungals - pyrimidine analogues
cell wall antifungals - chinocandins
how do azole antifungals work
inhibit ergosterol productio
how do echinocandin antifungals work
inhibit synthesis of beta (1,3) D glucan (component of cell walls)
active against candida and aspergillus species
eg caspofunin
how do polyene antifungals work
binds to ergosterol in the membrane
creates transmembrane channels - electrolyte leakage
amphoteracin B = main
active against most fungi except: aspergillus terreus, scedosporium spp.
how do flucytosine antifungals work
inhibits DNA in the fungal cells
candidiasis and cryptococcis
