Microbiology 18: Fungal Infections

Question 1

Name 3 yeasts ?

Answer 1

Candida
Cryptococcus
Histoplasma

Question 2

Name 2 Moulds ?

Answer 2

Aspergillus

Dermatophytes

Question 3

What does it mean if a fungi is dimorphic?

Answer 3

It can change between yeasts and moulds depending on environmental conditions

Question 4

Which groups of people are particularly at risk of systemic candidiasis ?

Answer 4

Very low birth weight infants
Immunocompromised
Patients on ITU
Patients receiving TPN

Question 5

How do you differentiate Candida Albicans from other Candidas ?

Answer 5

They form Germ tubes

Question 6

What is the candida infection that affects skin folds in children called ?

Answer 6

Intertrigo

Question 7

Which yeast infection is particularly more common in HIV +ve patients ?

Answer 7

Cryptococcus

Question 8

Which yeast shows capsules when stained on India ink ?

Answer 8

Cryptococcus

Question 9

Name the Cryptococcus Neoformans variant which causes meningitis in immunosupressed people especially around SE asia and Australia where there are Eucalyptus trees ?

Answer 9

Cryptococcus Neoformans var. gatii

Question 10

Which antigen if detected in serology can suggest aspergillus infection ?

Answer 10

Galactomannan

Question 11

Name an aggressive disease caused by a mould which is considered a surgical emergency and requires debridement ?

Answer 11

Mucormycosis

Characterised by cellulitis of the orbit and face which progresses with discharge and black pus from the palate and nose

Question 12

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 ?

Answer 12

M.furfur

This is pityriasis versicolour

Question 13

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 ?

Answer 13

Sporothrix schenkii (rose gardener’s disease)

Question 14

This fungus causes loss of hair and scaly red lesions on the scalp.

Most likely organism ?

Answer 14

Tinea capatis

Question 15

List 3 types of infections caused by Tinea ?

Answer 15

Athletes foot (Tinea pedis)
Ringworm (Tinea Corporis)
Tinea capatis

Question 16

What is the main treatment for Aspergillus infection ?

Answer 16

Voriconazle

Question 17

Which anti fungal is used to treat Candida infection ?

Answer 17

Fluconazole (but losing sensitivity)
Amphotericin B (for invasive disease)

Question 18

Which anti fungal is used to treat Cryptococcus infection ?

Answer 18

Ampoterecin B

Question 19

Which organism causes Pityriasis versicolour ?

Answer 19

Malassezia. FurFur

Question 20

Which organism causes seborrheic dermatitis ?

Answer 20

Malassezia globosa

Question 21

features of candida

Answer 21

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

Question 22

how is candidiasis diagnosed

Answer 22

swabs
blood cultures for candidaemia
sabouraud agar
beta-D glucan assay

Question 23

how is candidiasis managed

Answer 23

treat for at least 2 weeks with antifungals from first negative blood cultures
echinicandins
fluconazole

Question 24

features of cryptococcus

Answer 24

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

Question 25

management of cryptococcus

Answer 25

3 weeks amphotericin B with or without flucytosine

secondary suppression with fluconazole

Question 26

features of aspergillus spp.

Answer 26

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

Question 27

diagnosis of aspergillosis

Answer 27

bloods
serology - look for IgE
antigen detection - galactomannan

Question 28

how is aspergillosis managed

Answer 28

amphoteracin
(fluconazole not very effective)
6 week therapy

Question 29

list examples of dermatophyte infections

Answer 29

tinea pedis - trichophyton rubrum 
tinea cruris - trichophyton rubrum 
tinea corporis 
tinea capitis 
onychomycosis (thickened nails)
pityriasis versicolor - malassezia furfur

Question 30

what is mucormycosis

Answer 30

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

Question 31

name common antifungals

Answer 31

polyene antifungals - amphoteracin B
azole antifungals - ketoconazole, itraconazole
DNA/RNA synthesis antifungals - pyrimidine analogues
cell wall antifungals - chinocandins

Question 32

how do azole antifungals work

Answer 32

inhibit ergosterol productio

Question 33

how do echinocandin antifungals work

Answer 33

inhibit synthesis of beta (1,3) D glucan (component of cell walls)
active against candida and aspergillus species
eg caspofunin

Question 34

how do polyene antifungals work

Answer 34

binds to ergosterol in the membrane
creates transmembrane channels - electrolyte leakage
amphoteracin B = main
active against most fungi except: aspergillus terreus, scedosporium spp.

Question 35

how do flucytosine antifungals work

Answer 35

inhibits DNA in the fungal cells

candidiasis and cryptococcis