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Micro > Microbiology 18: Fungal Infections > Flashcards

Microbiology 18: Fungal Infections Flashcards

1
Q

Name 3 yeasts ?

A

Candida (most common)
Cryptococcus
Histoplasma

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2
Q

Name 2 Moulds ?

A

Aspergillus
Dermatophytes

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3
Q

What does it mean if a fungi is dimorphic?

A

It can change between yeasts and moulds depending on environmental conditions

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4
Q

Which groups of people are particularly at risk of systemic candidiasis ? (5)

A
  • Very low birth weight infants
  • Immunocompromised
  • Patients on ITU
  • Patients receiving TPN
  • Pts on ABx - antibiotics will kill the commensals
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5
Q

How do you differentiate Candida Albicans from other Candidas ?

A

They form Germ tubes

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6
Q

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

A

Intertrigo

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7
Q

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

A

Cryptococcus - since impaired T cell immunity

NB second most common cause of death in AIDS

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8
Q

Which yeast shows capsules when stained on India ink ?

What is now preferred to Ix this organism instead of India Ink?

A

Cryptococcus - The ink will stain everything black EXCEPT for the capsule around the yeast

enzyme immunoassay (EIA) - to look for components of the capsule

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9
Q

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

A

Cryptococcus Neoformans var. gatii

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10
Q

Which antigen if detected in serology can suggest aspergillus infection ?

A

Galactomannan

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11
Q

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

Which 2 groups does it mainly affect?

What is Tx?

A

Mucormycosis - Characterised by cellulitis of the orbit and face which progresses with discharge and black pus from the palate and nose - eventually involves the brain (rhinocerebral mucormycosis)

  • Immunocompromised patients
  • Poorly controlled diabetics

Tx: ENT team + Amphotericin (HIGH DOSE)

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12
Q

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 ?

A

Malassezia furfur

This is pityriasis versicolour

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13
Q

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 ?

A

Sporothrix schenkii (rose gardener’s disease)

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14
Q

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

Most likely organism ?

A

Tinea capatis

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15
Q

List 4 types of infections caused by Tinea ?

A
  • Athletes foot (Tinea pedis)
  • Ringworm (Tinea Corporis) - body
  • Tinea capatis - head
  • Tinea cruris - groin
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16
Q

What is the main treatment for Aspergillus infection ?

A

Amphotericin - 6 weeks

17
Q

1st line antifungal in each situation

  • Skin- imidazole
  • Female genital area- clotrimazole
  • Oral- miconazole or if extensive, PO fluconazole

PLEASE CLOZE DELETE EACH DRUG (AND DO ALL AS C1)

Which drug is still effective for candida albicans but is slowly losing sensitivity?

A

(ANSWER TO SECOND Q): fluconazole

18
Q

Which anti fungal is used to treat Cryptococcus infection ?

A

amphotericin B +/- flucytosine

NB echinocandins are used as empirical therapy for Candida infections, however Cryptococcus is RESISTANT to echinocandins

19
Q

Fungus causing systemic infection or meningitic disease

A

Cryptococcus neoformans

20
Q

Which organism causes Pityriasis versicolour ?

A

Malassezia. FurFur

21
Q

Which organism causes seborrheic dermatitis ?

A

Malassezia globosa

22
Q

Which fungus can grow on Sabouraud agar?

What Ix are done for this infection?

A

Candidiasis

  • swabs
  • blood culture
  • Serology: beta-D Glucan assay
23
Q

features of cryptococcus

A

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

24
Q

Antifungal used for non-albican candida

A

Echinocandins

25
Q

galactomannan antigen on serology suggest which organism

A

Aspergillus

26
Q

3 organs involved in systemic candidiasis

A
  • spleen
  • liver
  • eyes: endophthalmitis
27
Q

Why does LP in Cryptococcal meningitis not work?

A

Cryptococcal meningitis can cause hydrocephalus which prevents the circulation of CSF so that the sample you have taken from an LP is NOT mixing with the CSF in the brain

28
Q

Dx of aspergillus

A

Microscopy - look at SPORES, not hyphae

29
Q

In which pts does aspergillus mainly invade in?

A

more common in immunocompromised patients (Normal tissue is usually quite resistant to invasion by Aspergillus)

30
Q

Group of antifungal that disrupts membrane of fungal cell, and what is MoA?

A

Azole (ketoconazole, itraconazole, fluconazole)

  • Inhibit Ergosterol Production
  • They do this by inhibiting the cytochrome P450 enzyme lanosterol 14a demethylase
  • NB Fluconazole = water soluble, Itraconazole = Lipophilic Triazoles
31
Q

Main type of polyene antifungal, and what is MoA

A
  • Main = Amphotericin B
  • MoA: binds to ergosterol in the fungal cell membrane, creating transmembrane channels, leading to electrolyte leakage and so fungal death
32
Q

Main problem with Amphotericin B

A

Nephrotoxicity

33
Q

Antifungal that disrupts DNA/RNA synthesis

A

flucytosine (Pyrimidine analogues)

34
Q

Antifungal that targets cell wall of fungus

A

Echocandins e.g. Caspofungin acetate

35
Q

Which fungus is resistant to Echinocandin antifungals?

What is this effective against tho?

A

Cryptococcus neoformans

Candida, aspergillus

36
Q

MoA of echinocandin antifungals

A

Inhibits b-(1,3) D-glucan synthase (component of fungal cell wall) - results in osmotic fragility

Micro (20 decks)

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