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Path - Microbiology > fungal infections > Flashcards

fungal infections Flashcards

1
Q

what do fungi have in their;

  1. cell walls
  2. plasma membranes
A

cell wall; Chitin

plasma membrane; ergosterol

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2
Q

Small protein packages containing genetic material; some also contain enzymes are __?

A

viruses

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3
Q

Single-celled organisms with prokaryotic cells are __?

A

bacteria

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4
Q

Single-celled eukaryotes that are either free living or parasitic are __?

A

protozoa

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5
Q

what type of RNA do fungi possess?

A

80S

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6
Q

in fungi, what is the difference between yeasts and moulds?

A

yeast single celled, reproduce by budding

moulds - multicellular hyphae, grow by branching and extension

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7
Q

list some examples of moulds

A

Dermatophytes
Aspergillus
Agents of mucormycoses

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8
Q

list some examples of yeasts

A

Candida
Cryptococcus
Histoplasma (dimorphic)

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9
Q

Which is the commonest cause of fungal infections in human?

A

candida spp

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10
Q

what medium do you grow cryptoccocus neoformans on?

which sample do you take to culture

A

india ink

use CSF

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11
Q

what medium do you grow candida on?

A

sabouraud dextrose agar;

Raised, cream coloured colonies

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12
Q

how does Oral candidiasis present?

A

painful mouth

Scraping removes the lesions, leading a sore bleeding tongue

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13
Q

who are those susceptible to oral candida?

A

underlying immunodeficiency,
malignancy,
inhaled steroids – wash mouth after steroid inhalers

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14
Q

list 4 Superficial Candida infections?

A

Mouth - Oral thrush

Throat - Candida oesophagitis

Vulva - Vulvovaginitis

Skin - Cutaneous
- Localised or generalised

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15
Q

list some oral medications for superficial thrush rx?

A

Vulvovaginitis: fluconazole
Oesophagitis: fluconazole

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16
Q

list some topical medications for superficial thrush rx?

A

Oral thrush: nystatin
Vulvovaginitis: cotrimazole
Localised cutaneous: cotrimazole

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17
Q

what does candida look like on gram stain?

A

looks like gram positive cocci but larger more ovoid

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18
Q

list some risk factors for candideamia

A

Malignancies, esp haematological
Burns patients
Complicated post-op courses (eg Tx or GIT Sx)
Long lines

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19
Q

How to manage candideamia?

A
  1. Ivx for source of dissemination
  2. Anidulafungin for 2wks from 1st blood cultre whilst awaiting species identification
  3. Cultures every 48hrs
  4. Remove lines
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20
Q

risk factors for (candida) endocarditis?

A

Abnormal valves/prosthetic valves,
long lines,
IVDU

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21
Q

which causes of candidaemia is treated with Ambisome/voriconazole ?

A

CNS
Endocarditis
Bone and joint

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22
Q

which causes of candidaemia is treated with Fluconazole?

A

Urinary tract

intra-abdominal

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23
Q

cryptococci are __ ?

A

Encapsulated yeast

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24
Q

which cryptococcus serotypes cause C neoformans?

A

A and D

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25
Q

which cryptococcus serotypes cause C gattii ?

in who

A

B and C

people who are FINE immunologically

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26
Q

which system does cryptococcus like to infect?

A

CNS

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27
Q

Which animal is cryptococcus associated with?

A

PIGEONS

28
Q

what is the lifecycle of cryptococcus infection?

A

pigeon excretions -> spores -> inhaled aerosols -> lungs -> CNS -> culture positive

29
Q

which immune cell deficiency puts you at MASSIVE risk of cryptococcus infectoin?

A

Impaired T-cell immunity

E.g patients with HIV, who have reduced CD4 helper T-cell numbers (typically less than 200/ml)

Patients taking T-cell immunosuppressants* for solid organ transplant also have a 6% lifetime risk

*tacrolimus

30
Q

what is the presentation of Cryptococcosis gattii?

A

Causes a meningitis

in immunocompetent individuals

in tropical latitudes, esp. SE Asia and Australia

31
Q

what MRI finding Is common in Cryptococcal infection?

where?

A

MULTIPLE cryptococcoma’s - space occupying lesions

In brain and lung

32
Q

Management OF Cryptococcal infection?

A

Amphotericin B + flucytosine (at least 2/52)

maintenance; fluconazole for 1 year

33
Q

aspergillosis causes Mycotoxicosis when?

A

upon ingestion of contaminated foods

34
Q

You are the FY1 on a respiratory ward. Your consultant has referred a patient from clinic who is experiencing heamoptysis and weight loss. PMHx includes treated pulmonary TB.

list some differentials? and why?

A

TB

CANCER

ASPERGILLOMA - past hx of TB so there are cavities for the aspergillum to grow !

35
Q

How would you ivx aspergillum?

A

CXR - round lesion; aspergilloma

Sputum MCS

blood culture - galactomannan

36
Q

what is galactomannan?

A

Galactomannan is a component of the cell wall of the mold Aspergillus and is released during growth.

aka aspergillus antigen

Detection of galactomannan in blood is used to diagnose invasive aspergillosis infections in humans.

37
Q

rx for aspergillum?

A

Voriconazole

for 6 weeks

38
Q

name 1 feature of Pneumocystis jiroveci that differentiates from other fungal infections?

A

Lacks ergosterol in it’s cell wall

39
Q

Pneumocystis jiroveci often presents how?

A

Pneumonia

Extrapulmonary disease = rare

40
Q

most common cause of pneumonia in HIV patients?

A

PCP

41
Q

You are the FY1 on the renal team. You have been asked to go and review a patient in the renal assessment unit who has a cough and SOB.

The nurse tells you that the patient is desaturating when she walks. what does this mean?

A

desaturating - 02 Sats ae fine when resting but drop on activity.

42
Q

You are the FY1 on the renal team. You have been asked to go and review a patient in the renal assessment unit who has a cough and SOB.

The nurse tells you that the patient is desaturating when she walks.

diagnosis?
what would you see on CXR?

A

PCP

CXR - bilateral patchy/perihilar shadowing or bats wing shadowing

43
Q

Rx for PCP?

A

High dose cotrimoxazole 2-3/52

44
Q

Ivx for PCP?

A

Microscopy
PCR
Beta-D-glucan - cell wall polysaccharide, non-specific

45
Q

Beta-D-glucan can aid in the datection of?

A

PCP

Aspergillus

Candida

46
Q

Why might antifungals targeting the cell membrane not work in PCP?

A

no ergosterol there

47
Q

Diabetic patient presents with decreasing levels of consciousness.

there is Cellulitis of the orbit and face progress with discharge of black pus from the palate and nose.

which infection ?

A

Mycormycoses

48
Q

rx for mycormycoses?

A

Ambisome

49
Q

what are Dermatophytes?

A

A group of fungi capable of invading dead keratin of skin, hair and nails

50
Q

Trichophyton rubrum causes?

A

Tinea pedis - athlete’s foot
, fungal infection of nail
, jock itch,
ringworm

51
Q

T rubrum or E floccosum cause?

A

tine cruris - around groin

52
Q

tine capitis is caused by which dermatophytes?

A

T rubrum or T Tonsurans

53
Q

Trichophyton spp, Epidermophyton spp, Microsporum spp. causes which condition?

A

onchomycosis - Tinea unguium, is a fungal infection of the nail.

54
Q

Malassezia furfur causes which condition?

A

Pityriasis versicolor

55
Q

most common side effect of Azoles?

A

abnormal LFTs - hepatotoxicity

56
Q

most common side effect of Polyenes antifungals?

A

Nephrotoxicity - kidney

57
Q

most common side effect of Echinocandins antifungals?

A

harmless

58
Q

most common side effect of Pyrimidine analogues antifungals?

A

Blood disorders

59
Q

What are the targets for antifungal therapy?

A

Cell membrane - ergosterol

DNA Synthesis

Cell Wall

60
Q

list some Cell Membrane Active Antifungals?

A

Azole antifungals
- Ketoconazole

Polyene antibiotics
- Amphotericin B ; used in candida etc

61
Q

how do azoles work?

A

Azoles bind to

the cytochrome P450-enzyme lanosterol 14a-demethylase

thus inhibiting the production of ergosterol

62
Q

how does Amphotericin B work?

A

polyene abx that

Binds sterols in fungal cell membrane

Creates transmembrane channel and electrolyte leakage

63
Q

which is most toxic?

Amphotericin B deoxycholate
Liposomal amphotericin B
Amphotericin B colloidal dispersion
Amphotericin B lipid complex

A

Amphotericin B deoxycholate

64
Q

list some Cell Wall Active Antifungals?

A

Echinocandins - are actually antibiotics

65
Q

who do Echinocandins work?

A

interfere with fungal cell wall synthesis by inhibition of ß-(1,3) D-glucan synthase

Loss of cell wall glucan results in osmotic fragility

66
Q

name an an anti-metabolite type of antifungal drug that is a synthetic fluorinated pyrimidine ?

A

flucytosine

67
Q

what is the issue with flucytosine

A

rapid acquired resistance due to mono therapy

Path - Microbiology (27 decks)

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