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BDS2 PMI > PMI02-2010 > Flashcards

PMI02-2010 Flashcards

1
Q

Are fungi eukaryotic or prokaryotic?

A

Eukaryotic

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2
Q

What are the two main types of fungi?

A

Yeast

Mould

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3
Q

Contrast yeast and mould.

A

Yeast = unicellular, reproduce by budding, some produce hyphae and pseudohyphae

Mould = multicellular, reproduce using specialised spore structures, always produce hyphae

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4
Q

Which type of fungi always produces hyphae?

A

Mould

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5
Q

Which type of fungi is unicellular and how does it reproduce?

A

Yeast

Reproduce by budding (making copies of itself)

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6
Q

What is budding?

A

Small cell forms off yeast cell and enlarges until its a complete cope

Separates and process repeats

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7
Q

Describe the growth of pseudohyphae.

A

Bud elongation

At max length, it buds again and elongates

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8
Q

What food do pseudohyphae resemble?

A

String of sausages

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9
Q

Describe true hyphae.

A

Produced by apical extension

Even and parallel sides which may have buds on its sides

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10
Q

What kind of appearance is produced by most yeasts?

A

Moist-looking colonies

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11
Q

Describe mould colonies.

A

Round (looking for nutrition in all directions)

Sub-surface growth occurs - hyphae above and below surface

Specialised spore structures on surface (to be distributed by air or water)

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12
Q

How could you tell the difference between a mould or yeast infection in skin using microscopy?

A

Mould = parallel-sided, regularly septate hyphae (true hyphae)

Yeast = budding yeasts, pseudohyphae and true hyphae

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13
Q

Name a species which is known to show budding, pseudohyphae and true hyphae.

A

Candida albicans

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14
Q

Name some commensal yeasts and where they’re typically found.

A

Candida albicans = GI tract and oral cavity

Other Candida species = GI tract

Malassezia species = skin

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15
Q

What does the presence of mould indicate?

A

Always infection (no commensal moulds)

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16
Q

Which yeasts cause candidiasis?

A

Candida species

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17
Q

List some factors that predispose for candidiasis.

A

Age - infancy and elderly due to immune function

Endocrine disorders (eg diabetes)

Defects in cell-mediated immunity

Cancer (impaired immunity)

Drug addiction - contaminated needles

Drug therapy - antibiotics, corticosteroids, immunosuppression

Surgery

Intravenous catheters - Candida biofilm

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18
Q

Are most Candida infections endogenous or exogenous?

A

Endogenous (found in GI tract)

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19
Q

Name some common Candida species in the body.

A

C. albicans

C. glabrata

C. tropicalis

C. parapsilosis

C. krusei

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20
Q

Which Candida species has some strains which are resistant to fluconazole?

A

C. glabrata

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21
Q

Which Candida species is completely resistant to fluconazole?

A

C. krusei

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22
Q

What is the most common type of exogenous Candida infection?

A

Nosocomial (in hospital)

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23
Q

Which Candida species is the most common culprit for hospital outbreaks?

A

C. albicans

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24
Q

Why is Candida auris a recent nosocomial issue?

A

Colonises people very quickly

Persistent in environment

Highly resistant to many antifungals

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25
Q

What are some oral manifestations of candidiasis?

A

Acute pseudomembranous candidiasis (detachable plaques)

Chronic pseudomembranous candidiasis - AIDS associated

Chronic mucocutaneous candidiasis

Angular cheilitis

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26
Q

What is chronic pseudomembranous candidiasis associated with?

A

AIDS

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27
Q

Describe chronic mucocutaneous candidiasis.

A

Presents in infancy/childhood and is usually inherited

Associated with hypothyroidism or hypoparathyroidism or hypoadrenalism or idiopathic

Recurrent oral, skin and nail infections

Skin lesions crusted on face and scalp = “Candida granuloma”

Immunological abnormality involved

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28
Q

Describe angular cheilitis.

A

4-8% of infants

HIV+ = much increased risk

Affects corners of mouth, across lips and tongue

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29
Q

How does Candida infection affect interdigital regions?

A

Moist, wet, sore

30
Q

What causes onychomycosis and paronychia and how do they present?

A

Candida

Discolouration and swollen and red bed of nails

31
Q

Describe intertrigo.

A

Candida infection

Submammary region

Red, scaly with satellite lesions

32
Q

What are risk factors for Candida infection?

A

Occlusion of skin (fingerwebs, finger nails, obesity)

Wetness in folds

Diabetes

33
Q

Describe nappy dermatitis.

A

Affects buttocks, perianal and groin regions (nappy rash)

Erythema, scaling and satellite lesions

Candida may be a primary or secondary invader (damage due to urine and faecal matter)

34
Q

What are some disposing factors to systemic candidiasis?

A

Age

Immune state or suppression

Antibiotics

Abdominal surgery

Catheters

Prolonged hospitalisation

35
Q

What areas are affected in systemic candidiasis?

A

Blood

Lungs

Internal organs

Skin

36
Q

List the virulence factors/mechanisms of Candida albicans.

A

Able to adapt to changes in environment

Able to adhere to different surfaces

Produces destructive enzymes (aspartyl proteinases, phospholipases, hyaluronidase)

Can change cellular morphology to avoid recognition

Produce biofilm structures as protection

Evade host defence (kill monocytes, block degranulation)

Produce toxins (candidalysin)

37
Q

What surfaces/molecules is Candida albicans able to adhere to?

A

Has surface molecules that bind to iC3b, fibrinogen, laminin, epithelial cells

Can aggregate with Streptococci and Fusobacterium

38
Q

Describe the destructive enzymes produced by Candida albicans.

A

Secreted aspartyl proteinases, phospholipases, hyaluronidase

Degrade ECM proteins to get nutrition and enable invasion

Secreted aspartyl proteinases (SAP) have roles in adherence, invasion and development of disease

39
Q

What are the functions of the different secreted aspartyl proteinases in Candida albicans infection?

A

1, 2, 3 = active during adhesion and are critical for mucosal infection

1 = skin penetration

4, 5, 6 = active in systemic infection

40
Q

How can Candida albicans evade host defence mechanisms?

A

Block ROS production and degranulation of PMNs

Kill monocytes

Immunomodulatory effects of cell wall components cause cytokine release and complement activation

41
Q

What is the toxin produced by Candida albicans and what does it do?

A

Candidalysin

Cytolytic peptide secreted during hyphal invasion which damages tissues and activates the immune response

42
Q

Describe cryptococcosis.

A

Chronic

Subacute to acute pulmonary infection resulting from inhalation of Cryptococcus yeasts

On dissemination, shows predilection for CNS –> cryptococcal meningtitis

43
Q

What is Cryptococcus neoformans associated with?

A

Large amounts of bird droppings

44
Q

Which patients are at major risk of cryptococcosis?

A

HIV/AIDs

45
Q

Which Cryptococcal yeast is associated with large amounts of bird droppings?

A

Cryptococcus neoformans

46
Q

Which Cryptococcal yeast is more likely to infect healthy people and what is it associated with?

A

Cryptococcus gattii

Trees and soil

47
Q

In what form does Cryptococcus grow?

A

Yeast form only - no hyphae

48
Q

What is the major virulence factor of Cryptococcus?

A

Capsule - protective against drugs and prevents phagocytosis

49
Q

Are mould infections endogenous or exogenous?

A

Exogenous

50
Q

What are some predisposing factors to mould infections?

A

History of trauma to the site

Host immune status - affects extent, duration and outcome of systemic infection

Underlying disease

Exposure to souce

Portal of entry

51
Q

What kind of infections do dermatophytes cause?

A

Tinea (superficial infections) - “ringworm fungi”

52
Q

Who can be affected by dermatophytes and how is it spread?

A

Infects healthy and immunocompromised people

Spread between people, animals and soil

53
Q

What organism causes tinea?

A

Dermatophyte (mould)

54
Q

Why do dermatophytes affect hair, skin and nails?

A

Uses keratin as a substrate

55
Q

What is the commonest cause of skin and nail mould infections?

A

Trichophyton rubrum

56
Q

What is the commonest cause of hair/scalp mould infection?

A

Trichophyton tonsurans

57
Q

Describe tinea capitis.

A

Highly contagious scalp infection of children, often a bacterial infection too

Highest incidence before puberty as sebum production inhibits fungal growth

Minor trauma required to inoculate (scratching, sharing hats)

More severe in immunocompromised than healthy but equal incidence

Scaling, hair loss/patchy alopecia, mild erythema

Lymphadenopathy at back of neck, kerion

58
Q

What is a kerion?

A

Painful inflammatory mass where the body is fighting infection

59
Q

Considering tinea capitis, why do we clean the headrest/chairs between patients?

A

Endothrix hair infection - spores within hair shaft and breakage will release them

Clean to prevent spread to other patients

60
Q

What pathogenicity mechanisms do dermatophytes have?

A

Adherence with adhesins, enzymes and fibrillar projections on cell surface

Invasion with phospholipases, subtilisins, MMPs, carboxy proteinases

Use a sulphite pump to reduce disulphide bonds in keratin to allow cleavage and access

Immunomodulatory effect via cell wall mannans which suppress lymphoproliferative activity

Different enzymes produced by fungi when attacking different hosts

61
Q

What are the two main types of mould?

A

Dermatophytes

Aspergillus

62
Q

Describe Aspergillus.

A

Common in environment (ubiquitous) but uncommon infections

Often infects immunocompromised hosts and cause systemic infection

Involved in decay of leaves (compost), highest during autumn

Disease type determined by host status

63
Q

Name some of the commonest Aspergillus species.

A

A. fumigatus

A. flavus

A. nidulans

A. niger

A. terreus

64
Q

Why are Aspergillus species referred to as a “species complexes”?

A

Each species comprises of closely-related organisms that can only be distinguished genetically

65
Q

What is allergic aspergillosis?

A

Temporary presence of Aspergillus in respiratory tract in healthy hosts

Mainly affects agricultural and horticultural workers

66
Q

What is aspergilloma?

A

Inhalation of Aspergillus and colonisation of pre-existing cavities in lungs and form a fungal ball

Predisposed by anything that causes lung cavitation but otherwise healthy hosts

67
Q

Describe invasive aspergillosis.

A

Caused by A. fumigatus

Has a pulmonary focus but can disseminate

Linked to immunocompromised hosts

68
Q

What is systemic aspergillosis?

A

When invasive aspergillosis leaves lungs and spreads to other organs, brain

Only immunocompromised hosts

69
Q

What may cause cutaneous aspergillosis?

A

Primary infection from skin damage and entry

Secondary infection due to dissemination/systemic aspergillosis by travelling via blood

Usually A. fumigatus or A. flavus

70
Q

How is A. flavus often linked to food (eg peanuts)?

A

In contaminated food (peanuts usually), produces aflatoxin

Causes aflatoxicosis when ingested so affects all hosts

Liver damage and death

71
Q

Which Aspergillus species is most common?

A

A. fumigatus

BDS2 PMI (21 decks)

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