Concepts in microbiology - fungi Flashcards

1
Q

What does mycology mean?

A

study of fungi

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2
Q

What are medical mycologists?

A

scientists who study pathogenic fungi

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3
Q

What is mycotoxicology?

A

the study of fungal toxins and their effects

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4
Q

What are mycoses (s. mycosis)?

A

diseases caused by fungi

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5
Q

Which domain are fungi a part of?

A

eukaryota

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6
Q

What is the variation in size and complexity of fungi?

A

Can be microscopic single cell yeasts, macroscopic mushrooms, humungous fungus

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7
Q

Beneficial impacts of mycology

A

fungi are decomposers, used as industrial fermenters (foods, beverages, and steroids, antibiotics, drugs), used to model eukaryotes in research

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8
Q

Detrimental impact of fungi

A

cause of many animal and plant diseases

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9
Q

How is DNA in fungi arranged?

A

fungi is eukaryotic so DNA is arranged into chromosomes

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10
Q

Example of fungi having different morphological states

A

hyphae (can be 100s times the biovolume of a different fungi)

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11
Q

Examples of eukaryotic microbes

A

yeasts and molds

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12
Q

Are yeasts multi or unicellular?

A

unicellular

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13
Q

How do yeasts reproduce?

A

Budding (a form of asexual reproduction in which nucleus divides by mitosis)

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14
Q

What colour do yeasts appear in a gram stain?

A

Blue/purple because they are gram positive (due to cell wall)

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15
Q

How do fungi gain their nutrients?

A

they are heterotrophs

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16
Q

Use of yeasts

A

ferment beer, wine, bread

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17
Q

How are yeasts grown in vitro?

A

25-37C, acidic conditions, enriched with Sabouraud’s dextrose, potato dextrose, nutrients

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18
Q

Are molds uni or multicellular?

A

multicellular

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19
Q

How can molds reproduce?

A

Sexual or asexual (sporulation) reproduction

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20
Q

Usual habitat for molds

A

dark/moist conditions

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21
Q

How do molds grow?

A

grow in multicellular, fibre-like structures called hyphae

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22
Q

Components of the cell wall of fungi

A

chitin, glucans, glycoproteins

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23
Q

What is the most abundant component of the fungi cell wall?

A

Glucans

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24
Q

Components of fungi cell membrane

A

phospholipids and ergosterol (equivalent to cholesterol)

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25
Q

Which component of the fungi cell membrane is a target for some antifungals?

A

ergosterol

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26
Q

Why is the fungi cell wall a key virulence factor?

A

Cell wall can be reorganised

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27
Q

Dimorphic meaning

A

ability to have different shape/phenotype/morphism

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28
Q

Examples of single cell fungi demonstrating dimorphism

A

spores, yeasts, pseudohyphae, hyphae, filaments

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29
Q

How many people do fungal infections kill annually?

A

2 - 3.75 million

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30
Q

Examples of fungi on WHO’s priority list

A

invasive candidiasis, invasive aspergillosis, cryptococcosis, cryptococcal meningitis, crytococcaemia, azole and multidrug resistance fungi (Candida auris)

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31
Q

Scale of fungal infection severity

A

superficial, cutaneous, subcutaneous, opportunistic, invasive

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32
Q

Name of group of fungi that affect hair, skin and nails (superficial / cutaneous)

A

dermatophytes (require keratin)

33
Q

What are subcutaneous fungal infections?

A

Fungal infections beneath the skin caused by ubiquitous organisms entering (found in environment)

34
Q

What are opportunistic fungal infections?

A

When common commensals become pathogenic if the host is vulnerable

35
Q

When may a patient be vulnerable to opportunistic fungal infections?

A

on immunosuppressants, antibiotics, suffering from disease, diabetes

36
Q

Example of fungus that has multidrug resistance

A

Candida auris

37
Q

What is a mycobiome?

A

Total composition of fungal species in a community

38
Q

Which part of the body has the most diverse fungi ecosystem?

A

oral cavity

39
Q

What is candidiasis?

A

group of infections affecting different tissues of the oral cavity

40
Q

What fraction of the world’s population has a fungal infection?

A

1/3 rd

41
Q

What type of eukaryotic microbes are Candida?

A

yeasts

42
Q

Name of imbalance of common commensals

A

dysbiosis

43
Q

Name of most commonly isolated yeast

A

Candida albicans

44
Q

Why is Candida albicans problematic?

A

It has multidrug resistance (not a common commensal)

45
Q

What stage of fungal infection severity do Candidiasis infections fall into?

A

Opportunistic (common commensals that become pathogenic in immunocompromised individuals)

46
Q

Why did Hippocrates call Candidiasis “a disease of the diseased”?

A

Candidiasis is usually a second infection to other diseases and disorders

47
Q

Examples of risk factors for oral candidiasis

A

HIV, diabetes, dentures, antibiotics and corticosteroids, smoking, cancer

48
Q

How may HIV lead to Candidiasis infection?

A

HIV immunosuppressant reduces T cells, enabling proliferation of Candida

49
Q

How may diabetes lead to Candidiasis?

A

High glucose allows proliferation of Candida

50
Q

How many corticosteroids lead to Candidiasis?

A

The reducing in inflammation in tissues reduces number of immune cells.

51
Q

How may antibiotics lead to Candidiasis?

A

Wipes out normal bacterial flora allowing proliferation of Candida

52
Q

What is denture stomatitis?

A

Candida oral infection caused by combination of poor oral hygiene, ill fitting dentures (inflammation) and Candida plaque.

53
Q

Example of Candida virulence factor

A

mycotoxins

54
Q

Which is the most common and most virulent type of Candidiasis (can be over 70%)?

A

Candida albicans (one of only a few Candida pathogens)

55
Q

Why is Candida albicans the most common Candida?

A

C. albicans has a large number of virulence factors allowing it to evade and persist in the environment.

56
Q

Examples of C. albicans virulence factors

A

adhesion, biofilm formation, phenotypic switching, thigmotropism (tissue penetration)

57
Q

Example of polymorphic switching of Candida

A

Budding to produce unicellular yeast form, or can switch to hyphal /pseudo hyphal states (polymorphic)

58
Q

How can the morphology of Candida act as a mechanical force?

A

Formation of hyphae can physically damage and invade host tissues by exerting pressure.

59
Q

Factors that may trigger change in Candida morphology

A

temperature, serum, pH, nutrient starvation, osmolarity, stress

60
Q

Biofilm definition

A

matrix-enclosed microbial (bacterial + fungal) populations that are adherent to each other and/or surfaces.

61
Q

Stages in biofilm formation

A

adhesion, initiation (proliferation), maturation, dispersal

62
Q

How does the biofilm aid bacterial and fungal communities?

A

provides protection from immune system, antifungals, detergent and antiseptics. Allows sharing of nutrients and resources.

63
Q

Examples of proteins that are virulence factors of Candida

A

ALS (agglutinin-like sequence), HWP1 (hyphal cell wall protein), SAP’s (secreted aspartyl proteinases)

64
Q

What are ALS?

A

Agglutinin-like sequence. Gene for glycoprotein that helps Candida adhesion

65
Q

What is HWP1?

A

Gene that encodes a surface mannoprotein (Hyphal cell wall protein) which aids covalent binding to buccal cells.

66
Q

What are SAP’s?

A

Secreted Aspartyl Proteinases which are involved in phenotypic switching, adhesion, cavitation, invasion and nutrient acquisition from the host.

67
Q

Which antifungals do SDCEP and NICE guidelines indicate should be used for oral candidiasis?

A

Azole and Polyenes

68
Q

Which common antiseptic has a high efficacy against Candida species?

A

CHX

69
Q

What is the most commonly used antifungal class of drug?

A

Azoles including Fluconazole

70
Q

What do the antifungals echinocandins target?

A

Inhibits beta-glucan synthesis in cell wall of fungi

71
Q

What do the antifungals azoles target?

A

inhibit the synthesis of ergosterol which reduces membrane integrity

72
Q

What do the antifungals polyenes target?

A

Bind to ergosterol and reduce pores causing membrane disruption

73
Q

Changes that can cause antifungal resistance

A

overexpression of cellular components (e.g. ergosterol), mutations of target, changes in drug transporter expression

74
Q

What are High Biofilm Formers (HBF)?

A

Some strains of the same Candida species that are more readily able to form a biofilm due to heterogeneity.

75
Q

What is heterogeneity?

A

genetic and metabolic differences. Heterogeneity of Candida species plays a large role in biofilm formation.

76
Q

Why do HBFs confer a higher drug resistance?

A

Because these strains from a thicker biofilm. Biofilm reduces the permeability of antimicrobials.

77
Q

What does polymicrobial refer to?

A

Fungi associating with commensal and pathogenic bacteria (more than one infectious agent)

78
Q

Examples of infections that are polymicrobial

A

denture stomatitis, endodontic infections, caries, periodontal disease, angular cheilitis