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Microbiology (DEN 303) > Actinomyces and Candida > Flashcards

Actinomyces and Candida Flashcards

Morphology and pathogenic features of Actinomyces and Candida species Main pathological conditions caused by these organisms Aspects of treatment

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1
Q

Actinomyces are

A

Gram-positive filaments, unevenly staining, sometimes showing branching

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2
Q

Actinomyces species

A

21 species - 5 cause majority of disease in man

  • A. israelii
  • A. oris (naeslundii)
  • A. odontolyticus
  • A. gerencseriae
  • A. meyeri
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3
Q

A. israelii

A

Most frequent in actinomycosis

-sometimes with Ag. actinomycetemcomitans

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4
Q

A. oris (naeslundii)

A

2nd most frequent

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5
Q

A. odontolyticus

A

Important in caries

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6
Q

A. gerencseriae

A

Important in caries

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7
Q

A. meyeri

A

Brain abscess

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8
Q

Actinomyces habitat

A

Mouth, gut, vagina

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9
Q

Actinomyces culture

A

Fastidious - usuallu use brain-heart infusion
Microaerophilic/ facultatively anaerobic
Slow growing - 3-7 days, ‘molar tooth’ colonies

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10
Q

Actinomycosis cervicofacial

A

55-65%
Acute painful
Chronic indolent with sinus
No lymphadenopathy

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11
Q

Abdominopelvic actinomycosis

A

10-20% ileocaecal; IUDs

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12
Q

Thoracic actinomycosis

A

Aspiration; farmer’s lung

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13
Q

Cerebral Actinomycosis

A

Haematogenous spread

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14
Q

Locations of actinomycosis

A

Cervicofacial
Abdominopelvic
Thoracic
Cerebral

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15
Q

Actinomycosis entry

A

Mucosal break

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16
Q

Actinomycosis histology

A

Chronic inflammation, fibrosis, eosinophilic terminal clubs

17
Q

Actinomycosis in pus

A

‘Sulphur granules’

18
Q

Actinomyces pathogenic factors

A 
No toxins, no aggressive enzymes
Virulence associated with
-induction of chronic inflammation
-walling off from defences
-slow growth as large aggregates in a matrix
19
Q

Actinomyces treatment

A 
Attempt at thorough surgical drainage
Antibiotics - 6-8 weeks
-amoxicillin
-penicillin
-tetracycline
20
Q

Candida

A

Dimorphic fungus (trimorphic)

  • blastospore (yeast)
  • hyphae
  • chlamydospores
21
Q

Candida species

A 
C. albicans (most frequent)
C. tropicalis
C. krusei
C. glabrata
C. dubliniensis
22
Q

Candida habitat

A

Mouth, gut, vagina

23
Q

Candida culture and identification

A 
Sabouraud's dextrose medium - creamy colonies
C. albicans - germ-tube test
-3hr in serum, 37 degrees C
Sugar utilisation tests
-as sole source of carbon
24
Q

Candidosis

A 
Predisposing factor
Affects mucosa and/ or skin
-systemic infection uncommon but serious
Oral
Vulvo-vaginal
Cutaneous; mucocutaneous
Bronchopulmonary
Systemic - endocarditis, speticaemia
25
Q

Oral candidosis types

A 
Acute pseudomembranous
Chronic atrophic
Chronic hyperplastic
Acute atrophic
Erythematous - HIV
Angular cheilitis
26
Q

Predisposing factors for oral candidosis: mainly

A 
Prosthesis - no exfoliation
Low saliva - no flow; soluble defences 
-low pH induced by high sugar diet
Antibiotics - reduced bacterial competition
Immuno-suppression - no cellular defence
-diabetes
27
Q

Pathogenic factors oral candidosis

A

Hypha - invasive structure
-blastospores - pro-inflammatory cytokines
-hyphae - anti-inflammatory cytokines
Proteases - secreted aspartyl proteases
-sap 1-3 needed for mucosal infection
-sap 1-3 degrade complement
-sap 4-6 contribute to systemic infection
Phospholipases
Adhesins
-e.g. Ala3 and Ssa1 bind to E-cadherin
Acid by-products of metabolism cause cell damage

28
Q

pH on pathogenic factors of oral candidosis

A

pH <6 favours blastospores

pH >7 favours hyphae production

29
Q

Other pathogenic factors C. albicans

A

IL-10 (immuno suppressive)
Slow TNF alpha production
no IL-12 or IFN gamma

30
Q

Treatment of oral candidosis

A 
Identify and remove predisposing factors
Antifungal drugs
-nystatin
-miconazole
-fluconazole
-amphotericin B
31
Q

Topical antifungal drugs

A

Nystatin

Miconazole

32
Q

Systemic antifungal drugs

A

Fluconazole

Amphotericin B

33
Q

Polyenes antifungal drugs

A

Nystatin and amphotericin B

Bind to ergosterol, membrane leakage

34
Q

Imidazoles antifungal drugs

A

Miconazole and fluconazole
Inhibit cytochrome P450 demethylase
-converts lanosterol to ergosterol, so affects membrane synthesis

Microbiology (DEN 303) (8 decks)

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