Actinomyces and Candida Flashcards

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1
Q

What are actinomyces?

A

Gram pos filamentous bac, uneven staining, sometimes show branching

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2
Q

How many actinomyces species exist?

A

21 species - 5 cause majority of disease in man

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3
Q

List the main actinomyces that cause disease

A
A.isreelii - most frequent in actinomycosis, sometimes with AA
A.oris - 2nd most freq
A.odontolyticus - important in caries
A.gerencseriae - caries
A.meyeri - brain abscess
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4
Q

What is the habitat of actinomyces species?

A

Mouth, gut, vagina

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5
Q

How is actinomyces cultured in the lab?

A

Fastidious - usually use brain-heart infusion
Microaerophilic/facultatively anaerobic
Slow growing - 3-7 days - colonies look like molar teeth

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6
Q

What is Actinomycosis?

How to diagnose it?

A

Rare infec disease
Painful slow growing abscess - months
Affected people often just had dental treatment, poor oh, PD

Diagnosis - microbiological culture, immunoassay, MRI

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7
Q

Where is actinomycosis located?

A
  • Cervicofacial - 55-65% = acute, painful or chronic indolent (little pain) with sinus - no lymphadenopathy
  • Abdominopelvic - 10-20% IUDs
  • Thoracic - aspiration
  • Cerebral - mucosal break
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8
Q

Entry of actinomycosis?

A

Mucosal break

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9
Q

Histological presentation of actinomycosis?

A

Chronic inflam, fibrosis, eosinophilic terminal clubs

In pus - sulphur granules

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10
Q

Pathogenic factors of actinomyces?

A
No toxins or aggressive enzymes
Virulence associated with;
- Induction of chronic inflam
- Walling off from defences
- Slow growth as large aggregates in a matrix
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11
Q

Treatment of actinomycosis?

A
Surgical drainage
Antibiotics - 6-8 weeks:
- Amoxicillin
- Penicillin
- Tetracycline
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12
Q

What is candida?

A
Dimorphic fungus; can exist as a:
- Blastospore (round)
- Hyphae
- Chlamydospores (oval)
Cause opportunistic infecs
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13
Q

List candida species

A
C.albicans - most frequent
C.tropicalis
C.krusei
C.glabrata
C.dubliniensis
C.auris - 2009 increasing systemic infection
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14
Q

Candida species habitat?

A

Mouth, gut, vagina

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15
Q

How to culture and identify candida? (how to grow it)

A
  • Sabouraud’s dextrose medium - creamy colonies
  • C.albicans - germ tube test = 3hr in serum, 37°C
  • Sugar utilisation tests = as sole source of carbon
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16
Q

Candidosis features?

A
Predisposing factor
Affects mucosa and/or skin - systemic infec uncommon but serious 
Red lesions - epi disrupted
Oral
Vulvo-vaginal
Cutaneous; mucocutaneous
Bronchopulmonary
Systemic - endocarditis, septicaemia
17
Q

Name the types of oral candidosis and their features

A

Acute pseudomembranous (thrush) (when white layer removed = red underneath)

Chronic atrophic = associated with dentures, not very painful just irritating - difficult to eat

Chronic hyperplastic = forms in gap in tissues, more difficult to rub off, associated with premalignant lesions, speckled white lesions

Acute atrophic = tongue is cracked and split, usually on dorsum of tongue

Erythematous-HIV = red lesions

Angular chelitis = at corners of mouth, cracking of mucosa

18
Q

Predisposing factors of candidosis?

A

Prostheses - no exfoliation
Low saliva - no flow; soluble defences
- Low pH indued by high sugar diet
Antibiotics - reduced bacterial competition
Immuno-suppression - no cellular defence - diabetes

19
Q

Pathogenic factors of candida?

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

Ph<6 favours blastospores
Ph>7 favours hyphae production

C.albicans - IL-10 (immunosuppressive) slow TNFα production, no IL-12 or IFNγ, C. albicans avoid host defence
Phospholipids
Adhesins - Ala3 or Ssa1 bind to E-cadherin
Acid by-products of metabolism - cause cell damage

20
Q

Treatment of candida?

A
Identify and remove predisposing factor 
Antifungal drugs;
- Nystatin = topical, polyenes
- Miconazole = topical, imidazoles
- Fluconazole = systemic, imidzoles
- Amphotericin B = systemic, polyenes

Polyenes - bind to ergosterol, membrane leakage
Imidazoles - inhibit cytochrome P450 demethylase = affects membrane synthesis