Actinomyces and Candida

Question 1

What are actinomyces?

Answer 1

Gram pos filamentous bac, uneven staining, sometimes show branching

Question 2

How many actinomyces species exist?

Answer 2

21 species - 5 cause majority of disease in man

Question 3

List the main actinomyces that cause disease

Answer 3

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

Question 4

What is the habitat of actinomyces species?

Answer 4

Mouth, gut, vagina

Question 5

How is actinomyces cultured in the lab?

Answer 5

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

Question 6

What is Actinomycosis?

How to diagnose it?

Answer 6

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

Diagnosis - microbiological culture, immunoassay, MRI

Question 7

Where is actinomycosis located?

Answer 7

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

Question 8

Entry of actinomycosis?

Answer 8

Mucosal break

Question 9

Histological presentation of actinomycosis?

Answer 9

Chronic inflam, fibrosis, eosinophilic terminal clubs

In pus - sulphur granules

Question 10

Pathogenic factors of actinomyces?

Answer 10

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

Question 11

Treatment of actinomycosis?

Answer 11

Surgical drainage
Antibiotics - 6-8 weeks:
- Amoxicillin
- Penicillin
- Tetracycline

Question 12

What is candida?

Answer 12

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

Question 13

List candida species

Answer 13

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

Question 14

Candida species habitat?

Answer 14

Mouth, gut, vagina

Question 15

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

Answer 15

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

Question 16

Candidosis features?

Answer 16

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

Question 17

Name the types of oral candidosis and their features

Answer 17

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

Question 18

Predisposing factors of candidosis?

Answer 18

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

Question 19

Pathogenic factors of candida?

Answer 19

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

Question 20

Treatment of candida?

Answer 20

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