Actinomycosis: Actinomyces israelii Complex

Question 1

Classify Actinomyces israelii:

Answer 1

Gram +
Pleomorphic non-spore forming
Non-acid-fast anaerobic

branching filament-like structure to resemble fungal hyphae

Question 2

Is Actinomyces israelii a normal flora organism?

Answer 2

Yes.

Found in mouth and GI tract.

Question 3

4 diseases this bug can cause:

Answer 3

1) Pulmonary actinomycosis
2) Facial actinomycosis
3) Jaw actinomycosis (lumpy jaw)
4) GI infections

Question 4

How can this bug cause disease?

Answer 4

Opportunistically.

• -endogenous after local trauma, organisms invade tissues (dental plaque, tonsillar crypts, deep infections, trauma surgery)
• -post injury environment has low oxygen, so they multiply
• -forms a chronic disease

Question 5

When they cause disease, how do they present locally?

Answer 5

• -Bacteria burrow sinuses tracts to skin/mucosa
• -Painless eroding abcesses form over damaged mucous membranes
• -These abscesses contain hard yellow sulfur granules (mycelial masses) in their pus

Question 6

Dx of this pathogen requires:

Answer 6

1) aspiration material with sulfur granules
2) Gram stain, IF stain, histopathology
3) Slow growth on blood culture

Question 7

Tx for this pathogen?

Answer 7

IV penicillin for 4-6 weeks followed by oral penicillin for months

Alternatively, give them tetracyclines, macrolides, or clindamycin.

Question 8

Presentation of pulmonary actinomycosis?

Answer 8

1) Chest pain with deep breath + SOB
2) Sputum producing cough
3) Lethargy, night sweats, weight loss

**initially looks like pneumonia or TB. May take months for good dx

Question 9

BONUS: What alternative abx would definitely NOT work in treating this pathogen?

Answer 9

Aminoglycosides.

These abx require oxygen in order for them to work. (they enter cells via an oxygen dependent electron chain transport mechanism)

*Actinomycosis is an anaerobe.