Introduction

Classification

Taxonomy

• Genus: Actinomyces (Arcanobacterium).
• Family: Actinomycetaceae.
• Order: Actinomycetales.

Etymology

• Gk: actino myces- ray fungus; pyogenes- pus-producing.

Active Forms

Clinical Effects

Epidemiology

Habitat

• Colonizes the mucous membranes and skin of susceptible species.

Lifecycle

• Reproduces on the mucous membranes of the host by binary fission.

Transmission

• Endogenous infection.
• Bites.

Pathological effects

• Killed by phagocytes.
• Man: cell-mediated and humoral allergy - circulating antibody, produced during infection does not confer protection.
• Specific resistance, if any, is probably cell mediated.

• Trauma or infection by another agent   →   stimulates latent infection   →   active infection (Actinomycosis Actinomycosis)   →   pyogranulomatous reaction (bacterial colonies with suppuration)   →   surrounding granulation, mononuclear infiltration and fibrosis.

Cattle, sheep and pigs

• Suppurative mastitis (acute and chronic).
• Suppurative pneumonia.
• Septic arthritis.
• Endometritis.
• Umbilical infections.
• Wound infections. Abscesses.
• Mixed infections withFusobacterium necrophorum.

Bulls and boars

• Seminal vesiculitis.

Cattle alone

• Summer mastitis (mixed infection with an anaerobe, eg Peptostreptococcus indolicus).
• Vegetative endocarditis.

Other Host Effects

• Present on host's skin and mucous membranes - mouth or orophanynx, secondarily gastrointestinal tract.

Control

Control via animal

• Drainage of abscesses.

Control via chemotherapies

• Penicillin G Benzylpenicillin, tetracycline Tetracycline, trimethoprim-sulfamethoxasole Trimethoprim.
  Response to treatment in summer mastitis is disappointing, presumably due to involvement of other bacteria.

Vaccination

• None.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Lynch M, O'Leary J, Murnaghan D et al (1998) Actinomyces pyogenes septic arthritis in a diabetic farmer. J Infect 37 (1), 71-73 PubMed.
• Carlson P, Kontiainen S (1994) Evaluation of a commercial kit in the identification of Arcanobacterium hemolyticum and Actinomyces pyogenes. Eur J Clin Microbiol Infect Dis 13 (6), 507-509 PubMed.