Actinomycosis

Actinomycosis is rare, chronic bacterial infection which results in a slowly progressive granulomatous disease.

• the bacteria which is a filamentous Gram positive anaerobic bacteria from the Actinomycetaceae family (genus Actinomyces) is a normal colonizing organism of the human oropharynx, gastrointestinal tract, and urogenital tract.
• it is mainly an endogenous infection where a breech in the mucous membrane results in bacteria invading the local structures and organs and causing a disease
• A israelii is the commonest human pathogen while less common species include A naeslundii, A odontolyticus, A viscosus, A meyeri, A turicensis, and A radingae.

Often the bacteria coexists with other normal commensals e. g - Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans), fusobacteria, bacteroides, staphylococci (including S aureus),streptococci (including β haemolytic streptococci and S pneumoniae), or Enterobacteriaceae but precise pattern of organisms depends on the site of infection (1).

The infection spreads along the fascial planes and occasionally by the blood-stream, but not via the lymphatics.

Thermophilic actinomycetes found in hay are the cause of the extrinsic allergic alveolitis termed farmer's lung.

Reference

1. Wong VK, Turmezei TD, Weston VC. Actinomycosis. BMJ. 2011;343:d6099