Pathogenesis and Immunity
Actinomyces species are present as normal flora of the oral cavityand also in the lower gastrointestinal tract and female genital tract of human hosts.
These companion bacteria are believed to act as copatho-gens that enhance the virulence of Actinomyces. These com-panion bacteria include Bifidobacterium dentium, Actinobacillusactinomycetemcomitans, Eikenella corrodens, Haemophilus aphrophi-lus,Bacteroides, Fusobacterium, staphylococci, and anaerobicstreptococci.
Once the infection is established by Actinomyces, the immune system of the infected human host stimulates an intense inflammatory response in the form of a suppurative granulo-matous and fibrotic reaction. Infection by Actinomyces typically spreads contiguously and invades surrounding tissues and organs. Finally, the infection results in the production of drain-ing sinus tracts, which contain lot of damaged tissue. Bacteria from this site may disseminate through blood circulation to distant organs.