Actinomycosis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Pathophysiology

• Actinomycosis is caused by the bacteria Actinomyces.

Transmission

• Actinomyces are part of natural flora of human body,resides in the oral cavity, lower gastrointestinal tract and urogenital tract.
• They are non virulent under normal conditions
• When there is break in the mucosa, anywhere from the mouth to the rectum they reach tissues and cause damage.

Incubation

Incubation period of Actinomycosis varies from one to four weeks. But occasionally, it may be as long as several months. 

Dissemination

Following transmission, lesions spread by direct extension.

Seeding

• Once the endogenous bacteria are introduced into the tissues, they multiply due to low oxygen tension.
• It triggers an inflammatory reaction which results in formation of hard yellow hard granules(sulfur granules).
• These are solidified bacterial filaments with surrounding tissue exudates.
• Abscesses with fibrous walls and pus along with sulfur granules develop.
• It finally drain out through sinuses.

Immune response

Actinomycosis elicits both humoral and cell-mediated immune responses

Microscopic pathology

• Positive for sulphur granules in pus
• Gram positive organism with branching filaments forming segment-like structures
• Surrounded by neutrophils

Types	Site of Infection	Source of infection
Cervicofacial actinomycosis	Neck Jaw Mouth	Dental problems like tooth decay
Thoracic actinomycosis	Lungs Pleura Chest wall Mediastinum	Inhalation of droplets of contaminated fluid Aspiration of oropharyngeal secretions or gastric contents Direct extension of cervicofacial infection into the mediastinum Transdiaphragmatic or retroperitoneal spread from the abdomen Hematogenous spread
Abdominal actinomycosis	Abdomen	Secondary to abdominal infections like appendicitis Accidental swallowing of a foreign body such as chicken bone containing the actinomycetes bacteria Penetrating trauma Perforation of the gut (e.g., the colon or appendix) Surgical manipulation of GI tract
Pelvic actinomycosis	Pelvis	Occurs most commonly in woman as the bacteria passes from the female genitals into the pelvis Long-term use of IUD type of contraceptive
Central nervous system actinomycosis	CNS	Secondary to hematogenous spread from primary infection in the lung, abdomen, or pelvis Direct extension from paranasal sinuses, ears, and cervicofacial regions

References

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