Actinomycosis pathophysiology

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

Overview

Actinomycosis is a chronic pyogenic bacterial infection caused by Actinomyces species. Infection most frequently follows dental work, trauma, surgery, or other medical conditions

Pathophysiology

  • Actinomycosis is caused by the bacteria Actinomyces. The pathophysiology of Actinomycosis can be described in the following steps. [1]

Transmission

  • Actinomyces are part of natural flora of human body,resides in the oral cavity, lower gastrointestinal tract and urogenital tract.[2]
  • 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.
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[3]

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

Genetics

There is no known genetic association to Actinomycosis

Microscopic pathology

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

References

  1. Volante M, Contucci AM, Fantoni M, Ricci R, Galli J (2005). "Cervicofacial actinomycosis: still a difficult differential diagnosis". Acta Otorhinolaryngol Ital. 25 (2): 116–9. PMC 2639881. PMID 16116835.
  2. Peipert, Jeffrey F. (2004). "Actinomyces: Normal Flora or Pathogen?". Obstetrics & Gynecology. 104 (Supplement): 1132–1133. doi:10.1097/01.AOG.0000145267.59208.e7. ISSN 0029-7844.
  3. Smego RA (1987). "Actinomycosis of the central nervous system". Rev Infect Dis. 9 (5): 855–65. PMID 3317731.

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