Actinomyces israelii but sometimes also caused by Actinomyces naeslundii.

Clinical picture:

  • Cervicofacial (the most common):
    Commonly occurs after tooth extraction or injury to the oral mucosa. Cheeks become swollen (lumpy jaw). Sometimes the swelling bursts, causing the occurrence of fistula producing pus.
  • Pulmonary:
    Usually preceded by cervicofacial infection. Aspiration of Actinomyces israelii causing this clinical type. Symptoms are cough with purulent sputum accompanied by increased body temperature. If not treated properly it will cause empyema.
  • Abdominal Infection:
    Usually occurs after appendix surgery. Can also occur after perforation of the colon. These infections can occur in all parts of the gastrointestinal tract but most commonly occurs in the caecum and appendix.

Actinomycosis under the microscope with GMS stain

Actinomycosis under the microscope with HE stain

Actinomycosis under the microscope with Gram stain