Actinomycosis is a rare, but serious chronic suppurative bacterial infection most commonly caused by Actinomyces israelii, an anaerobic, Gram-positive, filamentous bacteria, which normally inhabits the flora of the oral cavity, gastrointestinal and genital tract [1,2].
Actinomycosis occurs in the abdominopelvic regions in approximately 20% of the cases [3].
Frequent causative factors [1-4]:
- the integrity disruption of the gastrointestinal mucosa in patients with a history of abdominal surgery, penetrating trauma, accidentally foreign body ingestion, appendicitis, colonic diverticulitis (this allows the spread of actinomyces into the deeper tissues);
- the long-term use of intrauterine contraceptive devices (IUD).
Clinical context [4]:
- indolent and latent disease evolution; extensive dissemination across tissue planes; pseudotumoral features; abscess formation with sinus drainage;
- response to antibiotic therapy; frequent relapses.
Symptoms, laboratory, and imaging findings are nonspecific in most cases; the definite diagnosis is made through microscopic histopathologic evaluation (Fig. 1). The hematoxylin-eosin stain allows the identification of “sulfur granules”, which are conglomerates of Actinomyces species confined in biofilm, while special stains such as Gomori methenamine-silver are necessary to depict the filamentous branching bacteria [1].
Fig. 1: A. Hematoxilin eosin (HE) stain reveals “sulfur granules” surrounded by numerous neutrophils.
B. Gomori methenamine silver (GMS) stain highlights numerous filamentous bacteria - Actinomyces israelii - radiating outwards.
References: Regional Center of Gastroenterology and Hepatology, Department of Radiology - Cluj- Napoca/RO
Treatment:
- prolonged high dose of Penicillin G or Amoxicillin (drugs of choice). Complicated cases require surgical intervention, alongside antibiotic therapy [1].