Colon
Infectious colitis
Actinomycosis
Author: Elliot Weisenberg, M.D.
Topic Completed: 1 January 2017
Minor changes: 7 December 2020
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: actinomycosis
Table of Contents
Definition / general | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Prognostic factors | Case reports | Treatment | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Differential diagnosis | Additional referencesCite this page: Weisenberg E. Actinomycosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colonactinomycosis.html. Accessed April 19th, 2021.
Definition / general
- Infection of large intestine by actinomycotic microorganisms
- Colonic actinomycosis is a subset of abdominal actinomycosis, but some sources do not discriminate between actinomycosis of abdomen and pelvis
- Other common sites are oral cervicofacial actinomycosis ("lumpy jaw", see secondary chronic osteomyelitis), skin, thoracic and pelvic (cervix, kidney, ovary)
Epidemiology
- Rare, but abdominal actinomycosis comprises 15 - 20% of actinomycosis in humans
- Males are more commonly affected
Sites
- Most common site is cecum, most often with concurrent ileal disease
- Some cases are secondary to disease in appendix or female genital tract
Pathophysiology
- Due to infection by anaerobic or microaerophilic, saprophytic bacteria of genus Actinomyces, a normal commensal of mouth, large intestine, vagina
- Disruption of mucosa is necessary for disease - causes are trauma, surgery, diverticular disease, ingestion of foreign body, or less commonly other inflammatory processes
- In surgery related cases, disease may appear months after perforation leading to appendectomy or bowel resection, but without evidence of actinomycosis at the time
- In some cases, no inciting event is identified; rare cases may originate through hematogenous spread
- While actinomycotic colonies may dominate the histologic picture, it is likely that companion, or "co-pathogenic" bacteria may also be necessary for disease to occur, possibly by lowering oxygen tension
Etiology
- Actinomyces israelii is the most common etiologic agent; however, at least five other species are implicated in human disease
- Using comparative 16s ribosomal RNA, some bacteria traditionally associated with actinomycotic disease have been reclassified as Aracanobacterium, Actinobaculum or Cellulomonas
Clinical features
- Usually indolent disease, but more severe in immunocompromised patients
- Patients usually present with non-specific symptoms including abdominal pain, fever, change in bowel habits, sensation of a mass
- Imaging studies reveal a mass-like lesion, cystic lesion or an abscess, often suggestive of malignancy
- May coexist with other inflammatory lesions of colon with fistula or sinuses
- Clumps of yellow bacteria known as sulfur granules are characteristically present
- No cases of human to human transmission have been reported and Actinomyces has not been cultured from nature
Diagnosis
- Usually by tissue biopsy or resection where the characteristic microorganisms are seen
- Abdominal actinomycosis is rarely suspected clinically and most patients are diagnosed after major surgery
- Diagnosis by microbiologic culture is uncommon as strict anaerobic conditions are necessary and antibiotics interfere with growth in culture
Prognostic factors
- Most patients respond well to therapy
Case reports
- 17 year old boy with mass over sigmoid colon (APSP J Case Rep 2011;2:4)
- 38 year old woman with severe large bowel obstruction (Scand J Infect Dis 2006;38:231)
- 41 year old man with renal, colonic and retroperitoneal actinomycosis (West Afr J Med 2005;24:343)
- 50 year old woman with combined intra- and extraabdominal actinomycosis (Rom J Gastroenterol 2004;13:337)
- 53 year old man with abdominal actinomycosis containing a fish bone (Surg Today 2006;36:187)
- 57 year old liver transplant recipient with abdominal actinomycosis (Transpl Infect Dis 2012;14:86)
- 58 year old man with actinomycosis simulating malignant large bowel obstruction (Braz J Infect Dis 2004;8:186)
- 63 year old man with abdominal actinomycosis and multiple myeloma (Oncol Lett 2014;8:1876)
- 67 year old woman with actinomycosis of the sigmoid colon (World J Gastrointest Surg 2009;1:62)
- 72 year old woman with ascending colon actinomycosis mimicking cancer (BMC Gastroenterol 2005 Jan 4;5:1)
- 74 year old woman with abdominal actinomycosis (Acta Clin Belg 2014;69:152)
- 79 year old man with colonic actinomycosis invading abdominal wall (Int J Surg Case Rep 2010;1:9)
Treatment
- Prolonged high dose antibiotics
- Even with advanced clinical disease, most patients can be effectively treated with medical management alone; however, this is very uncommon with abdominal disease
Gross images
Images hosted on other servers:
Sigmoid colon mass
Microscopic (histologic) description
- Characteristic clumps of basophilic filamentous bacteria in a vaguely rosette-like configuration surrounded by acute inflammatory cells are characteristic
- Acute inflammation is accompanied by dense fibrosis described as "woody"
- Eosinophilic clubs may be found at periphery (Splendore-Hoeppli phenomena)
- Granulomatous inflammation may be present
Microscopic (histologic) images
Contributed by Asmaa Gaber Abdou, M.D.
Intestinal actinomycosis
Images hosted on other servers:
Bacteria and sulfur granules
Colonies of actinomyces
Gram+ staining
Filamentous microorganisms (GMS)
Negative stains
- Regular and modified acid fast stains
Differential diagnosis
- Chronic granulomatous infection
- Malignancy (especially by imaging)
- Nocardiosis
