Actinomyces viscosus

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Actinomyces viscosus
Scientific classification edit
Domain: Bacteria
Phylum: Actinomycetota
Class: Actinomycetia
Order: Actinomycetales
Family: Actinomycetaceae
Genus: Actinomyces
A. viscosus
Binomial name
Actinomyces viscosus
(Howell et al. 1965) Georg et al. 1969 (Approved Lists 1980)
  • "Odontomyces viscosus" Howell et al. 1965

Actinomyces viscosus is a human and animal pathogen/pathobiont which colonises the mouths of 70% of adult humans.[1] A. viscosus has a low level of virulence and is often mistaken with other actinomycetes.[1]


A. viscosus is Gram-positive, facultatively anaerobic, rod-shaped, and filamentous.[2] It grows slowly on nonselective media, forming gray and white colonies.[citation needed]


a)Chest X-ray and b,c) thorax computed tomography scan revealing multifocal pneumonia

A. viscosus causes periodontal disease in animals and has been isolated from human dental calculus and root surface caries, as well as the oral cavity of hamsters and actinomycotic lesions in swine, cats, and dogs.[3][4] Furthermore, it has been shown to cause endocarditis in humans.[5] A. viscosus has also been known to cause lung infections, but only in very few cases.[1] Infections are treatable with penicillin for three-week therapies.[1]


A. viscosus infection symptoms are indistinguishable from Actinomyces israelii infection symptoms or Actinomyces bovis infection symptoms.[1] A. israelii and A. bovis infections usually cause actinomycotic infections, but sometimes and very rarely will the pathogen be A. viscosus.[1] A. viscosus colonies test positive for catalase and negative for indole.[1][6]


Multiple-week antibiotic therapies have cured actinomycotic infections caused by A. viscosus in every recorded case.[1] Therapies include treatment with penicillin, sulfadimethoxine, flucloxacillin, clindamycin, tetracycline, and ticarcillin.[1] A. viscosus is usually resistant to vancomycin, metronidazole, cefalexin, and dicloxacillin.[1] Treatments last at least three weeks, with some exceptions.[1] Although A. viscosus is difficult to distinguish from other closely related actinomycetes, the general determination of being an actinomycete is sufficient for treatment of infections.[citation needed]


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Eng, RH; Corrado, ML; Cleri, D; Cherubin, C; Goldstein, EJ (January 1981). "Infections caused by Actinomyces viscosus". American Journal of Clinical Pathology. 75 (1): 113–6. doi:10.1093/ajcp/75.1.113. PMID 7457420.
  2. Kunkel, Dennis. "Oral bacterium - Actinomyces viscosus". Dennis Kunkel Microscopy, Inc. Archived from the original on 22 December 2015. Retrieved 19 December 2015.
  3. "Actinomyces viscosus. (n.d.)". Medical Dictionary for the Dental Professions. Archived from the original on 22 December 2015. Retrieved 19 December 2015.
  4. "Actinomyces viscosus". Archived from the original on 12 October 2015. Retrieved 19 December 2015.
  5. Mardis, JS; Many, WJ Jr (February 2001). "Endocarditis due to Actinomyces viscosus". Southern Medical Journal. 94 (2): 240–3. doi:10.1097/00007611-200194020-00014. PMID 11235043.
  6. Gerencser, Mary; Slack, John (1 April 1969). "Identification of Human Strains of Actinomyces viscosus" (PDF). Applied and Environmental Microbiology. 18: 80–87. doi:10.1128/AEM.18.1.80-87.1969. PMID 4896106. Archived (PDF) from the original on 25 November 2016.

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