''Actinomyces viscosus'' is a human and animal pathogen/pathobiont which colonises the mouths of 70% of adult humans. ''A. viscosus'' has a low level of

virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its ability to ca ...

and is often mistaken with other actinomycetes.

Morphology

''A. viscosus'' is Gram-positive, facultatively anaerobic,

rod-shaped A bacillus (), also called a bacilliform bacterium or often just a rod (when the context makes the sense clear), is a rod-shaped bacterium or archaeon. Bacilli are found in many different taxonomic groups of bacteria. However, the name ''Bacillu ...

, and filamentous. It grows slowly on nonselective media, forming gray and white colonies.

Pathogenesis

''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. Furthermore, it has been shown to cause

endocarditis Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the ...

in humans. ''A. viscosus'' has also been known to cause lung infections, but only in very few cases. Infections are treatable with

penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...

for three-week therapies.

Diagnosis

''A. viscosus'' infection symptoms are indistinguishable from Actinomyces israelii infection symptoms or Actinomyces bovis infection symptoms. ''A. israelii'' and ''A. bovis'' infections usually cause actinomycotic infections, but sometimes and very rarely will the pathogen be ''A. viscosus''. ''A. viscosus'' colonies test positive for

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...

and negative for indole.

Treatment

Multiple-week antibiotic therapies have cured actinomycotic infections caused by ''A. viscosus'' in every recorded case. Therapies include treatment with penicillin,

sulfadimethoxine Sulfadimethoxine (or sulphadimethoxine, trade names Di-Methox or Albon) is a long-lasting sulfonamide antimicrobial medication used in veterinary medicine. It is used to treat many infections, including respiratory, urinary tract, enteric, and so ...

, flucloxacillin,

clindamycin Clindamycin is an antibiotic medication used for the treatment of a number of bacterial infections, including osteomyelitis (bone) or joint infections, pelvic inflammatory disease, strep throat, pneumonia, acute otitis media (middle ear infec ...

tetracycline Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections, including Acne vulgaris, acne, cholera, brucellosis, plague (disease), plague, malaria, and sy ...

, and

ticarcillin Ticarcillin is a carboxypenicillin. It can be sold and used in combination with clavulanate as ticarcillin/clavulanic acid. Because it is a penicillin, it also falls within the larger class of beta-lactam antibiotics. Its main clinical use is as an ...

. ''A. viscosus'' is usually resistant to

vancomycin Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infections, ...

metronidazole Metronidazole, sold under the brand name Flagyl among others, is an antibiotic and antiprotozoal medication. It is used either alone or with other antibiotics to treat pelvic inflammatory disease, endocarditis, and bacterial vaginosis. It is ef ...

cefalexin Cefalexin, also spelled cephalexin, is an antibiotic that can treat a number of bacterial infections. It kills gram-positive and some gram-negative bacteria by disrupting the growth of the bacterial cell wall. Cefalexin is a beta-lactam antibi ...

, and dicloxacillin. Treatments last at least three weeks, with some exceptions. 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.

References

External links

Type strain of ''Actinomyces viscosus'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q2690800 Actinomycetales Gram-positive bacteria