''Actinomyces naeslundii'' is a

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bac ...

, rod-shaped

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were a ...

found in the mouth of humans. The species has been implicated in

periodontal disease Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main cau ...

, as well as various tooth cavities. In other cases, ''A. naeslundii'' is associated with good oral health. It is one of the first bacteria to occupy the oral cavity and colonize the

tooth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...

's surface. It has also been isolated from women with

bacterial vaginosis Bacterial vaginosis (BV) is a disease of the vagina caused by excessive growth of bacteria. Common symptoms include increased vaginal discharge that often smells like fish. The discharge is usually white or gray in color. Burning with urinatio ...

Description

''A. naeslundii'' appears

and pleomorphic by

microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of mi ...

. It does not form spores, and is considered

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: *Adhesive#Anaerobic, Anaerobic ad ...

microaerophilic A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than that are present in the atmosphere (i.e. < 21% O₂; typically 2–10% O₂) for optimal growth. A more re ...

. In 2009, the species ''A. naeslundi'' was split. Bacteria formerly known as "''Actinomyces naeslundi'' genospecies 2" were reclassified under the new species name '' Actinomyces oris''. Those formerly known as "''Actinomyces naeslundi'' genospecies WVA 963" were reclassified as '' Actinomyces johnsonii''.

Role in disease

Many species of the genus ''Actinomyces'', including ''A. naeslundii'', cause a chronic disease called

actinomycosis Actinomycosis is a rare infectious bacterial disease caused by ''Actinomyces'' species. The name refers to ray-like appearance of the organisms in the granules. About 70% of infections are due to either ''Actinomyces israelii'' or '' A. gerencseria ...

, which is characterized by swelling and formation of an abscess which may exude

pus Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection ...

. This can be accompanied by tissue fibrosis. Infections of the mouth, face, and neck are the most commonly recognized infections; however, the thoracic region, abdomen, pelvis, and the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

can also be involved.

References

External links

''Actinomyces'' naeslundii MG1 Genome Page

Type strain of ''Actinomyces naeslundii'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
Actinomycetales Bacterial vaginosis Bacteria described in 1951 {{Actinobacteria-stub