''Actinomyces'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of the Actinomycetia class of

bacteria 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 am ...

. They all are

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 bact ...

. ''Actinomyces'' species are facultatively anaerobic and they grow best under anaerobic conditions. ''Actinomyces'' species may form

endospore An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive of a spore or seed-like form (''endo'' means 'within'), but it is not a true spore (i.e., n ...

s, and while individual bacteria are

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 '' Baci ...

, ''Actinomyces'' colonies form

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

-like branched networks of

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

e. The aspect of these colonies initially led to the incorrect assumption that the organism was a fungus and to the name ''Actinomyces'', "ray fungus" (from Greek , ray or beam, and , fungus). ''Actinomyces'' species are

ubiquitous Omnipresence or ubiquity is the property of being present anywhere and everywhere. The term omnipresence is most often used in a religious context as an attribute of a deity or supreme being, while the term ubiquity is generally used to descr ...

, occurring in

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

and in the

microbiota Microbiota are the range of microorganisms that may be commensal, symbiotic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found ...

of animals, including the human microbiota. They are known for the important role they play in soil ecology; they produce a number of enzymes that help degrade organic plant material,

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity a ...

, and

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

. Thus, their presence is important in the formation of

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...

. Certain species are commensal in the

skin flora Skin flora, also called skin microbiota, refers to microbiota ( communities of microorganisms) that reside on the skin, typically human skin. Many of them are bacteria of which there are around 1,000 species upon human skin from nineteen phyla.P ...

, oral flora,

gut flora Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut m ...

, and

vaginal flora Vaginal flora, vaginal microbiota or vaginal microbiome are the microorganisms that colonize the vagina. They were discovered by the German gynecologist Albert Döderlein in 1892 and are part of the overall human flora. The amount and type of ...

of humans and

livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to ani ...

. They are also known for causing diseases in humans and livestock, usually when they opportunistically gain access to the body's interior through

wound A wound is a rapid onset of injury that involves lacerated or punctured skin (an ''open'' wound), or a contusion (a ''closed'' wound) from blunt force trauma or compression. In pathology, a ''wound'' is an acute injury that damages the epider ...

s. As with other

opportunistic infection An opportunistic infection is an infection caused by pathogens (bacteria, fungi, parasites or viruses) that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened immun ...

s, people with

immunodeficiency Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...

are at higher risk. In all of the preceding traits and in their branching filament formation, they bear similarities to ''

Nocardia ''Nocardia'' is a genus of weakly staining Gram-positive, catalase-positive, rod-shaped bacteria. It forms partially acid-fast beaded branching filaments (acting as fungi, but being truly bacteria). It contains a total of 85 species. Some sp ...

''. Like various other anaerobes, ''Actinomyces'' species are fastidious, thus not easy to

culture Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups ...

and isolate. Clinical laboratories do culture and isolate them, but a negative result does not rule out infection, because it may be due simply to reluctance to grow ''

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology a ...

''.

Genomics

Phylogenetic trees based on 16S ribosomal RNA (16SrRNA) sequences have shown that the genus ''Actinomyces'' is quite diverse, exhibiting polyphyletic branching into several clusters. The genera ''Actinomyces'' and '' Mobiluncus'' form a monophyletic clade in a phylogenetic tree constructed using RpoB, RpoC, and DNA gyrase B protein sequences. This clade is also strongly supported by a

conserved signature indel Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers ...

consisting of a three-amino-acid insertion in isoleucine tRNA synthetase found only in the species of the genera ''Actinomyces'' and ''Mobiluncus''.

Pathology

Actinomycota are normally present in the gums, and are the most common cause of infection in dental procedures and oral abscesses. Many ''Actinomyces'' species are opportunistic pathogens of humans and other mammals, particularly in the oral cavity. In rare cases, these bacteria can cause actinomycosis, a disease characterized by the formation of

abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends ...

es in the mouth, lungs, or the

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

. Actinomycosis is most frequently caused by ''A. israelii'', which may also 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 ...

, though the resulting symptoms may be similar to those resulting from infections by other bacterial species. ''

Aggregatibacter actinomycetemcomitans ''Aggregatibacter actinomycetemcomitans'' is a Gram-negative, facultative anaerobe, nonmotile bacterium that is often found in association with localized aggressive periodontitis, a severe infection of the periodontium. It is also suspected t ...

'' has been identified as being of note 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 caus ...

. The genus is typically the cause of oral-cervicofacial disease. It is characterized by a painless "lumpy jaw". Lymphadenopathy is uncommon in this form of the disease. Another form of actinomycosis is thoracic disease, which is often misdiagnosed as a neoplasm, as it forms a mass that extends to the chest wall. It arises from aspiration of organisms from the oropharynx. Symptoms include chest pain, fever, and weight loss. Abdominal disease is another manifestation of actinomycosis. This can lead to a sinus tract that drains to the abdominal wall or the perianal area. Symptoms include fever, abdominal pain, and weight loss.El Sahli, MD, MS. "Anaerobic Pathogens." ''Infectious Disease Module 2007.'' Baylor College of Medicine, 2007. ''Actinomyces'' species have also been shown to infect the central nervous system in a dog "without history or evidence of previous trauma or other organ involvement." Pelvic actinomycosis is a rare but proven complication of use of

intrauterine device An intrauterine device (IUD), also known as intrauterine contraceptive device (IUCD or ICD) or coil, is a small, often T-shaped birth control device that is inserted into the uterus to prevent pregnancy. IUDs are one form of long-acting revers ...

s. In extreme cases, pelvic abscesses might develop. Treatment of pelvic actinomycosis associated with intrauterine devices involves removal of the device and antibiotic treatment.

Diagnosis

Actinomycosis may be considered when a patient has chronic progression of disease across tissue planes that is mass-like at times, sinus tract development that may heal and recur, and refractory infection after a typical course of antibiotics.

Treatment

Treatment for actinomycosis consists of antibiotics such as

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 usin ...

amoxicillin Amoxicillin is an antibiotic medication used to treat a number of bacterial infections. These include middle ear infection, strep throat, pneumonia, skin infections, and urinary tract infections among others. It is taken by mouth, or less c ...

for 5 to 12 months, as well as surgery if the disease is extensive.

Species

The genus ''Actinomyces'' comprises the following species: * "'' A. actinomycetemcomitans''" Iinuma et al. 1994 * "'' A. bouchesdurhonensis''" Fonkou et al. 2018 * '' A. bovis'' Harz 1877 (Approved Lists 1980) * '' A. bowdenii'' Pascual et al. 1999 * "'' A. capricornis''" Saito et al. 2021 * '' A. catuli'' Hoyles et al. 2001 * "'' A. culturomici''" Fonkou et al. 2018 * '' A. dentalis'' Hall et al. 2005 * '' A. denticolens'' Dent and Williams 1984 * '' A. faecalis'' Zhou et al. 2021 * '' A. gaoshouyii'' Meng et al. 2017 * '' A. gerencseriae'' Johnson et al. 1990 * "'' A. glycerinitolerans''" Palakawong Na Ayudthaya et al. 2016 * '' A. graevenitzii'' Pascual Ramos et al. 1997 * '' A. haliotis'' Hyun et al. 2014 * "'' A. houstonensis''" Clarridge and Zhang 2002 * '' A. howellii'' Dent and Williams 1984 * "'' A. ihuae''" Fonkou et al. 2018 * "'' A. ihumii''" Ndongo et al. 2016 * '' A. israelii'' (Kruse 1896) Lachner-Sandoval 1898 (Approved Lists 1980) * '' A. johnsonii'' Henssge et al. 2009 * '' A. lilanjuaniae'' Li et al. 2019 * "'' A. lingnae''" Clarridge and Zhang 2002 * '' A. marmotae'' Yang et al. 2021 * "'' A. marseillensis''" Fonkou et al. 2018 * '' A. massiliensis'' Renvoise et al. 2009 * "'' A. mediterranea''" Fonkou et al. 2018 * "'' A. minihominis''" Bilen et al. 2018 * '' A. naeslundii'' corrig. Thompson and Lovestedt 1951 (Approved Lists 1980) * "'' A. oralis''" Fonkou et al. 2018 * '' A. oricola'' Hall et al. 2003 * '' A. oris'' Henssge et al. 2009 * "'' A. pacaensis''" Fonkou et al. 2018 * "'' A. polynesiensis''" Cimmino et al. 2016 * '' A. procaprae'' Yang et al. 2021 * "'' A. provencensis''" Ndongo et al. 2017 * '' A. qiguomingii'' Zhu et al. 2020 * '' A. radicidentis'' Collins et al. 2001 * '' A. respiraculi'' Zhou et al. 2021 * '' A. ruminicola'' An et al. 2006 * '' A. slackii'' Dent and Williams 1986 * "'' A. succiniciruminis''" Palakawong Na Ayudthaya et al. 2016 * '' A. timonensis'' Renvoise et al. 2010 * '' A. trachealis'' Zhou et al. 2021 * "'' A. urinae''" Morand et al. 2016 * '' A. urogenitalis'' Nikolaitchouk et al. 2000 * '' A. viscosus'' (Howell et al. 1965) Georg et al. 1969 (Approved Lists 1980) * '' A. vulturis'' Meng et al. 2017 * '' A. weissii'' Hijazin et al. 2012 * '' A. wuliandei'' Zhu et al. 2020

Gallery

Image:Actinomyces - high mag.jpg,

Micrograph A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken on a m ...

of actinomycosis,

H&E stain Hematoxylin and eosin stain ( or haematoxylin and eosin stain or hematoxylin-eosin stain; often abbreviated as H&E stain or HE stain) is one of the principal tissue stains used in histology. It is the most widely used stain in medical diag ...

Image:Actinomycosis GROCOTT'S.JPG, Micrograph of actinomycosis, GMS stain Image:Actinomycosis GRAM'S.JPG, Micrograph of actinomycosis,

Gram stain In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish b ...

References

External links

''Actinomyces'' naeslundii MG1 Genome Page''Actinomyces'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q312213 Actinomycetales Gram-positive bacteria Bacteria genera es:Actinomycetes nl:Actinomycetes