''Actinomyces'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of the

Actinomycetia The Actinomycetia are a class of bacteria. Taxonomy The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI). * Acidothermales Sen et ...

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 among ...

. 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 bacte ...

. ''Actinomyces'' species are

facultatively anaerobic A facultative anaerobic organism is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent. Some examples of facultatively anaerobic bacteria are ''Staphylococcus' ...

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., no ...

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 ''Bacillu ...

, ''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 from th ...

-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 Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

, 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 describ ...

, 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 te ...

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 t ...

of animals, including the

human microbiota This article lists some of the species recognized as belonging to the human microbiome. Whole-body distributed *''Acinetobacter calcoaceticus'' *'' Burkholderia cepacia'' *''Pseudomonas pseudoalcaligenes'' *''Peptostreptococcus spp'' Natur ...

. They are known for the important role they play in

soil ecology Soil ecology is the study of the interactions among soil organisms, and between biotic and abiotic aspects of the soil environment. It is particularly concerned with the cycling of nutrients, formation and stabilization of the pore structure, the ...

; 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 ...

, 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 m ...

. Certain species are

commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...

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 Oral microbiology is the study of the microorganisms (microbiota) of the oral cavity and their interactions between oral microorganisms or with the host. The environment present in the human mouth is suited to the growth of characteristic microo ...

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 mi ...

, 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 animals ...

. 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 laceration, lacerated or puncture wound, punctured skin (an ''open'' wound), or a bruise, contusion (a ''closed'' wound) from blunt force physical trauma, trauma or compression. In pathology, a '' ...

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 immune ...

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 spec ...

''. Like various other anaerobes, ''Actinomyces'' species are

fastidious A fastidious organism is any organism that has complex or particular nutritional requirements. In other words, a fastidious organism will only grow when specific nutrients are included in its medium. The more restrictive term fastidious microorga ...

, 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.Tyl ...

and

isolate Isolate may refer to: Arts, entertainment, and media * ''Isolate'' (film), a 2013 Australian film * ''Isolate'' (Circus Maximus album), 2007 * ''Isolate'' (Gary Numan album), 1992 Language * Isolating language, with near-unity morpheme/word ...

. 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 an ...

''.

Genomics

Phylogenetic trees A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

based on

16S ribosomal RNA 16 S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as 16S rRNA ...

(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 The ''rpoB'' gene encodes the β subunit of bacterial RNA polymerase and the homologous plastid-encoded RNA polymerase (PEP). It codes for 1342 amino acids in ''E. coli'', making it the second-largest polypeptide in the bacterial cell. It is targe ...

, 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 animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...

. In rare cases, these bacteria can cause

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 ...

, 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 b ...

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 organ (biology), organs of the digestive syste ...

. 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 to b ...

'' 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 rever ...

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 using ...

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 mic ...

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 diagnos ...

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 ...

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