''Actinomyces'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of the

Actinomycetia Actinomycetia is 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 al ...

class of

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

. 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. The Gram stain is ...

and

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' ...

, growing 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., not ...

s, and while individual bacteria are

rod-shaped Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archae ...

, ''Actinomyces'' colonies form

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

-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 o ...

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: 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 of all kno ...

, 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, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

and in the

microbiota Microbiota are the range of microorganisms that may be commensal, mutualistic, 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 Human microbiota are microorganisms (bacteria, viruses, fungi and archaea) found in a specific environment. They can be found in the stomach, intestines, skin, genitals and other parts of the body. Various body parts have diverse microorganisms. S ...

. They are known for the important role they play in

soil ecology Soil ecology studies interactions among soil organisms, and their environment. It is particularly concerned with the cycling of nutrients, soil aggregate formation and soil biodiversity. Overview Soil is made up of a multitude of physical, ch ...

; 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 rigidit ...

, and

chitin Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...

. 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 Decomposition, decomposing plant and food waste, recycling organic materials, and man ...

. 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 f ...

in the

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

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 micro ...

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 g ...

, 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 ba ...

of humans and

livestock Livestock are the Domestication, domesticated animals that are raised in an Agriculture, agricultural setting to provide labour and produce diversified products for consumption such as meat, Egg as food, eggs, milk, fur, leather, and wool. The t ...

. 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 any disruption of or damage to living tissue, such as skin, mucous membranes, or organs. Wounds can either be the sudden result of direct trauma (mechanical, thermal, chemical), or can develop slowly over time due to underlying diseas ...

s. As with other

opportunistic infection An opportunistic infection is an infection that occurs most commonly in individuals with an immunodeficiency disorder and acts more severe on those with a weakened immune system. These types of infections are considered serious and can be caused b ...

s, people with

immunodeficiency Immunodeficiency, also known as immunocompromise, 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 aff ...

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, catalase-positive, rod-shaped bacteria. It forms partially acid-fast beaded branching filaments (appearing similar to fungi, but being truly bacteria). It contains a total of 8 ...

''. 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 microorgan ...

, thus not easy to

culture Culture ( ) is a concept that encompasses the social behavior, institutions, and Social norm, norms found in human societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, Attitude (psychology), attitudes ...

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'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...

''.

Genomics

Phylogenetic trees A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA. In o ...

based on

16S ribosomal RNA 16S 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 ...

(16SrRNA) sequences have shown that the genus ''Actinomyces'' is quite diverse, exhibiting polyphyletic branching into several clusters. The genera ''Actinomyces'' and ''

Mobiluncus ''Mobiluncus'' is a genus of Gram-positive, anaerobic, rod-shaped bacteria. These bacteria may be stained either Gram-negative or Gram-variable. However, they are classified as Gram-positive rods due to the fact that they possess a Gram-positive ...

'' 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 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 gingiva, 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 A mouth also referred to as the oral is the body orifice through which many animals ingest food and vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also the first part of the alime ...

. In rare cases, these bacteria can cause

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

, 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, usually caused by bacterial infection. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pre ...

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 Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...

. 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, o ...

, though the resulting symptoms may be similar to those resulting from infections by other bacterial species. 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 an 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 a 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 beta-lactam antibiotic, β-lactam antibiotics originally obtained from ''Penicillium'' Mold (fungus), moulds, principally ''Penicillium chrysogenum, P. chrysogenum'' and ''Penicillium rubens, P. ru ...

amoxicillin Amoxicillin is an antibiotic medication belonging to the aminopenicillin class of the penicillin family. The drug is used to treat bacterial infections such as middle ear infection, strep throat, pneumonia, skin infections, odontogenic inf ...

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 is an image, captured photographically or digitally, taken through a microscope or similar device to show a magnify, magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken ...

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 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. It may also be used to diagnose a fungal infection. The name comes ...

References

External links

''Actinomyces'' naeslundii MG1 Genome Page

''Actinomyces'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Authority control Actinomycetales Gram-positive bacteria Pathogenic bacteria Bacteria genera es:Actinomycetes nl:Actinomycetes