Actinomyces is a genus of the Actinomycetia class of bacteria. They all are Gram-positive and facultatively anaerobic, growing best under anaerobic conditions.
Actinomyces species are , occurring in soil and in the microbiota 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, and chitin. Thus, their presence is important in the formation of compost. Certain species are commensalism in the skin flora, oral flora, gut flora, and vaginal flora
Like various other anaerobes, Actinomyces species are fastidious, thus not easy to culture 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.
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
Gyrase 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.
In rare cases, these bacteria can cause
actinomycosis, a disease characterized by the formation of
in the mouth, lungs, or the gastrointestinal tract.
Actinomycosis is most frequently caused by
A. israelii, which may also cause
endocarditis, 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 devices. In extreme cases, pelvic abscesses might develop. Treatment of pelvic actinomycosis associated with intrauterine devices involves removal of the device and antibiotic treatment.[Joshi C, Sharma R, Mohsin Z. Pelvic actinomycosis: a rare entity presenting as tubo-ovarian abscess. Arch Gynecol Obstet. 2010 Feb;281(2):305-6]
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 or
amoxicillin 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
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A. bovis Harz 1877 (Approved Lists 1980)
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A. bowdenii Pascual et al. 1999
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" A. capricornis" Saito et al. 2021
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A. catuli Hoyles et al. 2001
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" A. culturomici" Fonkou et al. 2018
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A. dentalis Hall et al. 2005
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A. denticolens Dent and Williams 1984
-
A. faecalis Zhou et al. 2021
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A. gaoshouyii Meng et al. 2017
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A. gerencseriae Johnson et al. 1990
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" A. glycerinitolerans" Palakawong Na Ayudthaya et al. 2016
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A. graevenitzii Pascual Ramos et al. 1997
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A. haliotis Hyun et al. 2014
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" A. houstonensis" Clarridge and Zhang 2002
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A. howellii Dent and Williams 1984
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" A. ihuae" Fonkou et al. 2018
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" A. ihumii" Ndongo et al. 2016
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A. israelii (Kruse 1896) Lachner-Sandoval 1898 (Approved Lists 1980)
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A. johnsonii Henssge et al. 2009
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A. lilanjuaniae Li et al. 2019
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" A. lingnae" Clarridge and Zhang 2002
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A. marmotae Yang et al. 2021
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" A. marseillensis" Fonkou et al. 2018
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A. massiliensis Renvoise et al. 2009
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" A. mediterranea" Fonkou et al. 2018
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" A. minihominis" Bilen et al. 2018
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A. naeslundii corrig. Thompson and Lovestedt 1951 (Approved Lists 1980)
-
" A. oralis" Fonkou et al. 2018
-
A. oricola Hall et al. 2003
-
Actinomyces oris Henssge et al. 2009
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" A. pacaensis" Fonkou et al. 2018
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" A. polynesiensis" Cimmino et al. 2016
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A. procaprae Yang et al. 2021
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" A. provencensis" Ndongo et al. 2017
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A. qiguomingii Zhu et al. 2020
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A. radicidentis Collins et al. 2001
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A. respiraculi Zhou et al. 2021
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A. ruminicola An et al. 2006
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A. slackii Dent and Williams 1986
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" A. succiniciruminis" Palakawong Na Ayudthaya et al. 2016
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A. timonensis Renvoise et al. 2010
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A. trachealis Zhou et al. 2021
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" A. urinae" Morand et al. 2016
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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 of actinomycosis, H&E stain
Image:Actinomycosis GROCOTT'S.JPG|Micrograph of actinomycosis, GMS stain
Image:Actinomycosis GRAM'S.JPG|Micrograph of actinomycosis, Gram stain
External links
