Actinomyces is a genus of facultatively anaerobic, gram-positive bacteria belonging to the Actinomycetaceae family. These microorganisms are commonly found in soil and in the oral and intestinal flora of animals and humans. Actinomyces species are shaped like rods or cocci, with branching filaments that resemble fungal hyphae.
Infections caused by Actinomyces, known as actinomycosis, are usually chronic and localized to soft tissue, bones, or lungs. The pathogenesis of the disease usually occurs due to the disruption of the mucosal barrier, allowing the microorganism to invade adjacent tissues. Diagnosing actinomycosis can be challenging due to its similarity to other bacterial and fungal infections.
Taxonomically, the genus Actinomyces is divided into several species, the most common being A. israelii, A. naeslundii, and A. odontolyticus. Recent studies have explored the genetic diversity and virulence of these species, aiming to improve the diagnosis and treatment of Actinomyces infections.
Understand what actinomycosis is and its clinical and microbiological characteristics.
Actinomycosis is a chronic infection caused by bacteria of the genus Actinomyces, which are gram-positive anaerobic bacilli. These bacteria are part of the normal microbiota of the oral cavity, gastrointestinal tract, and female genital tract. Infection with Actinomyces It usually occurs when there is trauma to the mucosa, allowing these bacteria to invade the underlying tissues.
The clinical features of actinomycosis include abscess formation with purulent pus drainage, the presence of sulfur granules, fibrosis, and fistula formation. Abscesses can spread to neighboring tissues, leading to serious complications if not treated appropriately.
From a microbiological point of view, bacteria of the genus Actinomyces are strictly aerobic and grow slowly in culture media. They form yellowish-white colonies with a filamentous appearance and a slimy texture. Accurate identification of these bacteria requires specific laboratory techniques, such as biochemical analysis and the Gram stain.
Regarding taxonomy, the species most commonly associated with actinomycosis are Actinomyces israelii e Actinomyces naeslundii, but other species of the genus may also be involved. These bacteria are sensitive to some antibiotics, such as penicillin and clindamycin, and are the standard treatment for infection by Actinomyces.
In short, actinomycosis is a chronic bacterial infection caused by bacteria of the genus Actinomyces, which presents distinct clinical characteristics, such as abscesses with purulent pus drainage and fistula formation. From a microbiological perspective, these bacteria are strictly aerobic and grow slowly in culture media. Treatment for actinomycosis involves the use of specific antibiotics, such as penicillin and clindamycin.
How is Actinomyces bacteria transmitted?
The transmission of bacteria Actinomyces It occurs primarily through direct contact with contaminated secretions from infected individuals. This bacterium is part of the normal microbiota of the mouth, throat, and intestines of humans and animals and can cause infections when the mucosal barrier is disrupted.
When there is an injury to the mucosa, whether due to trauma, surgery or other factors, bacteria Actinomyces Bacteria present in the oral cavity can invade adjacent tissues, leading to chronic and suppurative infections. Furthermore, ingesting contaminated food can also be a route of transmission of the bacteria.
It is important to emphasize that the transmission of Actinomyces It is not as common as that of other pathogenic bacteria, and generally occurs in individuals with some type of immunosuppression or condition that favors colonization and invasion of tissues.
Therefore, preventing the transmission of the bacteria Actinomyces includes maintaining good oral hygiene, appropriate treatment of mucosal lesions, and adopting infection control measures in healthcare settings.
Treatment for actinomycosis: learn how to effectively combat this bacterial infection.
Actinomycosis is a rare bacterial infection caused primarily by the bacterium Actinomyces. This condition can affect various parts of the body, including the lungs, brain, abdomen, and skin. To effectively combat this infection, proper treatment is essential.
Treatment for actinomycosis typically involves prolonged use of antibiotics, such as penicillin or amoxicillin, for six to twelve months. In more severe cases, surgical procedures may be necessary to drain abscesses or remove infected tissue.
Furthermore, it's important to maintain good hygiene and take care of the patient's overall health, including a healthy diet and physical activity. Regular medical follow-up is also essential to monitor the progress of treatment and prevent potential complications.
In short, treatment for actinomycosis requires long-term antibiotics, combined with surgical procedures in more severe cases. Following medical advice and maintaining healthy habits are essential to effectively combat this bacterial infection.
Actinomyces: characteristics, taxonomy, morphology, pathogenesis
Actinomyces is a genus of bacteria composed of Gram-positive bacilli, characterized by a filamentous growth pattern similar to tree branches. In the past, this genus was mistaken for fungi due to its morphology, but later it was discovered that its species behave like bacterial agents.
There are 42 identified species, but its main species are : A. israelii, A. naeslundii, A. odontolyticus, A. viscosus, A. meyeri, A. pyogenes, A. georgiae, A. turicensis, A. gerencseriae, A. graevenitzii.
This bacterial genus is part of the usual microbiota of the gastrointestinal tract in humans and animals, ranging from the oropharynx to the colon.
Recently, it has been suggested that this organism could be a relatively common residing organism residing in the skin and mucous membranes of the urogenital region.
These species are highly adapted to living on the surface of mucous membranes without causing damage. However, they can cause infections when they cross the epithelial barrier under conditions that produce oxygen tension low enough to produce multiplication (tissue necrosis).
Therefore, the pathologies they produce are not contagious, as the infection occurs endogenously, through trauma, surgery or a foreign body.
Among the most frequent pathologies are orocervicofacial, thoracic and abdominoplasty actinomycosis. The disease can also appear as cutaneous actinomycosis, musculoskeletal disease, pericarditis, central nervous system (CNS) infection or disseminated disease.
Features
Some species are strictly anaerobic, while others are microaerophilic. They grow slowly; some strains require up to 7 days or more to emerge.
They grow at 35 to 37°C. They are non-motile and do not form spores. Like acid-fast bacilli, their cell wall bears some resemblance to that of mycobacteria.
Os Actinomyces have low virulence potential, causing disease are breached only when mucosal barriers, trauma, surgery or inflammation – infection, favored by conditions of low O tissue pressure 2 .
Actinomyces infection promotes pelvic invasion of other germs, such as Escherichia coli , streptococci, anaerobic bacteria, among others.
Usual microbiota
They appear at an early age as oral and gastrointestinal microbiota. One study found that 2-month-old babies were already colonized by A . odontolytic in the oral cavity.
At 2 years of age there is already a wide variety of species A. naeslundii, A. viscosus, A. graevenitzii and A. gerencseriae at the time of eruption of deciduous teeth.
Actinomyces species have been described to play a central role in the early stages of biofilm formation on teeth (dental plaque), both above (supragingival) and below (subgingival) the gum line.
This continues into adulthood and is not related to periodontal disease. However, A. turicensis was found to be the most common species of Actinomyces on the surface of the tongue in patients with halitosis, followed by A. odontolyticus, A. israelii and A. radingae.
Similarly, some species of this genus have been isolated from the female urogenital tract in the absence of actinomycete infection. They are considered native microbiota, which migrated from the perineal area or as a result of oral sex and anovaginal intercourse.
Among them are A. meyeri, A. neuii, A. radingae, A. turicensis and A. urogenitalis.
On the other hand, the following species were isolated from urine samples: A. neuii, A. turicensis, A. urogenitalis, A. europaeus, A. odontolyticus, A. graevenitzii, A. naeslundii and A. oris as an integral part of the female bladder microbiota.
Meanwhile, A. Socranski is a normal colonizer of the vagina, colon and mouth.
Biochemical characteristics
General growth characteristics
Taxonomy
Domain: Bacteria.
Phylum: Actinobacteria.
Order: Actinomycetales.
Suborder: Actinomycineae.
Family: Actinomycetaceae.
Genre Actinomyces.
Morphology
They are Gram-positive bacilli measuring 1 µm in diameter but of variable length, as they can form branched or unbranched filaments. They can also be presented as short diphtheria bacilli or in the form of a club.
Depending on the species, they can grow slowly, moderately, or rapidly on blood agar. Their colonies are rough or smooth, depending on the strain involved.
The color of colonies on blood agar varies according to the species, including white, gray, red or translucent, and may be opaque or shiny and have irregular or lobed edges.
In infected human tissue, they are concentrated as microcolonies, together with tissue elements, which form yellow-orange granules, called sulfur granules because of their similarity to sulfur grains.
Pathologies
Actinomycosis
It is a chronic inflammatory and granulomatous condition that originates in the tissues adjacent to mucosal surfaces. The lesions follow a slow course of lateral and deep expansion with considerable induration and draining fistulas.
Its exact nature depends on the organs and structures involved. It is more common in adult patients and in males.
Signs and symptoms can be very nonspecific, such as swelling, cough, low-grade fever, and weight loss.
Diagnosis is often difficult, as the observation of a growing fibrotic mass, which spreads across tissue planes, can be confused with a malignant tumor.
Among the types of actinomycosis are:
Cervicofacial actinomycosis
It's related to poor dental hygiene, tooth extraction, or trauma to the mouth or jaw. It causes lymphadenopathy.
Infection can lead to bisphosphonate-related osteonecrosis of the jaw.
The most isolated species in this type of lesion are A. israelii (42%), A. gerencseriae (26,7%), A. naeslundii e A. viscosus (9%), while A. odontolyticus, A. meyeri, A. georgiae e A. neuii subsp. neuii se recovers occasionally.
Thoracic actinomycosis
They are uncommon and result from traumatic aspiration or introduction of infected oropharyngeal material that leads to erosion through the pleura, chest, or abdominal wall. They can also enter through the bloodstream, but this is rarer.
In the case of thoracic actinomycosis, a differential diagnosis with lung cancer, pneumonia and tuberculosis is necessary.
Actinomyces graevenitzii has a special predilection for the thoracic area, with Actinomyces being the main isolated from this type of infection.
However, A. meyeri, A. israelii, A. odontolyticus e A. cardiffensis recovered from actinomycotic lesions in the pulmonary sites and sporadically A. naeslundii and A. viscosus.
Abdominal-pelvic actinomycosis
Abdominal actinomycosis occurs primarily as a consequence of invasive procedures such as laparoscopic cholecystectomy, missed gallstones, or abdominal infections such as appendicitis.
Although pelvic actinomycosis has been associated with prolonged use of intrauterine contraceptive devices (chronic endometritis). This occurs because the microorganism grows in a synthetic intrauterine medium attaching and forming spider-like colonies until a porous biofilm is established.
Another form of infection is after certain manipulations, such as transvaginal oocyte retrieval, which can lead to a tubo-ovarian abscess due to Actinomyces.
Actinomyces naeslundii, A. meyeri , A. israelii, A. funkei, A. odontolyticus e A. turicensis are the most isolated in the disturbances abdominals.
In the pelvic A. israelii A. odontolyticus , A. urogenitalis, A. hongkongensis, A. cardiffensis and A. turicensis are the most frequent.
Cutaneous actinomycosis
Cutaneous actinomycosis is usually a secondary infectious process, with an underlying focus in the deeper tissues, with a tendency to form fistulas through which the characteristic granules flow.
They can rarely appear as a result of hematogenous spread of an actinomycotic lesion anywhere in the body.
Manifestations with single or multiple draining breasts can occur in various locations on the body, including the face, chest, diaphragm, hips, and upper and lower extremities.
Actinomyces meyeri and A. viscosus have been the most frequently isolated strains in cutaneous actinomycosis.
Musculoskeletal Actinomycosis
It is possible to see cases of osteomyelitis in the spine; the organism can isolate the cerebrospinal fluid and the entire spinal cord, which can leave the patient with severe neurological symptoms.
Actinomyces israelii e A. meyeri are the most frequent in this case.
Cerebral actinomycosis
Actinomycotic lesions in the central nervous system cause the most severe form of actinomycosis.
Actinomyces organisms usually gain access to this area, either by hematogenous spread from remote sites or directly through local actinomycotic lesions of the head. The disease usually presents as one or several brain abscesses.
The possibility of actinomycosis in the CNS should be suspected, especially in patients with neurological symptoms and a history of actinomycosis in other parts of the body.
Actinomyces israelii e A. naeslundii are the most important species in this type of injury.
Discovery
Diagnosis is based on the nature of the lesion, the course of slow progression, and the history of trauma or disease that predisposes to mucosal invasion by Actinomyces.
Diagnosis is difficult because microorganisms are generally scarce in the pus, as they are concentrated in microcolonies of sulfur granules deeply hidden in the hardened tissue.
On the other hand, these lesions are often contaminated with other bacteria, mainly Gram-negative bacilli, which divert or confuse the real etiological diagnosis, if an aerobic culture is taken into account.
The infallible diagnosis is given by biopsy (histopathological study) if it is possible to observe that the sulfur granules have diagnostic value.
For histopathological study, the granules are crushed, stained with Gram and observed under a microscope.
The study will reveal a core of typical Gram-positive intertwined branching filaments, with individual bacilli branching at the periphery, surrounded by inflammatory cells, mainly polymorphonuclear neutrophils.
However, several samples may need to be examined before granules are observed, as they are scarce.
Treatment
The first is debridement of the lesion and then antibiotic treatment.
Penicillin G is the treatment of choice for actinomycosis. Ampicillin, doxycycline, erythromycin, and clindamycin are also active. Penicillin treatment should be prolonged (6 to 12 months) and in high doses.
Prevention
It is important for physicians to prescribe prophylactic treatment each time they perform surgical procedures in the oral cavity and gastrointestinal tract.
This may prevent the invasion and progression of diseases caused by Actinomyces.
In general, the prognosis is excellent if the diagnosis is made and treatment is followed.
References
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- López-Olmos J, Gasull J. and Vivar B. Actinomyces and mixed infections in cervicovaginal cytology in IUD carriers. Clin Invest Gin Obst. 2010; 37 (4): 134–140
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