Actinomycosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Actinomycosis is a rare infectious bacterial disease of humans generally caused by Actinomyces israelii, A. gerencseriae and Propionibacterium propionicus. It is characterized by formation of painful abscesses in mouth, lungs, and digestive organs. The abscesses tend to grow larger as the disease progresses. In such conditions, the abscesses may penetrate the surrounding bone, muscle and skin, forming a sinus tract leaking large amounts of pus. Actinomycosis is also seen in cattle and is known as lumpy jaw. as the abscesses tend to grow on the head and neck of the animal.

Acitnomycosis was first discovered in 1877 in cattle by pathologist Otto Bollinger. Later in the same year, James Israel discovered it in humans and classified it under fungal origin. In 1939, Bergey classified to be bacteria.

Actinomycosis can be classified based on the anatomical site involved into^[1]

• Orocervicofacial actinomycosis
• Thoracic actinomycosis
• Abdominopelvic actinomycosis
• Central nervous system actinomycosis
• Musculoskeletal actinomycosis
• Disseminated actinomycosis

Actinomycosis is a chronic pyogenic bacterial infection caused by Actinomyces species. Infection most frequently follows dental work, trauma and surgery. When there is break in the mucosal layer, anywhere from the mouth to the rectum they reach tissues and cause damage. Incubation period of actinomycosis varies from one to four weeks. But occasionally, it may be as long as several months. Actinomycosis elicits both humoral and cell-mediated immune responses.^{[2][3][4][5][6][7]}

Actinomyces is a genus of Gram-positive bacteria. Some species are anaerobic, while others are facultatively anaerobic. Actinomyces species do not form spores, and, while individual bacteria are rod-shaped, morphologically Actinomyces colonies form fungus-like branched networks of hyphae. 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 abscesses in the mouth, lungs, or the gastrointestinal tract.^[8][9][10]

The differential diagnosis of actinomycosis consists of blastomycosis, brain abscess, colon cancer, crohn disease, diverticulitis, liver abscess, lung abscess, lymphoma, nocardiosis, pelvic inflammatory disease, pneumonia, tuberculosis and uterine cancer.

In 1970, its annual incidence was estimated to be 1 per 300,000. Its incidence has been declined due the advent of widespread use of antibiotics following dental surgeries. Actinomycosis is commonly found between 4th to 6th decade of life and very rare in infants and children. Males are more commonly affected by actinomycosis than females.

Common risk factors in the development of actinomycosis include dental abscess, oral surgery, and facial trauma.

According to the Centers for disease control and prevention, screening for actinomycosis is not recommended.

If left untreated, patients with actinomycosis may progress to develop focal organ involvement with mass-like features and dvelopment of sinus tracts (which can heal and reform leading to multiple abscesses complications that can develop as a result of actinomycosis include local extension of disease resulting in osteomyelitis of the mandible, ribs, or vertebrae.The prognosis is generally excellent with prompt and effective antimicrobial treatment in patients in uncomplicated actinomycosis. Mortality range from 0% to 28%.^{[2][3][4][5][6][7][11]}

Actinomycosis can present with diverse clinical presentation, which include systemic flu-like symptoms and symptoms due to focal involvement of organs by the bacteria.^{[12][13][14][15][16][17][5]}

The physical examination findings of actinomycosis are mostly nonspecific and are described according to the organ involved ^[1]

The gold standard for diagnosing actinomycosis is histological examination and bacterial culture.^[18][19]

There are no specific chest X-ray findings for actinomycosis.

Antibiotics are the mainstay of treatment in actinomycosis. The exact antibiotic regimen depends on the site of infection, the severity of disease, and the patient’s response to treatment. For cervicofacial actinomycosis, Ampicillin is administered followed by Penicillin V. Patients with a more extensive disease requires surgery.

Surgery is indicated when the disease involves chest, abdomen, pelvis, and central nervous system (CNS). Surgical resection is required for infected tissue with extensive necrosis and presence of multiple sinus tracts, or fistulas. It is also indicated if malignancy cannot be excluded or if large abscesses cannot be drained by percutaneous aspiration.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S[2]

Actinomycosis was first discovered in 1877 in cattle by pathologist Otto Bollinger. Later in the year, James Israel discovered it in humans and classified it under fungal origin. In 1939, Bergey classified it into bacteria.

• In 1877, pathologist Otto Bollinger discovered for the first time, presence of Actinomyces bovis in cattle
• In 1877, James Israel discovered Actinomyces Israelii in humans.
• In 1890, Eugene Bostroem isolated the causative organism from a culture of grasses, grain, and soil.
• In 1939, Bergey’s Manual of Systematic Bacteriology classified the organism as bacterial.^[1]

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S[2]

Actinomycosis is bacterial infection most commonly involving oro-facial tissues. It can be classified based on the anatomical site involved.

Actinomycosiscan be classified based on the anatomical site involved into^[1]

• Orocervicofacial actinomycosis
• Thoracic actinomycosis
• Abdominopelvic actinomycosis
• Central nervous system actinomycosis
• Musculoskeletal actinomycosis
• Disseminated actinomycosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Actinomycosis is a chronic pyogenic bacterial infection caused by actinomyces species. Infection most frequently follows dental work, trauma, surgery, or other medical conditions. When there is break in the mucosa, anywhere from the mouth to the rectum they reach tissues and cause damage. Incubation period of actinomycosis varies from one to four weeks. But occasionally, it may be as long as several months. Actinomycosis elicits both humoral and cell-mediated immune responses

• Actinomycosis is caused by the bacteria Actinomyces. The pathophysiology of actinomycosis can be described in the following steps. ^{[1][2][3][4][5][6]}

• Actinomyces are part of the natural flora of human body, resides in the oral cavity, lower gastrointestinal tract and urogenital tract.

• They are nonvirulent under normal conditions
• When there is a breach in normal mucosal architecture, anywhere from the mouth to the rectum they enter tissues and cause damage.

Incubation period of actinomycosis varies from one to four weeks.

Following transmission, lesions spread by direct extension.

• Once the endogenous bacteria are introduced into the tissues, they multiply due to low oxygen tension.
• It leads to the formation of hard yellow hard granules (sulfur granules).
• These granules represent solidified bacterial filaments with surrounding tissue exudates.
• These triggers an inflammatory reaction.
• Inflammatory mediators along with various bacterial toxins and proteolytic enzymes from the neutrophils are released leading to abscess formation.
• A fibrous wall develops around the abscess.
• Extension of the abscess to skin leads to the formation of sinus tracts and pus drains out through these sinuses.

Actinomycosis elicits both humoral and cell-mediated immune responses

There is no known genetic association to actinomycosis

On gross pathology, the following features can be noticed:

• Single or multiple abscesses
• Indurated masses with hard fibrous walls and soft central loculations containing white or yellow pus.
• Granules are seen grossly.
• Sinus tracts extended from abscesses to the skin surface or into organs; vertebral bone, and retroperitoneal tissue.
• Pleural, pericardial, or serosal thickening if the infection involves lung, heart, and wall of the bowel.

Microscopic findings include

• Liquefaction type of necrosis in the center of abscess with a surrounding outer layer of granulation tissue along with lymphocytes and neutrophils.
• Gram-positive organism with branching filaments like structures appear as colonies.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Actinomyces israelii is a species of Gram-positive, rod-shaped bacteria within the Actinomyces. Known to live commensally on and within humans, A. israelii is an opportunistic pathogen and a cause of actinomycosis. Many physiologically diverse strains of the species are known to exist, though all are strict anaerobes.^[1]

Actinomycosis is most frequently caused by A. israelii. It is a normal colonizer of the vagina,^[2] colon, and mouth. Infection is established first by a breach of the mucosal barrier during various procedures (dental, gastrointestinal), aspiration, or pathologies such as diverticulitis. The chronic phase of this disease is also known the “classic phase” because the acute, early phase is often missed by health care providers. This is characterized by slow, contiguous growth that ignores tissue planes and forms a sinus tract that can spontaneously heal and recur, leading to a densely fibrotic lesion. This lesion is often characterized as “wooden”. Sulfur granules form in a central purulence surrounded by neutrophils. This conglomeration of organisms is virtually diagnostic of A. israelii.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Based on the organ system involved and duration of symptoms, differential diagnosis of actinomycosis consists of blastomycosis, brain abscess, colon cancer, crohn disease, diverticulitis, liver abscess, lung abscess, lymphoma, nocardiosis, pelvic inflammatory disease, pneumonia, tuberculosis and uterine cancer.

• Actinomycosis is a chronic pyogenic bacterial infection caused by Actinomycesspecies and most commonly involves orocervicofacial region
• It rarely infects other organ systems. If involved it has a wide variety of presentation.
• Most common symptoms of actinomycosis includes abscess with draining sinus tracts.
• Other symptoms are mostly non-specific for actinomycosis.
• Based on the organ system involved and duration of symptoms it should be differentiated from other conditions:^{[1][2][3][4][5][6][7][8][9] [10]}

• The clinical manifestations of actinomycosis and nocardiosis are similar. The following table helps in differentiating actinomycosis from nocardiosis.^[11][12]
• Differentiation of actinomycosis from nocardiosis is very important in selection of appropriate antimicrobial therapy.^[13][14]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

In 1970, the annual incidence of actinomycosis was estimated to be 1 per 300,000. Since then it’s incidence has been declined due to the widespread use of antibiotics following dental surgeries. Actinomycosis is commonly found between 4th to 6th decade of life and very rare in infants and children. Males are more commonly affected by actinomycosis than females.

• Actinomycosis is a rare disease, and not all cases gets reported.
• Estimating its annual incidence is difficult because, most of the infections are are not diagnosed and are treated empirically^[1][2]
• Widespread use of antibiotics following dental surgeries also lead to its decreased incidence.
• In 1970, its annual incidence was 1 per 300,000.

Actinomycosis is commonly found between 4th to 6th decade of life and very rare in infants and children

Males are more commonly affected by actinomycosis than females.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Common risk factors in the development of actinomycosis include dental abscess, oral surgery, and facial trauma.

Risk factors of actinomycosis include:^[1][2]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

There are no screening recommendations for actinomycosis.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Once in the tissue, actinomyces multiply and forms an abscess, producing a hard, red to reddish-purple lump, most commonly on the jaw. Eventually, the abscess ruptures through the skin surface producing a draining sinus tract. If left untreated, patients with actinomycosis may progress to develop multiple abscesses which can heal and reappear. The prognosis is excellent with prompt and effective antimicrobial treatment. Complications that can develop as a result of actinomycosis are osteomyelitis, endocarditis, pericarditis and meningitis.

• Once in the tissue, actinomyces multiply and forms an abscess, producing a hard, red to reddish-purple lump, often on the jaw.
• Eventually, the abscess ruptures through the skin surface to produce a draining sinus tract and are completely treatable.
• If left untreated, patients with actinomycosis may progress to develop focal organ involvement with mass-like features and multiple abscesses which can heal and reform.^{[1][2][3][4][5][6]}

• The prognosis is excellent with prompt and effective antimicrobial treatment in patients with uncomplicated actinomycosis that does not affect the CNS.
• The factors that define the outcomes of the disease include:
  • Site of infection
  • The time to diagnose
  • The time to the start of appropriate treatment
• Mortality range from 0% to 28% highest being in CNS.

Complications that can develop as a result of actinomycosis are ^[7]

• Extension of disease can result in osteomyelitis of the mandible, ribs, or vertebrae.
• Endocarditis
• Pericarditis
• Brain abscess
• Meningitis

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