Actinomycosis overview

# Overview
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.

# Historical Perspective
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.

# Classification
Actinomycosis can be classified based on the anatomical site involved into
- Orocervicofacial actinomycosis
- Thoracic actinomycosis
- Abdominopelvic actinomycosis
- Central nervous system actinomycosis
- Musculoskeletal actinomycosis
- Disseminated actinomycosis

# Pathophysiology
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.

# Causes
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.

# Differentiating Actinomycosis from other diseases
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.

# Epidemiology and Demographics
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.

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

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

# Natural history, Complications and Prognosis
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%.

# Diagnosis

## History and Symptoms
Actinomycosis can present with diverse clinical presentation, which include systemic flu-like symptoms and symptoms due to focal involvement of organs by the bacteria.

## Physical Examination
The physical examination findings of actinomycosis are mostly nonspecific and are described according to the organ involved 

## Laboratory findings
The gold standard for diagnosing actinomycosis is histological examination and bacterial culture.

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

# Treatment

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

## 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.