Mycobacterium abscessus overview

# Overview
Mycobacterium abscessus (M. abscessus) is a rapidly growing mycobacterium (RGM) that is a common water contaminant.  Mycobacterium abscessus is a bacterium distantly related to the ones that cause tuberculosis and leprosy. It is part of a group known as rapidly growing mycobacteria and is found in water, soil, and dust. It has been known to contaminate medications and products, including medical devices.  M. abscessus can cause a variety of infections. Healthcare-associated infections due to this bacterium are usually of the skin and the soft tissues under the skin. It is also a cause of serious lung infections in persons with various chronic lung diseases, such as cystic fibrosis, post-traumatic wound infections, and disseminated cutaneous diseases, mostly in patients with suppressed immune systems.

# Historical Perspective
M. abscessus was first isolated in 1953 from gluteal abscesses in a 62-year-old patient who had injured her knee as a child and had a disseminated infection 48 years later.  It was until 1992 that M. abscessus is considered a separate organism from Mycobacterium chelonae.  The species M. bolletii, named after the late microbiologist and taxonomist Claude Bollet, was described in 2006. In current taxonomy, M. bolletii and M. massiliense (named for Massilia, the ancient Greek and Roman name for Marseille, where the organism was isolated) have been incorporated into M. abscessus subsp. bolletii. 

# Causes
M. abscessus is a bacterium distantly related to the ones that cause tuberculosis and leprosy. It is part of a group known as rapidly growing mycobacteria (RGM) and is found in water, soil, and dust. It has been known to contaminate medications and products, including medical devices.

# Epidemiology and Demographics
M. abscessus infection can occur worldwide.  Although M. abscessus infection has been reported throughout the United States, South Eastern states such as Florida and Texas have the highest incidence.  In July 2014, an outbreak of M. abscessus infection was reported in South Carolina among surgical patients.  Moreover, 80% of rapidly growing mycobacterial related respiratory disease are caused by M. abscessus infection in the United States.  While infected patients who have no predisposing factors are likely non smoker females older than 60 years of age, M. abscessus infection among patients with predisposing factors occurs at an earlier age. Approximately 15% of patients who have M. abscessus infection also have a co-infection with mycobacterium avium complex (MAC).

# Risk Factors
Skin, soft tissue, and bone infection with M. abscessus has been associated with penetrating injuries, open wounds, intramuscular injections, and inappropriate disinfection of medical devices. Some of the risk factors for respiratory M. abscessus infection are chronic lung diseases such as cystic fibrosis and previous untreated mycobacterial infection.

# Natural History, Complications and Prognosis
Infection with M. abscessus can lead to skin, soft tissues and bone infections, bronchopulmonary infections, and disseminated infection in non-AIDS immunocompromised patients  Minor infections with M. abscessus can resolve either spontaneously or following surgical debridement.  The majority of pulmonary M. abscessus infection are chronic and incurable.  When pulmonary M. abscessus infection occurs in the absence of any predisposing conditions, the course of the disease is slowly progressive and indolent.  Whereas, when the pulmonary infection is associated with underlying predisposing factors, such as gastrointestinal or pulmonary conditions, the disease is rapidly progressive and fulminant.

# Diagnosis

## Diagnostic Criteria
When symptoms suggestive skin and soft tissues infection with M. abscessus are present, the definitive diagnosis requires the isolation of the organism from the infection site or, in severe cases, from a blood culture.  The diagnosis of pulmonary M. abscessus infection requires the presence of clinical, radiological and microbiological diagnostic criteria.

## History and Symptoms
Symptoms of of skin and soft tissue infection with M. abscessus (M.abscessus) red/purple, warm, tender to the touch, swollen, and/or painful skin.  The most commonly reported symptom in respiratory infection with M.abscessus is cough.  Constitutional symptoms increase as the disease progresses.  The patient should be asked about any recent history of procedures, such as surgery or injections, as well as any risk factor for the infection.

## Physical Examination
The physical exam of patients with skin and soft tissue infection with M. abscessus reveals red, warm, tender to the touch, swollen, and/or painful.  Infected areas can also develop boils or pus-filled vesicles. The assessment of vital signs might reveal fever.

## Laboratory Findings
To reach a definitive diagnosis, the organism has to be cultured from the infection site or, in severe cases, from a blood culture.  The diagnosis is made by growing this bacterium in the laboratory from a sample of the pus or biopsy of the infected area.

## Chest X Ray
Chest X-ray findings in patients with pulmonary M. abscessus infection include upper lobe infiltrates, cavitation, and/or patchy, reticulonodular, or mixed interstitial-alveolar opacities.  The chest X-ray abnormalities can be bilateral or multilobal.

## Other Imaging Findings
High-resolution CT (HRCT) scan of the chest might be ordered to assess the pulmonary abnormalities in M. abscessus infection.  Abnormal findings may include bronchiectasis, as a result of the infection or as a predisposing factor for it, and/or patchy small nodules.

# Treatment

## Medical Therapy
The treatment of M. abscessus skin and soft tissue infection includes draining collections of pus, surgical debridement, and administration of combination of antibiotics.  M. abscessus has a variable in vitro drug susceptibilities profile; therefore, antibiotic susceptibility testing is required. The treatment of pulmonary M. abscessus infection includes a combination of antibiotics and surgical resection of the localized disease.  M. abscessus infection is treated by a macrolide-based multidrug antibiotic regimen.  The duration of the antibiotic regimen depends on the site of infection: 2-4 months in pulmonary infection, at least 4 months in skin and soft tissue infection, and 6 months for bone infection.

## Surgery
The treatment of M. abscessus skin and soft tissue infection includes draining collections of pus, surgical debridement, and administration of combination of antibiotics.  Surgical resection should be considered particularly in extensive disease or unefficacious antibiotic therapy.  In addition, removal of foreign bodies that are likely the source of the mycobacterium, such as catheters or breast implants, is advised.  The treatment of pulmonary M. abscessus infection also includes a combination of antibiotics for a prolonged period of time as well as surgical resection of the localized disease.  The majority of pulmonary M. abscessus infection are chronic and incurable.  Successful treatment is more likely if the patient undergoes surgical resection following the initial antibiotic therapy.

## Primary Prevention
Primary prevention of M. abscessus requires avoiding exposure to tap water or tap water ice of surgical wounds, intravenous catheters, and injection sites.  Tap water or tap water ice should not be used in the operating rooms, particularly in cardiac surgeries or mammoplasty, or in outpatient clinics where plastic surgery procedures are performed.  Subjects should avoid receiving procedures or injections by unlicensed persons.