Clinicians

Overview

• There are more than 180 recognized species of nontuberculous mycobacteria (NTM) and some of these cause disease in humans. NTM can be divided into two groups based on how long they take to grow in a culture:
  • Rapid-growing species: Usually grow within 7 to 10 days
  • Slow-growing species: May need >14 days to grow

Selected NTM rapid-growing and slow-growing species associated with healthcare
For a more comprehensive list see: Opportunistic Pathogens of Premise Plumbing

• When you see a patient with potential NTM disease, carefully evaluate for risks and potential exposures as detailed below.
• Signs and symptoms can be vague and are dependent on the site of infection.
• Both rapid-growing and slow-growing species can cause infections at a variety of different body sites.

Pulmonary Infections

• Pulmonary infection is the most common clinical manifestation of NTM infection and are primarily community acquired.
• Signs and symptoms are vague and nonspecific and may include shortness of breath, cough, fatigue, malaise, and weight loss.
• Pulmonary infections most commonly occur in patients with underlying lung disease such as:
  • cystic fibrosis
  • bronchiectasis
  • emphysema
  • In addition, a specific disorder known as “Lady Windermere syndrome” occurs in elderly, thin women without pre-existing lung disease, particularly those with:
    • scoliosis
    • pectus excavatum
    • mitral valve prolapse

• It is usually not possible to trace pulmonary disease back to a particular exposure given an extended latency period and multiple potential exposures.
• NTM may be found in municipal water supplies and can become aerosolized in showers and hot tubs and inhaled from the air.

• Diagnosing an NTM pulmonary infection requires a combination of clinical and microbiologic criteria. Table 1 lists the American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) criteria for NTM pulmonary disease.

Table 1. ATS/IDSA Criteria for Diagnosis of NTM Pulmonary Disease*

An Official ATS/IDSA Statement: Diagnosis, Treatment, and Prevention of Nontuberculous Mycobacterial Diseasesexternal icon

*A patient must fulfill criteria from all 3 categories to be diagnosed with NTM pulmonary disease

Extrapulmonary infections

• Extrapulmonary infections can result from exposures in or out of healthcare setting. Infections related to healthcare or commercial establishments (e.g., tattoo parlor, salon or spa) warrant further investigation to identify a particular exposure and potential environmental reservoir that would require mitigation.
• Signs and symptoms will vary depending on the site of infection and the patient’s immune status. Table 2 lists body systems, signs and symptoms, and examples of risk factors and exposures.

Table 2. Exposures and Signs/Symptoms Associated with Extrapulmonary NTM Disease

Clinical Diagnosis and Microbiologic Testing

• Healthcare providers should have a high level of suspicion to diagnose illness caused by NTM because nonspecific symptoms are common and routine bacterial cultures are often inadequate to diagnose these infections. Time from exposure to clinical manifestation can be prolonged. Similarly, time from clinical manifestation to diagnosis may be delayed due to various factors including the failure to order appropriate tests.
• Specific laboratory testing, such as acid-fast bacilli (AFB) stain and culture, should be ordered when NTM infection is suspected.
• Culture of the site of infection is needed for definitive diagnosis. Examples include AFB culture of sputum or bronchial alveolar lavage for suspected pulmonary infections, AFB culture of wound for suspected skin infection, AFB culture of blood for disseminated infections, or AFB culture of appropriate tissue or body fluid for musculoskeletal infections or lymphadenitis.
• AFB stain can detect the presence of mycobacteria. The laboratory will then perform additional testing to differentiate NTM from M. tuberculosis.
• It may take several weeks for a laboratory to grow NTM by culture and identify the species.
• Not all hospital labs have the infrastructure to identify NTM to the species-level. You may need to work with your laboratory to ensure testing is done at an appropriate reference laboratory.
• Nucleic acid amplification tests (NAAT) can be used to classify NTM into groups or complexes and are also helpful in identifying M. gordonae, which is usually a contaminant. Further speciation using a testing method such as matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is highly encouraged. However, MALDI-TOF MS identification does not always generate an acceptable match. Sanger DNA sequencing should be used to supplement MALDI-TOF MS in instances where it fails to produce acceptable results.

Treatment

• Treatment typically requires consultation with an infectious disease or pulmonary specialist.
• NTM are intrinsically resistant to many antibiotics. Treatment varies depending on individual patient infection susceptibility and the body site of infection and frequently requires a combination of 2 to 3 antimicrobial agents for a prolonged period of time (often 6 months to a year).
• Antibiotic susceptibility testing can be performed at appropriate reference laboratories. Selection of antibiotics are often empirically chosen based on guidance (An Official ATS/IDSA Statement: Diagnosis, Treatment, and Prevention of Nontuberculous Mycobacterial Diseasesexternal icon).
• Surgical or wound care management may also be required, particularly for extrapulmonary disease.

Clinicians should:

• Maintain a high index of suspicion for NTM infection in patients particularly those with risk factors such as immunosuppression, trauma, or recent healthcare exposures involving injections or surgery
• Obtain acid-fast bacilli (AFB) smears and cultures if suspicious for NTM disease
• Consult with specialists such as those trained in infectious diseases or pulmonary medicine for treatment recommendations
• Report all extrapulmonary infections to facility infection control staff as this may help promptly identify outbreaks
• Report potential NTM outbreaks (pulmonary and extrapulmonary) to facility infection control staff
• Notify public health of NTM infections as per state reporting requirements

Reports/Resources

• M. abscessus in Healthcare Settings
• Medical tourism
• Contaminated Heater Cooler Devices leading to M. chimaera infections in cardiothoracic surgery patients
• Reduce Risk from Water
• Nontuberculous Mycobacteria NTM Overviewexternal icon (National Jewish Health)
• ATS/IDSA Statement: Diagnosis, Treatment, and Prevention of Nontuberculous Mycobacterial Diseasesexternal icon