Clinical Overview of Nontuberculous Mycobacteria (NTM)

Overview

Risk for NTM infections increases for patients who are older, immunocompromised or have conditions like open wounds.

NTM outbreaks typically happen in healthcare settings if procedures expose patients to contaminated water.

Pulmonary infections are the most common clinical manifestation (observable symptom) of NTM infection. Extrapulmonary infection surveillance can help find healthcare-associated infections (HAIs) and outbreaks faster.

Types

There are more than 190 recognized species (types) of NTM. 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 more than 14 days to grow.

Rapid-growing species

• M. abscessus
• M. chelonae
• M. fortuitum
• M. mucogenicum

Slow-growing species

• M. avium complex (MAC)
• M. intracellulare subsp. chimaera (M. chimaera)
• M. kansasii
• M. marinum

Risk factors

Susceptibility to NTM infections increases for patients who are older, immunocompromised or have other medical conditions like open wounds.

How it spreads

NTM can form difficult-to-eliminate biofilms. Biofilms are collections of microorganisms that stick to each other and adhere to surfaces in moist environments, like the insides of pipes. Potable water in residential buildings and healthcare settings is a common source of exposure to NTMs.

Contaminated water can spread through:

• Decorative fountains and water features.
• Hydrotherapy equipment, such as jetted therapy baths.
• Ice machines.
• Intravenous infusions or intramuscular or intradermal injections.
• Medical equipment such as respiratory machines, bronchoscopes and heater-cooler devices.
• Shower heads and sink faucets.

Large healthcare buildings pose certain challenges because of their complex water systems. This can result in water stagnation (standing still or not flowing) and growth of microorganisms like NTM.

Outbreaks

NTM outbreaks have been related to a variety of medical procedures and practices, including:

• Cosmetic surgery.
• Dental procedures.
• Injection preparation and administration.
• Manufacturing of medical products.
• Medical tourism.
• Medication preparation.
• Medicine compounding and mixing.
• Surgery, such as breast surgery; heart surgery, including the use of heater-cooler devices; eye surgery with exposure to consumer-grade humidifiers.

Clinical features

Pulmonary infections are the most common clinical manifestation of NTM infection and are primarily community-acquired. These infections:

• Have vague/non-specific signs and symptoms, including shortness of breath, cough, fatigue, malaise and weight loss.
• Most commonly occur in patients with underlying lung disease such as cystic fibrosis, bronchiectasis and emphysema. A disorder known as "Lady Windermere syndrome" occurs in elderly, thin women without pre-existing lung disease, particularly those with scoliosis, pectus excavatum or mitral valve prolapse.
• Are usually not possible to trace back to a particular exposure given an extended latency period and multiple potential exposures.

Extrapulmonary infections can result from exposures in or out of healthcare settings.

Prevention

Healthcare facilities should:

• Establish a healthcare water management program.
• Follow the Centers for Medicare & Medicaid Services healthcare facility requirement to prevent Legionella infections as outlined in CMS Memo S&C 17-30-Hospitals/CAHs/NHs.
• Consider conducting surveillance for NTM infections.
• Coordinate with their health department to investigate clusters of NTM infections (both pulmonary and extrapulmonary) to determine common exposures and potential sources of infections.
• Recognize that finding NTM species can help determine public health actions.
• Determine their lab capacity for NTM testing. If testing capabilities are limited, identify reference laboratories that can assist.
• Prepare injections and intravenous fluids away from sinks or other water sources.
• Store materials and equipment used in invasive procedures (including injections) away from water sources.
• Follow manufacturer's instructions for maintenance and use of medical devices that use water (e.g., hydrotherapy equipment, heater cooler devices).
• Avoid using tap water or non-sterile ice in invasive procedures.

Testing and diagnosis

Diagnosing an NTM pulmonary infection requires a combination of clinical and microbiologic criteria. Laboratory identification of the species of NTM is important as it helps identify infections related to a common source.

NTM infections can be difficult to diagnose because nonspecific symptoms are common and routine bacterial cultures are often inadequate. Remember to consider NTM diagnoses in patients with risk factors such as weakened immune systems, trauma or recent healthcare exposures like injections or surgery.

Time from exposure to clinical manifestation can be long. Similarly, time from clinical manifestation to diagnosis may be delayed due to various factors including the failure to order appropriate tests.

American Thoracic Society (ATS)/Infectious Diseases Society of America (IDSA) Criteria for Diagnosis of NTM Pulmonary Disease*

*A patient must fulfill criteria from all 3 categories.

Microbiologic testing

• Providers should order specific laboratory testing when they suspect NTM infection (e.g., acid-fast bacilli (AFB) stain and culture). The laboratory will then perform additional testing to differentiate NTM from M. tuberculosis.
• Definitive diagnosis requires culture of the site of infection (e.g., 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).
• 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. Providers may need to work with their laboratory to ensure testing is done at an appropriate reference laboratory.

Treatment and recovery

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

Reporting cases

Clinicians and healthcare facilities should:

• Report all potential NTM infections and outbreaks (both pulmonary and extrapulmonary) to facility infection control staff.
• Notify health departments of all potential NTM outbreaks (both pulmonary and extrapulmonary).

Some states require reporting of all extrapulmonary NTM infections.

Case definitions

• Council of State and Territorial Epidemiologists Standardized Case Definition for Extrapulmonary Nontuberculous Mycobacteria Infections.

Case studies

Resources and tools

Reports/Resources

• Medical tourism.
• ATS/IDSA Statement: Diagnosis, Treatment, and Prevention of Nontuberculous Mycobacterial Diseases.
• Center for Clinical Standards and Quality/Survey & Certification Group sample letter "Requirement to Reduce Legionella Risk in Healthcare Facility Water Systems".
• Council of State and Territorial Epidemiologists Standardized Case Definition for Extrapulmonary Nontuberculous Mycobacteria Infections.

Tools

• Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings.