Speaker's Highlight

• Don Sin University of British Columbia, St. Paul Hospital (Canada)
  Kenneth R. Chapman Toronto General Hospital Research Institute (Canada)
• Parameswaran Nair McMaster University (Canada)
  Carolyn Calfee UCSF (U.S.A.)
• Gregory P. Downey University of Colorado School of Medicine (U.S.A.)
  David A. Schwartz University of Colorado School of Medicine (U.S.A.)
• Neil Schluger Tuberculosis Control Branch, California Department of Public Health (U.S.A.)
  Nick Kim Critical Care & Sleep Medicine, University of California San Diego (U.S.A.)
• Nicola Hananiah Baylor College of Medicine (U.S.A.)
  Jae-Joon Yim Seoul National University College of Medicine (Republic of Korea)
• Koichiro Asano Tokai University School of Medicine (Japan)
  Diahn-Warng Perng Taipei Veterans General Hospital (Taiwan)
• Konstantinos Kostikas University of Ioannina (Greece)
  Karin Klooster University Medical Center Groningen (Kingdom of the Netherlands)

• Nontuberculous mycobacteria: epidemiology and treatment challenges

  Nontuberculous mycobacteria (NTM) are environmental organisms found in soil, dust, natural water, and municipal water systems. Unlike Mycobacterium tuberculosis, they are not generally transmitted between people, yet they can cause persistent pulmonary disease, lymphadenitis, skin infections, and disseminated illness in susceptible patients.

  The growing clinical burden reflects several converging factors: an aging population, improved recognition, advanced imaging, more sensitive laboratory methods, and a rising number of people living with bronchiectasis, chronic obstructive pulmonary disease, cystic fibrosis, or immune suppression. The organisms are also diverse, and their clinical behavior varies considerably by species.

  Respiratory specialists, infectious disease physicians, microbiologists, and public health teams must therefore interpret NTM findings in context. A positive culture may represent contamination, transient airway colonization, or active disease. Distinguishing among these possibilities is the first major treatment challenge.

  Why NTM disease is increasingly recognized

  Pulmonary NTM disease is reported more frequently in many regions, although surveillance methods and reporting practices differ. The most commonly identified organisms include members of the Mycobacterium avium complex, M. kansasii, M. abscessus complex, and several rapidly growing mycobacteria. Their distribution is influenced by local ecology, water exposure, healthcare practices, and host characteristics.

  Disease often develops in people with structural lung abnormalities. Bronchiectasis is particularly important because impaired mucus clearance creates a favorable environment for persistent infection. Other risk factors include prior tuberculosis, emphysema, silicosis, gastroesophageal reflux, low body mass, and therapies that suppress cellular immunity.

  The epidemiology is also shaped by sex and age. In some populations, nodular-bronchiectatic disease is especially common among older women without severe smoking-related lung disease. These patterns should guide clinical suspicion, but they cannot replace microbiological confirmation.

  Environmental exposure and regional variation

  NTM are widespread in the environment, so exposure is difficult to avoid completely. Aerosolized water from showers, humidifiers, hot tubs, and plumbing systems may provide opportunities for inhalation. Soil and dust are additional sources, particularly for people with frequent gardening or construction exposure. However, identifying an exposure rarely proves the source of an individual infection.

  Geographic differences matter because the prevalence of species and antimicrobial resistance is not uniform. A regimen that performs well against M. avium complex may be inadequate for M. abscessus. Local laboratory capacity, referral patterns, and access to specialist care can also affect reported incidence and treatment outcomes.

  The scientific program of a respiratory congress helps place these issues alongside advances in diagnostics, immunology, and clinical management. The detailed program illustrates how multidisciplinary discussion can connect epidemiological observations with practical care.

  Establishing a diagnosis with confidence

  NTM pulmonary disease should be diagnosed using a combination of clinical, radiographic, and microbiological evidence. Symptoms may include chronic cough, sputum production, fatigue, weight loss, fever, or breathlessness, but some patients have mild or nonspecific complaints. Computed tomography may show bronchiectasis, small nodules, tree-in-bud changes, cavities, or progressive consolidation.

  A single positive respiratory specimen is usually insufficient because environmental contamination and transient colonization are possible. Repeated cultures of the same species, compatible imaging, and an appropriate clinical picture provide stronger evidence. Bronchoscopy may be useful when sputum cannot be obtained or when the diagnosis remains uncertain.

  Diagnostic element	What it contributes	Common limitation
  Symptoms and examination	Establishes clinical plausibility and disease burden	Findings are often nonspecific
  Chest radiography or CT	Shows nodular, bronchiectatic, or cavitary patterns	Imaging cannot identify the organism
  Repeated sputum cultures	Supports persistent infection and species identification	Collection quality can vary
  Bronchoscopy	Provides targeted lower-airway samples	Invasive and not always necessary
  Molecular testing and susceptibility assays	Clarifies species and selected resistance markers	Results may not predict every clinical response

  Species-level identification is essential. Closely related organisms can have very different intrinsic resistance profiles, and some laboratory methods may misidentify uncommon species. Susceptibility testing should be interpreted with expert guidance, particularly for macrolides, amikacin, and agents used against rapidly growing mycobacteria.

  Treatment decisions are individualized

  Not every patient with positive cultures requires immediate antibiotics. A period of observation may be reasonable when symptoms are limited, radiographic disease is stable, and the risk of medication toxicity is high. Conversely, cavitary disease, significant symptoms, progressive imaging abnormalities, or repeated positive cultures may favor prompt treatment.

  For macrolide-susceptible M. avium complex pulmonary disease, therapy commonly includes a macrolide, ethambutol, and a rifamycin, with the schedule and route selected according to disease severity. More advanced or cavitary disease may require an initial parenteral aminoglycoside. Treatment generally continues for at least 12 months after culture conversion, making adherence, monitoring, and patient education central to success.

  M. abscessus complex presents a greater challenge because of inducible or acquired macrolide resistance, frequent drug intolerance, and variable outcomes. Management often requires multiple active agents, expert microbiological interpretation, and sometimes prolonged intravenous therapy. Surgical resection can be considered for localized disease when medical treatment is insufficient, although operative risk must be carefully assessed.

  Resistance, toxicity, and recurrence

  Drug resistance may be present before treatment or emerge during inadequate therapy. Macrolide resistance is especially consequential in M. avium complex and M. abscessus disease. Poor adherence, unsuitable companion drugs, delayed susceptibility testing, and prolonged exposure to ineffective regimens can all promote failure.

  Treatment toxicity is another major barrier. Ethambutol can affect vision, aminoglycosides can damage hearing and renal function, and rifamycins interact with many medications. Macrolides may prolong the QT interval or cause gastrointestinal effects, while prolonged intravenous treatment can create line-related complications. Baseline assessment and regular monitoring should be built into the care plan rather than added after problems arise.

  Culture conversion does not eliminate the possibility of relapse or reinfection. Patients with persistent bronchiectasis or ongoing environmental exposure may acquire a different strain or species after successful therapy. Long-term follow-up should therefore include symptom review, imaging when clinically indicated, and periodic microbiological assessment.

  Practical priorities for multidisciplinary care

  Effective management depends on coordination between respiratory medicine, infectious diseases, microbiology, radiology, pharmacy, nursing, and, when necessary, thoracic surgery. Care plans should reflect the organism, disease pattern, comorbidities, patient preferences, and the feasibility of prolonged monitoring.

  Useful priorities include:

  • Confirm that clinical, radiographic, and microbiological criteria are all reasonably aligned before committing to lengthy therapy.
  • Request species-level identification and targeted susceptibility testing from an experienced laboratory.
  • Assess vision, hearing, renal function, liver function, electrocardiographic risk, and drug interactions before treatment.
  • Explain expected duration, adverse effects, culture monitoring, and the importance of reporting new symptoms early.
  • Reassess regularly for culture conversion, treatment toxicity, adherence, and evidence of relapse or reinfection.

  Turning evidence into respiratory practice

  The central challenge of NTM care is balancing the uncertain significance of detection against the consequences of progressive disease and prolonged treatment. A careful diagnostic process prevents unnecessary exposure to toxic drugs, while timely specialist input can improve outcomes for patients with aggressive or resistant infection.

  Respiratory medicine meetings provide an important setting for sharing regional surveillance data, laboratory advances, and real-world treatment experience. Clinicians can use these insights to refine local pathways, strengthen collaboration, and give patients clearer explanations of what a positive NTM result means. Apply that evidence through consistent diagnosis, individualized therapy, and structured follow-up.

  Richard Russell Nuffield Department of Clinical Medicine, University of Oxford (United Kingdom)
• Mona Bafadhel King’s College London (United Kingdom)
  David Jackson Guy’s and St Thomas’ Hospital, King’s College London (United Kingdom)
• James Chalmers University of Dundee (United Kingdom)
  David Price University of Aberdeen (United Kingdom)