Specialist management of treatment-refractory NTM lung infection

Managing Refractory MAC Pulmonary Disease

Mycobacterium avium complex pulmonary disease can be difficult to treat. When sputum cultures remain positive after at least six months of an appropriate guideline-based multidrug regimen, the disease may be classified as treatment refractory. Management requires a careful review of the diagnosis, antibiotic exposure, resistance, airway clearance, disease severity and the patient’s treatment priorities.

Culture conversion
Persistent positive cultures
Macrolide resistance
ALIS
Intravenous amikacin
Surgery
Adverse-effect monitoring
Bronchiectasis care

First confirm that treatment was truly adequate

Persistent cultures can reflect resistance, poor absorption, interactions, missed doses, intolerance, inadequate companion drugs or another organism rather than unavoidable treatment failure.

Escalation must remain a combination strategy

ALIS, intravenous amikacin and other medicines should not be used as unsupported monotherapy. Protecting the macrolide and preventing further resistance are central priorities.

What is refractory MAC pulmonary disease?

Treatment-refractory MAC pulmonary disease generally describes persistent positive MAC cultures after at least six months of an appropriate guideline-based antibiotic regimen.

Mycobacterium avium complex is a group of nontuberculous mycobacteria found naturally in water, soil and other environmental sources. Exposure is common, but pulmonary disease develops mainly in susceptible lungs or immune systems.

MAC pulmonary disease frequently occurs in people with bronchiectasis , COPD, previous tuberculosis, cystic fibrosis or another structural lung condition.

Standard treatment for macrolide-susceptible disease commonly combines azithromycin or clarithromycin with ethambutol and rifampicin. Treatment intensity and frequency depend on disease severity, cavities, smear status, drug susceptibility and tolerability.

Treatment duration is counted from culture conversion

Successful treatment is not usually defined by feeling better alone. Guideline-based therapy ordinarily continues for at least 12 months after sputum culture conversion.

What does culture conversion mean?

Culture conversion means that serial sputum cultures have become consistently negative for the disease-causing MAC organism. A single negative sample is encouraging but is not enough to confirm sustained conversion.

Serial sputum samples

Sputum is normally collected regularly during treatment so that microbiological response can be followed over time.

Laboratory identification

Species identification and susceptibility testing help confirm that persistent growth represents the same clinically relevant organism.

Symptoms and cultures may differ

Cough and fatigue may improve while cultures remain positive. Conversely, symptoms may continue after conversion because of bronchiectasis or permanent lung damage.

Relapse and reinfection

MAC can recur after successful treatment. Molecular comparison, where available, may help distinguish relapse from a new environmental strain.

Diagnosis and treatment monitoring are not the same process

At initial diagnosis, at least two positive cultures from separate expectorated sputum samples commonly support microbiological criteria. During treatment, serial cultures are used to determine response and the date of conversion.

Understanding treatment for NTM pulmonary disease

Consultant respiratory guidance

Why MAC treatment needs several medicines

MAC pulmonary disease is treated with a combination regimen because no single medicine reliably eradicates the infection and unsupported treatment can select antibiotic resistance.

The exact regimen depends on susceptibility, CT pattern, cavities, sputum smear status, previous antibiotic exposure, kidney and liver function, hearing, eyesight and the person’s ability to tolerate long-term therapy.

Confirming refractory disease before changing treatment

Before labelling MAC pulmonary disease as refractory, the entire diagnostic and treatment pathway should be reviewed. Adding more antibiotics without understanding the reason for failure can increase toxicity without improving the chance of conversion.

Confirm ongoing microbiological positivity Obtain good-quality sputum samples on separate occasions and verify the species or complex reported by the laboratory.
Review the original diagnosis Symptoms, CT abnormalities and microbiology should still support active MAC pulmonary disease rather than colonisation or another diagnosis.
Check the prescribed regimen Confirm that appropriate companion drugs, doses and dosing frequency were used for the disease pattern.
Assess adherence and tolerability Missed doses, treatment interruptions, vomiting and adverse effects may reduce effective antibiotic exposure.
Review absorption and drug interactions Rifampicin and other medicines can interact with several drugs. Gastrointestinal disease may also affect absorption.
Repeat relevant susceptibility testing Macrolide and amikacin susceptibility are particularly important because resistance strongly influences the treatment strategy.
Reassess structural lung disease CT imaging can identify cavities, mucus plugging, progressive nodules or disease that remains localised to one resectable area.
Optimise the underlying lung condition Airway clearance, aspiration, immune deficiency, nutrition and other infections may all influence treatment response.

Why might MAC cultures remain positive?

Macrolide resistance

Resistance to azithromycin or clarithromycin is one of the most important predictors of poor outcome and requires expert regimen redesign.

Inadequate companion therapy

Macrolide monotherapy or unsuitable two-drug combinations can allow resistance to develop and should be avoided.

Cavitary or extensive disease

Cavities, smear-positive disease and extensive structural damage are associated with a higher organism burden and a more difficult treatment course.

Poor medication absorption

Gastrointestinal disease, vomiting or interactions can reduce drug exposure even when medicines are taken as prescribed.

Treatment interruptions

Toxicity, access problems or an unmanageable regimen can lead to gaps that reduce treatment effectiveness.

Persistent mucus and infection burden

Poor airway clearance can leave infected secretions trapped in bronchiectatic airways.

Coexisting organisms

Pseudomonas, fungi or another NTM species may contribute to symptoms and radiological progression.

Ongoing aspiration

Reflux, swallowing dysfunction or recurrent aspiration can worsen lower-airway inflammation and infection.

Persistent symptoms do not automatically prove persistent MAC

Bronchiectasis itself can cause cough, sputum, fatigue and recurrent exacerbations. Treatment decisions should use cultures, imaging and clinical progression rather than symptoms alone.

Strategies for treating refractory MAC pulmonary disease

Macrolide

Confirm susceptibility, dose, interactions and whether azithromycin or clarithromycin remains appropriate.

Ethambutol

Check dose, adherence and visual monitoring. Ethambutol helps protect against emergence of macrolide resistance.

Rifamycin

Review rifampicin or rifabutin exposure, interactions, liver tests and whether the prescribed drug is tolerated.

ALIS

Liposomal inhaled amikacin may be added after failure of at least six months of guideline-based treatment.

Intravenous amikacin

May be considered for severe, cavitary or resistant disease where benefits justify systemic toxicity.

Monitoring

Hearing, balance, kidney function and concomitant toxic medicines require careful review.

Susceptibility and evidence

Additional drugs are chosen using previous treatment, resistance, disease severity and the limited evidence base.

Individualisation

Clofazimine or another agent may be considered in selected cases under specialist NTM supervision.

Avoid random substitution

A poorly active replacement can leave the patient functionally receiving monotherapy and encourage further resistance.

Localised disease

Resection may be considered when severe disease is confined to an area that can be removed safely.

Physiological reserve

Lung function, exercise capacity, nutrition and operative risk must be assessed carefully.

Experienced centre

Surgery should follow expert respiratory, microbiology, radiology and thoracic-surgical discussion.

Amikacin liposome inhalation suspension for refractory MAC

Amikacin liposome inhalation suspension, often abbreviated to ALIS, delivers liposomal amikacin into the lungs through a specific nebuliser system. It is used with other active antibiotics rather than as stand-alone treatment.

In the CONVERT trial, adding ALIS to guideline-based treatment increased six-month culture conversion compared with guideline-based treatment alone. Approximately 29% of patients receiving ALIS plus background treatment converted by six months, compared with approximately 9% receiving background treatment alone.

This means ALIS can improve the chance of culture conversion, but most patients in the trial still had not converted by six months. Response therefore requires ongoing microbiological and clinical monitoring rather than an assumption that adding ALIS will eradicate MAC.

Area	What patients may experience	Clinical response
Voice	Hoarseness, altered voice or dysphonia	Review inhalation technique, timing, severity and whether treatment interruption is necessary
Airways	Cough, wheeze, chest discomfort or bronchospasm	Assess airway disease and consider supervised pre-treatment where clinically appropriate
Hearing and balance	Tinnitus, hearing change, dizziness or imbalance	Prompt audiological or vestibular review may be needed
Kidneys	Systemic exposure is lower than with intravenous therapy but renal risk is not absent	Monitor renal function according to individual risk and concomitant medicines
Microbiology	Cultures may remain positive despite symptomatic improvement	Continue regular sputum cultures and review amikacin susceptibility if failure persists

ALIS requires specialist initiation and follow-up

It is not an ordinary nebulised antibiotic that should be added informally. The indication, background regimen, inhalation technique, respiratory tolerance, hearing and renal risks must be reviewed by a team experienced in NTM pulmonary disease.

Intravenous amikacin and other parenteral therapy

Intravenous amikacin may be considered in severe, cavitary, smear-positive or macrolide-resistant disease and in selected refractory cases. It is normally used as part of a wider combination regimen.

Kidney toxicity

Amikacin can damage renal function. Baseline and repeat blood tests are needed, with dose adjustment where appropriate.

Hearing loss

Ototoxicity may be permanent. Baseline and interval hearing assessment can identify early changes.

Vestibular toxicity

Dizziness, oscillating vision, imbalance or difficulty walking require prompt review.

Drug-level monitoring

Dosing and serum levels may be individualised according to the schedule, kidney function, age and treatment setting.

More antibiotic is not always better

The purpose of intravenous therapy is to improve the activity of a carefully designed regimen. Continuing despite progressive toxicity may reduce quality of life without producing culture conversion.

When might lung surgery be considered?

Surgical resection is not routine treatment for refractory MAC. It may be considered when severe disease is localised, antibiotic response is inadequate and the person has sufficient lung function and general fitness to tolerate an operation.

Localised cavitary disease

A destructive cavity confined to one lobe may be more amenable to resection than widespread bilateral disease.

Persistent haemoptysis

Recurrent or significant bleeding may influence the balance between continued medical treatment and intervention.

Resistant organisms

Surgery may be discussed where resistance substantially limits the chance of medical cure.

Multidisciplinary planning

Antibiotic timing, operative extent, postoperative treatment and respiratory rehabilitation require coordinated planning.

Surgery should take place in an experienced centre

Potential benefits must be weighed against air leaks, respiratory complications, reduced lung reserve and the possibility that MAC remains elsewhere in the lungs.

Monitoring treatment effectiveness and adverse effects

Monitoring area	Why it matters	Examples
Sputum cultures	Determine microbiological response and culture conversion	Regular expectorated or induced sputum samples
Liver function	Rifamycins, macrolides and companion drugs may cause hepatotoxicity	ALT, AST, bilirubin and symptom review
Kidney function	Aminoglycosides can cause renal injury	Creatinine, estimated filtration and electrolyte review
Vision	Ethambutol can affect optic function	Visual acuity, colour vision and urgent review of changes
Hearing and balance	Amikacin can cause cochlear or vestibular toxicity	Audiometry and assessment of tinnitus, dizziness or imbalance
ECG	Selected medicines can prolong cardiac repolarisation	QT interval and interacting-drug review
Imaging and lung function	Assess structural progression and physiological impact	CT when indicated and lung-function testing
Quality of life	Treatment burden may become greater than the achievable benefit	Symptoms, appetite, weight, activity, mood and patient goals

Supportive care alongside antibiotic treatment

Antibiotics are only one component of successful MAC care. Optimising the lung environment can improve symptoms, preserve function and make a long treatment course more manageable.

Airway clearance

Specialist respiratory physiotherapy helps mobilise retained mucus. Learn more about airway clearance in bronchiectasis .

Nutrition

Low weight and loss of muscle mass are common concerns. Dietetic support may improve resilience and treatment tolerance.

Pulmonary rehabilitation

Structured exercise can improve stamina, breathlessness, confidence and recovery from prolonged illness.

Aspiration and reflux review

Swallowing dysfunction or aspiration may perpetuate lower-airway inflammation and should be addressed where suspected.

Other airway infections

Bacterial and fungal infections may need separate treatment without disrupting the core MAC regimen unnecessarily.

Psychological support

Long treatment courses, uncertainty and toxicity can affect mood, work, relationships and confidence.

What happens when culture conversion is not achieved?

Some people do not achieve sustained conversion despite expert treatment. This does not mean that care has failed or that increasingly toxic treatment must continue indefinitely.

Treatment goals may need to be reconsidered

The clinical team and patient may discuss whether continued treatment is likely to reduce symptoms, slow progression or prevent complications. The expected benefit must be balanced against toxicity, treatment burden and quality of life.

Continued active treatment

A revised regimen may remain appropriate when there is a realistic prospect of conversion or meaningful disease control.

Suppressive strategy

In selected circumstances, treatment may aim to reduce organism burden or slow progression rather than guarantee eradication.

Treatment pause or cessation

Stopping may be reasonable when toxicity or burden outweighs likely benefit, but it requires a clear monitoring plan.

Active supportive care

Airway clearance, nutrition, rehabilitation, vaccination and treatment of other infections remain important.

“Suppressive treatment” is not a universal standard regimen

Long-term antibiotics can create toxicity and resistance. Decisions must be individualised by clinicians experienced in NTM disease rather than continued automatically because cultures remain positive.

Why specialist NTM review is important

Refractory MAC usually requires input from respiratory medicine, microbiology or infectious diseases, pharmacy, radiology, respiratory physiotherapy and, in selected cases, thoracic surgery.

Regimen reconstruction

Previous medicines, durations, gaps, susceptibility and adverse effects are reconstructed before the next regimen is chosen.

CT and microbiology correlation

Imaging progression and culture burden are reviewed together rather than relying on either in isolation.

Toxicity prevention

Monitoring plans are established before treatment escalation, with clear thresholds for review.

Shared decisions

The chance of conversion, treatment burden and personal goals are discussed openly before major changes.

When urgent medical assessment is needed

Seek prompt help for significant deterioration or toxicity

Heavy or increasing coughing of fresh blood
Severe or rapidly worsening breathlessness
A marked fall in oxygen saturation
High fever, confusion or severe weakness
Sudden chest pain or suspected pneumothorax
New hearing loss, severe tinnitus or disabling imbalance
Reduced urine output or symptoms of acute kidney injury
New visual blurring or altered colour vision
Severe rash, facial swelling or another allergic reaction

Call 999 for severe breathing difficulty, collapse, heavy haemoptysis or another immediately life-threatening symptom.

Conclusion

Refractory MAC pulmonary disease describes persistent positive cultures after at least six months of appropriate guideline-based therapy. Before escalating treatment, the diagnosis, drug exposure, adherence, absorption, interactions, susceptibility and underlying lung disease should be reviewed carefully.

For macrolide-susceptible disease, the macrolide, ethambutol and rifamycin backbone remains central. Unsupported monotherapy and poorly active combinations should be avoided because they can promote further resistance.

ALIS can improve the chance of culture conversion when added to guideline-based treatment in appropriate refractory disease, but it does not guarantee conversion and may cause respiratory, voice, hearing or other adverse effects.

Intravenous amikacin may be appropriate for selected severe cases but requires careful renal, auditory and vestibular monitoring. Lung surgery is reserved for selected localised disease following expert multidisciplinary assessment.

Airway clearance, nutrition, rehabilitation and management of bronchiectasis or aspiration remain important throughout treatment. Where conversion cannot be achieved, care should focus on realistic goals, disease control, symptom management and quality of life.

Frequently asked questions

When is MAC pulmonary disease considered refractory?

It is generally considered treatment refractory when sputum cultures remain positive after at least six months of an appropriate guideline-based regimen.

Does one positive sputum culture mean treatment has failed?

Not necessarily. Serial samples and the wider microbiological pattern are needed. A single sample can be affected by intermittent shedding, contamination or sample quality.

What is ALIS?

ALIS is liposomal amikacin delivered by inhalation through a specific nebuliser. It is added to other active antibiotics for selected adults with treatment-refractory MAC pulmonary disease.

Can ALIS be used by itself?

No. It should be used as part of an appropriate combination regimen rather than unsupported monotherapy.

Does ALIS cure every refractory MAC infection?

No. It increases the chance of culture conversion in appropriate patients, but many patients do not convert and continued monitoring is essential.

How long is MAC treatment continued?

Guideline-based treatment is normally continued for at least 12 months after culture conversion, subject to clinical response, toxicity and specialist advice.

Can intravenous amikacin damage hearing?

Yes. It can cause hearing and balance toxicity as well as kidney injury. Monitoring is required before and during treatment.

Can surgery cure refractory MAC?

Surgery may improve the chance of disease control when severe infection is localised, but it does not guarantee cure and is unsuitable for many patients.

Why is ethambutol included in treatment?

Ethambutol contributes antibacterial activity and helps protect the macrolide from resistance. Visual monitoring is required because optic toxicity can occur.

Can MAC return after successful treatment?

Yes. Recurrence may represent relapse of the original strain or reinfection from a new environmental strain.

What happens when treatment becomes intolerable?

The regimen should be reviewed rather than stopped or altered independently. Dose adjustment, substitution, treatment interruption or a change in treatment goals may be considered.

References and further information

Daley CL, Iaccarino JM, Lange C, et al. Treatment of nontuberculous mycobacterial pulmonary disease: an official ATS/ERS/ESCMID/IDSA clinical practice guideline. Clinical Infectious Diseases. 2020. View the international guideline
Haworth CS, Banks J, Capstick T, et al. British Thoracic Society guidelines for the management of non-tuberculous mycobacterial pulmonary disease. Thorax. 2017;72(Suppl 2):ii1–ii64. View the BTS guideline
Griffith DE, Eagle G, Thomson R, et al. Amikacin liposome inhalation suspension for treatment-refractory lung disease caused by Mycobacterium avium complex: CONVERT. American Journal of Respiratory and Critical Care Medicine. 2018;198:1559–1569. View the CONVERT trial
European Medicines Agency. Arikayce liposomal: product information. View regulatory information