Mycobacterium avium complex infection is a bacterial illness that affects people with weakened immune systems or existing lung problems, and while treatment is challenging and often lengthy, advances in antibiotic combinations and supportive care are helping patients manage symptoms and control the disease.

Understanding Treatment Goals for MAC Infection

When doctors diagnose a Mycobacterium avium complex (MAC) infection, they face an important decision about how and when to begin treatment. MAC is a bacterial infection caused by organisms found everywhere in our environment—in water, soil, dust, and even food. While most people with healthy immune systems can fight off these bacteria without getting sick, those with weakened immune systems or damaged lungs may develop serious infections that require medical attention.^[1]

The main goals of treating MAC infection are to control symptoms, prevent the disease from spreading, reduce the number of bacteria in the body, and improve overall quality of life. Treatment decisions depend heavily on several factors: where the infection is located in the body, how severe the symptoms are, whether the patient has other medical conditions, and the overall state of their immune system. For people with HIV and very low immune cell counts, treatment becomes especially critical, as MAC can spread throughout the body and cause life-threatening complications.^[2]

Not every person diagnosed with MAC needs to start antibiotics immediately. Some patients with mild lung infections may benefit from what doctors call “watchful waiting,” where they are monitored regularly without starting medication right away. This approach exists because MAC treatments come with significant side effects and require long-term commitment. However, certain patients—especially those with cavities in their lungs, positive sputum tests showing many bacteria, or severe symptoms—should begin treatment as soon as possible to prevent disease progression.^[6]

The decision to treat MAC is individualized. Medical societies and expert groups have developed guidelines to help doctors determine which patients will benefit most from immediate treatment versus careful monitoring. These recommendations are based on years of research and clinical experience with thousands of patients. At the same time, scientists continue studying new therapies in clinical trials, searching for more effective treatments with fewer side effects.^[3]

Standard Treatment Approaches

The standard treatment for MAC infection involves using multiple antibiotics at the same time. This combination approach is essential because MAC bacteria can easily develop resistance if only one drug is used. The bacteria become resistant when they survive despite the presence of the antibiotic, making future treatment much more difficult. Using several medications together prevents this from happening and gives patients the best chance of clearing the infection.^[7]

The cornerstone of MAC treatment is a class of antibiotics called macrolides. The two main drugs in this category are clarithromycin (sold as Biaxin) and azithromycin (sold as Zithromax). These medications work by stopping the bacteria from making proteins they need to survive and multiply. Doctors typically prefer azithromycin for many patients because it causes fewer side effects, has fewer interactions with other medications, and can be taken just once daily. Clarithromycin, while equally effective, may cause more stomach problems and can interact with many other drugs.^[6]

Along with a macrolide, patients also take ethambutol (Myambutol). This drug works differently—it interferes with the bacterial cell wall, making it easier for the body’s immune system to fight the infection. Ethambutol is an important part of the treatment regimen, but it can cause problems with vision, especially at higher doses or with long-term use. Patients taking this medication need regular eye examinations to catch any vision changes early.^[2]

The third medication in the standard combination is usually a rifamycin, either rifampin (Rifadin, Rimactane) or rifabutin (Mycobutin). These drugs work by blocking the bacteria’s ability to make RNA, which is essential for their survival. Rifamycins are powerful antibiotics, but they can cause several side effects including upset stomach, changes in liver function, and interactions with many other medications. Rifabutin is often preferred for patients taking certain HIV medications because it has fewer drug interactions than rifampin.^[7]

For patients with more severe disease—especially those with cavities in their lungs or very advanced infection—doctors may add a fourth medication called an aminoglycoside. The most common choices are amikacin or streptomycin. These are powerful antibiotics that must be given by injection, either into a muscle or through an intravenous line. Because they can damage hearing and kidney function, patients receiving these medications need careful monitoring with regular blood tests and hearing checks. Aminoglycosides are typically used for the first few months of treatment in severe cases, then stopped while the other medications continue.^[6]

The dosing schedule for MAC treatment depends on the type and severity of disease. Patients with severe disease or cavities in their lungs usually take their medications every single day. However, those with milder, non-cavity lung disease may be able to take their medications only three times per week. This intermittent schedule can be easier to tolerate and causes fewer side effects, but it’s only appropriate for certain patients with less advanced disease.^[7]

Clinical guidelines from major medical organizations—including the American Thoracic Society, European Respiratory Society, and Infectious Diseases Society of America—strongly recommend performing susceptibility testing on the bacteria before or during treatment. This laboratory test tells doctors which antibiotics the specific MAC bacteria are sensitive to, allowing for more targeted treatment. Testing is especially important for macrolides and amikacin, as resistance to these drugs significantly affects treatment success.^[7]

Managing Side Effects of Standard Treatment

All MAC medications can cause unwanted side effects, and managing these problems is an important part of successful treatment. Many patients experience stomach upset, including nausea, vomiting, diarrhea, or belly pain. These symptoms can often be reduced by taking medications with food or adjusting the timing of doses throughout the day.^[2]

Vision problems are a specific concern with ethambutol. This medication can cause optic neuropathy, a condition where the nerve that carries visual information from the eye to the brain becomes damaged. Symptoms include blurred vision, difficulty seeing colors (especially red and green), or blind spots in the visual field. Anyone taking ethambutol should have their vision checked before starting treatment and then regularly during therapy—usually every month for the first few months, then every few months afterward.^[9]

Hearing loss and ringing in the ears can occur with aminoglycosides like amikacin and streptomycin. These medications can damage the delicate hair cells in the inner ear that are responsible for hearing. The damage may be permanent, which is why these drugs are used carefully and only when necessary. Patients should report any hearing changes immediately to their doctor.^[2]

Rifamycins can affect the liver and kidneys, so patients taking these medications need regular blood tests to monitor organ function. These drugs also interact with many other medications, including birth control pills, blood thinners, and some HIV drugs. Women taking birth control pills should use additional contraceptive methods while on rifamycin therapy because these antibiotics can make hormonal birth control less effective.^[2]

Another concern with long-term antibiotic use is the development of other infections, particularly Clostridioides difficile (C. diff), a bacterial infection that causes severe diarrhea. This problem is more common in older adults taking antibiotics for extended periods. Any patient who develops persistent or severe diarrhea during MAC treatment should contact their doctor immediately, as C. diff infections require specific treatment.^[9]

Some patients experience metallic taste in their mouth while taking these antibiotics, which can affect appetite and nutrition. Maintaining good nutrition during treatment is important for recovery, so patients struggling with taste changes should work with their healthcare team to find solutions, such as adjusting medication timing or trying different foods and flavors.^[9]

Monitoring Treatment Progress

Once treatment begins, regular monitoring is essential to ensure the medications are working and not causing serious problems. The 2020 guidelines from major medical societies recommend frequent follow-up visits, especially in the first few months of treatment. During these visits, doctors typically collect sputum samples—the thick mucus coughed up from the lungs—every one to two months to test for the presence of MAC bacteria.^[6]

A successful response to treatment is indicated by culture conversion, which means the bacteria stop growing in laboratory tests of sputum samples. Most patients who respond well to treatment achieve culture conversion within six months of starting antibiotics. If bacteria continue to grow in cultures after six months of appropriate treatment, doctors consider this treatment failure and may need to change the medication regimen.^[6]

Blood tests are performed regularly to check for side effects, particularly monitoring liver function, kidney function, and blood cell counts. These tests help doctors catch problems early before they become serious. Patients also need regular assessments of their symptoms—such as cough, fatigue, weight, and breathing ability—to determine if the infection is improving.^[7]

Treatment for Disseminated MAC in AIDS Patients

People living with HIV who develop MAC infection face additional challenges. When the immune system is severely weakened—specifically when CD4 cell counts drop below 50 cells per cubic millimeter—MAC can spread throughout the body, causing disseminated disease. This form of MAC is particularly serious and can affect the blood, bone marrow, liver, spleen, and lymph nodes.^[3]

For these patients, the most important treatment is starting or optimizing antiretroviral therapy (ART) for HIV. ART medications help rebuild the immune system, which is essential for controlling MAC. In fact, with effective HIV treatment that raises CD4 counts above 100 cells per cubic millimeter, many people with HIV can prevent MAC infection entirely.^[2]

When disseminated MAC does occur in HIV patients, treatment typically includes the same combination of antibiotics used for pulmonary MAC: a macrolide (azithromycin or clarithromycin) plus ethambutol, and often a rifabutin. The key difference is that these patients also need to start or continue their HIV medications. Doctors must carefully consider drug interactions between HIV medications and MAC antibiotics, particularly with rifamycins, which can affect blood levels of many HIV drugs.^[4]

For HIV patients with very low CD4 counts who don’t yet have MAC, doctors may prescribe preventive antibiotics—usually azithromycin taken once or twice weekly—to prevent infection from developing. This preventive approach, called prophylaxis, can be stopped once the patient’s immune system recovers with ART and their CD4 count stays above 100 cells per cubic millimeter for at least three months.^[4]

Airway Clearance Techniques

Beyond antibiotics, physical techniques to clear mucus from the airways play an important role in managing MAC lung disease. Airway clearance techniques (ACTs) help remove the thick, bacteria-laden mucus that accumulates in damaged airways. This is especially important for patients who also have bronchiectasis—a condition where the airways are permanently widened and damaged—or chronic obstructive pulmonary disease (COPD).^[9]

These techniques include various breathing exercises, devices that create vibrations to loosen mucus, and postural drainage (positioning the body to help gravity drain mucus from different parts of the lungs). Some patients use handheld devices that create positive pressure in the airways, helping to keep them open and move secretions. Others may benefit from working with a respiratory therapist who can teach specific coughing techniques and breathing exercises.^[9]

Regular physical exercise is also beneficial for lung health in MAC patients. Exercise helps improve breathing muscle strength, promotes mucus clearance, and enhances overall fitness and quality of life. Patients should work with their healthcare team to develop an appropriate exercise program based on their individual condition and capabilities.^[11]

Maintaining good nutrition and a healthy body weight is another important aspect of managing MAC disease. Studies have shown that low body mass index and poor nutritional status are associated with worse outcomes in MAC patients. Eating a balanced diet with adequate protein and calories supports the immune system and helps the body fight infection.^[6]

Treatment in Clinical Trials

For patients who don’t respond well to standard treatment, or whose MAC bacteria are resistant to macrolide antibiotics, several promising new therapies are being studied in clinical trials. These investigational treatments offer hope for patients with difficult-to-treat infections.^[8]

One medication that has shown promise is clofazimine, an antibiotic originally developed to treat leprosy. Clofazimine works by interfering with bacterial DNA function and also has anti-inflammatory properties. In clinical studies involving patients with treatment-refractory or macrolide-resistant MAC pulmonary disease, adding clofazimine to standard therapy has improved outcomes for some patients. The drug can cause skin discoloration—turning the skin a reddish-brown color—which usually fades after the medication is stopped, but this side effect can be concerning for patients.^[6]

A major advancement in MAC treatment is inhaled amikacin liposome suspension, marketed as Arikayce. This medication delivers the powerful antibiotic amikacin directly to the lungs through inhalation, achieving high drug concentrations in the airways while minimizing systemic side effects like kidney damage and hearing loss that occur with injected aminoglycosides. The amikacin is encapsulated in tiny fat particles called liposomes, which help the drug stay in the lungs longer and penetrate into bacterial biofilms—the slimy protective layers that bacteria create to shield themselves from antibiotics.^[9]

Clinical trials testing inhaled amikacin in patients whose MAC infection didn’t improve after at least six months of standard treatment showed that adding this inhaled therapy helped more patients achieve culture conversion compared to standard treatment alone. However, the medication can cause side effects including hoarseness, cough, and sometimes breathing difficulties. Long-term safety data is still being collected as more patients use this relatively new treatment option.^[9]

Bedaquiline is another drug being explored for treatment-refractory MAC disease. Originally developed and approved for multi-drug resistant tuberculosis, bedaquiline works by blocking an enzyme that bacteria need to produce energy. Early studies in patients with MAC disease that didn’t respond to standard therapy have shown some promising results. Bedaquiline is being studied in combination with other antibiotics to determine the most effective and safe treatment regimens. Because it’s a relatively new drug, ongoing clinical trials continue to evaluate its role in MAC treatment.^[6]

Researchers are also investigating various fluoroquinolone antibiotics—including moxifloxacin (Avelox), levofloxacin, and ciprofloxacin—as potential additions to MAC treatment regimens. These drugs work by interfering with bacterial DNA replication. While they have shown some activity against MAC in laboratory studies, clinical evidence of their effectiveness in treating human MAC infections is still limited, and they are not routinely recommended as first-line therapy. However, they may be useful additions in patients with drug-resistant disease or those who cannot tolerate standard medications.^[7]

Several clinical trials are also examining different combinations and durations of existing antibiotics to optimize MAC treatment. For example, studies are evaluating whether certain patients might benefit from shorter or longer treatment courses, or whether specific medication combinations work better for particular types of MAC disease. These trials often compare outcomes like time to culture conversion, rates of disease recurrence after treatment completion, and quality of life during and after therapy.^[8]

The development of better treatments for MAC is challenging because the bacteria grow very slowly—taking weeks to months in laboratory cultures—which makes testing new drugs time-consuming. Additionally, MAC bacteria can form biofilms and live inside human cells, making them difficult for antibiotics to reach. Researchers are exploring ways to overcome these bacterial defense mechanisms, including developing drugs that can penetrate biofilms more effectively and formulations that can deliver antibiotics inside cells where MAC bacteria hide.^[13]

Geographic availability of clinical trials varies, with studies being conducted in the United States, Europe, Asia, and other regions. Eligibility for trials depends on many factors including the type of MAC disease, previous treatments tried, presence of drug resistance, overall health status, and other medications being taken. Patients interested in clinical trials should ask their healthcare provider about available studies or can search clinical trial databases to find relevant opportunities.^[6]

Surgical Treatment Options

For some patients with localized MAC lung disease that doesn’t respond to antibiotics, surgical removal of the affected lung tissue may be considered. This option is typically reserved for patients who have disease limited to one area of the lung, continue to have positive cultures despite appropriate antibiotic treatment, and are healthy enough to tolerate surgery. The most common procedure is removing a lobe of the lung (lobectomy) that contains the majority of diseased tissue.^[6]

Surgery is not appropriate for everyone and carries significant risks, including bleeding, infection, air leaks from the lung, and complications from anesthesia. The decision to proceed with surgery must be made carefully by a team of specialists including pulmonologists, infectious disease doctors, and thoracic surgeons. Success rates are higher when surgery is performed in specialized centers with extensive experience in treating NTM lung disease. Even after successful surgery, patients typically continue antibiotic treatment for many months to treat any remaining bacteria.^[6]

For children with MAC lymphadenitis—infection of the lymph nodes in the neck—the preferred treatment is complete surgical removal of the affected lymph nodes. This approach is more effective than antibiotics alone for this form of MAC disease. The surgery is typically straightforward and has good outcomes when performed by experienced surgeons.^[3]

Most Common Treatment Methods

• Macrolide-Based Antibiotic Combinations
  • Standard regimen includes a macrolide (azithromycin or clarithromycin) combined with ethambutol and a rifamycin (rifampin or rifabutin)
  • Treatment continues daily or three times weekly depending on disease severity, for at least 12 months after cultures become negative
  • Azithromycin is often preferred due to better tolerability, fewer drug interactions, and once-daily dosing
  • Macrolides work by preventing bacteria from making proteins essential for survival
• Aminoglycoside Therapy
  • Amikacin or streptomycin added to treatment for severe disease, especially in patients with lung cavities or extensive disease
  • Given by injection (intramuscular or intravenous) typically three times per week
  • Usually administered for the first few months of treatment when disease is most severe
  • Requires monitoring for hearing loss and kidney function changes
• Inhaled Antibiotic Therapy
  • Amikacin liposome inhalation suspension (Arikayce) approved for treatment-refractory MAC lung disease
  • Delivers high concentrations of antibiotic directly to the lungs through daily inhalation
  • Reduces systemic side effects compared to injected aminoglycosides
  • Added to standard oral antibiotic regimen in patients not responding to standard treatment after six months
• Antiretroviral Therapy for HIV Patients
  • Starting or optimizing HIV treatment is the most critical step for preventing and treating MAC in AIDS patients
  • Helps rebuild immune system to fight MAC infection naturally
  • Combined with MAC-specific antibiotics when disseminated disease is present
  • Preventive antibiotics may be prescribed when CD4 counts are very low, discontinued after immune recovery
• Alternative Antibiotics for Resistant or Refractory Disease
  • Clofazimine added to regimen for patients with macrolide-resistant MAC or treatment failure
  • Bedaquiline being studied in clinical trials for treatment-refractory disease
  • Fluoroquinolones (moxifloxacin, levofloxacin) may be used in specific situations when standard drugs cannot be tolerated or disease is resistant
  • Combinations tailored based on laboratory susceptibility testing results
• Airway Clearance Techniques
  • Physical therapy techniques including breathing exercises, chest percussion, and postural drainage
  • Handheld devices that create vibrations or positive pressure to loosen and mobilize mucus
  • Regular exercise to improve lung function and promote natural mucus clearance
  • Especially important for patients with bronchiectasis or other underlying lung disease
• Surgical Resection
  • Removal of diseased lung tissue (usually one lobe) in select patients with localized disease not responding to antibiotics
  • Reserved for otherwise healthy patients with disease limited to one area of the lung
  • Performed in specialized centers with multidisciplinary evaluation
  • Complete surgical excision is preferred treatment for MAC lymphadenitis in children