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What is a MAC Infection?

Mycobacterium avium complex (MAC) is pervasive in our surroundings. Since it is present in food, water, and soil, it enters the body when a person breathes or drinks water. MAC infections don’t affect healthy individuals. However, it is an opportunistic bacteria. Meaning it only infects a person with a severely weakened immune system. Otherwise, it stays dormant and does not cause infections in healthy individuals. 

Risk Factors Of Mycobacterium Avium Complex

A prominent risk factor of mycobacterium avium complex could be a compromised immune system. Individuals with HIV/AIDS, cancer, or other lung diseases are susceptible to MAC infection. For instance, people with HIV/AIDS and a low CD4 count are more vulnerable to this infection.

Types of MAC Diseases.

The mycobacterium avium complex belongs to the nontuberculous mycobacteria group (NTM). 

Microbes cause nontuberculous mycobacterial infections (NTM). According to Cleveland Clinic, there are around 200 types of NTM. Moreover, they reported that MAC causes almost 80% of pulmonary diseases in the United States.

But there are two most prevailing types:

  • Nodular Bronchiectatic:

Nodular bronchiectasis happens when an infection spreads to the air spaces and airways, for instance, creating what appear to be lung nodules on imaging. In addition, these tumors develop gradually. Although, this type is more prevalent in older, thin, nonsmoking ladies. 

However, if left untreated, MAC infections lead to bronchitis and pneumonia.

  • Fibrocavitary Infection:

Fibro-cavitary is an acute type of MAC lung disease. Firstly, it causes holes in the lung tissues forcing individuals to seek immediate medical attention. Secondly, if you don’t get the fibro-cavitary infection treated immediately, curing it can become more challenging as time passes. It develops in people who smoke or suffer from emphysema most of the time.

Types of Mycobacterium Avium Complex Infection.

There are three types of MAC infection:

  • Pulmonary Mycobacterium Avium Complex Infection:

Pulmonary MAC causes infection in the lung and respiratory system

  • Disseminated Mycobacterium Avium Complex Infection:

It causes infection of the bloodstream and affects organs through infected blood. This type of MAC infection is most common in people having AIDS or who are immune-compromised.

  • Lymphadenitis Caused By MAC:

This type causes swollen lymph nodes in the neck. However, lymphadenitis affects children.

MAC Lung Disease Causes

Mycobacterium Avium complex is a group of bacteria that causes mild to severe infections, especially in people with reduced immune efficiency. 

  • Gene Variation:

Importantly, MAC infections are not inherited. A person must be exposed to one of the associated types of bacteria to become ill. However, variation in genes might increase some people’s susceptibility to infection. Because numerous genes regulate the immune responses, no specific gene relates to causing MAC diseases.

  • Presence In The Environment:

Since MAC is present in soil or water, activities involving soil and water put the person at risk. For example, if a person likes gardening, the bacteria in the soil become airborne and more likely to be inhaled. Similarly, the Mycobacterium Avium complex is also present in the water in your homes. Using disinfectants or chlorine does not kill the bacteria. It may sound frightening, but MAC infections do not affect healthy people even on exposure. 

  • Predisposing Factors:

However, in people with predisposing factors, the bacteria stay in the lungs and cause irreversible changes in the lungs over time.

Who is Most Susceptible to Mycobacterium Avium Complex Infection?

MAC disease, however, can affect people of all genders and ages. But, more commonly, individuals above 65 and women who have gone through menopause are more susceptible.

People who smoke or have underlying lung conditions such as: 

  • Emphysema.
  • Cystic Fibrosis
  • Tuberculosis
  • Bronchiectasis
  • Chronic obstructive pulmonary disorders

Symptoms of Mycobacterium Avium Complex Infections

Symptoms vary according to the type and site of infection. For instance, symptoms of pulmonary MAC infection appear slowly and develop over time. However, symptoms often are not limited to the respiratory system.

  • Wheezing and coughing up blood:

The patient experiences wheezing sounds from the chest with persistent cough and blood streaks mixed with mucous.

  • Fever:

A  low-grade fever of 100 degrees brought on by chills is prevalent.

  • Unidentified weight loss:

Weight loss is not associated with a known cause.

  • Stomach ache:

Stomachaches and stomach discomfort are common symptoms. A person may experience nausea as well.

  • Unidentified Anemia:

Hemoglobin deficiency that is not related to active bleeding or h-pylori in less common instances.

  • Brain or skin abscess:

Brain abscess is rare, but they can lead to delirium and hallucination. Similarly, skin abscesses are rare too.

  • Skeletal muscle infection:

Infections in skeletal muscles, also known as myositis, are infections of larger skeletal muscles.

  • Mastitis:

Mastitis is inflammation, stiffness, and pain in breast tissues.

Diagnosis of Mycobacterium Avium Complex Infection.

Diagnosis of a MAC infection requires tests that include X-rays and CT scans to rule out any other illnesses. 

  • Diagnosis Of Pulmonary MAC Infection :

A doctor may advise a sputum culture test to identify pulmonary MAC disease. The physician takes a sputum sample to perform this test. Moreover, the physician then places the sputum cells in an environment that encourages bacterial growth, which takes up to seven days to appear. The bacterial cell growth is stained and tested under the microscope. This test is known as acid-fast bacillus.

  • Disseminated MAC Infection:

Similarly, identifying disseminated MAC infection requires a blood culture. Moreover, testing liver, stool, and urine samples help in identifying the MAC infection. The physician performs a whole-body scan to examine if the infection has spread.

  • Lymphadenitis:

The physician takes a tissue sample from the lymph node and examines it to identify lymphadenitis.

Treatment for MAC Disease.

Depending on the type of MAC infections and the patient’s comorbidities, for example, HIV/AIDS, COPD, or cancer, multiple treatments are available. 

  • Antibiotics:

A three-drug regimen of antibiotics consisting of Azithromycin, Rifampicin, and Ethambutol treat both pulmonary and disseminated MAC disease. However, this regimen tends to last for 15-18 months. A 2018 research study showed promising results for an inhaled amikacin therapy.

  • Use Of Novel Antibiotics:

However, increased antimicrobial resistance has coerced research organizations to develop new treatments for MAC infections. A promising approach is the use of novel antibiotics such as Bedaquiline. The antibiotic targets different pathways in the bacteria’s metabolism and reduces the likelihood of developing resistance. 

  • Immuno-Modulators:

In addition, researchers are investigating the use of immune system modulators. These modulators are interferon-gamma and granulocyte-macrophage colony-stimulating factors (GM-CSF), which enhance immune defenses against MAC.

Moreover, various new treatments are under research as well.

Management of Mycobacterium Avium Complex Infections

Following these measures may reduce the symptoms of MAC lung disease:

  • Remove Mucus From The Lungs:

Identify methods for removing mucus from the lungs. Options include at least 150 minutes per week of moderate-intensity exercise (especially enrolling in pulmonary rehab if you qualify).

  • Chest Physiotherapy:

In addition, respiratory therapists focus on chest and breathing techniques such as controlled coughing, positions to drain mucus out of the lung, and chest percussions to shake the mucous loose.

  • Quit Smoking:

Moreover, getting support to stop smoking and keeping other respiratory irritants and secondhand smoke to a minimum helps fight MAC infections.

  • Getting Vaccinated On Schedule:

Get vaccinated to reduce your chance of contracting COVID-19, pneumonia, and other respiratory diseases.

  • Healthy Eating:

Maintain a healthy weight by eating a balanced meal. 

Prognostication of Mycobacterium Avium Complex Infections

The long-term health outcomes for individuals with MAC infections vary depending on the type of infection a person has and the co-occurring illnesses.

  • Immune Responses:

Depending on the health of their immune system and how well they respond to antiviral medicines, people with HIV may live shorter lives. 

  • Infection Relapse:

People who suffer from MAC disease need to be observed throughout their recovery, even if treatment is effective because these infections can return over time.

  • Survival Rate:

However, individuals with MAC lung infection but no history of HIV have a survival rate of 20%-90%. According to the BMJ, the cumulative 5-10 year mortality rates are 12.5% and 27.4%.

MAC Infection Lead Complications.

Your chance of developing antibiotic resistance increases with prolonged antibiotic use. 

Adverse Reactions Caused By Antibiotics:

Antibiotics cause mild to severe adverse reactions like nausea, vomiting, and abdominal discomfort. However, conversing with your doctor will be crucial because each antibiotic has particularly adverse reactions.

Chances Of C. Difficile Infection On Long-Term Antibiotic Use:

Long-term antibiotic use in older individuals increases the risk of developing Clostridium difficile. Antibiotics destroy the good bacteria in the stomach resulting in a C. difficile infection causing diarrhea and can be life-threatening.

Similarly, MAC lung disease negatively impacts the daily activities a person once enjoyed. Moreover, you might experience anxiety or depression as a consequence.

Key Facts:

  • MAC infections are serious infections that may infect the whole body.
  • It is not a contagious infection.
  • Common symptoms related to pulmonary MAC infections include persistent cough, mucous with blood, fever, abdominal pain, anemia, and weight loss.
  • Symptoms may appear over time and can worsen gradually.
  • Diagnosis includes chest X-ray, CT scans, and sputum culture tests.
  • Treatments involve a combination of antibiotics taken for 15-18 months.
  • Mycobacterium Avium Complex infection infiltrates the blood and infects body organs. This type is known as disseminated MAC infection. In addition, it affects the lymph nodes and occurs significantly in children, and is called Lymphadenitis.


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