Mycobacterial infections
medical conditions

Mycobacterial infections

Explore the available health information, treatment context, and integrative evidence for Mycobacterial infections.

Background
  • A large group of bacteria, called mycobacteria, can cause infections in humans. These bacteria have waxy cell walls that help protect them against attacks and digestion. As a result, the unique outer coating of mycobacteria makes them difficult to destroy.
  • The most common types of mycobacterial infections include tuberculosis, leprosy, and mycobacterium avium complex.
  • Tuberculosis (TB) is a bacterial infection of the lungs that is caused by the microorganism Mycobacterium tuberculosis. Tuberculosis is transmitted through airborne droplets of infected mucus or phlegm (called sputum). Individuals can have the bacteria in their bodies without actually being infected or experiencing symptoms. This is called a latent TB infection. Individuals who have latent TB infections have healthy immune systems that are able to suppress the infection. Patients with latent TB do not require any medical treatment. Only 10% of individuals with latent TB ever develop the infection.
  • Leprosy is an infectious disease that is characterized by disfiguring skin sores and nerve damage. A mycobacterium, called Mycobacterium leprae, causes leprosy. This bacterium is present in the soil and on some armadillos.
  • There are two types of leprosy: tuberculoid and lepromatous. Both forms cause skin sores and nerve damage that leads to decreased sensations. However, lepromatous is more severe. Researchers believe that the lepromatous form is contagious and may be transmitted from person to person. The tuberculoid form is not contagious.
  • Mycobacterium avium complex (MAC) is a bacterial infection that is caused by either Mycobacterium avium or Mycobacterium intracellulare. MAC infections are classified under a subgroup of mycobacteria called nontuberculous mycobacteria (NTM). Because the bacteria that cause MAC are found almost everywhere in the environment, they are present in almost all humans. However, an infection only develops if the person has a weakened immune system. This type of infection is most common in HIV/AIDS patients.
  • Mycobacterial infections can be successfully treated with antibiotics. However, if left untreated, mycobacterial infections may spread to vital organs and become life threatening. Therefore, individuals should visit their healthcare providers to diagnose and treat an infection as soon as symptoms develop.
Risk Factors and Causes
  • Tuberculosis: Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB), is highly contagious. It is transmitted when a person inhales airborne droplets of mucus from someone with the untreated, active form of the disease. These microscopic droplets may be present after an infected person coughs, sneezes, talks, or laughs.
  • Leprosy: Individuals can become infected with either form of leprosy after coming into contact with Mycobacterium leprae when they are exposed to soil or armadillos that carry the bacteria. Exposure may occur during gardening, hiking, or other outdoor activities.
  • The tuberculoid form of leprosy cannot pass from person to person. Instead, it can only be transmitted through direct contact with the bacteria in soil or on armadillos.
  • The lepromatous form, on the other hand, may be passed from person to person. However, researchers do not consider the disease to be highly contagious. Experts currently believe that the lepromatous form of leprosy is passed from person to person through mucus droplets that are released into the air from the mouth or nose of an infected person. Most cases of transmission occur after close, long-term contact with an infected individual. Individuals are most likely to catch leprosy from someone else if they live with an infected person. This means it is unlikely that an individual will develop leprosy after short-term or casual contact with an infected individual.
  • Contrary to popular belief, neither form of leprosy can be spread after touching someone who has the disease.
  • Mycobacterium avium complex (MAC): Individuals with weakened immune systems may develop mycobacterium avium complex after exposure to either Mycobacterium. avium or Mycobacterium intracellulare. These mycobacteria are so common that they are present in almost every human. The mycobacteria are found in water, soil, dust, and food. However, individuals who have healthy immune systems are able to prevent the bacteria from multiplying uncontrollably and causing an infection. Therefore, individuals with weakened immune systems or immune disorders, especially HIV/AIDS patients, have the greatest risk of developing MAC.
Signs and Symptoms
  • Tuberculosis: Latent tuberculosis (TB) infection is not contagious and causes no symptoms.
  • Symptoms of active TB may include cough, shortness of breath, inflamed membranes around the lungs (called pleurisy), fever, weight loss, night sweats, chills, and loss of appetite. The disease can cause serious breathing problems, which can be life threatening, especially if left untreated.
  • Leprosy: The tuberculoid form of leprosy causes a rash, consisting of one or more flat, whitish areas on the skin. Areas that are affected are usually numb because the mycobacterium damages the peripheral nerves, which are located outside of the brain and spinal cord.
  • Lepromatous leprosy is more disfiguring than tuberculoid leprosy. Lepromatous leprosy typically causes many small bumps (called nodules) or raised rashes on the skin. Symptoms of numbness and muscle weakness are generally much worse in patients who have lepromatous leprosy than patients who have tuberculoid leprosy. As a result of this decreased sensation, patients with lepromatous leprosy often develop blisters and skin wounds on the soles of the feet. Because patients cannot feel pain, these wounds often go unnoticed and eventually progress to disfiguring sores and eruptions.
  • If left untreated, leprosy may lead to serious complications, such as permanent nerve damage, physical deformities, eye damage that may lead to blindness, erectile dysfunction, infertility (in males), generalized inflammation that may be painful, chronically stuffy nose, and decreased quality of life. Without treatment, the inside of the nose may become damaged and scarred. Eventually, this may lead to complete collapse of the nose.
  • Mycobacterium avium complex (MAC): MAC infection can be limited to one part of the body, or it may enter the bloodstream and spread throughout the body. When several parts of the body are affected, the condition is typically called disseminated mycobacterium avium complex or
    DMAC.
  • In general, common symptoms of MAC include enlarged lymph nodes and fever. Other symptoms may include drenching sweats, diarrhea, weight loss, abdominal pain, fatigue, weakness, shortness of breath, inflamed mammary glands, inflamed muscle tissue, and skin abscess and lesions. The liver or spleen may also be enlarged. A brain abscess may also, causing symptoms such as headache, dizziness, aching neck, confusion, drowsiness, irritability, decreased responsiveness, seizures, and loss of coordination. Patients usually feel tired, weak, and have pale skin because the infection causes low levels of iron in the blood (called anemia), low levels of white blood cells, and thrombocytopenia (low levels of platelets).
  • The most common complication of DMAC is anemia, which may require a blood transfusion. This is because the bacteria need iron to survive. Depending on the organs involved, DMAC may become life threatening. For instance, if the infection spreads to the lungs, it may cause fatal respiratory failure.
Diagnosis
  • General: An infection is suspected if a patient has a fever, swelling, and/or pain. Mycobacterial infections are diagnosed after the bacteria are identified in the patient's blood, sputum, skin, or bone marrow.
  • Tuberculosis: A Mantoux test is the standard diagnostic skin test for tuberculosis. During the test, a small amount of purified protein derivative (PPD) tuberculin is injected under the skin of the patient's forearm. The PPD contains a very small amount of tuberculosis proteins, called antigens. A patient with tuberculosis will have a delayed hypersensitivity reaction to the proteins. After 48 to 72 hours, a healthcare provider checks the arm for a reaction. A positive response is indicated by a hard, raised bump at the injection site.
  • However, the test cannot determine if the infection is active or latent. Patients with active or latent tuberculosis will have positive test results. The test also cannot tell the difference between a TB infection and a TB vaccination. Therefore, additional tests, such as a chest X-ray, sputum culture, or both, are usually performed to determine if the patient has an active TB infection.
  • Leprosy: Leprosy is diagnosed after a skin scraping test. During the procedure, a small sample of skin cells are removed from an area of affected skin. The sample is then analyzed in a laboratory. If the Mycobacterium leprae is present, the patient has leprosy.
  • Once leprosy is diagnosed, a lepromin skin test can be used to distinguish between tuberculoid and lepromatous leprosy. During the procedure, an extract of inactivated leprosy-causing bacteria is injected under the patient's skin. The healthcare provider observes the injection site three days and 28 days after the injection. Patients with tuberculoid leprosy will develop an area of red and swollen skin at the injection site, indicating a positive reaction to the test. Patients with lepromatous leprosy will not experience any reaction to the injection.
  • Mycobacterium avium complex: Blood and bone marrow cultures are the most sensitive diagnostic tests for MAC. Since bone marrow cultures are more invasive, a blood culture is most often used to make a diagnosis. During a blood culture, a sample of the patient's blood is placed in a special laboratory preparation, and then it is incubated in a controlled environment for one to two weeks. If the disease-causing bacterium is present, a positive diagnosis is made.
  • A bone marrow culture is an invasive procedure that is only used when all other tests are negative, but the doctor suspects MAC. First, a bone marrow biopsy is performed to obtain a tissue sample. Patients receive sedatives to help them relax, and an anesthetic is injected to numb the skin around the biopsy site. During the biopsy procedure, a needle is inserted into the marrow in the back of the pelvis, and a small sample is removed. The sample is then placed in a special laboratory preparation and incubated in a controlled environment for one to two weeks. If the disease-causing bacterium is present, a positive diagnosis is made. The biopsy site is usually sore for one to two days after the procedure, and bruising may occur. Serious complications may include bleeding and infection.
Treatment
  • General: Mycobacterial infections are curable. They are treated with medications called antibiotics.
  • Patients should take medications exactly as prescribed. Even if symptoms appear to go away, patients should take all of their medication because there may still be bacteria in the body. Stopping medication early may allow the infection to return. Also, stopping medication early may lead to antibiotic resistance. The few remaining bacteria in the body that survive most of the antibiotic therapy are the most difficult to kill. If the bacteria become resistant to treatment, the medications will no longer be effective if taken in the future. Therefore, antibiotic resistance limits treatment options and increases the risk of a fatal outcome.
  • Patients should tell their healthcare providers if they are taking any other drugs (prescription or over-the-counter), herbs, or supplements because they may interact with treatment.
  • Tuberculosis: Patients with latent tuberculosis do not require any medical treatment.
  • Patients with active tuberculosis typically receive a combination of four different antibiotics: isoniazid (Nydrazid® or INH), rifampin (Rifadin®), ethambutol (Myambutol®), and pyrazinamide.
  • Depending on the severity of the infection, one or two of the four drugs may be discontinued after a few months of treatment. In general, treatment lasts six to 12 months. After a few weeks of treatment, the individual will not be contagious and symptoms may start to improve. However, medication should not be stopped early.
  • Medications should be taken on an empty stomach, either one hour before or two hours after a meal, with a full glass of water. Wait at least one hour before taking an antacid, as antacids may interfere with the antibiotics used to treat TB. Common side effects of drugs that are used to treat tuberculosis may include diarrhea, dizziness, drowsiness, gas, headache, heartburn, upset stomach, cramps, and trouble sleeping.
  • Leprosy: Patients with either type of leprosy receive a combination of antibiotics, called multidrug therapy (MDT). These medications cure the infection, but they do not reverse nerve damage or physical disfiguration that has already occurred. The standard combination is dapsone, rifampin (Rifadin® or Rimactane®), and clofazimine (Lamprene®). Dapsone usually does not cause serious side effects. Rifampin is a stronger drug that may cause more serious side effects that may lead to liver damage. Symptoms of liver damage may include yellowing of the skin or eyes (jaundice) or fatigue.
  • Other antibiotics have also been used to treat leprosy. Examples include ethionamide (Trecator-SC®), minocycline (Dynacin®, Minocin®, or Myrac®), clarithromycin (Biaxin®), and ofloxacin (Floxin®).
  • Patients with leprosy may develop sores on their heels, which in severe cases, may lead to decreased tissue on the feet. In some cases, tissue from other parts of the body may be surgically removed from one part of the body, such as the leg, and transplanted to the heels.
  • Some patients with leprosy may develop a collapsed nose. In such cases, surgery may be performed to reconstruct the nose.
  • Patients should discuss the potential health benefits and risks of surgery before making a decision about medical treatment.
  • Mycobacterium avium complex (MAC): In order to control MAC, the patient's immune system must be restored. For instance, all HIV patients who are not taking anti-HIV drugs, called antiretrovirals, should begin treatment to help boost their immune systems.
  • In general, MAC infections are treated with two or three antimicrobials for life in order to prevent the infection from recurring. These medications are given to both HIV-negative and HIV-positive patients that have MAC infections. Commonly prescribed antibiotics include clarithromycin (Biaxin®), ethambutol (Myambutol®), and azithromycin (Zithromax®). HIV patients who have disseminated (DMAC) infections usually receive a combination of newer macrolide antibiotics (clarithromycin, azithromycin) with ethambutol and rifabutin (Mycobutin®).
Prevention
  • Immune system health: Individuals who have strong immune systems are less likely to acquire infections. Healthcare professionals recommend eating a balanced diet that consists of plenty of fresh fruits and vegetables. Adequate amounts of sleep and exercise regularly also help keep the immune system healthy.
  • HIV/AIDS patients should take anti-HIV medications exactly as prescribed. These medications suppress the virus and help boost the immune system.
  • Avoid/minimize exposure: Individuals should also avoid or minimize contact with individuals who have active tuberculosis. Individuals should avoid close, long-term contact with others who have lepromatous leprosy. Patients should also avoid touching armadillos because some carry Mycobacterium leprae. For this reason, individuals should also avoid eating undercooked armadillo.
  • Practicing good hygiene and regularly washing the hands with soap and water may help reduce the risk of acquiring infections.
  • Prompt treatment: Patients who have symptoms of mycobacterial infections should visit their healthcare providers as soon as possible. Patients who receive prompt treatment are less likely to experience serious complications.
References
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