Mycobacterium avium complex (MAC), or mycobacterium avium intracellulare (MAI), is a bacterial infection that is caused by either Mycobacterium avium or Mycobacterium intracellulare. These bacteria are very common. They are present in water, soil, dust and food. In fact, these bacteria are present in almost every human. However, a healthy immune system will prevent the bacteria from causing an infection. Therefore, individuals with a weakened immune system, especially HIV/AIDS patients, are at risk of developing MAC.
It is estimated that up to 50% of individuals with HIV/AIDS may develop MAC, especially if their CD4 count (helper T-cells that HIV infects and destroys) is lower than 50 cells per microliter of blood. The CD4 cells play a vital role in the immune system. When HIV destroys these cells, the body is vulnerable to infection and disease. MAC almost never causes infections in people who have a CD4 cell counts higher than 100 cells per microliter of blood.
MAC infection can be localized (limited to one part of the body) or disseminated (spread throughout the entire body, sometimes called DMAC). MAC infection often occurs in the lungs, intestines, bone marrow, liver and spleen.
Common symptoms of MAC include weight loss, fever, chills, night sweats, swollen glands, abdominal pain, diarrhea, inflammation and overall weakness. MAC usually affects the intestines and inner organs first.
The most common complication of DMAC is anemia, which may require a blood transfusion. If the infection involves many organs, it can cause fatal respiratory failure. Patients who have a localized infection have a low mortality rate.
In order to control, MAC, the immune system must be restored. Therefore, all patients who are not taking antiretroviral therapy (ART) should begin treatment. In general, MAC infection is treated with two or three antimicrobials for life in order to prevent the infection from recurring. HIV patients who have DMAC infections usually receive a combination of newer macrolide antibiotics (clarithromycin, azithromycin) with ethambutol and rifabutin.
Before macrolide antibiotics were developed, patients who had both AIDS and DMAC typically lived four months after diagnosis. According to a 1999 study, patients who received treatment with rifabutin, ethambutol and clarithromycin lived an average of nine months after diagnosis. Now that highly active antiretroviral therapy (HAART) is available to help reconstitute (restore) the immune system of HIV/AIDS patients, the prognosis has improved. According to a recent study, about 50% of HIV/AIDS patients were alive five years after being diagnosed with MAC.
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