Opportunistic Infections: Mycobacterium Avium
Basic Information
Mycobacterium avium complex or MAC disease is now regarded as one of the most common opportunistic infections in persons with AIDS and the most common bacterial infection. It is:
- usually one of the last opportunistic infections to be seen in persons with AIDS and is usually a sign of advanced HIV progression and significant immune suppression, most often appearing in those with a CD4 lymphocyte account below 50 cells per mm.
- is most often preceded by a prior HIV-related opportunistic infection
- does not occur in any specific HIV-infected group more than another -- occurring in all risk groups, races and ages who have advanced HIV disease.
Development of disseminated MAC occurs more slowly now than it did in the earlier stages of the HIV epidemic, most likely due to PCP prophylaxis and antiretroviral therapy -- however it is believed that patients whose immune systems progressively worsen and reach CD4 lymphocyte counts as low as 10 cells per mm are at high risk for ultimately developing the disease.
MAC is made up of:
- M. avium
- M. avium-intracellulare (MAI)
- other independent strains
Yet most cases in HIV-related immunodeficiency are caused by M. avium (95%).
The causative organisms are thought to be extensively distributed in the environment, found in:
- soil
- water
- dust
- animal products (MAC has been isolated from both wild and domestic animals.)
It is believed to be either ingested or inhaled -- person-to-person transmission is possible but not documented -- and at the moment there are no guidelines or recommendations for reducing exposure (although there have been documented cases of MAC transmission from hospital water supplies).
Disseminated MAC (unusual in immunocompromised persons except for those with AIDS) can be insidious, affecting numerous organs -- it is believed to originate in the intestines but can spread from there to:
- lymph nodes
- bone marrow
- blood
- lungs
- spinal fluid
- spleen
Most patients with MAC are found to have anemia.
Symptoms
Symptoms can include:
- night sweats
- diarrhea
- enlarged spleen
- weight loss
- malaise
- abdominal pain
- fever
- loss of appetite
- fatigue
- malabsorption (which can aid wasting syndrome)
Diagnosis/Treatment
Diagnosis is usually made when MAC is cultured from the blood or less frequently from bone marrow, liver or lymph node.
Treatment can be complex. As with other treatments for HIV and HIV-related illnesses and opportunistic infections, drug regimens are in constant flux, based on the newest information from current clinical drug trials. However, with multi-drug, antimicrobial therapy, length of survival improves. Finding the appropriate drug combination and dosage appropriate for the patient remains key; under- and overdosing sometimes occur, there are drug interaction precautions to take, and =drug resistance issues to consider. To be treated by a health care provider and medical team experienced and knowledgeable about risks and benefits of current therapy options is obviously valuable to the patient.
Prolonged multidrug treatment, when successful, has been shown not only to relieve symptoms (usually within two to eight weeks) and can help clear bacteria from the blood. It is not eliminated from the body, hence recurrence is possible.
A two-to-five drug regimen active against MAC has been helpful in preventing drug resistance associated with the use of one drug only, or monotherapy. Antimacrobacterial drugs used in combination can include among others:
- clarithromycin
- ethambutol
- azithromycin
- rifamtin
- rifambutin
- citrofloxacin
Newer drugs are being tried in clinical trials. This article does not advise specific drug-regimens or combinations; an individual's current health status and past health history must absolutely be taken into consideration before multi-drug therapy is instituted.
Deciding which drugs to use for disseminated MAC prophylaxis can be complicated as well. But prophylaxis has been shown to be associated with prolonged survival and is recommended for patients whose CD4 count goes below 50 cells per mm. There are several drugs that can be administered for prophylaxis.
For patients who can tolerate treatment, drug therapy should almost always be continued indefinitely.
We at Always Your Choice have had experience diagnosing and treating many cases of MAC, and if you have this disease, would like information about it or need prophylaxis we would be happy to see you.