Disseminated infection with mycobacterium avium complex

Other Names: DMAC

Disseminated MAC-infection is one of the most frequent opportunistic infections occurring in HIV-infected patients.

Cause

MAC bacteria are common in the environment and cause infection when inhaled or swallowed. Recently, M. avium has been found to deposit and grow in bathroom shower heads from which it may be easily aerosolized and inhaled. Mycobacterium avium complex (MAC) infections are caused by two types of bacteria: Mycobacterium avium and Mycobacterium intracellulare.These bacteria are found in many places including water (fresh or salt), household dust, and soil. MAC bacteria get into the body when the bacteria are inhaled into the lungs or swallowed. Most people have MAC bacteria in their bodies and never get sick. MAC bacteria primarily cause illness in people who have poorly working immune systems or lung disease. Touching the same objects or having a close relationship with people who are sick from a MAC infection does not seem to increase the chance of getting sick. MAC infections are not thought to be contagious from one person to another.

Risk factors

Severely immunocompromised patients with CD4-counts < 50/microliter are at greatest risk for the disease. Survival of untreated infection is very poor (5 to 6 months). With therapy survival is prolonged by about 4 months.

Symptoms

The leading symptom of MAC-infection is fever eventually accompanied by weight lost, night sweats, enlarged lymph nodes, hepatosplenomegaly, abdominal pain and anemia.

Diagnosis

Blood cultures are very sensitive and the most appropriate examination. Other diagnostic procedures include bone marrow cultures, biopsies of the gastrointestinal tract, lymph nodes and the liver. Detection of MAC in sputum and stool samples only proves colonisation but not dissemination. However, colonisation of the gastrointestinal tract frequently precedes disseminated disease.

Treatment

For people who have both HIV/AIDS and a MAC infection, treatment usually involves a combination of different antibiotics for the MAC infection and antiretroviral therapy to treat the HIV infection. Combination of clarithromycin, rifabutin and ethambutol has proven to be the most efficacious therapy and therefore has to be considered as standard therapy for disseminted MAC-infection. Problems most frequently encountered with this medication include uveitis (rifabutin) gastrointestinal disturbances (clarithromycin) and leucopenia (rifabutin) as well as drug interactions with protease-inhibitors (rifabutin). the medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition.

• Rifabutin (Brand name: Mycobutin) Prevention of disseminated Mycobacterium avium complex disease in patients with advanced HIV infections.

Prophylaxis

Clarithromycin, rifabutin and azithromycin given as primary prophylaxis can diminish the risk of disseminated MAC-infection. Although a survival benefit has been seen with clarithromycin, primary prophylaxis of MAC-infection is not standard care in many centers.

Prognosis

People who are HIV-positive with MAC infections may have a shortened lifespan depending on their immune systems and their response to HIV medications. For people who have had successful treatment, there is still a chance that the infection will come back, so people who have been sick from a MAC infection need to be monitored over time.