From the Guidelines
Risk factors for Mycobacterium avium complex (MAC) infection include advanced HIV infection with CD4 counts below 50 cells/mm³, as evidenced by studies showing that almost 40% of patients with less than 10 CD4 T cells/l developed disseminated NTM within 1 year 1.
Key Risk Factors
- Advanced HIV infection with low CD4 counts is a significant risk factor for MAC infection, with the risk increasing with progressively lower numbers of cells 1
- Disseminated NTM disease is very rare with any form of immunosuppression other than advanced HIV disease, but has been reported in immunosuppressed patients with renal or cardiac transplantation, chronic corticosteroid use, and leukemia 1
- Other potential risk factors may include structural lung disease, genetic disorders affecting immune function, advanced age, and environmental exposures to MAC in soil and water, although these are not as strongly supported by the provided evidence
Prevention and Management
- For HIV patients with CD4 counts below 50 cells/mm³, prophylaxis with azithromycin or clarithromycin is recommended to prevent MAC infection until immune reconstitution occurs with antiretroviral therapy, although the provided evidence does not specifically support this recommendation 1
- Patients with underlying lung conditions should be aware of potential environmental sources of MAC and take steps to avoid them when possible
Diagnosis and Treatment
- The method of diagnosis of disseminated MAC is usually noninvasive, with over 90% of persons diagnosed with disseminated MAC having positive blood cultures 1
- Treatment options are not discussed in the provided evidence, but would typically involve a combination of antibiotics and management of underlying immune suppression.
From the Research
Risk Factors for MAC Infection
- Low CD4 cell counts are a significant risk factor for developing MAC infection, as stated in 2 and 3
- Younger age is also associated with an increased risk of developing MAC infection, as mentioned in 2
- Not using highly active antiretroviral therapy (HAART) is a risk factor for MAC infection, as noted in 2
- Enrollment before 1996 is another factor associated with developing MAC, as stated in 2
- Having a CD4 count of less than 50 cells/mL increases the risk of MAC infection, as mentioned in 2 and 3
- Having a CD4 count of less than 75-100 cells/μL is also a risk factor for MAC bacteremia, as stated in 3
Prevention and Treatment
- Prophylaxis with azithromycin or clarithromycin is recommended for patients with CD4 counts less than 50 cells/mL, as stated in 2 and 4
- Rifabutin is also effective in preventing MAC infection, as mentioned in 3 and 5
- Combination therapy with clarithromycin and rifabutin may be more effective than monotherapy, as stated in 4 and 5
- Azithromycin or clarithromycin may be preferred over rifabutin due to their efficacy and potential drug interactions with protease inhibitors, as noted in 5
Impact of HAART on MAC Infection
- The introduction of HAART has resulted in a significant decline in the incidence of MAC infection, as stated in 2 and 6
- HAART has also shifted the clinical picture of MAC infections from disseminated disease to localized infection, as mentioned in 6
- Discontinuing primary and secondary prophylaxis against disseminated MAC infections may be considered at stable CD4+ cell counts >100 cells/μL, as stated in 6