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MAC causes disseminated disease in immunocompromised patients, most commonly in patients in the late stages of HIV infection, when the CD4 cell count is less than 50/mcL (see Pulmonary Disease caused by Nontuberculous Mycobacteria, Chapter 9, for a discussion of the infection in immunocompetent persons). Persistent fever and weight loss are the most common symptoms. The organism can usually be cultured from multiple sites, including blood, liver, lymph node, or bone marrow. Blood culture is the preferred means of establishing the diagnosis and has a sensitivity of 98%.
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Agents with proved activity against MAC are rifabutin, azithromycin, clarithromycin, and ethambutol. Amikacin and ciprofloxacin work in vitro, but clinical results are inconsistent. A combination of two or more active agents should be used to prevent rapid emergence of secondary resistance. Clarithromycin, 500 mg orally twice daily, plus ethambutol, 15 mg/kg/day orally as a single dose, with or without rifabutin, 300 mg/day orally, is the treatment of choice. Azithromycin, 500 mg orally once daily, may be used instead of clarithromycin. Insufficient data are available to permit specific recommendations about second-line regimens for patients intolerant of macrolides or those with macrolide-resistant organisms. MAC therapy may be discontinued in patients who have been treated with 12 months of therapy for disseminated MAC, who have no evidence of active disease, and whose CD4 counts exceed 100 cells/mcL for 6 months while receiving antiretroviral therapy (ART).
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Antimicrobial prophylaxis of MAC prevents disseminated disease and prolongs survival. It is the standard of care to offer it to all HIV-infected patients with CD4 counts of 50/mcL or less. In contrast to active infection, single-drug oral regimens of clarithromycin, 500 mg twice daily, azithromycin, 1200 mg once weekly, or rifabutin, 300 mg once daily, are appropriate. Clarithromycin or azithromycin is more effective and better tolerated than rifabutin, and therefore preferred. Primary prophylaxis for MAC infection can be stopped in patients who have responded to antiretroviral combination therapy with elevation of CD4 counts of greater than 100 cells/mcL for 3 months.
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Griffith
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et al; ATS Mycobacterial Diseases Subcommittee; American Thoracic Society; Infectious Disease Society of America. An official ATS/IDSA statement: diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases. Am J Respir Crit Care Med. 2007 Feb 15;175(4):367–416.
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et al. Prevention and treatment of opportunistic infections in HIV-infected adults and adolescents: updated guidelines from the Centers for Disease Control and Prevention, National Institutes of Health, and HIV Medicine Association of the Infectious Diseases Society of America. Clin Infect Dis. 2014 May;58(9):1308–11.
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