Chemotherapy of Mycobacterium avium Complex Disease

Vocabulary-style flashcards covering the definition, epidemiology, pathogenesis, clinical manifestations, diagnosis, and pharmacological treatment of Mycobacterium avium Complex (MAC) disease.

Mycobacterium avium Complex (MAC)

A group of non-tuberculous mycobacteria (NTM), primarily composed of Mycobacterium avium and Mycobacterium intracellulare, which are ubiquitous environmental pathogens.

Disseminated MAC disease

A systemic infection common in HIV patients with CD4 counts below $50\,\text{cells/mm}^3$, characterized by fever, night sweats, anemia, diarrhea, hepatosplenomegaly, and weight loss.

Pulmonary MAC disease

A MAC infection increasingly recognized in older adults with lung diseases like bronchiectasis and COPD, presenting with symptoms like chronic cough, hemoptysis, and sputum production.

Acid-fast staining

A diagnostic method that demonstrates the presence of mycobacteria but cannot distinguish between MAC and tuberculosis.

Drug Susceptibility Testing

A laboratory test used to guide MAC management, particularly important for monitoring sensitivity to macrolides and amikacin.

Macrolides (Mechanism of Action)

Agents that form the cornerstone of MAC therapy by inhibiting bacterial protein synthesis through binding to the $50S$ ribosomal subunit.

Azithromycin

The preferred macrolide for MAC therapy due to having fewer drug interactions compared to clarithromycin.

Clarithromycin

A macrolide that serves as a cornerstone for MAC therapy but strongly inhibits $CYP3A4$, leading to many drug interactions.

Ethambutol (Mechanism of Action)

An anti-MAC drug that inhibits arabinosyl transferase, an enzyme involved in the synthesis of the bacterial cell wall.

Ethambutol (Adverse Effects)

Medication known to cause optic neuritis and red-green color blindness, requiring regular visual acuity monitoring.

Rifamycins (Mechanism of Action)

A class of drugs including rifampicin and rifabutin that inhibit DNA-dependent RNA polymerase.

Rifabutin

A rifamycin preferred for HIV patients because it has fewer interactions with antiretroviral therapy (ART) compared to rifampicin.

Rifamycins (Adverse Effects)

A class of drugs noted for causing hepatotoxicity and a harmless orange discoloration of body fluids.

Non-cavitary nodular bronchiectatic disease treatment

A clinical presentation of MAC typically treated with a three-times-weekly macrolide-based regimen.

MAC Treatment Duration

Therapy usually continues for at least $12$ months after culture conversion (negative cultures).

Primary Prophylaxis

Preventative treatment recommended for HIV patients with CD4 counts below $50\,\text{cells/mm}^3$ who are not on effective ART, using agents like weekly azithromycin.

Amikacin

An additional or second-line agent available in IV or inhaled liposomal formulations, used for severe or refractory MAC disease.

Macrolide Resistance

A condition associated with poor outcomes that commonly develops when inappropriate monotherapy is used for MAC disease.