Chapter 22: Drug Therapy for Tuberculosis and Mycobacterium avium Complex Disease

Definition and Affected Organs

Tuberculosis (TB) is an infectious disease primarily caused by Mycobacterium tuberculosis. While it most commonly affects the lungs, it can also involve other organs such as lymph nodes, pleurae, bones, joints, kidneys, and the gastrointestinal tract.

• Pathogenic bacilli multiply slowly and may remain dormant for years.

• These bacteria resist phagocytosis and can develop drug resistance.

Example: A patient with TB may present with pulmonary symptoms, but extrapulmonary manifestations (e.g., bone or kidney involvement) are also possible.

Global Prevalence and Risk Factors

• TB is prevalent worldwide; about one-third of the global population is affected.

• In 2020, approximately 1.5 million people died from TB.

• Most new cases in low-incidence countries occur among foreign-born immigrants.

• Large numbers of people have inactive (latent) TB infection.

• Contributing factors include immigration from high-prevalence countries and increasing immunosuppression (e.g., HIV infection).

Phases of Tuberculosis Infection

Initiation and Progression

There are four recognized phases in the initiation and progression of TB:

1. Transmission: Inhalation of infectious droplets.

2. Primary infection: Initial infection, often asymptomatic.

3. Latent tuberculosis infection (LTBI): Bacteria remain dormant; no symptoms.

4. Active tuberculosis: Bacteria multiply, causing clinical disease.

Drug-Resistant Tuberculosis

Types and Development

• Drug resistance is a major public health concern.

• Resistance develops due to poor patient compliance and the emergence of new strains, especially in immunocompromised individuals.

• Multidrug-resistant TB (MDR-TB): Resistant to the most effective first-line medications.

• Extensively drug-resistant TB (XDR-TB): Resistant to second-line medications; very limited treatment options.

Factors contributing to resistance:

• Delayed diagnosis and determination of drug efficacy.

• Lack of adequate diagnostic laboratories.

• Most common in regions such as India, China, and Russia, and among HIV-positive individuals.

Control and Prevention of Tuberculosis

Public Health Strategies

• Efforts focus on identifying and treating LTBI, especially in high-risk populations (children, adolescents, foreign-born persons, HIV-positive, homeless, and residents of facilities such as prisons).

• Nurses play a key role in TB control by performing and reading TB tests, managing clinics, tracking contacts, assessing risk factors, educating patients, and administering medications (including Directly Observed Therapy, DOT).

• Failure to diagnose and treat MDR-TB promptly leads to further transmission and resistance.

• There is a need for better diagnostics, new medications, and standardized susceptibility testing.

Antitubercular Medications

Classification and Use

• Primary (first-line) agents: Used to treat latent, active, and drug-resistant TB when possible.

• Second-line medications: Used for patients intolerant to first-line drugs or infected with resistant strains.

Treatment of Active Tuberculosis

• Adequate therapy leads to improvement within 2–3 weeks (decreased fever/cough, weight gain, improved well-being).

• Treatment duration: At least 6 months, or 3 months after cultures become negative.

• Sputum cultures usually become negative within 3–6 months.

• Persistent symptoms or positive cultures after 3 months may indicate nonadherence or drug resistance, requiring alternate therapy.

Directly Observed Therapy (DOT)

• DOT involves a healthcare provider or responsible adult observing the ingestion of anti-TB medications.

• Recommended for all regimens; mandatory for intermittent dosing and MDR-TB.

Mycobacterium avium Complex (MAC) Disease

Characteristics and Transmission

• MAC consists of two similar pathogenic mycobacteria found in water and soil in the U.S.

• Transmitted by inhalation of infected water droplets.

• No evidence of human-to-human or human-to-animal transmission.

• Rarely causes disease in immunocompetent individuals.

Goals and Guidelines for Therapy

Therapeutic Goals

• Cure latent or active infection.

• Avoid development of drug-resistant TB.

• Minimize transmission to others.

• For active infection: decrease symptoms, make patient noninfectious, ensure adherence.

General Guidelines for Drug Therapy

• Multiple drugs are required to prevent resistance.

• Therapy duration depends on disease extent, adherence, and clinical response.

• MDR-TB requires more medications, longer therapy, and DOT; treatment is costly.

• XDR-TB has extremely limited treatment options.

Strategies to Increase Adherence

• Use short-course regimens, DOT, and intermittent dosing.

• Educate patients and families; provide support services.

• Individualize regimens and promote continuity of care.

Monitoring Anti-TB Therapy

Clinical and Laboratory Monitoring

• All patients require clinical monitoring for adverse effects and regular assessment.

• Monitor for signs of liver disease.

• Baseline laboratory tests are indicated for those with possible liver disease, HIV, pregnancy, postpartum status, or alcohol use.

Special Populations

• Special considerations are needed for HIV-positive patients, children, older adults, and those with abnormal kidney or liver function.

• Home care may be appropriate in some cases.

Table: Types of Drug-Resistant Tuberculosis

Key Signs and Symptoms of Active Tuberculosis

• Persistent cough

• Chest pain

• Chills and fever

• Hemoptysis (coughing up blood)

• Night sweats

• Weight loss, weakness, anorexia

• Abnormal chest X-ray

• Positive smear/culture for M. tuberculosis

Summary Table: Phases of Tuberculosis Infection

Additional info:

• First-line anti-TB drugs typically include isoniazid, rifampin, ethambutol, and pyrazinamide.

• Second-line drugs may include fluoroquinolones and injectable agents such as amikacin.

• DOT is especially important in preventing the development of drug resistance.