Tuberculosis (TB) remains an important infectious disease for primary care physicians. In some parts of the world, significant problems exist in recognizing and diagnosing active TB and in using correct treatment to prevent the development of multidrug-resistant TB (MDR-TB). People infected with TB bacteria have a 5–15% lifetime risk of falling ill with TB. However, persons with compromised immune systems, such as people living with human immunodeficiency virus (HIV), malnutrition, or diabetes or people who use tobacco, have a higher risk of falling ill.
When a person develops active TB disease, the symptoms (eg, cough, fever, night sweats, or weight loss) may be mild for many months. This can lead to delays in seeking care and results in transmission of the bacteria to others. People with active TB can infect 10–15 other people through close contact over the course of a year. Without proper treatment, active TB will lead to death in about 45% of HIV-negative people and nearly all HIV-positive people. In the United States, nearly all people diagnosed with TB complete therapy, which limits the risk for further spread and prevents development of MDR-TB. Identification and treatment of people with latent TB infections (LTBI) will prevent active disease and is a public health priority in the United States.
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TB infection is caused by Mycobacterium tuberculosis, which generally affects the lungs but can occur at many locations in body.
LTBI is exposure to M tuberculosis without active disease on clinical evaluation.
Primary TB is infection occurring shortly after exposure to M tuberculosis, which typically evolves to LTBI as immunity develops but can progress to active TB.
Postprimary TB is TB infection in patients previously sensitized to M tuberculosis that usually occurs as reactivation TB, but may occur with reinfection with a new strain of M tuberculosis (usually identified by genotype testing).
Extrapulmonary TB is localized infection at a site other than lungs such as lymph nodes, pleura, kidneys, genitalia, bones or joints, heart, nervous system (particularly meninges), any intra-abdominal organ (particularly at terminal ileum and cecum), peritoneum, and pericardium.
MDR-TB is defined as M tuberculosis resistant to isoniazid and rifampin.
Extensively drug-resistant (XDR) TB is defined as M tuberculosis isolates resistant to isoniazid, rifampin, any fluroquinolone, and at least one of three injectable second-line drugs (amikacin, kanamycin, or capreomycin).
Treatment failure is defined as lack of symptom resolution or worsening symptoms, continued weight loss, or positive sputum smear after 2 months of treatment with anti-TB medication. Patients with advanced disease (ie, cavitary TB disease) may take longer to convert sputum cultures to negative but should be considered a treatment failure after ...