Tuberculosis Definition

An illness resulting from INFECTION with the MICROBE Mycobacterium tuberculosis. Though tuberculosis most commonly infects the LUNGS, the disease may involve other organs as well, notably the KIDNEYS. Health experts estimate more than 2 billion people worldwide have active (symptoms are present) or latent (symptoms are not present) tuberculosis. An important characteristic of mycobacteria is their ability to rapidly develop resistance to ANTIBIOTIC MEDICATIONS.

Untreated tuberculosis is debilitating and progressive, giving the appearance that it consumes the body. This characteristic accounts for the archaic common name of the disease, “consumption.” Tuberculosis was a leading cause of death throughout the world until the discovery of the FUNGUS-derived antibiotic streptomycin in 1944. Today’s treatment regimens seldom incorporate streptomycin, however, because of its high likelihood for causing HEARING LOSS (OTOTOXICITY) and because many strains of M. tuberculosis have developed resistance to it.

When breathed into the lungs, M. tuberculosis BACTERIA infect macrophages, white blood cells responsible for consuming invading pathogens, in the alveoli. Rather than the MACROPHAGEconsuming the M. tuberculosis bacterium, however, the bacterium takes over the macrophage. Other cells of the IMMUNE RESPONSE surround the infected macrophage, enclosing it within a GRANULOMA. The bacteria may remain dormant within the granuloma. When enough granulomas accumulate, they interfere with the normal function of the organ-typically the lungs, though also the kidneys, bones, and BRAIN when M. tuberculosis bacteria migrate to those structures.

Symptoms of Tuberculosis and Diagnostic Path

Many people who have tuberculosis do not have symptoms and do not know they have the infection. Chest X-RAY for other diagnostic reasons may detect lesions in the lungs; other people learn they have tuberculosis through routine tuberculin SKIN testing such as many states in the United States require for people who work with the public, such as health-care workers and food service workers. When symptoms are present they include

  • prolonged, productive COUGH that may include blood (HEMOPTYSIS)
  • unintended weight loss
  • FEVER
  • night sweats
  • fatigue
  • wheezing or feeling of tightness in chest

The diagnostic path includes chest X-ray, tuberculin skin test, and cultures of sputum samples. When the findings of these diagnostic procedures are inconclusive, the doctor may conduct additional tests, including BRONCHOSCOPY or COMPUTED TOMOGRAPHY (CT) SCAN.

Tuberculosis Treatment Options and Outlook

Current treatment regimens use multiple medications in a rotating pattern over 9 to 12 months. The first phase of treatment-the initial phase, which lasts two months-generally involves taking four medications. The second phase of treatment-the continuation phase, which lasts four to seven months-generally incorporates a combination of two medications. The specific drugs depend on numerous clinical factors, including the person’s HIV status and the sensitivities of the causative strain of M. tuberculosis from sputum cultures.

Symptoms in most people improve dramatically within three weeks of starting medication, though clinical changes (X-ray) often do not become apparent for several months. Treatment regimens are complex, and the medications can cause unpleasant side effects, the combination of which tempts people to stop taking the medications. Doing so is hazardous both for the person, who then remains infected with tuberculosis, and in the context of public health because it fosters DRUG resistance.

It is essential to take the medications as directed for the full course of treatment. When compliance is a significant concern, doctors may use a protocol called directly observed treatment (DOT), in which the person comes to a clinic and takes his or her medication under direct observation of a health-care provider. Such treatment cures the tuberculosis. Any damage to the lungs or the kidneys (granulomas) remains, however, and is permanent.

Medications to Treat Tuberculosis

MEDICATIONS TO TREAT TUBERCULOSIS
Standard Infection
ethambutolisoniazid
pyrazinamidrifabutin
rifampinrifapentine
Resistant Infection
amikacincapreomycin
cycloserineethionamide
gatifloxacinkanamycin
levofloxacinmoxifloxacin
p-aminosalicylic acidprotionamide
pyrazinamideviomycin

Risk Factors and Preventive Measures against Tuberculosis

Crowded, unsanitary living conditions present the greatest risk for tuberculosis infection. Active tuberculosis is contagious through contact with sputum (material coughed up from the lungs), which contains M. tuberculosis. Latent tuberculosis is not contagious, though may emerge as active disease and become contagious. Tuberculosis is a common OPPORTUNISTIC INFECTION in people who have HIV/AIDS. Prevention efforts focus on routine testing of people at risk for exposure.

In the United States, such testing takes place through public health programs, school-based programs, institutional programs (such as in the military and in prisons), and employer-based programs. People who have positive skin tuberculin tests should receive further evaluation from a doctor and may require a course of prophylactic treatment with anti-tuberculosis medications.

See also BONE; COMMUNITY SANITATIONPATHOGEN.

Tuberculosis (disease) – Symptoms and Treatment
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