TUBERCULOSIS (TB)

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TUBERCULOSIS (TB)
An infectious disease spread by airborne route. Infection is caused by inhalation of droplets that contain the tuberculosis bacteria (Mycobacterium tuberculosis). An infected person can spread the small airborne particles through coughing, sneezing, or talking. Close contact with those affected increases the chances of transmission. Once inhaled, the organism typically settles into the lung, but can infect any organ in the body. The organism has an outer capsule.

PATHOPHYSIOLOGY
Primary TB occurs when the patient is initially infected with the mycobacterium.
After being inhaled into the lung, the organism causes a localized reaction. As the macrophages and sensitized T-lymphocytes attempt to isolate and kill off the mycobacterium within the lung, damage is also caused to the surrounding lung tissue. A well-defined granulomatous lesion develops that contains the mycobacterium, macrophages and other cells. Necrotic changes occur within this lesion. Caseous granulomas develop along lymph node channels during the same time. These areas create a Ghon’s complex which is a combination of the area initially infected by the airborne bacillus called the Ghon’s focus and a lymphatic lesion. The majority of people with newly acquired infections and an adequate immune system will develop latent infection, as the body walls off the infecting organism within these granulomas. Disease is not active in these patients at this point and will not be transmitted until there is some manifestation of the disease.

In patients with inadequate immune response, the tuberculosis will be progressive, lung tissue destruction will continue, and other areas of the lung will also become involved. In secondary TB, the disease is reactivated at a later stage. The patient may be reinfected from droplets, or from a prior primary lesion. Since the patient has previously been infected with TB, the immune response is to rapidly wall off the infection.

Cavitation of these areas occurs as the organism travels along the airways. Exposure to TB occurs when a person has had recent contact with a person suspected or confirmed having TB. These patients do not have positive skin test, signs or symptoms of disease, or chest x-ray changes. They may or may not have disease.

Latent TB infection occurs when a person has a positive tuberculin skin test but no symptoms of disease. Chest x-ray may show granuloma or calcification. of drug-resistant organisms. Initial treatment times generally range from 6 to 12 months. Longer treatment plans may be necessary for those with HIV infection or drug-resistant strains of TB. Some patient populations are monitored closely for compliance with direct observation of drug treatment. Patient teaching is important for medication protocol compliance and monitoring for side effects. Repeat sputum cultures are typically taken to see that the treatment for active disease is effective.
• Administer antitubercular medications to treat and prevent transmission:
• Isoniazid, rifampin, pyrazinamide, ethambutol, streptomycin
• Respiratory isolation for in-hospital care—the bacteria is spread by droplet.
• Increase protein, carbohydrates, and vitamin C diet for patients.

TB disease is confirmed when a person has signs and symptoms of tuberculosis. The chest x-ray typically has abnormalities in the apical aspects of the lung fields. In HIV patients other areas may also be affected.


PROGNOSIS
Some patients develop drug-resistant TB, making treatment more difficult. The drug-resistant TB may be resistant at the time of initial infection, or may develop as a result of medications during treatment. This occurs either because the treatment was not adequate or not taken appropriately.

SIGNS AND SYMPTOMS
• Weight loss and anorexia
• Night sweats
• Fever, possibly low-grade, due to infection
• Productive cough with discolored, blood-tinged sputum
• Shortness of breath due to lung changes
• Malaise and fatigue due to active illness affecting lungs

INTERPRETING TEST RESULTS
• Positive Mantoux (PPD) skin test shows exposure to tuberculosis due to development of cell-mediated immunity; typically takes between 2 and 10 weeks from time of exposure.
• Chest x-ray may show areas of granuloma or cavitation.
• Sputum test identifies M. tuberculosis bacteria:
• Acid fast-staining done to initially screen for TB—bacillus will hold stain
• Culture confirms the diagnosis but is slow-growing.

TREATMENT
Patients with active TB are initially placed on respiratory isolation as inpatients to reduce the risk of spreading the organism by droplet infection or aerosolization. Medications are initiated to treat TB and prevent transmission to others. Treatment may be initiated for active disease or for those without active disease who have had recent exposure. Combination therapy is typically used to decrease the likelihood.
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