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Chapter 24 Coordinating Care for Patients With Infectious Respiratory Disorders
Symptomatic TB Infection Symptomatic TB infection, referred to as primary pro- gressive TB infection (PPTBI) , develops in a very small percentage of individuals who have been exposed to the bacterium. Initial symptoms are relatively nonspecific and consist of fatigue, weight loss, and night sweats. A cough develops eventually and produces a rusty-colored or blood-streaked sputum. As the disease progresses, dyspnea, orthopnea, and rales become evident. Drug-Resistant Mycobacterium Tuberculosis Drug-resistant M. tuberculosis (MDR TB) can be mono-drug or poly-drug resistant. This means that one or more of the first-line medications used for the treatment of TB are not effective. Drug-resistant TB can be caused by primary or secondary means. Primary resistance is caused by person-to-person transmission of the resistant organ- ism. Secondary (acquired) resistant TB develops during treatment and results from an ineffective treatment regi- men or an incomplete treatment regimen. The diagnosis of TB infection is made by laboratory testing, a skin test, and chest x-ray. Laboratory testing consists of a sputum test for culture and acid-fast staining. Suspicious cavitating lesions (resulting from pathological processes leading to necrosis and formation of a “gas-filled” space within the lung tissue) are seen on chest x-rays. The skin test is a positive purified protein derivative (PPD) screen skin test, also called a Mantoux test . The Mantoux tuber- culin skin test is the standard method for determining if an individual is infected with the TB-causing organism. The test is administered by injecting 0.1 mL of PPD intrader- mally into the tissue of the forearm. Within 48 to 72 hours after injection, the administration site should be observed for any reaction (Table 24.10). Interprofessional Management Medical Management Diagnosis Individuals who have received a bacille Calmette-Guérin (BCG) immunization may show a false-positive PPD when not infected with the TB bacteria. Further testing in these individuals is required, such as a chest x-ray and/or blood testing using an interferon gamma release assay (IGRA). There are currently two IRGAs approved for use by the FDA: QuantiFERON®-TB Gold In-Tube (QTF-GIT) and T-SPOT® TB test (T-SPOT). These blood tests can determine if an individual has been infected with TB bac- teria. A negative result indicates unlikely TB infection. A positive test confirms TB infection, and further workup is necessary to establish whether the infection is latent TB or
at exceptional risk of contracting TB or reactivating latent TB. This population poses a particular concern because of the extent of immunosuppression and the risk of con- tracting and spreading new strains of drug-resistant TB (MDR TB). An estimated 11 million people with HIV (one-third of the HIV population) are infected with M. tuberculosis . Tuberculosis is the leading killer of people with HIV infection.
Pathophysiology and Clinical Manifestations
Mycobacterium tuberculosis is typically transmitted by aero- solized droplets inhaled from the coughing or sneezing of an infected individual in close-contact situations. Drop- lets of M. tuberculosis are tiny and can remain suspended in the air for several hours. It is estimated that up to 3,000 infectious nucleated droplets can be released in one cough. After the small, infected droplets are inhaled, most of the bacilli remain within the upper airway and rarely cause active disease. Bacilli that manage to evade the mucociliary escalator defense are deposited within the alveoli and are quickly engulfed by phagocytic pulmonary macrophages. Once they are ingested by the macrophages, there is a slow but continued multiplication of the Mycobacterium . Tuber- culosis is classified as follows:
l Latent tuberculosis infection (LTBI) l Primary tuberculosis infection (PTBI) l Primary progressive TB infection (PPTBI) l Drug-resistant M. tuberculosis (MDR TB) Latent Tuberculosis Infection
In those individuals with an intact immune system, a gran- uloma forms and limits further proliferation and spread of the Mycobacterium . Necrosis at the center of the granuloma leads to fibrosis and calcification. A calcified granuloma evident on chest x-ray is a classic sign of the type of TB termed latent tuberculosis infection (LTBI) . The inac- tive bacilli remain dormant within the healed granuloma. Patients with LTBI have no symptoms, do not feel ill, and are not contagious. As long as the immune system remains intact, the bacilli remain in the healed tissue of the gran- uloma for the individual’s lifetime and do not progress to TB infection. It is only when the immune system becomes compromised that the disease can become reactivated. The most common factors associated with reactivation are HIV infection, long-term diabetes, chronic renal disease, long- term steroid administration, sepsis, and malnutrition. Primary Tuberculosis Infection Individuals with a weakened immune response are unable to control the multiplication of Mycobacterium. Granuloma formation is initiated but is unable to progress to calcifi- cation and results in a primary tuberculosis infection (PTBI) . Primary TB infection is often asymptomatic and is confirmed only by positive sputum cultures and a posi- tive skin test. This person is not infectious.
TB disease. Treatment
According to the American Thoracic Society, the CDC, and the Infectious Diseases Society of America, the goals of treatment for TB infection are (1) to cure the patient and (2) to minimize the transmission of M. tuberculosis to
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