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  • image Respiratory infections remain the major cause of morbidity from acute illness in the United States and likely represent the most common reasons why patients seek medical attention.
  • image The majority of pulmonary infections follow colonization of the upper respiratory tract with potential pathogens, whereas microbes less commonly gain access to the lungs via the blood from an extrapulmonary source or by inhalation of infected aerosol particles. The competency of a patient’s immune status is an important factor influencing the susceptibility to infection, etiologic cause, and disease severity.
  • image An appropriate treatment regimen for the patient with uncomplicated lower respiratory tract infection can be established by evaluating the patient history, physical examination, chest radiograph, and properly collected sputum for culture and interpreted in light of current knowledge of the most common lung pathogens and their antibiotic susceptibility patterns within the community.
  • image Acute bronchitis is caused most commonly by respiratory viruses and almost always is self-limiting. Therapy targets associated symptoms, such as lethargy, malaise, or fever (ibuprofen or acetaminophen), and fluids for rehydration. Routine use of antibiotics should be avoided and medication to suppress cough is rarely indicated.
  • image Chronic bronchitis is caused by several interacting factors, including inhalation of noxious agents (most prominent are cigarette smoke and exposure to occupational dusts, fumes, and environmental pollution) and host factors including genetic factors and bacterial (and possibly viral) infections. The hallmark of this disease is a chronic cough, excessive sputum production, and expectoration with persistent presence of microorganisms in the patient’s sputum.
  • image Treatment of acute exacerbations of chronic bronchitis includes attempts to mobilize and enhance sputum expectoration (chest physiotherapy, humidification of inspired air), oxygen if needed, aerosolized bronchodilators (albuterol) in select patients with demonstrated benefit, and antibiotics.
  • image Respiratory syncytial virus is the most common cause of acute bronchiolitis, an infection that mostly affects infants during their first year of life. In the well infant, bronchiolitis usually is a self-limiting viral illness.
  • image The most prominent pathogen causing community-acquired pneumonia in otherwise healthy adults is S. pneumoniae, whereas the most common pathogens causing hospital-acquired and healthcare-associated pneumonia are Staphylococcus aureus and gram-negative aerobic bacilli. Anaerobic bacteria are the most common etiologic agents in pneumonia that follows aspiration of gastric or oropharyngeal contents.
  • image Treatment of community-acquired pneumonia may consist of humidified oxygen for hypoxemia, bronchodilators (albuterol) when bronchospasm is present, rehydration fluids, and chest physiotherapy for marked accumulation of retained respiratory secretions. Antibiotic regimens should be selected based on presumed causative pathogens and pulmonary distribution characteristics and should be adjusted to provide optimal activity against pathogens identified by culture (sputum or blood).
  • image Treatment of nosocomial pneumonia requires aggressive therapy with careful consideration of the dominance and susceptibility patterns of the pathogens present within the institution.

On completion of the chapter, the student will be able to:

  1. Identify host defenses for preventing lower respiratory tract infections.

  2. Discuss the epidemiology, etiology, and pathogenesis of common lower respiratory tract infections.

  3. Compare and contrast the clinical manifestations of various lower respiratory ...

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