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Source: Blackford MG, Glover ML, Reed MD. Lower respiratory tract infections. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey L, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861§ionid=146071234. Accessed January 16, 2017.
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Majority of cases in otherwise healthy adults caused by Streptococcus pneumoniae (pneumococcus).
Atypical pathogens include:
Mycoplasma pneumoniae
Legionella species
Chlamydophila pneumoniae
Other common pathogens include Haemophilus influenza and a variety of viruses including influenza.
Staphylococcus aureus and Gram-negative rods causative agents in elderly nursing home patients and in association with alcoholism and other debilitating conditions.
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Microorganisms gain access to lower respiratory tract by three routes:
Inhaled as aerosolized particles.
Via bloodstream from extrapulmonary site of infection.
Aspiration of oropharyngeal contents.
Viral lung infections suppress bacterial clearing activity of lung by impairing alveolar macrophage function and mucociliary clearance, setting stage for secondary bacterial pneumonia.
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One of the most common causes of severe sepsis and infectious causes of death in the United States.
Occurs in persons of all ages, although clinical manifestations most severe in very young, elderly, and chronically ill.
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Age >65 years.
Diabetes mellitus.
Asplenia.
Chronic cardiovascular, pulmonary, renal, and/or liver disease.
Smoking and/or alcohol abuse.
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CLINICAL PRESENTATION
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Tachypnea and tachycardia.
Dullness to percussion.
Increased tactile fremitus, whisper pectoriloquy, and egophony.
Chest wall retractions and grunting respirations.
Diminished breath sounds over affected area.
Inspiratory crackles during lung expansion.
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MEANS OF CONFIRMATION AND DIAGNOSIS
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Sputum Gram stain and culture.
Complete blood count (CBC)
Arterial blood gas or pulse oximetry.
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DIAGNOSTIC PROCEDURES
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DIFFERENTIAL DIAGNOSIS
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