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Pneumococcal meningitis is caused by the bacteria Streptococcus pneumoniae (also called pneumococcus). The bacteria is the most common cause of meningitis in adults, and the second most common cause of meningitis in children older than age 6.
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The actual incidence of pneumonia in ambulatory patients is difficult to estimate because the etiologic agent is rarely identified except in clinical trials, and CAP is not currently considered a reportable disease. Each year in the United States there are 2 to 3 million cases of CAP.
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Introduction Pneumonia has been recognized as a disease entity since remote times, with definitions of the condition traceable in ancient Greek, Roman, and Arabic writings. Definitive recognition of the etiologic role of microorganisms in pneumonia, and the identification of Streptococcus pneumoniae as the most common causative agent was only achieved roughly 120 years ago.
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The following Clinical Topic Tour provides an overview of pneumococcal pneumonia and was adapted by materials published by the National Institute of Allergy and Infectious Diseases and the CDC.
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The most common mechanism by which the lung is inoculated with pathogenic organisms is through microaspiration of oropharyngeal contents, a process that occurs in otherwise healthy individuals during sleep ( Chapter 82 ). Colonization of the oral pharynx with pathogenic organisms, such as Streptococcus pneumoniae ( Chapter 303 ), can thereby lead to delivery of sufficient quantities of organisms to infect the lung.
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