Pneumoni2 - every year. The virulence factor of the...

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Pneumonia 1. Pathogenesis The pathogenesis of pneumonia differs according to the clinical setting. 1.1. Younger patients In relatively healthy, younger patients, most pneumonias occur by the inhalation of pathogens from the air. These pathogens typically possess “adhesins”, structures in the outer coat of the infecting microbe which allow the microbe to anchor itself to the tracheobronchial epithelium and to avoid being swept away by the mucociliary elevator. Common causes of pneumonia in this population are viruses (especially influenza virus), “atypical pneumonia” pathogens (Mycoplasma pneumoniae in young people, Chlamydia pneumoniae and Legionella pneumophila in others – called “atypical” in contrast to “typical” pneumococcal pneumonia), and Streptococcus pneumoniae. Influenza virus has two adhesins, the hemagglutinin and the neuraminidase. Because of frequent mutations in these adhesins, immunizations must be given
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Unformatted text preview: every year. The virulence factor of the pneumococcus is not an adhesin but the anti-phagocytic capsule: immunization raises protective anticapsular antibody. 1.2. Elderly patients By contrast, in elderly, debilitated patients, the pathogenesis is more like that in hospitalized patients, often including gram-negative bacilli, which colonize the nasopharynx and are aspirated into the lung.Nevertheless, the pathogens which affect healthier, younger, people can also affect the elderly. Frank episodes of gross aspiration tend to result in pneumonia caused by oral anaerobes (aspiration pneumonia). Such pneumonias often cavitate and produce putrid empyemas. 2. Two Important Pathogens In any patient with pneumonia, it is important to keep in the back of ones mind two unusual but important pathogens, namely, TB and Pneumocystis carinii....
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