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Community acquired pneumonia (CAP) refers to a serious infection or inflammation of the lungs that is generally acquired outside of a hospital or long term care facility. When this infection is acquired, the air sacs in your lungs fill with pus or other liquid, making it difficult for oxygen to penetrate through your lungs to reach your bloodstream. If CAP is not treated properly with antibiotics or spreads throughout your body, it can result in death, especially in the elderly or in people with weakened immune systems.
Community acquired pneumonia is a common disease with a reducing incidence. It usually occurs in children or the elderly, or in people with an underlying pathology. Streptococcus is the most common bacterial cause of community-acquired pneumonia. Other causes of community-acquired pneumonia include Haemophilus influenzae, Legionella, mycoplasma, chlamydia, and viruses. Staphylococcus may rarely cause community-acquired pneumonia, but this organism is more often a cause of hospital-acquired pneumonia. Community-acquired pneumonia occurs most commonly in very young and very old people. Typical symptoms of community-acquired pneumonia include cough, purulent sputum production, shortness of breath, pleuritic chest pain, fevers and chills. On examination, one notes rapid respiratory rate and heart rate and signs of pulmonary consolidation.
In the elderly, symptoms and signs are vague and non-specific. They may consist of headache, malaise, diarrhea, confusion, falling, and decreased appetite. Diagnosis is confirmed by chest x-ray. In general, patients who present with what appears to be CAP, with findings confined to the lungs and no laboratory evidence of extrapulmonary involvement, have CAP caused by a typical pathogen. Patients who have pneumonia plus extrapulmonary physical findings or laboratory features (such as elevations in liver function test results) have an atypical pneumonia.
Pneumonia is an infection of the lung parenchyma. Community-acquired pneumonia refers to pneumonia acquired outside of hospitals or extended-care facilities. Nursing home-acquired pneumonia refers to infection acquired in an extended care facility. Nosocomial pneumonia and hospital-acquired pneumonia are used to describe infections acquired in the hospital setting. The signs and symptoms of acute pneumonia develop over hours to days, while the clinical presentation of chronic pneumonia often evolves over weeks to months.
Streptococcus pneumoniae remains the most commonly identified pathogen in community-acquired pneumonia. A variety of other pathogens have been reported to cause pneumonia in the community, with their order of importance dependent on the location and population studied. These include long-recognized pathogens such as Haemophilus influenzae, Mycoplasma pneumoniae, and influenza A, along with newer pathogens such as Legionella species and Chlamydophilia pneumoniae. Other common causes in the immunocompetent patient include Moraxella catarrhalis, Mycobacterium tuberculosis, and aspiration pneumonia. The causative agent of community acquired pneumonia remains unidentified in 30% to 50% of cases.
Many pathogens listed as potential agents of bioterrorism are spread by the respiratory route. Among the most likely candidate agents are Bacillus anthracis, Francisella tularensis, and Yersinia pestis. A more extensive discussion of the agents of bioterror can be found in the chapters on chemical and biologic weapons in the Cleveland Clinic Disease Management Project.
Nursing home-acquired pneumonias are often caused by community-acquired pathogens. However, there is an increased influence of pathogens seen with relatively low frequency in the community, such as S. aureus (in the setting of aspiration or following influenza) or gram-negative organisms.
Community Acquired Pneumonia Causes
Community Acquired Pneumonia Symptoms
Community Acquired Pneumonia Diagnosis and Treatment
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