Community acquired pneumonia (CAP) is a serious infection that causes inflammation of the lungs and is generally acquired outside the hospital or long term care facility. The infection affects the air sacs in the lungs and fills them with pus or other liquid, and thus making it difficult for oxygen to penetrate through the lungs to reach the bloodstream. If not treated promptly and properly with antibiotics, CAP spreads throughout the body, and thus can lead to death, especially in old people or people with weakened immune systems.
Community acquired pneumonia usually occurs in children or the elderly, or in people with an underlying pathology. Community-acquired pneumonia is commonly caused by streptococcus, however there are other organisms that are known to cause community acquired pneumonia and they are Legionella, Haemophilus influenzae, mycoplasma, chlamydia, and viruses. Staphylococcus may rarely be associated with community-acquired pneumonia, but it often causes hospital-acquired pneumonia. Purulent sputum production cough, pleuritic chest pain, shortness of breath, fevers and chills are typical symptoms of community-acquired pneumonia.
The elderly patients show vague and non-specific symptoms. The symptoms include headache, diarrhea, malaise, confusion, falling, and decreased appetite. Diagnosis is done with the help of chest x-ray. In general, patients suspected with CAP, with test findings confined to the lungs and no laboratory evidence of extrapulmonary involvement, suffer from CAP caused by a typical pathogens. Patients suffering from pneumonia and show evidence of extrapulmonary involvement or laboratory findings such as elevations in liver function test results, have atypical pneumonia.
Pneumonia is an infection of the lung parenchyma and community acquired pneumonia is acquired outside of hospitals, Nursing homes or extended-care facilities. Nosocomial pneumonia is also an example of pneumonia acquired in the hospital setting. It may take hours or days for the signs and symptoms of acute pneumonia to develop, while it may take over weeks to months for the clinical presentation of chronic pneumonia to evolve.
Though Streptococcus pneumonia is the common pathogen in communityacquired pneumonia, a variety of other pathogens is known to cause pneumonia in the community. The order of importance depends on the location and population studied. These pathogens are Haemophilus influenzae, Mycoplasma pneumoniae, and influenza A, and other newer pathogens such as Legionella species and Chlamydophilia pneumoniae. Other common causes known to cause CAP in the immunocompetent patient are Moraxella catarrhalis, Mycobacterium tuberculosis, and aspiration pneumonia. In about 30% to 50% cases of community acquired pneumonia, the causative agent remains unidentified.
Many pathogens like Bacillus anthracis, Francisella tularensis, and Yersinia pestis are listed as potential agents of bioterrorism. The mode of transmission is through the respiratory route. A more elaborate discussion on the agents of bioterrorism is found in the chapters of chemical and biologic weapons in the Cleveland Clinic Disease Management Project.
Nursing home-acquired pneumonia is an example of pneumonia caused by community-acquired pathogens. However, it is observed that there is an increased influence of pathogens such as S. aureus (aspiration or following influenza) or gram-negative organisms that have relatively low frequency in the community.
Community Acquired Pneumonia Causes
Community Acquired Pneumonia Symptoms
Community Acquired Pneumonia Diagnosis and Treatment