Community-acquired pneumonia (CAP) is a common and potentially serious illness, particularly in older patients and those with significant comorbidities. Recent evidence indicates diverse communities of microbes reside within the alveoli as part of the lung microbiome and may play a role in the development of pneumonia. A CAP diagnosis is based on the demonstration of a new infiltrate on imaging in a patient with symptoms and signs of pneumonia. Although vaccination has decreased its incidence, Streptococcus pneumoniae (pneumococcus) remains the most common bacterial cause of CAP. Macrolide resistance to S pneumoniae has increased in the United States. With their increasing availability, newer molecular testing methods (eg, respiratory pathogen polymerase chain reaction panel) play a significant role in the evaluation of respiratory viruses. Antimicrobial therapy for hospitalized patients should be based on the results of diagnostic studies to allow pathogen-directed therapy and optimal antimicrobial stewardship. The recommended duration for antimicrobial therapy is 3 to 5 days if there is good clinical improvement by day 2 or 3. Procalcitonin levels can be useful as an adjunct to clinical judgment for determining the appropriate duration of therapy. Smoking cessation and vaccination should be prioritized because they significantly reduce the incidence and severity of CAP.
Case 1. TM is a 68-year-old man presenting in January to an urgent care center with a 2-day history of fever, chills, unproductive cough, and dyspnea. The patient has a history of congestive heart failure with decreased ejection fraction and was previously immunized for influenza, Streptococcus pneumoniae, and COVID-19.
On examination, the patient is slightly confused. Vital signs include a temperature of 100.9°F (38.3°C), blood pressure of 140/80 mm Hg, respiratory rate of 24/min, pulse rate of 100/min, and pulse oximetry result of 91% on room air. Chest radiography reveals a patchy reticular infiltrate in the right lower lobe. The white blood cell count is 9,000/μL (9 × 10 9/L), and polymerase chain reaction (PCR) tests are negative for influenza, respiratory syncytial virus, and SARS-CoV-2.
Community-acquired pneumonia (CAP) is an acute infection of the pulmonary parenchyma that is acquired outside the hospital setting.1 It is a common and potentially serious illness, particularly in older patients and those with significant comorbidities.2,3 The term health care–associated pneumonia is no longer used clinically because this categorization may be overly sensitive, leading to increased inappropriate use of broad-spectrum antibiotics.1
Patients with health care–associated infections often present from the community and are initially cared for in emergency departments. Patients who would have been classified as having health care–associated pneumonia should be assessed for the risk of drug-resistant organisms, but they are generally managed similarly to those with CAP.
Disease Burden
In the United States, there are approximately 6 million cases of CAP reported each year, and CAP is a leading cause of hospitalization and mortality.2–6 There are 1.5 million unique CAP hospitalizations in the United States annually (approximately 650 per 100,000 adults).6 The mortality rate ranges from less than 1% for outpatients to 27% for those with severe CAP requiring admission to the intensive care unit (ICU). The annual economic cost exceeds $17 billion.7,8
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