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.