These key learning points summarize the consensus- and evidence-based recommendations included in this edition. The sources listed here for each statement recommend that physicians perform or implement these actions directly in a clinical setting.

1. For patients with community-acquired pneumonia requiring hospitalization, initiate a comprehensive diagnostic evaluation to identify the causative pathogen and allow for pathogen-directed, optimized antimicrobial therapy.
Evidence Rating: SORT C
Sources: Section One, references 2 and 30

2. Monotherapy with a macrolide is not recommended to treat community-acquired pneumonia in the United States due to the high level of pneumococcal resistance.
Evidence Rating: SORT B
Sources: Section One, references 1 and 2

3. Once nosocomial pneumonia is clinically diagnosed, initiate early empiric antimicrobial treatment based on the presence of risk factors for antimicrobial resistance and knowledge of prevailing pathogens within the hospital and unit. This should be followed by pathogen-directed antimicrobial therapy (de-escalation) once a pathogen is identified.
Evidence Rating: SORT C
Source: Section Two, reference 1

4. Immunocompromised patients are at risk of pulmonary infections caused by both common and opportunistic pathogens. Consider empiric therapy for opportunistic pathogens when risk factors for these pathogens are present and a delay in empiric therapy would increase mortality risk.
Evidence Rating: SORT C
Source: Section Three, reference 6