The science of selecting antimicrobials for community-acquired pneumonia (CAP)

Among infectious diseases, community-acquired pneumonia (CAP) is the leading cause of death in the United States and is associated with a substantial economic burden to the health care system. Initiating appropriate empiric therapy can be challenging given elevated resistance rates among Streptococcus pneumoniae strains.

To present current recommendations for management of CAP with respect to (a) choosing the appropriate site of care, and (b) antimicrobial selection based on bacterial etiology and the prevalence of resistance.

Mortality prediction tools, such as the PORT (Pneumonia Outcomes Research Team) Severity Index, CURB-65 (Confusion, Urea concentration, Respiratory rate, Blood pressure, and age>65), or CRB-65 (Confusion, Respiratory rate, Blood pressure, and age>65), can be invaluable in determining which CAP patients require hospitalization. These tools can help reduce overall costs for CAP by limiting hospitalizations of low-risk patients. S. pneumoniae remains the most common causative pathogen for CAP across all disease severities, and elevated rates of resistance to penicillin and macrolides can hinder selection of appropriate antimicrobial therapy. Antimicrobial resistance can impact clinical outcomes, including increasing the risk of treatment failure and breakthrough bacteremia. Current management guidelines recommend monotherapy with a respiratory fluoroquinolone or combination therapy with a beta-lactam and a macrolide (for patients admitted to the general medical ward) or with a beta-lactam and either a respiratory fluoroquinolone or a macrolide (for patients admitted to the intensive care unit [ICU] and who do not have risk factors for methicillin-resistant S. aureus or Pseudomonas). Optimized dosing regimens aim to ensure that pharmacokinetic and pharmacodynamic targets are met to achieve successful clinical outcomes and minimize resistance development.

Effective management of patients with CAP requires selection of the proper site of care and appropriate empiric antimicrobial. Given the elevated rates of resistance among S. pneumoniae, local resistance patterns must be considered when choosing empiric therapy.