Pneumonia
Corey Diamond, PharmD
Updated guidance from the American Thoracic Society (ATS), published online on July 17, 2025 in The American Journal of Respiratory and Critical Care Medicine, revises and reverses recommendations on antimicrobial and corticosteroid therapy for community-acquired pneumonia (CAP), a major cause of adult morbidity and mortality.
The guideline reflects a systematic review of current evidence to refine antibiotic use, treatment duration, and the role of adjunctive corticosteroids in hospitalized adults with CAP.
Authors of the 2025 guideline emphasize antibiotic use restrictions based on presentation, propose shorter antibiotic durations for clinically stable patients, and limit corticosteroid use to severe CAP.
The recommendations are based on systematic evidence demonstrating that shorter antibiotic courses maintain efficacy and safety while reducing potential harms from prolonged antimicrobial exposure.
Corticosteroids provide measurable mortality benefit only in severe cases, with no observed advantage in non-severe disease, according to the guidelines.
The committee recommends against corticosteroid use in non-severe CAP (strong recommendation, low-quality evidence) and conditionally recommends corticosteroids for adults hospitalized with severe CAP, excluding cases caused by influenza virus.
Empiric antibacterial therapy
For outpatients with clinical as well as imaging evidence of CAP who test positive for a respiratory virus and have no comorbidities, empiric antibacterial therapy is not recommended by the ATS panel.
For outpatients with comorbidities, empiric antibiotics are conditionally recommended by the panel due to concern for bacterial–viral co-infection.
Particularly among hospitalized adults, empiric antibacterial therapy is conditionally recommended for those with non-severe CAP and strongly recommended for those with severe CAP who test positive for a respiratory virus.
Comorbidities that justify empiric antibiotic coverage include chronic heart, lung, liver, or renal disease; diabetes; alcoholism; malignancy; and asplenia. These conditions increase the risk of poor outcomes from delayed antibacterial therapy or bacterial–viral co-infection.
Epidemiologic data show bacterial–viral co-infection in approximately 25% to 35% of patients with CAP who test positive for respiratory viruses. Current evidence indicates that withholding antibiotics in low-risk outpatients does not worsen outcomes, while delaying or omitting antibiotics in inpatients with severe disease could increase mortality. However, the overall quality of evidence was rated very low by the guideline authors due to limited comparative trials.
Antibiotic duration
For adults who reach clinical stability, shorter antibiotic courses were supported by the ATS panel’s recommendations.
The panel presented four randomized controlled trials that compared antibiotic courses of fewer than 5 days to those lasting 5 days or more. Across these studies, clinical cure rates were similar between shorter and longer therapy groups (approximately 86% vs. 88%), and no significant difference in mortality was observed (2.0% vs. 1.3%).
The panel concluded that for outpatients and non-severe inpatients who reach clinical stability, fewer than 5 days of antibiotic therapy (minimum 3 days) is appropriate. For severe CAP, a minimum of 5 days of therapy is recommended because inadequate antibiotic exposure in this group is associated with increased risk of treatment failure and death. However, the certainty of evidence for these conclusions was low due to limited patient diversity and variability among studies.
Corticosteroid therapy
The guideline reassessed systemic corticosteroids as adjunctive treatment in hospitalized adults with CAP.
Fifteen randomized controlled trials were included in the pooled analysis. Among patients with severe CAP, corticosteroid use reduced mortality from 15.1% to 9.8%, representing a 35% relative reduction in death risk. This effect corresponded to one death prevented for every 17 patients treated. Corticosteroid therapy also shortened hospital stays by about 1 day on average. No significant increase in adverse events, including hyperglycemia or secondary infections, was observed in severe cases.
In patients with non-severe CAP, corticosteroid treatment did not significantly affect mortality (4.4% vs. 6.7%) or clinical stability. Adverse drug events were more frequent in this population without evidence of improved outcomes. ■