2025 American Thoracic Society Clinical Practice Guideline Updates for the Diagnosis and Management of Community-Acquired Pneumonia

Community-acquired pneumonia (CAP) is a lower respiratory tract infection that can be caused by bacteria, fungi, viruses, and other organisms. Patients who develop CAP can present with fever, chills, and respiratory symptoms such as cough, shortness of breath, and heavy sputum production.

The joint American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA) guidelines for the management of community-acquired pneumonia were last updated in 2019, before the SARS-CoV-2 pandemic. This new update does not include much evidence in patients with SARS-CoV-2 pneumonia, as the infection responds markedly differently to therapy than other viruses, so caution is advised when extrapolating these recommendations to that patient population.

The 2025 update was reviewed and approved independently from the IDSA. However, like the structure of the ATS/IDSA guidelines, the 2025 ATS update also breaks down these recommendations based on care setting, disease severity, and patient stability. These updates focused on these four areas: diagnostic imaging, empiric antibiotic therapy, shortened duration of antibiotic therapy, and the role of corticosteroids in hospitalized patients with CAP.

Upon the publication of the 2025 ATS guideline update, new recommendations are summarized as follows:

Diagnostic Imaging Alternative

Lung ultrasound is an acceptable diagnostic alternative to a chest X-ray or CT scan in cases where the preferred imaging is not readily available and if the clinical staff is appropriately trained in using point-of-care ultrasound equipment (conditional, low-quality evidence).¹

Empiric Antibiotics for Patients with Clinical and Imaging Evidence of CAP with Positive Respiratory Virus Testing

The 2019 guidelines called for antibiotic therapy to be prescribed to all adults with confirmed CAP and a positive test for influenza, regardless of care setting (strong, low quality of evidence). Their rationale for this decision was the epidemiology of bacterial and viral co-infection, which increases mortality for this patient population. Notably, the guidelines also indicate that for patients with a low procalcitonin level (indicating a low likelihood of bacterial infection) and achieving early clinical stability, empiric antibiotics can be discontinued between 48 and 72 hours.

The new update is more conservative in its approach to prescribing antibiotics, as there is not as strong a concern for bacterial and viral co-infections in immunocompetent patients. Empiric antibiotic therapy is conditionally recommended due to concerns of possible co-infection for adults with comorbidities who are being treated for CAP in an outpatient setting and for all adults who are being treated for CAP in an inpatient setting, regardless of disease severity.

To determine which comorbidities indicate prescribing empiric antibiotics for a patient, the ATS focuses on conditions that would put patients at an increased risk of bacterial infections or at risk for complications stemming from a bacterial co-infection, such as immunocompromised patients.¹ There is literature that suggests mortality with co-infections is increased in patients whose antibiotic therapy is delayed.

A 2004 study conducted by Houck et al looked at timing of antibiotic administration in older patients with CAP, currently being treated inpatient, and who had not yet been treated with antibiotics outpatient. They concluded that antibiotic administration within 4 hours of arrival was associated with decreased mortality (in-hospital and mortality within 30 days of admission) and length of stay. In-hospital mortality showed 15% lower odds of in-hospital mortality when antibiotics were administered within 4 hours of arrival (6.8% vs 7.4%; adjusted odds ratio [AOR], 0.85; 95% confidence interval [CI], 0.74-0.98). Mortality within 30 days of admission also showed 15% lower odds when antibiotics were administered within 4 hours of arrival (11.6% vs 12.7%; AOR, 0.85; 95% CI, 0.76-0.95). The efficacy in terms of length of stay was measured based on whether the patient’s length of stay exceeded the 5-day median (42.1% vs 45.1%; AOR, 0.90; 95% CI, 0.83-0.96), and that was significant for 10% lower odds of extended length of stay.³

Adjusted Duration of Antibiotic Therapy

Clinical stability is defined as afebrile, heart rate < 100 beats per minute, respiratory rate of < 24 breaths per minute, SpO₂ ≥ 90% or PaO₂ ≥ 60 mmHg on room air, systolic blood pressure ≥ 90 mmHg, and normal mental status.¹ The ATS/IDSA guidelines recommended a duration of at least 5 days of antibiotic therapy for patients with CAP, provided that the patient is clinically stable (strong recommendation, moderate quality of evidence).²

ATS now conditionally recommends a shortened duration of antibiotic therapy (3-5 days) for adult outpatients (with comorbidities) and adult inpatients with non-severe CAP who achieve clinical stability (low-quality evidence). This recommendation is strengthened for patients who are at high risk for harm from prolonged antibiotic use, have a preference to reduce antibiotic exposure, and have resolution of inflammatory markers.

Patients who are not recommended for this abbreviated duration are those who have risk factors for severe disease, such as organisms requiring longer durations of therapy, high disease burden, complications, or risk factors for multidrug-resistant organisms (MDRO). For adults with severe CAP who are being treated inpatient and reach clinical stability, a duration of ≥5 days is recommended (strong, low-quality evidence).¹

A study by Dinh et al, published in 2021, evaluated the efficacy and safety of a 3-day beta-lactam therapy course for treatment of moderately severe community-acquired pneumonia in patients over 18 years of age. The participants were randomly assigned to receive either 5 days’ worth of placebo or beta-lactam therapy after already receiving 3 days of beta-lactam antibiotics (comparing a total antibiotic duration of 3 vs 8 days). The primary outcome was cure after 15 days of the first antibiotic dose, and this was marked by a resolution of symptoms associated with the infection and the absence of a fever above 38 degrees C.

78% of participants in the placebo group and 68% of participants in the beta-lactam treatment group demonstrated cure at day 15. This difference of 9.44% (95% CI, -0.15-20.34) showed non-inferiority based on the study’s predetermined margin of 10%. Reported incidents of adverse events were similar between treatment groups. The placebo group did have 3 deaths by day 30 (due to bacteremia, cardiogenic shock after acute pulmonary edema, and heart failure complicated by acute renal failure), and the beta-lactam group also had 2 deaths (pneumonia recurrence and possible acute pulmonary edema).⁴

Systemic Corticosteroids

The ATS strongly recommends against prescribing systemic corticosteroids for adult inpatients with non-severe disease (strong, low-quality evidence). However, there is a conditional recommendation for adult inpatients with severe disease (low-quality evidence), which can be strengthened by a short interval between the onset of symptoms and presentation, the ability to take steroids within 24 hours of meeting criteria for severe CAP, admission to ICU, complicated by respiratory failure, and elevated inflammatory markers. Corticosteroids have not been associated with any therapeutic benefits in patients with confirmed influenza virus infection. Currently, the guidelines do not recommend corticosteroids in patients with influenza based on data from a few observational studies.¹ Further research is needed to recommend the use of steroids in that patient population.