Most cases are caused by bacteria, especially aerobic gram-negative bacilli, such as Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Acinetobacter species.
Patients usually present with a combination of fever (or hypothermia), leukocytosis (or leukopenia), purulent sputum, and poor oxygenation. A new and/or persistent alveolar shadowing on chest x-ray or computed tomography scan confirms the diagnosis.
A sputum (or other non-invasive respiratory) sample should be obtained before initiating antibiotics; the result of the culture should be used to de-escalate antibiotics and focus on the offending pathogen.
Intravenous broad-spectrum antimicrobials should be used initially for patients with severe symptoms/signs or at higher risk of resistance.
Hospital-acquired pneumonia (HAP) is an acute lower respiratory tract infection that is by definition acquired after at least 48 hours of admission to hospital and is not incubating at the time of admission.
During the COVID-19 pandemic, for patients with suspected or confirmed COVID-19 viral pneumonia with symptoms and signs that start at any point after hospital admission, see our topic Coronavirus disease 2019 (COVID-19) external link opens in a new window. Consider all patients with cough and fever or suggestive symptoms to have COVID-19 until proven otherwise. Pneumonia due to COVID-19 is not covered in this topic.
For patients with symptoms and signs consistent with bacterial pneumonia (not secondary to COVID-19) that start on days 1 or 2 after hospital admission, see our topic Community-acquired pneumonia (non-Covid-19). Non-hospitalised patients with pneumonia who have had significant experience with the healthcare system (formerly defined as having healthcare-associated pneumonia) should be managed as for community-acquired pneumonia, using local epidemiology and validated risk factors for MRSA or P aeruginosa to guide treatment decisions.
For patients with suspected pneumonia of any cause developing after endotracheal intubation, consult a senior specialist in critical care. Ventilator-associated pneumonia is not covered in this topic.
History and exam
Honorary Professor of Respiratory Sciences
University of Leicester
JB is Chair of the British Thoracic Society.
JB declares that he has no competing interests.
BMJ Best Practice would like to gratefully acknowledge the previous expert contributor, whose work has been retained in parts of the content:
Forest W. Arnold, DO MSc, FIDSA
Associate Professor of Medicine
Division of Infectious Diseases
Department of Medicine
School of Medicine
University of Louisville
FWA declares that he has no competing interests.
Professor of Respiratory Infection/Honorary Consultant
University College London
JB was a member of the NICE pneumonia guidelines committee.
Section Editor, BMJ Best Practice
HDC declares that she has no competing interests.
Lead Section Editor, BMJ Best Practice
RW declares that she has no competing interests.
Comorbidities Editor, BMJ Best Practice
JC declares that she has no competing interests.
Drug Editor, BMJ Best Practice
AM declares that he has no competing interests.
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