Pneumonia

The answer first

Pneumonia is an acute infection of the lung parenchyma (alveoli and distal airways) that produces cough, fever, purulent sputum, dyspnoea, and radiographic consolidation. It is one of the commonest reasons for hospital admission and a leading cause of infectious death worldwide. ^[1]

Three facts must land before everything else: ^[1]

1. Severity determines everything. The first clinical decision is not which antibiotic — it is where to treat (home, ward, ICU). A validated severity score (CURB-65 or PSI) must be calculated at presentation. Missing severe pneumonia and sending a deteriorating patient home is a fatal and litigated error.
2. The setting determines the organism, and the organism determines the antibiotic. Community-acquired pneumonia (CAP) is overwhelmingly Streptococcus pneumoniae, atypicals (Mycoplasma, Legionella, Chlamydia), and Haemophilus influenzae. Hospital-acquired and ventilator-associated pneumonia (HAP/VAP) shift toward Gram-negative bacilli, Pseudomonas aeruginosa, and MRSA. Empiric therapy must cover the likely organisms for that patient's setting.
3. Empiric therapy is time-critical. In septic pneumonia, the first dose of antibiotics should be given within one hour of recognising sepsis. The IDSA/ATS 2019 guideline provides a clear, site-of-care-driven algorithm that works across ANZ, UK, and US practice ^[1].

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References8ShowHide

1. [1]Metlay JP, Waterer GW, Long AC, et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America Am J Respir Crit Care Med, 2019.PMID 31573350
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5. [5]Siemieniuk RAC, Meade MO, Alonso-Coello P, et al. Corticosteroid Therapy for Patients Hospitalized With Community-Acquired Pneumonia: A Systematic Review and Meta-analysis Ann Intern Med, 2015.PMID 26258555
6. [6]Blum CA, Nigro N, Briel M, et al. Adjunct prednisone therapy for patients with community-acquired pneumonia: a multicentre, double-blind, randomised, placebo-controlled trial Lancet, 2015.PMID 25608756
7. [7]Schuetz P, Wirz Y, Sager R, et al. Effect of procalcitonin-guided antibiotic treatment on mortality in acute respiratory infections: a patient level meta-analysis Lancet Infect Dis, 2018.PMID 29037960
8. [8]Mandell LA, Wunderink RG, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults Clin Infect Dis, 2007.PMID 17278083