Community acquired pneumonia

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See main article pneumonia.

The British Thoracic Society published revised treatment guidelines for community acquired pneumonia (CAP) in 2004 (here) Use the CURB65 score for risk stratification.


The main isolated pathogen is Streptococcus pneumoniae, explaining 35% of presentations in Europe, with some variation by population and time of year (typically winter peaks of metapneumovirus, influenza A and B viruses, RSV, Staphylococcus aureus, and Streptococcus pneumoniae. For example in those from the USA requiring hospitalisation it is somewhat rarer in terms of potential pathogen's actually isolated/demonstrated by PCR where recent figures were[1]:

Intensive care need doubles the rate of Streptococcus pneumoniae to 8%, increases rate for Staphylococcus aureus by five times to 5% and enterobacteriaceae by three times to 3%. Such data is important as it suggests in Western countries that the viral load may have been underestimated and that we have an incomplete understanding of aetiology based upon extrapolation. Indeed some have difficulty with assigning viruses as the cause of pneumonia given classic pathophysiology teaching. Also important is that organisms such as Pseudomonas aeruginosa, ESBL+ enterobacteriaceae and MRSA are much commoner in the immunocompromised.

Guides to treatment

  • Antibiotics (at least 5 days) consistent with local guidelines (which may include biomarker measurement to determine duration)
  • In primary community treatment CRP measurement can reduce exposure to antibiotics safely and NICE recommends no use of antibiotics if chest symptoms without convincing evidence of CAP and CRP<20 ng/L.
  • Procalcitonin (PCT) is increasingly being used in the ITU and new dysponea hospital presentations to distinguish between bacterial and non-bacterial presentations. The cut off is 0.25 &microg/L.[2][3][4]
  • Microbiology testing is only recommended where probability of changing the initial empirical antibiotic is high such as hospitalised CAP[5]:
    • Sputum culture should be universal if productive of sputum
    • Blood culture, legionella and pneumococcal urinary antigen if moderately ill
  • Role of corticosteroids unclear but they appear to reduce hospital length of stay[5]
  • Follow up interval minimum is 72 hours, shorter if hospitalised.