Sputum Gram stain and culture for CAP in adults

For adults with high-severity CAP, collect sputum samples for Gram stain and culture.

For adults with low- or moderate-severity CAP, routine collection of sputum for Gram stain and culture is not recommendedDel Rio-Pertuz, 2019File, 2023Metlay, 2019. Consider collecting samples if the patient is not improving, there is diagnostic uncertainty, or a resistant or rare pathogen is suspected (eg Mycobacterium tuberculosis). Collect samples only if the patient can produce sputum, preferably before or soon after starting antibiotic therapy.

If sputum samples can be collected before starting antibiotic therapy, sputum Gram stain and culture can indicate the likely pathogen, provided the sample is of good quality (presence of polymorphs but few or no squamous epithelial cells on microscopy).

For a list of other clinical and microbiological investigations for CAP in adults, see Clinical and microbiological investigations for community-acquired pneumonia (CAP) in adults.