Empirical therapy for suspected pseudomonal high-severity CAP in adults

Pseudomonas aeruginosa is a rare cause of CAP in adultsRestrepo, 2018Sando, 2021. Identification of P. aeruginosa in sputum may represent colonisation rather than pneumonia. For treatment of P. aeruginosa exacerbations of bronchiectasis, see Antibiotic management of bronchiectasis in adults or, for cystic fibrosis, see Airway infection and antibiotic therapy in cystic fibrosis.

Consider empirical antipseudomonal therapy for high-severity CAP in adults with known colonisation of sputum with P. aeruginosa (eg bronchiectasis) and one of the following:

• gram-negative bacilli predominant on Gram stain or identified by culture of sputum¹ or blood (pending identification)
• sepsis or septic shock.

Do not use previous susceptibility results to guide current antipseudomonal therapy unless the sample was taken recently (eg in the last month).

If empirical antipseudomonal therapy is indicated for high-severity CAP in adults, replace the empirical therapy regimen with:

The choice of aminoglycoside may be influenced by several factors, including:

• the spectrum of activity
• the availability of aminoglycoside therapeutic drug monitoring
• whether the laboratory reports aminoglycoside susceptibility
• drug cost.

There are limited clinical data to support tobramycin over gentamicin; however, the minimum inhibitory concentration [MIC] for tobramycin is slightly lower than gentamicin in vitro (particularly for P. aeruginosa) and has a greater likelihood of target attainment.

For adults with high-severity CAP who have had a nonsevere (immediate or delayed) hypersensitivity reaction to a penicillin, use the cefepime-based regimen above.

For adults with high-severity CAP who have had a severe immediate⁶ hypersensitivity reaction to a penicillin, the cefepime-based regimen above can be considered if a beta-lactam antibiotic is strongly preferred (for considerations, see Severe immediate hypersensitivity: Implications of cross-reactivity between penicillins and cephalosporins).

For adults with high-severity CAP who have had a severe immediate⁶ hypersensitivity reaction to a penicillin in whom cefepime is not used, or for patients who have had a severe delayed⁷ hypersensitivity reaction to a penicillin, replace the empirical therapy regimen with:

If P. aeruginosa is confirmed, modify therapy based on the results of culture and susceptibility testing, if available – see Pseudomonas aeruginosa pneumonia. If P. aeruginosa is not identified, switch to a narrower-spectrum empirical regimen or, if another pathogen is identified, see Directed therapy for pneumonia.