Blue-Green Sputum: Sign of Pseudomonas Infection

Blue or green sputum strongly suggests Pseudomonas aeruginosa infection.

Why the Color?

• P. aeruginosa produces pigments: pyocyanin (blue-green) and pyoverdine (fluorescent yellow-green).
• These color the purulent sputum in airway infections.

Clinical Context

• Common in: cystic fibrosis, bronchiectasis, ventilator-associated pneumonia, immunocompromised hosts, chronic wounds.
• Rare in healthy community-acquired pneumonia.
• Biofilm formation → antibiotic resistance (intrinsic + acquired).

Action

• Sputum culture + sensitivity essential.
• Empiric anti-pseudomonal coverage (piperacillin-tazobactam, meropenem, ceftazidime, cefepime, ciprofloxacin) in high-risk patients.
• Inhaled antibiotics (tobramycin, aztreonam) for chronic CF/bronchiectasis colonization.

Green sputum alone ≠ Pseudomonas (neutrophil myeloperoxidase also green), but blue-green is highly suggestive. Always culture.