Differential Diagnosis for Green Colour Sputum

Single Most Likely Diagnosis

• Pseudomonas aeruginosa: This bacterium is known for producing pigments, including pyocyanin, which gives sputum a greenish color. It is a common cause of respiratory infections, especially in patients with cystic fibrosis or those who are immunocompromised.

Other Likely Diagnoses

• Streptococcus pneumoniae: While not typically associated with green sputum, some strains can produce a greenish discoloration due to the presence of pneumolysin.
• Haemophilus influenzae: This bacterium can cause respiratory infections and, in some cases, may produce a greenish tint in sputum due to its enzymatic activity.
• Moraxella catarrhalis: Though less common, it can also be associated with green sputum production in respiratory infections.

Do Not Miss Diagnoses

• Burkholderia cepacia complex: These bacteria can cause severe respiratory infections, particularly in patients with cystic fibrosis, and may produce a greenish sputum. Missing this diagnosis could lead to inappropriate treatment and severe outcomes.
• Stenotrophomonas maltophilia: This bacterium is an emerging pathogen in respiratory infections, especially in immunocompromised patients, and can produce green sputum. It has intrinsic resistance to many antibiotics, making correct identification crucial.

Rare Diagnoses

• Achromobacter xylosoxidans: A less common cause of respiratory infections that can produce pigments leading to green sputum.
• Chlamydophila pneumoniae: Though typically causing mild infections, in rare cases, it might be associated with green sputum production, especially in atypical pneumonia presentations.