In patients with “so-called” acute bronchitis (productive cough, malaise, difficulty breathing, wheezing), the presence of coloured (yellow, green or brown) sputum is associated with an increased risk of bacterial infection: 22 - 24% in people with coloured sputum vs 5 - 6% in people with clear or white sputum. However, antibiotic treatment has no clinical benefit in patients with coloured sputum.
To confirm pneumonia as a cause of cough, the patient would need to be sicker, febrile, have chest pain, and have consistent pneumonia breath sounds.1