Bronchitis is an inflammation of the large bronchi (meium-size airways) in the lungs. It can lead to pneumonia. Acute bronchitis is usually caused by viruses or bacteria and may last several days or weeks.Acute bronchitis is characterized by cough and sputum (phlegm) production and symptoms related to the obstruction of the airways by the inflamed airways and the phlegm, such as shortness of breath and wheezing. Diagnosis is by clinical examination and sometimes microbiological examination of the phlegm. Treatment may be with antibiotics (if a bacterial infection is suspected), bronchodilators (to relieve breathlessness) and other treatments.