Which of the following is least likely to be a symptom of acute bronchitis?

In cases of acute bronchitis, a productive cough is a common symptom, and the sputum produced can range in color from clear to yellow or green. A productive cough with green sputum is more characteristic of a respiratory infection or another lung disease, rather than an isolated case of acute bronchitis.

In contrast, a persistent cough, chest tightness, and fever are typical symptoms associated with acute bronchitis. The condition often results from viral infections that lead to inflammation of the bronchial tubes, causing these symptoms. While green sputum can occur, it is not as defining for acute bronchitis and is more indicative of a bacterial infection or a more serious underlying condition. Thus, productive cough with green sputum is least likely to be directly associated with acute bronchitis among the options provided.