A 58 year old man with chronic obstructive pulmonary disease presents with acute worsening dyspnea, increased sputum volume, and purulent sputum for 3 days. He is a chronic smoker with FEV1 40 percent predicted. On examination he is tachypnoeic with wheezes but haemodynamically stable. This is his second exacerbation this year. According to COPD guidelines, which of the following is an indication for antibiotics in this exacerbation?