A 24-year-old patient with cystic fibrosis (CF) is seen in the clinic for routine follow-up. She reports no change in pulmonary symptoms and specifically has not had any increase in cough, sputum production, chest tightness, or wheezing. The patient has mild lung disease with FEV₁ of 85% predicted. During the visit, sputum culture is obtained and grows Pseudomonas aeruginosa. The patient has never had this grow on samples collected in the past.