Rossa Brugha (Junior Doctor): A 3-year-old boy with cystic fibrosis (CF) diagnosed on newborn screening (sweat chloride 90 mmol/L, F508del homozygous) attended routine follow-up in the CF clinic. He had had a wet cough for the previous 3 weeks. In addition to CF, he had previously been diagnosed with gastro-oesophageal reflux (oesophageal pH <4.0 for 13% of study at age 2 months) and an unsafe swallow with risk of aspiration on thin fluids (on videofluoroscopy at age 23 months). He had completed a 2-week course of co-amoxiclav 400/57 5 mL twice daily and then started a 2-week course of ciprofloxacin 250 mg twice daily in view of a previous growth of Pseudomonas aeruginosa at 14 months of age. He was not wheezing but his mother said that she could feel crackling in his chest. He was otherwise well, with no fever or coryzal symptoms. A cough swab taken at this clinic showed no bacterial growth. Three months prior to this he had similar symptoms, during which an induced sputum grew Haemophilus influenzae, which was ampicillin resistant and treated with a course of cefixime.

Andrew Bush (Professor of Respiratory Paediatrics): In summary, this preschool child with CF has ongoing symptoms despite appropriate empiric courses of antibiotics. At this point, the differential includes CF-related issues and …