Background: The care of patients with cystic fibrosis (CF) has improved after the appearance of cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapies, especially ITE, although not much is known about their effectiveness in the pediatric population.

Objectives: To describe the effectiveness of ITE treatment in terms of microbiological evolution in children with CF.

Methods: Descriptive study of pediatric patients with CF followed in a tertiary hospital in active treatment with ITE. We included 24 patients that started ITE after November of 2021, and completed 6 months of treatment. Microbiological evolution in patients after starting treatment with ITE was analyzed after accepted participation. 

Results: Before starting Kaftrio 54% showed colonization by Staphylococcus aureus (85% of them continuous colonization) and 25% colonization by Pseudomona aeruginosa (63% intermittent colonization). After 6 months, there was a 50% decrease in colonization by Staphylococcus aureus (p=0.500 McNemar test) and a 64% decrease in colonization by Pseudomona aeruginosa (p=0.980 McNemar test). Before ITE, 3 patients had 1 exacerbation per year, after treatment no patients had one (p=0.083 Wilcoxon test).

Conclusion: Continuous colonization of the airway by Staphilococcus aureus and Pseudomona aeruginosa is related with higher complications in patients with CF. We observed a decrease in the colonization by those microorganisms six months after the start of treatment with ITE. The correlation of this decrease and the patient?s clinic must be established by studies with a bigger population and following time.