Grant: Early Career Investigator Awards - Cystic Fibrosis Research

Background: Cystic fibrosis (CF) is among the most common life-limiting genetic disorders in Canada, with more than 4000 people living with this disease. The primary cause of death in CF is respiratory failure from chronic infection of the lung. In CF care, it is routine practice to monitor the sputum for bacterial infection. The most common bacterium isolated in the airways of children with CF is methicillin-sensitive Staphylococcus aureus (MSSA). Antibiotics are a mainstay of treatment in CF, and are of clear benefit when people with CF have increased pulmonary symptoms (cough, increased sputum etc). However, there is controversy in the CF community over whether we should treat people who are clinically well, but have bacteria in their airways. Part of this uncertainty has arisen from the fact that traditional pulmonary function measures are often not sensitive enough to detect subtle improvements in lung function following treatment in mild CF lung disease. The forced expiratory volume in one second (FEV1) is the most commonly used pulmonary function test in CF but is a poor marker of early lung disease. The lung clearance index (LCI) is a new marker that has been shown to be a more sensitive measure of early CF lung disease. In this study, we will use LCI and other outcomes measures to assess the effect of antibiotic treatment in clinically stable children with CF who have MSSA growing in their sputum. Question: Does treatment with three weeks of oral cephalexin (a common antibiotic used in CF care) result in an improvement in the lung function of children with CF who are symptomatically stable, but have MSSA growing in their sputum? Study Design: This is a randomised trial, comparing placebo to cephalexin. Children will receive a blinded medication for 3 weeks. We will use LCI, FEV1 and clinical symptoms to measure response. Hypothesis: Compared to placebo, a 3 week course of cepahalexin will result in an improvement in lung function in this population.