Airway microbiome studies challenge simplistic models of inhaled tobramycin benefit

In 1999, Ramsey and colleagues published the results of a clinical trial of aerosolised tobramycin in cystic fibrosis (CF) to target chronic Pseudomonas aeruginosa infection.1 In keeping with their earlier demonstration of efficacy,2 they reported treatment to be associated with a reduction in P. aeruginosa sputum density and substantial clinical benefit (improved lung function and reduced risk of hospitalisation). Consistent findings were reported in subsequent studies,3 4 leading tobramycin inhaled powder/solution (TIP/S) maintenance therapy to go on to become the most common antibiotic used to treat people with cystic fibrosis (PWCF). While none of these studies related clinical outcome to microbiological impact directly, it is widely assumed that depletion of P. aeruginosa underpins TIP/S benefit.