Increase in ventilated air spaces after eradication of chronic methicillin-resistant Staphylococcus aureus infection in cystic fibrosis patients.

Effective microbiogical eradication of methicillin-resistant Staphylococcus aureus (MRSA) in patients with cystic fibrosis (CF) can be obtained, but its effect is not always clear-cut in terms of spirometric indices. The aim of this observational prospective cohort study was to study the potential effect of eradication of chronic MRSA infection on lung function including ventilation distribution. Six CF patients, chronically colonized with MRSA (median age: 21 years (range 14-46); median FEV1: 76 (95%CI 58-98)%pred) were successfully eradicated using oral rifampicin and fusidic acid in combination with topical decolonization measures. Lung function and multiple breath washout test were performed at the start and at the end of the eradication protocol and after an average follow-up period of 7·5±1·5(SD) months. One patient cultured MRSA again 4 months after successful eradication. All patients reported reduced sputum production and viscosity. By the end of the follow-up period, there was an increase in ventilated FRCMBW and no change in plethysmographic FRCPL. This resulted in a significant decrease of trapped air by half a litre (from 579 to 40 ml; P = 0·013). Lung clearance index (LCI) also showed a small but significant decrease (from 7·2 to 6·7; P = 0·014) after eradication of MRSA. We conclude that MRSA eradication can be successful, also in terms of recruitment of previously unventilated air spaces, potentially due to reduced sputum production and/or viscosity.