123 A shotgun metaproteomics approach to study the faecal microbiome of patients with cystic fibrosis reveals a reduction of butyrate-producing bacteria G. Debyser1, B. Mesuere2, L. Clement2, G. Duytschaever1, P. Van Hecke1, P. Dawyndt2, K. De Boeck3, P. Vandamme1, B. Devreese1. 1Ghent University, Department of Biochemistry and Microbiology, Ghent, Belgium; 2Ghent University, Department of Applied Mathematics and Computer Science, Ghent, Belgium; 3University Hospital of Leuven, Department of Pediatrics, Leuven, Belgium