Results indicate that the severity of CF lung disease is associated with an imbalanced presence of antibiotic resistance genes and with differential abundance of genes involved in metabolic pathways putatively correlated with bacterial virulence. Sputum samples from CF patients were characterized by a pyrosequencing approach, to assess how lung microbiota composition changes following a severe decline in lung function. Patients with a substantial decline in their lung function and patients with a stable lung function showed a different bacterial composition, with the first group of patients reporting a more heterogeneous community of microbiota. Pseudomonas was the dominant genus followed by Staphylococcus and Prevotella. The authors also found the presence of the unusual anaerobic genus Sneathia. The ability to analyze the entire lung microbiome and identify biomarkers can lead to personalized medicine based on the microbiome.