Longitudinal monitoring of sinonasal and oral bacterial reservoirs to prevent chronic lung infection in people with cystic fibrosis

Background: Paranasal sinuses act as bacterial reservoirs and contribute to transmitting bacteria to the lower airway of patients with cystic fibrosis (CF). Also, passage of bacteria from the oral cavity to the lungs may occur. Methods: We evaluated the presence of Pseudomonas aeruginosa, Staphylococcus aureus, Stenotrophomonas maltophilia, Achromobacter xylosoxidans and Serratia marcescens in sputum and nasal lavage of 59 patients with CF, and also collected saliva and used toothbrushes from 38 of them. We assessed the clonal identity of the strains isolated from the different samples by pulsed-field gel electrophoresis. Results: About 80% of the patients were positive for at least one of the bacterial species examined in nasal lavage and sputum. Among the subjects with positive sputum, 74% presented the same species in the nasal lavage and saliva, and 26% on their toothbrush. S. aureus was the most abundant species in all samples. Clonal identity (⩾80% similarity) of the strains isolated among the different samples from each patient was confirmed in almost all cases. Longitudinal observation helped to identify five patients who were colonised in the lower airways after an initial period of nasal or oral colonisation. Conclusion: Nasal and oral sites act as bacterial reservoirs, favouring the transmission of potentially pathogenic microorganisms to the lower airway. The lack of eradication from these sites might undermine the antibiotic therapy applied to treat the lung infection, allowing the persistence of the bacteria within the patient if colonisation of these sites is not assessed, and no specific therapy is performed.