MONITORING BACTERIAL RESERVOIRS TO PREVENT CHRONIC LUNG INFECTION IN CYSTIC FIBROSIS

Cystic fibrosis (CF) is a disease caused by mutations in the CFTR (CF transmembrane conductance regulator) gene and associated with severe damage to the lungs and the gastrointestinal system. One of the most important challenges in CF is treating and solving chronic lung infections which are the major cause of morbidity and mortality in patients in that once bacteria are established in the lung; eradication is rarely successful. The main objective of this study has been to evaluate the possible role of nasal/paranasal sinuses, saliva, and toothbrush as bacterial reservoirs in the development of chronic pulmonary infection and to compare the molecular profile of bacterial strains isolated from different sites in the body to confirm they circulate within the airways and oral cavity. Differently from previous works, our study was not limited to P. aeruginosa and S. aureus (the most important CF pathogens) but also included other potentially pathogenic emerging bacterial species that are frequently isolated from the sputum of CF subjects but still lack a clear clinical role in CF. Moreover, in this study, we have considered not only the classical sputum sample but also nasal lavage, saliva, and toothbrushes and have monitored a significant number of patients longitudinally. We evaluated the presence of Pseudomonas aeruginosa, Staphylococcus aureus, Stenotrophomonas maltophilia, Achromobacter xylosoxidans and Serratia marcescens in sputum and nasal lavage of 59 CF patients and also in saliva samples and used toothbrushes from 38 of them. At the end of the study, 190 sputum samples, 189 nasal lavage samples, 79 samples of saliva, and 87 toothbrushes were obtained and examined recovering and analyzing a total of about 1000 bacterial strains. Patients were classified by age (adult and paediatric) and by stage of lung colonisation with P. aeruginosa at enrolment (chronic, occasional). Based on these criteria, patients were divided into four groups: adults with chronic P. aeruginosa lung infection (AC), paediatrics with occasional P. aeruginosa colonisation (PO), adults and paediatrics free from P. aeruginosa (AN and PN, respectively). 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 detected in all samples. Clonal identity (≥80% similarity) of the strains isolated among the different samples from each patient was confirmed in almost all cases indicating that most of them belong to single clones circulating in the upper and lower airways, the oral cavity, and in some cases, in the toothbrush too. We concluded that nasal and oral sites act as bacterial reservoirs favoring transmission of pathogenic and potentially pathogenic microorganisms to the lower airways and vice-versa. It can be deduced that only the eradication of the microorganism from the reservoirs might avoid a lung chronic infection. Based on the results obtained, it has been established an understanding with the clinician from the Cystic Fibrosis Centre of Verona of the need of eradicating bacterial reservoirs. A specific protocol for the monitoring of the analyzed bacterial reservoirs and the eradication of the microorganisms present to prevent lung infection, was proposed, and accepted by them.