Development of bacterial resistance during treatment with topical gentamicin for chronic rhinosinusitis in patients with cystic fibrosis and primary ciliary dyskinesis. Retrospective case series

Background: The management of chronic rhinosinusitis (CRS) in patients with cystic fibrosis (CF) and primary ciliary dyskinesia (PCD) is still a challenge. At our institution we have used gentamycin nasal spray, extemporaneously produced, for prophylactic treatment of moderate-to-severe CRS. The aim of this study was to investigate the gentamycin susceptibility of bacteria in sputum samples in CF and PCD patients treated for CRS. Methodology: Patients with CF and PCD who were prescribed gentamycin nasal spray for CRS and had sputum bacterial cultures taken pre-treatment and followed-up at least once after ≥6 months were retrospectively included. Microbiological data were descriptively analysed in terms of bacterial species and resistance to gentamycin. Results: A case series of 17 CF and 12 PCD patients passed the inclusion criteria. Of those cases, three (18%) CF patients and one (8%) PCD patient developed resistance to gentamycin during treatment with gentamycin nasal spray. In all four cases, the resistant bacterial isolates were P. aeruginosa. Additionally, two CF patients already had P. aeruginosa isolates resistant to gentamycin in the pre-treatment culture. In further two CF patients, the multi-resistant Burgdorferi cepacia complex, including gentamycin resistance, was identified. P. aeruginosa and S. aureus in CF and P. aeruginosa and H. influenza in PCD were the predominant bacterial species. Conclusions: The study showed that there was moderate incidence of gentamycin resistance in CF and PCD patients at our institution. However, further prospective studies are needed to confirm the outcomes.