(493) Bacterial and viral upper and lower airways infection in cystic fibrosis patients with stable condition

Background: Bacterial and viral airway infections are adverse factors for prognosis in patients with cystic fibrosis (CF). To date, the role of viral infections is unclear. Proper microbiological follow-up is essential and the correlation between upper (UAW) and lower airways (LAW) microbiology may be important for lung disease management.

We aim to evaluate airways microbiology in patients with stable clinical conditions.

Methods: Between September 2021 and March 2022 in Florence CF center, 144 nasal lavage-throat swab paired samples were collected from 72 clinically stable CF patients, not chronically colonized by P. aeruginosa (PA). The study enrolled 59 children (median age 9, range 2-16) and 13 adults (median age 28, range 18-59). LAW specimens (72) were sampled as throat swab and UAW specimens (72) were collected by nasal lavage with two methods, Mainz (44) or Ryno-set (28), using randomization. We performed conventional microbiological analyses on all samples. In order to screen for respiratory viruses, multiplex PCR (BIOFIRE® FILMARRAY® RP 2.1 Plus) was performed. Respiratory symptoms and forced expiratory volume (FEV1) values were evaluated for all patients.

Results: 21 (29%) patients tested positive for at least one virus in both UAW and LAW specimens. The most frequently identified viruses were Human rhinovirus/enterovirus (22%) and Respiratory syncytial virus (6%). Two (3%) patients tested positive for SARS-CoV-2. Concordance between sampling methods for viral detection in UAW and LAW specimens was observed in 59 paired-samples (82%), including 40 patients with no viral infections and 19 virus-positive for both samples. Discordance was described in 13 subjects, 10 out 13 did not show viral infection in nasal lavages. Concerning positive nasal lavages, 21% was performed by Ryno-set, while 36% by Mainz approach.

The prevalent bacterium was S. aureus (SA) in UAW (53%) and LAW (69%) cultures, followed by Enterobacteriaceae (UAW 8%, LAW 6%), Methicillin-resistant SA (UAW 7%, LAW 6%), PA (UAW 4%, LAW 6%) and other clinical relevant Gram-negative bacteria such as A. xylosoxidans, S. maltophilia and O. anthropi (UAW 7%, LAW 13%). Nasal lavages performed with Ryno-set tested positive in 72% of patients, while 64% of Mainz lavages were positive. Mainz nasal lavages showed different SA and PA isolations (48% and 5%, respectively) compared to the samples collected with Ryno-set technique (61% and 4%, respectively). Interestingly, concordance between sampling methods for bacterial detection in UAW and LAW was the same with the two methods (53%).

Bacterial and viral infections were found in UAW and LAW of stable CF patients, but no clinical correlation was observed.

Conclusions: The two methods of UAW lavage showed slight differences in the performance. Virus infection appeared to be less prevalent compared to the bacterial detection in both UAW and LAW. We did not find correlations between presence of viruses and respiratory symptoms. However further investigation is needed for a better understanding clinical role of viral infection in CF patients.

Acknowledgements: This work was supported by the Tuscany Region [grant number K37, K35].

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