Rationale: Lower airway (LAW) infection with Pseudomonas aeruginosa (P.a.) and Staphylococcus aureus (S.a.) is the leading cause of morbidity in Cystic Fibrosis (CF). The upper airways (UAW) were shown to be a gateway for acquisition and reservoir of opportunistic bacteria. Therefore, tools for UAW-assessment within CF-routine care require evaluation.
Objectives: Aims of the study were non-invasive assessment of UAW and LAW microbial colonization and genotyping of P.a. and S.a. strains from both segments.
Methods: 182 CF-patients were evaluated (age 0.4-68yrs, median 17yrs). LAW specimens were preferably sampled as expectorated sputum and UAW specimens by nasal lavage. P.a. and S.a.-isolates were typed in informative single nucleotide polymorphisms (SNPs) or by spa typing, respectively.
Results: Of the typable S.a. and P.a. isolates from concomitant UAW- and LAW-positive specimens, 31 of 36 patients were carrying identical S.a. spa types and 23 of 24 patients identical P.a. SNP-genotypes in both compartments. Detection of S.a. or P.a. in LAW specimens was associated with a 15- or 88-fold higher likelihood to also identify S.a. or P.a. in a UAW specimen from the same patient.
Conclusions: The presence of the same genotypes in UAW and LAW suggests a role of UAW as a reservoir of S.a. and P.a. in CF. Nasal lavage appears to be suitable for non-invasive UAW-sampling but further longitudinal analyses and comparison with invasive methods are required. While UAW bacterial colonization is typically not assessed in regular CF-care, our data challenge the need to discuss diagnostic and therapeutic standards for this airway compartment.