Mucin adhesion of serial cystic fibrosis airways Pseudomonas aeruginosa isolates

Abstract

The chronic airway infections with Pseudomonas aeruginosa are the major co-morbidity in people with cystic fibrosis (CF). Within CF lungs, P. aeruginosa persists in the conducting airways together with human mucins as the most abundant structural component of its microenvironment. We investigated the adhesion of 41 serial CF airway P. aeruginosa isolates to airway mucin preparations from CF sputa. Mucins and bacteria were retrieved from five modulator-naïve patients with advanced CF lung disease. The P. aeruginosa isolates from CF airways and non-CF reference strains showed a strain-specific signature in their adhesion to ovine, porcine and bovine submaxillary mucins and CF airway mucins ranging from no or low to moderate and strong binding. Serial CF clonal isolates and colony morphotypes from the same sputum sample were as heterogeneous in their affinity to mucin as representatives of other clones thus making 'mucin binding' one of the most variable intraclonal phenotypic traits of P. aeruginosa known to date. Most P. aeruginosa CF airway isolates did not adhere more strongly to CF airway mucins than to plastic surfaces. The strong binders, however, exhibited a strain-specific affinity gradient to O-glycans, CF airway and mammalian submaxillary mucins.

Keywords: Pseudomonas aeruginosa; airway mucin; bacterial adhesion; cystic fibrosis; submaxillary mucin.

Figure 1

Synthetic tetra-antennary N –glycan and benzylated O-glycan structures used for competition experiments (yellow square, N-acetylgalactosamine; yellow circle, galactose; blue square, N-acetylglucosamine; green circle, mannose). Structures have been drawn with the software tool ‘DrawGlycan-SNFG’ (Cheng et al., 2017).

Figure 2

Upper panel: Boxplot presentation of the adhesion of 14 P. aeruginosa strains to polystyrene, the CF mucin preparations from sputa of CF donors 2, 3, 4, 5, 6, 7 and to the submaxillary mucins OSM, a-OSM, PSM, a-PSM and BSM. Lower panel: Boxplot presentation of the adhesion of P. aeruginosa strains TBCF10839, CF1-7, CF1-8, CF1-10, CF2-7, CF2-8, CF3-7, CF4-4, CF5-8, CF5-9, PAO, IATS-O4, IATS-O6, IATS-O9 to six CF mucin preparations and five submaxillary mucins. The center line of the boxplot depicts the median (50th percentile). The lower and upper boundary of the box represent the first (25th percentile) and third (75th percentile) quartile, and hence define the interquartile range (IQR). Whiskers extend from the box to the largest/smallest non-outlier data point (1.5 × IQR). Outliers are indicated by the symbol ‘x’.