Intestinal mucus acts as a nutrient source and signal for Klebsiella pneumoniae

Background: Klebsiella pneumoniae can colonize the gastrointestinal tract, yet its interactions with intestinal mucus remain poorly defined. In this study, we examined the capacity of Klebsiella pneumoniae (K. pneumoniae) to adhere and use intestinal mucus and its associated glycans. Methods: Multiple commercial and clinical K. pneumoniae isolates were tested for adhesion to porcine and human Mucin 2 (MUC2) using fluorescence-based assays and microscopy. In vivo mucus localization was examined in colonized mice by fluorescent in situ hybridization (FISH). Genomic analyses of K. pneumoniae genomes were performed to identify glycosyl hydrolases and sugar utilization pathways. Growth on mucin-derived monosaccharides or intact mucus was assessed in minimal media. Biofilm formation and aminoglycoside susceptibility were measured in the presence or absence of mucus. Results: All K. pneumoniae strains adhered robustly to porcine and human MUC2 in vitro and we found K. pneumoniae localized to the murine mucus layer in vivo. Genomic analysis of over 1,000 K. pneumoniae isolates revealed that most strains possess glycosyl hydrolases targeting internal galactose, N-acetyl-glucosamine (GlcNAc), and N-acetyl-galactosamine (GalNAc) glycan sugars, though they lack enzymes to cleave terminal fucose or N-acetyl-neuraminic acid. Consistent with this finding, we found that K. pneumoniae alone could not grow in minimal media with intact mucus as a sole carbon source. However, we found that K. pneumoniae could grow with free mucus glycan-derived sugars galactose, GlcNAc, GalNAc fucose and N-acetyl-neuraminic acid. Mucus did not alter biofilm formation, but it significantly increased sensitivity to gentamicin, kanamycin and streptomycin. Conclusion: These findings identify mucus as an important modulator of K. pneumoniae colonization and antibiotic responsiveness.