Mucus and Mucin Environments Reduce the Efficacy of Polymyxin and Fluoroquinolone Antibiotics against Pseudomonas aeruginosa

Mucus, a biopolymer hydrogel that covers all wet epithelia of the body, is a potential site for infection by pathogenic bacteria. Mucus can bind small molecules and influence bacterial physiology, two factors that may affect the efficacy of antibiotics. In spite of this, the impact of mucus on antibiotic activity has not been thoroughly characterized. We examined the activity of polymyxin and fluoroquinolone antibiotics against the opportunistic pathogen Pseudomonas aeruginosa in native mucus and purified mucin biopolymer environments. We found that mucus reduces the effectiveness of polymyxins and fluoroquinolones against P. aeruginosa. Mucin biopolymers MUCSAC, MUC2, and MUCSB are primary contributors to this reduction. Our findings highlight that the biomaterial environmental context should be considered when evaluating antibiotics in vitro.