Reduction of antibiotic-induced biofilm accumulation of Pseudomonas aeruginosa by quaternized phytoglycogen.

Biofilms are oft cited as a factor in the unwanted persistence and recalcitrance of microbial life and a strong research initiative exists to identify, understand, and target vulnerabilities. Phytoglycogen is a biodegradable nanoparticulate biomaterial that is purified from crop plants. Importantly, the highly branched glucan structure provides a scaffold on which to construct novel polymers. Functionalized phytoglycogen (FP) was synthesized using green chemistry principles. Screening of several molecules identified a form of quaternized phytoglycogen which reduced biofilm formation and accretion by Pseudomonas aeruginosa. Exposing P. aeruginosa to modified phytoglycogen and antibiotic in combination not only substantively reduced biofilms, but also prevented increased biofilm formation, a biological response to suboptimal antibiotic concentrations. Treatment of pregrown biofilms with sub-minimum inhibitory concentration antibiotic alone also led to increased proliferation, whereas FP-antibiotic combinations prevented or reduced the extent of this. Swimming, swarming and twitching motility, all critical for biofilm development, were negatively affected by FP. This work supports phytoglycogen as a promising foundational molecule for novel polymers, including those with anti-biofilm function. Critically, in addition to published reports on how suboptimal antibiotic concentrations promote biofilm formation, we demonstrated a similar effect upon pre-existing biofilms, indicating a further route for the failure of antibiotic therapies.