Peptide nanonet trapping suppresses bacterial motility and delays antibiotic resistance emergence

In the presence of antibiotics, motile bacteria can navigate chemical gradients for adaptation and survival. Antimicrobial peptides (AMPs) have been widely explored as adjuvant to improve the activity potency of antibiotics, but mainly through the disruption of bacterial membranes. In this work, we investigated the impact of nanonet trapping using fibrillating peptides, a mechanistically unique sub-group of AMPs, on motility recovery of bacteria and their capacity to develop antibiotic resistance.

The ability of fibrillating AMPs to potentiate activity and delay resistance of antibiotics from diverse classes was evaluated against clinical isolates of Gram-negative pathogens. Using soft agar assay and live-tracking microscopy, shifts in the motility of the bacteria population subjected to different treatments were evaluated. To further elucidate the mechanism of action, the expression of major flagella-encoding genes was quantified and hypomotile bacteria strains were studied.

At sub-inhibitory concentrations, fibrillating peptides not only displayed synergistic interactions, but also significantly delayed the emergence of resistance to antibiotics such as rifampicin for at least 18 days. The peptide-antibiotic synergy profiles were lost after prolonged treatment with antibiotic monotherapy but preserved when co-administered with fibrillating peptides throughout the serial passage. The nanonet-forming peptides were shown to serve as a motility filter where the bacteria population gradually shifted towards homogeneous hypomotility associated with inferior survivability.

This work showcases the potential of AMPs as low-concentration adjuvants for extending the clinical lifespan of current antibiotics and highlights bacterial motility as an underexplored target for antibiotic development.