# Exploring the anti-biofilm effect of darobactin B and colistin in static and dynamic environments

## TL;DR

This study explores how darobactin B, a new antibiotic, can effectively disrupt and kill bacteria in biofilms, especially in a controlled environment.

## Contribution

The study introduces a novel application of darobactin B against Pseudomonas aeruginosa biofilms using a microfluidic model for real-time monitoring.

## Key findings

- Darobactin B reduced viable biofilm cells by six orders of magnitude in static assays.
- Repeated dosing of darobactin B killed 85%–97% of biofilm cells and suppressed regrowth for 48 hours.
- Multi-dose darobactin B caused biofilm disruption and reduced surface coverage by ~40%.

## Abstract

The increasing challenges of treating biofilm-associated infections highlight the importance to develop new options against biofilm-embedded bacteria. In this study, we evaluated darobactin B—a promising pre-clinical antibiotic candidate targeting the outer membrane protein BamA—against Pseudomonas aeruginosa biofilms. First, a static biofilm assay was used for primary screening and showed that darobactin B reduced the viable cells within a biofilm by six orders of magnitude compared to the untreated control. Subsequently, a microfluidic model was conducted to allow real-time monitoring of biofilm development, treatment, and potential regrowth under controlled hydrodynamic conditions. In this assay, the reference compound colistin exhibited strong activity after single-dose administration. Although less effective after single dosing, darobactin B showed notable anti-biofilm activity by killing 85%–97% of biofilm cells and suppressing biofilm recovery for at least 48 h when applied repeatedly once daily for 5 days. When administered repeatedly in the multi-dose regimen, darobactin B caused biofilm disruption and cell detachment, leading to ~40% surface coverage reduction. Our findings highlight the potential of darobactin B as an anti-biofilm agent.

Bacterial biofilms pose serious healthcare challenges, contributing to chronic and device-related infections. Biofilm-embedded bacteria are highly resistant to conventional antibiotics and lead to growing reliance on last-resort drugs, thus underscoring the need for new therapeutic approaches. This study shows that darobactin B consistently disrupts Pseudomonas aeruginosa biofilms and delays regrowth. The multi-dose microfluidic assay provides a flexible platform for real-time evaluation of biofilms, which may support the optimization of treatment regimens.