Antimicrobial resistance poses a significant threat to global health and is exacerbated by the propensity for pathogenic species to form biofilms.1Biofilms are communities of homo- or heterogeneous microorganisms encased in an extracellular polymeric matrix, which further impedes antibiotic diffusion to susceptible bacterial cells. The limited number of antibiotics in the drug development pipeline highlights the need for novel antimicrobials that target both planktonic and biofilm bacterial populations. This project aimed to address this need through the design and synthesis of dual-acting antimicrobials known as ‘hybrids’, which combine separate moieties to provide antibacterial and antibiofilm activity.2 Our approach to hybrid development involves installation of an azide to an antibiotic, and alkyne to an antibiofilm agent. The two are subsequently linked using copper-catalysed azide-alkyne cycloaddition 'click chemistry' methodology. Here, we report on our alkyne derivatised ammonium and phosphonium hybrids, designed to inhibit bacterial biofilm formation whilst maintaining activity against planktonic populations. Over 20 hybrids spanning six antibiotic classes were synthesized with these charged quaternary antibiofilm agents. These compounds were evaluated against Gram-negative and Gram-positive bacterial species to determine the minimum inhibitory concentration (MIC), minimum biofilm inhibition concentration (MBIC), cytotoxicity, and haemolytic activities. This synthesis and screening approach led to the identification of ROX-PCM5, a macrolide-based hybrid with enhanced MIC and MBIC against Staphylococcus aureus, including strains intrinsically resistant to macrolides. ROX-PCM5 also induced activity against a panel of Gram-negative strains, including multi-drug resistant isolates. Mechanistic studies are ongoing. These dual-acting antimicrobials have the potential to advance the management chronic bacterial infections and restock the antibiotic pipeline.