Novel Pyridine-Based Thiazolyl-Hydrazone as a Promising Attenuator of Pseudomonas aeruginosa Pathogenicity by Targeting Quorum Sensing

<i>Pseudomonas aeruginosa</i> biofilm-associated infections present higher recalcitrance to antimicrobial treatments, contributing to persistent and difficult-to-treat infections. Quorum sensing (QS) regulates various cellular processes that are important for the establishment and survival of microbial communities on the host. However, QS inhibitors for the treatment of <i>P. aeruginosa</i> biofilms remain under-researched, partly due to the complexity of QS signalling pathways and the challenge of developing non-toxic inhibitors. Herein, the bioactivity of 2-{(2<i>E</i>)-2-[1-(pyridin-2-yl)ethylidene]hydrazinyl}-1,3-thiazole-4-carboxylic acid (<b>TTNF37</b>), a novel pyridine-based thiazolyl-hydrazone (PTH), was investigated. The compound antimicrobial activity was evaluated against a broad spectrum of microorganisms, its antioxidant potential was assessed using different assays, and its QS-inhibitory effect on <i>P. aeruginosa</i> was studied using bioreporter strains. The effect on <i>P. aeruginosa</i> biofilm formation was analysed in terms of biomass, culturability, and metabolic activity, structure, and cell membrane integrity, while virulence factors were evaluated through absorbance measurements. In addition, molecular docking studies were performed to predict the drug's interactions with essential QS proteins and biological targets. <b>TTNF37</b> exhibited potent antimicrobial activity with low to moderate minimum inhibitory concentrations against clinically relevant Gram-negative and Gram-positive bacteria, as well as fungi and yeasts. It also showed antioxidant activity, with variable effectiveness across different radicals and systems. <b>TTNF37</b> inhibited the 3-oxo-C12-HSL-dependent QS system of <i>P. aeruginosa</i> in a dose-dependent manner, with reductions ranging from 26% to 98%. It also impaired the production and detection of 3-oxo-C12-HSL, resulting in a 56% and 65% decrease in bioluminescence, respectively. Molecular docking studies revealed strong binding interactions with LasI and LasR proteins, with affinity values exceeding those of furvina, a known potent QS inhibitor. Molecular dynamics simulations validated stable <b>TTNF37</b> binding to LasR and LasI. Both experimental and docking data indicate a significant interaction with human serum albumin (HSA). <b>TTNF37</b> also significantly reduced pyocyanin production and prevented biofilm set-up with a reduction of 50% in biomass with pronounced alterations in biofilm structure. These results indicate the potential of <b>TTNF37</b> and related PTHs for treating biofilm-associated infections.