Aeromonas hydrophila, a Gram-negative zoonotic bacterium, causes high mortality in fish farming and immunocompromised patients. This study aimed to extract methyl gallate (MG) from the flowers of Camellia nitidissima Chi and evaluate its potential as a quorum sensing inhibitor (QSI) against Aeromonas hydrophila SHAe 115. MG reduced QS-associated virulence factors, including hemolysis, protease, and lipase, while impairing swimming motility and biofilm formation. Additionally, MG down-regulated positive regulatory genes (ahyR, fleQ) and up-regulated negative regulators (litR, fleN). This highlights MG\'s promise as a potent QSI for A. hydrophila SHAe 115, advancing strategies against infections in aquaculture and human health.

OBJECTIVE: The present study investigated the anti-virulence and anti-biofilm effects of 1,2,6-tri-O-galloyl-β-ᴅ-glucose (TGG), isolated from Camellia nitidissima Chi flowers, on Proteus penneri ALK 1200.
RESULTS: TGG was isolated from C. nitidissima Chi flowers using various chromatographic techniques. The milk plate assay, azocasein assay, and exopolysaccharides (EPS) inhibition assay revealed that TGG effectively inhibited the production of crucial virulence factors, including protease and EPS, in P. penneri ALK 1200. Furthermore, fourier transform infrared spectroscopic (FT-IR) analysis indicated that TGG interfered with the composition of P. penneri ALK 1200\'s cellular component, potentially reducing the bacteria\'s pathogenicity. In addition, crystal violet assay, scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM) analysis indicated a significant reduction in biofilm formation following TGG treatment. The swimming and swarming assays also showed that TGG reduced the motility of P. penneri ALK 1200. Furthermore, the qRT-PCR assay demonstrated that TGG down-regulated the expression of positive regulatory genes (hfq and flhD) responsible for motility and biofilm formation, while up-regulating the expression of the negative regulator of the quorum sensing system, bssS, in P. penneri ALK 1200.
CONCLUSIONS: TGG displayed potent anti-QS and anti-biofilm activity towards P. penneri ALK 1200.

UNASSIGNED: Quorum sensing is bacteria\'s ability to communicate and regulate their behavior based on population density. Anti-quorum sensing agents (anti-QSA) is promising strategy to treat resistant infections, as well as reduce selective pressure that leads to antibiotic resistance of clinically relevant pathogens. This study analyzes the output, hotspots, and trends of research in the field of anti-QSA against clinically relevant pathogens.
UNASSIGNED: The literature on anti-QSA from the Web of Science Core Collection database was retrieved and analyzed. Tools such as CiteSpace and Alluvial Generator were used to visualize and interpret the data.
UNASSIGNED: From 1998 to 2023, the number of publications related to anti-QAS research increased rapidly, with a total of 1,743 articles and reviews published in 558 journals. The United States was the largest contributor and the most influential country, with an H-index of 88, higher than other countries. Williams was the most productive author, and Hoiby N was the most cited author. Frontiers in Microbiology was the most prolific and the most cited journal. Burst detection indicated that the main frontier disciplines shifted from MICROBIOLOGY, CLINICAL, MOLECULAR BIOLOGY, and other biomedicine-related fields to FOOD, MATERIALS, NATURAL PRODUCTS, and MULTIDISCIPLINARY. In the whole research history, the strongest burst keyword was cystic-fibrosis patients, and the strongest burst reference was Lee and Zhang (2015). In the latest period (burst until 2023), the strongest burst keyword was silver nanoparticle, and the strongest burst reference was Whiteley et al. (2017). The co-citation network revealed that the most important interest and research direction was anti-biofilm/anti-virulence drug development, and timeline analysis suggested that this direction is also the most active. The key concepts alluvial flow visualization revealed seven terms with the longest time span and lasting until now, namely Escherichia coli, virulence, Pseudomonas aeruginosa, virulence factor, bacterial biofilm, gene expression, quorum sensing. Comprehensive analysis shows that nanomaterials, marine natural products, and artificial intelligence (AI) may become hotspots in the future.
UNASSIGNED: This bibliometric study reveals the current status and trends of anti-QSA research and may assist researchers in identifying hot topics and exploring new research directions.

Quorum sensing (QS) plays an essential role in virulence factor production, biofilm formation, and antimicrobial resistance. As a potent QS inhibitor, hordenine can inhibit both QS and biofilm formation in Pseudomonas aeruginosa and Serratia marcescens. In this work, we tested the QS inhibitory potential of 27 hordenine analogs against QS and biofilm formation in P. aeruginosa and S. marcescens. Among the tested analogs, seven (12, 28, 27, 26, 2, 23, and 7) exhibited strong QS inhibitory activity against P. aeruginosa, five of which (12, 28, 27, 26, and 2) showed better inhibitory activity than hordenine. In addition, seven analogs (28, 12, 23, 7, 26, 2, and 27) exhibited better biofilm inhibition against P. aeruginosa than hordenine. Four analogs (7, 28, 2, and 12) showed QS inhibitory activity against S. marcescens, two of which (7 and 28) demonstrated better inhibitory activity than hordenine. Furthermore, analog 7 showed similar biofilm inhibition against S. marcescens as hordenine. Structure-activity relationship (SAR) analysis indicated that the inhibitory activities of the analogs were related to four factors, i.e., carbon chain length, presence or absence of an α,β-C[bond, double bond]C bond, amino group with/without lipophilic group, such as methyl group, and hydroxyl group in benzene ring.

Seafood spoilage can be prevented by inhibiting the quorum sensing (QS) system between bacteria. However, membrane materials combining freshness indicators with QS inhibition features have rarely been reported. Therefore, in this study, pH-sensitive polylactic acid-naringin coaxial electrospun fibers capable of maintaining and monitoring freshness were prepared and investigated. Surface analysis revealed that the fiber membranes exhibited a smooth surface and an average diameter of 243 nm. FTIR spectroscopy analysis revealed characteristic absorption peaks at 3265 and 1124 cm-1, confirming the successful loading of naringin and bromocresol purple. Release behavior analysis verified the uninterrupted release of naringin within 192 h, which enabled the fibers to achieve a protease inhibitory activity rate of 35.94%. Furthermore, the coaxial fibers successfully inhibited the expression of rhlI, rhlR, aprA, and fliA in Pseudomonas fluorescens. The real-world applicability of the coaxial fibers was evaluated by the salmon spoilage assay, where a 4-d extension to the shelf life of the coated fillets was attained. Additionally, the color of the coaxial fibers changed with the deterioration of salmon quality and the ΔE value increased from 4.75 to 26.51. These results verify that the prepared fibers can effectively monitor the freshness of seafood products and improve their storage conditions.

This study aimed to investigate the chemical composition, using GC-MS, and anti-biofilm potential of black cardamom essential oil (BCEO) against biofilms of Escherichia coli O157:H7 and Salmonella Typhimurium JSG 1748 through inhibition of bacterial quorum sensing. GC-MS quantification demonstrated that BCEO contains 1,8-cineole (44.24%), α-terpinyl acetate (12.25%), nerolidol (6.03%), and sabinene (5.96%) as the major bioactive compounds. Antioxidant assays for BCEO revealed the total phenolic and flavonoid mean values were 1325.03 ± 7.69 mg GAE 100/g and 168.25 ± 5.26 mg CE/g, respectively. In regards to antimicrobial potential, Candida albicans was the most sensitive species compared to Streptococcus mutans, Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and Salmonella Typhimurium with the following zones of inhibition; 14.4 ± 0.52, 13.2 ± 0.42, 11.2 ± 0.28, 11.0 ± 0.52, 8.2 ± 0.24 and 6.6 ± 0.18 mm in diameter, respectively. Biofilm inhibition by BCEO was concentration-dependent, when various concentrations of 0.03, 0.06, 0.12, 0.25 and 0.5% were applied, 33.67, 34.14, 38.66, 46.65 and 50.17% of Salmonella Typhimurium biofilm was inhibited, while 47.31, 54.15, 76.57, 83.36 and 84.63% of Escherichia coli biofilm formation was prevented. Chromobacterium violaceum ATCC 12,472 and its product violacein, was used as a microbial indicator for enhancement or inhibition of quorum sensing. Our data showed that 0.5% of BCEO inhibited violacein production without influencing the growth of Chromobacterium violaceum, while 1% of BCEO, caused 100% inhibtion of violacein production together with 30% inhibition of growth. This study shows that BCEO possesses promising antioxidant and antimicrobial potential, and found anti-biofilm activities linked to the quenching of the quorum sensing system of E. coli and S. Typhimurium.

Acinetobacter baumannii is a Gram-negative opportunistic nosocomial pathogen, which can cause ventilator-related and blood infection in critically ill patients. The resistance of A. baumannii clinical isolates to common antimicrobials and their tolerance to desiccation have emerged as a serious problem to public health. In the process of pathogenesis, bacteria release signals, which regulate virulence and pathogenicity-related genes. Such bacteria coordinate their virulent behavior in a cell density-dependent phenomenon called quorum sensing (QS). In contrast, the two main approaches of QS interference, quorum sensing inhibitors (QSIs) and quorum quenching (QQ) enzymes, have been developed to reduce the virulence of bacteria, thus reducing the pressure to produce bacterial drug resistance. Therefore, QSIs or QQ enzymes, which interfere with these processes, might potentially inhibit bacterial QS and ultimately biofilm formation. In this review, we aim to describe the state-of-art in the QS process in A. baumannii and elaborate on the use of QSIs or QQ enzymes as antimicrobial drugs in various potential sites of the QS pathway.

BACKGROUND: Multidrug-resistant pathogens are resistant to many antibiotics and associated with serious infections. Amomum tsaoko Crevost et Lemaire, Sanguisorba officinalis, Terminalia chebula Retz and Salvia miltiorrhiza Bge, are all used in Traditional Chinese Medicine (TCM) against multidrug-resistant pathogens, and the purpose of this study was to evaluate the antibacterial and anti-virulence activity of extracts derived from them.
METHODS: The antibacterial activity of ethanol and aqueous extracts from these four plants was examined against several multi-drug resistant bacterial strains, and their anti-virulence potential (including quorum quenching activity, biofilm inhibition, and blocking production of virulence factor δ-toxin) was assessed against different S. aureus strains. The chemical composition of the most effective extract was determined by LC-FTMS.
RESULTS: Only extracts from S. officinalis and A. tsaoko were shown to exhibit limited growth inhibition activity at a dose of 256 μg·mL-1. The S. officinalis ethanol extract, the ethanol and aqueous extract of A. tsaoko, and the aqueous extract of S. miltiorrhiza all demonstrated quorum quenching activity, but didn\'t significantly inhibit bacterial growth. The ethanol extract of S. officinalis inhibited bacterial toxin production and biofilm formation at low concentrations. Chemical composition analysis of the most effective extract of S. officinalis showed that it mainly contained saponins.
CONCLUSIONS: The most active extract tested in this study was the ethanol root extract of S. officinalis. It inhibited δ-toxin production and biofilm formation at low concentrations and saponins may be its key active components. While the four plants showed no direct antibacterial effects, their anti-virulence properties may be key to fighting bacterial infections.

A library of 23 pure compounds of varying structural and chemical characteristics was screened for their quorum sensing (QS) inhibition activity using a synthetic fluorescent Escherichia coli biosensor that incorporates a modified version of lux regulon of Vibrio fischeri. Four such compounds exhibited QS inhibition activity without compromising bacterial growth, namely, phenazine carboxylic acid (PCA), 2-heptyl-3-hydroxy-4-quinolone (PQS), 1H-2-methyl-4-quinolone (MOQ) and genipin. When applied at 50 µM, these compounds reduced the QS response of the biosensor to 33.7% ± 2.6%, 43.1% ± 2.7%, 62.2% ± 6.3% and 43.3% ± 1.2%, respectively. A series of compounds only showed activity when tested at higher concentrations. This was the case of caffeine, which, when applied at 1 mM, reduced the QS to 47% ± 4.2%. In turn, capsaicin, caffeic acid phenethyl ester (CAPE), furanone and polygodial exhibited antibacterial activity when applied at 1mM, and reduced the bacterial growth by 12.8% ± 10.1%, 24.4% ± 7.0%, 91.4% ± 7.4% and 97.5% ± 3.8%, respectively. Similarly, we confirmed that trans-cinnamaldehyde and vanillin, when tested at 1 mM, reduced the QS response to 68.3% ± 4.9% and 27.1% ± 7.4%, respectively, though at the expense of concomitantly reducing cell growth by 18.6% ± 2.5% and 16% ± 2.2%, respectively. Two QS natural compounds of Pseudomonas aeruginosa, namely PQS and PCA, and the related, synthetic compounds MOQ, 1H-3-hydroxyl-4-quinolone (HOQ) and 1H-2-methyl-3-hydroxyl-4-quinolone (MHOQ) were used in molecular docking studies with the binding domain of the QS receptor TraR as a target. We offer here a general interpretation of structure-function relationships in this class of compounds that underpins their potential application as alternatives to antibiotics in controlling bacterial virulence.

Emergence of multi-drug resistant bacterial pathogens is escalating and it is essential to develop novel strategies to combat these super bugs. LasR is a regulator switch that plays a vital role in quorum sensing (QS) and pathogenesis of Pseudomonas aeruginosa. The present study reports two novel Mannich base (1-(phenyl (o-tolylamino) methyl) urea and 3-((1H-Imidazole-1-yl) methylnaphthalene-2-ol with enhanced anti-QS and antibiofilm activities. Synthetic compound revealed prolific interaction patterns with LasR quorum sensing receptor and showed to exhibit LasR antagonistic activities in P. aeruginosa. In-vitro LasR-inhibitory activities were further confirmed by biofilm and pyocyanin inhibition assays which showed a dose-dependent activity. The Mannich base also repressed the mRNA transcripts levels of lasA and lasB genes, confirming its active role in LasR inhibitory activity. Importantly, C1 and C2 played a crucial role in antagonizing LasR receptor by forming H-bonds with Tyr47 in the LasR active site and the presence of urea moiety on one of the Mannich base was a discrete advantage. Taken together, the insilico and invitro assays revealed similar evidences, thus confirming the mode of action of the Mannich bases. Overall the findings will assist in drug designing and for developing newer drugs with Mannich bases and its derivatives for treatment of P. aeruginosa.