Lux Genes Research Articles

Antibacterial effects and mechanisms of quercetin-β-cyclodextrin complex mediated photodynamic on Escherichia coli O157:H7.

Quercetin is a natural flavonoid with antioxidant, anti-inflammatory, and antibacterial properties. This work aimed to formulate quercetin-cyclodextrin microcapsules (QT-β-CD) while examining their photodynamic antibacterial effects and underlying mechanisms in detail. Characterization of the QT-β-CD was conducted using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The bacteriostatic effects of UV-A irradiation on Escherichia coli O157:H7 (E. coli O157:H7) were investigated. The photodynamic impact of QT-β-CD was assessed by analyzing hydrogen peroxide (H₂O₂) production. The antimicrobial activity was further elucidated through examinations of cell membrane integrity, protein damage, changes in cellular motility, biofilm formation, and extracellular polysaccharide reduction. The effect of QT-β-CD on LuxS and motA gene expression in E. coli O157:H7 was investigated by RT-qPCR. The findings demonstrated that QT-β-CD exhibited potent photodynamic properties and functioned as an efficient photosensitizer, causing substantial damage to E. coli O157:H7 cells. These results underscore the potential of quercetin as an antimicrobial agent for food preservation.

ISOLATION AND CHARACTERIZATION OF BIOFILM FORMING ESCHERICHIA COLI FROM CHICKEN MEAT SAMPLES

The present study was aimed to investigate the presence of Escherichia coli (E.coli) in raw chicken meat samples collected from retail shops, as well as the biofilm-forming ability of field isolates, and to characterize different adhesion genes. Out of 20 chicken meat samples, 17 (85%) were positive for E. coli. Fifteen E. coli strains were characterized by PCR using the 16S rDNA primers and all the isolates were positive which confirmed that all the isolates were E.coli. Out of the 15 confirmed E.coli field isolates which were subjected to biofilm-forming assay, 46% of them were found to be strong biofilm producers. While all the isolates were screened for the presence of adhesion genes viz. luxS, csgA, fimH, fimA, and papC, the adhesion gene luxS was detected in all the strains (100%). The other adhesion genes csgA, fimH and fimA were detected in 93%, 93%, and 73% of the isolates, respectively. The E. coli field isolates were screened blaTEM gene was detected in only four strains, which was categorized under strong biofilm producers. This study demonstrated the presence of biofilm forming E. coli in the raw chicken meat samples as contaminants, causing spoilage and potentially posing risk to consumer’s health and safety.

The role and the determination of the LuxI protein binding targets in the formation of biogenic amines in Hafnia alvei H4

Hafnia alvei is a spoilage microorganism that possesses the LuxI/LuxR-type quorum sensing (QS) system. Biogenic amines (BAs) are important in food spoilage and safety, yet the role of QS in BA formation remains poorly understood. This study investigated the ability of H. alvei H4 to produce BAs in fish flesh and decarboxylase culture media. The findings showed that H. alvei H4 produced substantial amounts of putrescine and cadaverine in turbot flesh, with its enhanced amine-producing capacity potentially leading to the eventual deterioration of the fish. Furthermore, the deletion of the QS element—AHL synthase gene luxI—affected the concentrations of both BAs. Based on these observations, the present study conducted multifaceted experiments, including phenotypic assessments and analyses of gene expression, to explore the role of luxI and to identify its specific binding targets. The results indicated that putrescine formation in H. alvei H4 primarily occurred via the arginine deiminase (ADI) pathway, with luxI playing a positive role in the conversion of arginine to ornithine and subsequently to putrescine. The reduction in putrescine content observed in a luxI mutant (ΔluxI) was attributed to the direct binding of the LuxI protein to the promoters of the argF and speC genes, which code for ornithine carbamoyltransferase and ornithine decarboxylase, respectively. The findings of this study provided the basis to understand the influence of QS on BA production in H. alvei, by specifically demonstrating the involvement of the luxI gene on putrescine and cadaverine production.

LuxS/AI-2 system facilitate the dissemination of antibiotic-resistant plasmids in Klebsiella pneumoniae

Plasmid conjugation is a central mechanism driving the dissemination of antibiotic resistance in Klebsiella pneumoniae. However, the conjugative operon requires specific stimuli for activation. Identifying signals and elucidating the underlying mechanisms is crucial in combating plasmid spread. This study uncovers a key mechanism promoting the dissemination of high-risk plasmids, including IncFII, IncX3, and IncX4 types, in K. pneumoniae. We observed that increased donor density significantly enhanced conjugation, and transcript levels of both conjugation and AI-2 quorum sensing genes were markedly upregulated. By mutating the luxS and lsrR genes in K. pneumoniae 1678, we found that plasmid conjugation efficiency decreased in the 1678ΔluxS mutant, while it significantly increased in the 1678ΔlsrR mutant. RT-qPCR and β-galactosidase assays demonstrated that LsrR represses transcription of relaxosome and T4CP genes, while AI-2 (synthesized by LuxS) activates their expression. AlphaFold3 docking models suggest LsrR may bind directly to IncX plasmid relaxase promoters, inhibiting their expression. Adding external AI-2 signals revealed no effect on plasmid conjugation when LsrR was absent, confirming the dependence of AI-2 signals on LsrR repression. In conclusion, AI-2-mediated signaling enhances donor density effects on plasmid conjugation by de-repressing LsrR-mediated suppression.

Effect of the quorum sensing signal molecule auto-inducer-2 on fermentation performance of Lactobacillus delbrueckii subsp. Bulgaricus DPUL-F36

Fermented milk is a typically product of co-fermentation by a variety of lactic acid bacteria (LAB). Quorum sensing (QS), as an intercellular communication mechanism of bacteria, may serve as a key factor influencing the quality of fermented milk. In this study, the fermentation performance of Lactobacillus delbrueckii subsp. bulgaricus DPUL-F36 were evaluated after supplementation with auto-inducer-2 (AI-2). The protein-protein interaction network (PPIN) was used to retrieve the interactions between QS genes and four major metabolic pathway genes. The expression of luxS gene in DPUL-F36 may affect amino acid metabolism, carbohydrate metabolism and cell wall formation. The key differential metabolites were identified by metabolomics analysis. A variety of amino acids including L-Glutamic, L-Tryptophan, L-Threonine, L-Histidine and L-Glutamine were found to be up-regulated in response to the addition of AI-2. Malic acid and succinate gradually accumulate in the tricarboxylic acid cycle. The consumption of citric acid increased with the fermentation process. In terms of rheological and texture characteristics of fermented milk, addition of AI-2 could effectively improve its shear stress resistance, firmness and index of viscosity. Our research provided a theoretical basis for improving the fermentation performance of DPUL-F36 strains, and support for the screening of excellent composite starter culture.

Effects of AI-2 quorum sensing related luxS gene on Streptococcus suis formatting monosaccharide metabolism-dependent biofilm.

Biofilm is the primary cause of persistent infections caused by Streptococcus suis (S. suis). Metabolism and AI-2 quorum sensing are intricately linked to S. suis biofilm formation. Although the role of the AI-2 quorum sensing luxS gene in S. suis biofilm has been reported, its specific regulatory mechanism remains unclear. This study explored the differences in biofilm formation and monosaccharide metabolism among the wild type (WT), luxS mutant (ΔluxS) and complement strain (CΔluxS), and Galleria mellonella larvae were used to access the effect of luxS gene deletion on the virulence of S. suis in different monosaccharide medias. The results indicated that deletion of the luxS gene further compromised the monosaccharide metabolism of S. suis, impacting its growth in media with fructose, galactose, rhamnose, and mannose as the sole carbon sources. However, no significant impact was observed in media with glucose and N-acetylglucosamine. This deletion also weakened EPS synthesis, thereby diminishing the biofilm formation capacity of S. suis. Additionally, the downregulation of adhesion gene expression due to luxS gene deletion was found to be independent of the monosaccharide medias of S. suis.

HPLC-PDA Analysis of Polyacetylene Glucosides from Launaea capitata and Their Antibacterial and Antibiofilm Properties against Klebsiella pneumoniae.

Background/Objectives: Bacterial resistance and virulence are challenges in treating bacterial infections, especially in Klebsiella pneumoniae. Plants of the Launaea Cass. genus are used traditionally to address a variety of diseases, including infections, but the potential bioactive compounds are unknown. Our goals were to verify the potential contribution of two major polyacetylene glycosides isolated from our previous study, (3S,6E,12E)-6,12-tetradecadiene-8,10-diyne-1-ol 3-O-β-D-glucopyranoside (1) and bidensyneoside A (syn. gymnasterkoreaside A) [(3R,8E)-3-hydroxy-8-decene-4,6-diyn-1-yl β-D-glucopyranoside] (2), to the anti-infective properties of Launaea capitata and to develop a dependable HPLC method for their quantification; Methods: On a panel of K. pneumoniae clinical isolates, the antibacterial action of 1, 2, and the methanol extract of the whole L. capitata plant were evaluated by broth microdilution assay, while their antibiofilm action was evaluated by the crystal violet assay. qRT-PCR investigated luxS, mrkA, wzm, and wbbm genes that encode biofilm formation and quorum sensing (QS). The antibacterial activity of 1 was revealed by employing mice infection. Chromatographic separation was conducted using isocratic elution on a Hypersil BDS C18 column using a photodiode array (PDA) detector; Results: Compound 1 showed antibacterial activity with MIC values of 16-128 µg/mL. It remarkably reduced strong and moderate biofilm-forming bacterial isolates from 84.21% to 42.1% compared with the extract (68.42%) and 2 (78.95%). Compound 1 also downregulated the QS genes, luxS, mrkA, wzm, and wbbm, and exhibited in vivo antibacterial action through the enhancement of the histological construction of the liver and spleen, decreased TNF-α immunoreaction, bacterial burden, and the inflammatory mediators IL-1β and IL-6. A successful HPLC-PDA approach was developed to separate the binary mixture of 1 and 2 in less than 10 min with high sensitivity, with detection limits down to 0.518 and 0.095 µg/mL for 1 and 2, respectively; Conclusions: Compound 1 exhibited remarkable antibacterial and antibiofilm properties and may contribute to the anti-infectious traditional uses of L. capitata, meriting further clinical studies and serving as a reliable quality control biomarker for the plant.

Aeromonas salmonicida AI-1 and AI-2 quorum sensing pathways are differentially regulated by rainbow trout mucins and during in vivo colonization

Aeromonas salmonicida is an opportunistic pathogen with relevance for aquaculture. Fish epithelia are covered by a mucus layer, composed mainly by highly glycosylated mucins, which are the first point of contact between fish and pathogens. Quorum sensing (QS), a bacterial communication mechanism through secreted autoinducer signals that governs gene expression, influences bacterial growth and virulence. The main A. salmonicida autoinducers are mediated by the luxS and asaI genes, corresponding to inter- and intraspecies communication, respectively. The aim of this study was to determine the effect of the mucins that pathogens encounter during colonization of the gill and skin on A. salmonicida QS. We found that expression of A. salmonicida asaI, but not luxS, was increased after culture at 20 °C compared to 10 °C. Rainbow trout gill and skin mucins up-regulated asaI expression 2-fold but down-regulated luxS 10-fold. The downregulation of luxS was reflected by a reduction in autoinducer-2 secretion. Mucins isolated from skin had a stronger inhibitory effect than mucins isolated from gills on both luxS expression and A1-2 secretion, consistent with a higher relative abundance of N-Acetylneuraminic acid on skin mucins than on gill mucins. Reduction of AI-2 production by mucins or luxS-deletion lead to a reduced A. salmonicida auto-aggregation. Furthermore, after colonization of the gill, luxS was down regulated whereas asaI expression was upregulated. Both in vivo and in vitro, the expression of luxS and asaI were thus differentially regulated, frequently in an inverse manner. The strong AI-2 inhibiting effect of the skin mucins is likely part of the mucin-based defense against pathogens.

The absence of luxS reduces the invasion of Avibacterium paragallinarum but is not essential for virulence.

The contagious respiratory pathogen, Avibacterium paragallinarum, contributes to infectious coryza in poultry. However, commercial vaccines have not shown perfect protection against infectious coryza. To search for an alternative approach, this research aimed to investigate whether the quorum-sensing system of pathogens plays a crucial role in their survival and pathogenicity. The LuxS/AI-2 quorum-sensing system in many Gram-negative and Gram-positive bacteria senses environmental changes to regulate physiological traits and virulent properties, and the role of the luxS gene in Av. paragallinarum remains unclear. To investigate the effect of the luxS gene in the quorum-sensing system of Av. paragallinarum, we constructed a luxS mutant. Bioluminescence analysis indicated that the luxS gene plays a vital role in the LuxS/AI-2 quorum-sensing system. The analysis of the LuxS/AI-2 system-related genes showed the level of pfs mRNA to be significantly increased in the mutant strain; however, lsrR, lsrK, and lsrB mRNA levels were not significantly different compared with the wild type. The ability of the luxS mutant strain to invade HD11 and DF-1 cells was significantly decreased compared with the wild-type strain. In addition, all chickens challenged with various doses of the luxS mutant strain developed infections and symptoms, and those challenged with the lowest dose exhibited only minor differences compared to chickens challenged with the wild-type strain. Thus, the deletion of the luxS gene reduces the invasion, but the luxS gene does not play an essential role in the pathogenesis of A. paragallinarum.

LuxA Gene From Enhygromyxa salina Encodes a Functional Homodimeric Luciferase.

Several clades of luminescent bacteria are known currently. They all contain similar lux operons, which include the genes luxA and luxB encoding a heterodimeric luciferase. The aldehyde oxygenation reaction is presumed to be catalyzed primarily by the subunit LuxA, whereas LuxB is required for efficiency and stability of the complex. Recently, genomic analysis identified a subset of bacterial species with rearranged lux operons lacking luxB. Here, we show that the product of the luxA gene from the reduced luxACDE operon of Enhygromyxa salina is luminescent upon addition of aldehydes both in vivo in Escherichia coli and in vitro. Overall, EsLuxA is much less bright compared with luciferases from Aliivibrio fischeri (AfLuxAB) and Photorhabdus luminescens (PlLuxAB), and most active with medium-chain C4-C9 aldehydes. Crystal structure of EsLuxA determined at the resolution of 2.71 Å reveals a (β/α)8 TIM-barrel fold, characteristic for other bacterial luciferases, and the protein preferentially forms a dimer in solution. The mobile loop residues 264-293, which form a β-hairpin or a coil in Vibrio harveyi LuxA, form α-helices in EsLuxA. Phylogenetic analysis shows EsLuxA and related proteins may be bacterial protoluciferases that arose prior to duplication of the luxA gene and its speciation to luxA and luxB in the previously described luminescent bacteria. Our work paves the way for the development of new bacterial luciferases that have an advantage of being encoded by a single gene.

Antimicrobial resistance and prevalence of Listeria species from raw milk and dairy products in Burdur, Turkey.

Worldwide, but especially in emerging nations, concerns about food safety pose a serious obstacle to societal and economic progress. This research aimed to examine the prevalence of Listeria spp. in raw milk and dairy products in Burdur, as well as the presence of genes associated with biofilm formation and antibiotic resistance in the isolates. A total of 185 samples, including raw milk, curd, cream, butter, yogurt and cheese, were randomly collected in Burdur. The enrichment and isolation methods specified by the United States Department of Agriculture was used to identify Listeria species in milk and dairy product samples. Culture-positive strains were identified as Listeria genus and as species by PCR. Antibiotic susceptibility of the isolates was evaluated against 14 antibiotics using the disc diffusion technique (EUCAST). Of them, 2.2% (4/185) were positive for Listeria spp. Listeria species were isolated from cheese and yogurt samples. Two of them were Listeria innocua 1.1% (2/185), one was Listeria ivanovii 0.5% (1/185) and the other was Listeria welshimeri 0.5% (1/185). As a result of multiplex PCR of the biofilm genotypic marker luxS and flaA genes, the flaA gene was detected in three of four isolates, the luxS gene was detected in one isolate, and these two genes were not found in one isolate. Although all isolates were resistant to gentamicin and rifampicin, they also showed multidrug resistance. This study revealed that the diversity of prevalence of Listeria spp. in Burdur requires microbial risk assessment in the milk and dairy products value chain and the need to focus on the problem of multiple antibiotic resistance.

The quality and flavor profile of fermented milk produced by Streptococcus thermophilus ABT-T is influenced by the pfs gene in the quorum sensing system

The luxS/AI-2 quorum sensing (QS) system of Streptococcus thermophilus regulates strain acid tolerance, yet its impact on milk fermentation remains unclear. This study aimed to elucidate the mechanism of luxS and pfs gene overexpression in the luxS/AI-2 system of S. thermophilus ABT-T on fermented milk quality using metabolomics. Results showed that pfs gene overexpression had a greater impact on milk quality than the wild-type strain or luxS gene overexpression strain. Overexpression of the pfs gene significantly enhanced AI-2 secretion, reducing fermented milk pH, increasing acidity, improving fermented milk protein hydrolysis, and altering texture and water-holding capacity. Nineteen volatile flavor compounds were identified, with decreased ketone compounds due to the pfs gene overexpression. KEGG analysis suggested significant alterations in amino acid metabolism pathways due to the pfs gene overexpression. This study provides insights into the role of QS in fermented foods.

Subminimum Inhibitory Concentrations Tetracycline Antibiotics Induce Biofilm Formation in Minocycline-Resistant Klebsiella pneumonia by Affecting Bacterial Physical and Chemical Properties and Associated Genes Expression.

Biofilm formation of Klebsiella pneumoniae can protect bacteria from antibiotics and is difficult to eradicate. Thus, the influence of subinhibitory concentrations of antibiotics on bacteria is becoming increasingly important. Our study showed that subminimum inhibitory concentrations (sub-MICs) of tetracycline antibiotics can increase biofilm formation in minocycline-resistant Klebsiella pneumoniae clinical strains. However, in the bacterial adhesion and invasion experiments, the adhesion and invasion ability decreased and the survival rate of Galleria mellonella increased. Under sub-MICs of tetracycline antibiotics treatment, abnormal stretching of bacteria was observed by scanning electron microscopy. Treatment with sub-MICs of tetracyclines leads to increased surface hydrophobicity and eDNA content and decreased outer membrane permeability. The expression levels of the fimA, luxS, qseB, and qseC genes decreased, the expression level of mrkA increased, and the expression level of acrA was inconsistent under different tetracycline antibiotics treatments. Together, our results suggested that the increase in Klebsiella pneumoniae biofilm formation caused by sub-MICs of tetracycline antibiotics may occur by affecting bacterial physical and chemical properties and associated genes expression.

Effect of Quorum Sensing Systems on Biofilm Formation and Virulence in Salmonella

In recent years, as the paradigm of communication between cells has been clarified, the ability of bacteria to change their gene expression patterns in response to various extracellular signals has attracted great interest. In particular, intracellular and intercellular communication between bacterial populations, called quorum sensing (QS), is essential for coordinating physiological and genetic activities. QS studies are critical, particularly in elucidating the regulatory mechanisms of infectious processes in food-borne pathogens. Elucidating the QS mechanisms in Salmonella is effective in silencing the virulence factors in the fight against this bacterium. The aims of this study were; to create luxS gene mutants that play a vital role in the QS activity of Salmonella and to determine the effect of this mutation on the expression of virulence genes in the bacteria and to determine the impact of synthetic N-hexanoyl-homoserine lactone (C6HSL) on biofilm formation and AI-2 signaling pathway of Salmonella wild strain and luxS gene mutants. luxS gene mutants were constructed by recombining the gene region with the chloramphenicol gene cassette based on homologous region recombination. In the luxS mutants obtained in this way, the expression of eight different virulence genes (hilA, invA, inv, glgC, fimF, fliF, lpfA, gyrA), which have essential roles in Salmonella pathogenicity, was determined by quantitative real-time reverse transcriptase polymerase chain reaction (rRT-qPCR) method and compared with natural strains. As a result of these studies, it was determined that the expression of each gene examined was significantly reduced in luxS mutant strains. The relative AI-2 activities of Salmonella strains were analyzed depending on time. It was determined that the highest activity occurred at the fourth hour and the AI-2 activities of luxS mutants were reduced compared to the wild strain. Finally, it was determined that C6HSL increased the biofilm activity of Salmonella Typhimurium DMC4, SL1344 wild strains, and mutants, mainly at the 72nd hour. In conclusion, our results proved that C6HSL stimulated QS communication in all strains and increased biofilm of Salmonella formation and autoinducer activity. This situation determines that Salmonella responds to external signals by using QS systems. In addition, this research contributed to provide additional information on interspecies communication mechanisms to develop strategies to prevent biofilm formation of this pathogen.

AI-2 quorum sensing signal disrupts coral symbiotic homeostasis and induces host bleaching

Symbiotic microorganisms play critical ecophysiological roles that facilitate the maintenance of coral health. Currently, information on the gene and protein pathways contributing to bleaching responses is lacking, including the role of autoinducers. Although the autoinducer AI-1 is well understood, information on AI-2 is insufficient. Here, we observed a 3.7–4.0 times higher abundance of the AI-2 synthesis gene luxS in bleached individuals relative to their healthy counterparts among reef-building coral samples from the natural environment. Laboratory tests further revealed that AI-2 contributed significantly to an increase in coral bleaching, altered the ratio of potential probiotic and pathogenic bacteria, and suppressed the antiviral activity of specific pathogenic bacteria while enhancing their functional potential, such as energy metabolism, chemotaxis, biofilm formation and virulence release. Structural equation modeling indicated that AI-2 influences the microbial composition, network structure, and pathogenic features, which collectively contribute to the coral bleaching status. Collectively, our results offer novel potential strategies for coral conservation based on a signal manipulation approach.

Vairimorpha (Nosema) ceranae can promote Serratia development in honeybee gut: an underrated threat for bees?

The genus Serratia harbors opportunistic pathogenic species, among which Serratia marcescens is pathogenic for honeybees although little studied. Recently, virulent strains of S. marcescens colonizing the Varroa destructor mite's mouth were found vectored into the honeybee body, leading to septicemia and death. Serratia also occurs as an opportunistic pathogen in the honeybee's gut with a low absolute abundance. The Serratia population seems controlled by the host immune system, but its presence may represent a hidden threat, ready to arise when honeybees are weakened by biotic and abiotic stressors. To shed light on the Serratia pathogen, this research aims at studying Serratia's development dynamics in the honeybee body and its interactions with the co-occurring fungal pathogen Vairimorpha ceranae. Firstly, the degree of pathogenicity and the ability to permeate the gut epithelial barrier of three Serratia strains, isolated from honeybees and belonging to different species (S. marcescens, Serratia liquefaciens, and Serratia nematodiphila), were assessed by artificial inoculation of newborn honeybees with different Serratia doses (104, 106, and 108 cells/mL). The absolute abundance of Serratia in the gut and in the hemocoel was assessed in qPCR with primers targeting the luxS gene. Moreover, the absolute abundance of Serratia was assessed in the gut of honeybees infected with V. ceranae at different development stages and supplied with beneficial microorganisms and fumagillin. Our results showed that all tested Serratia strains could pass through the gut epithelial barrier and proliferate in the hemocoel, with S. marcescens being the most pathogenic. Moreover, under cage conditions, Serratia better proliferates when a V. ceranae infection is co-occurring, with a positive and significant correlation. Finally, fumagillin and some of the tested beneficial microorganisms could control both Serratia and Vairimorpha development. Our findings suggest a correlation between the two pathogens under laboratory conditions, a co-occurring infection that should be taken into consideration by researches when testing antimicrobial compounds active against V. ceranae, and the related honeybees survival rate. Moreover, our findings suggest a positive control of Serratia by the environmental microorganism Apilactobacillus kunkeei in a in vivo model, confirming the potential of this specie as beneficial bacteria for honeybees.

Baicalin Weakens the Virulence of Porcine Extraintestinal Pathogenic Escherichia coli by Inhibiting the LuxS/AI-2 Quorum-Sensing System.

Porcine extraintestinal pathogenic Escherichia coli (ExPEC) is a pathogenic bacterium that causes huge economic losses to the pig farming industry and considerably threatens human health. The quorum sensing (QS) system plays a crucial role in the survival and pathogenesis of pathogenic bacteria. Hence, it is a viable approach to prevent ExPEC infection by compromising the QS system, particularly the LuxS/AI-2 system. In this study, we investigated the effects of baicalin on the LuxS/AI-2 system of ExPEC. Baicalin at concentrations of 25, 50, and 100 μg/mL significantly diminished the survival ability of ExPEC in hostile environments and could inhibit the biofilm formation and autoagglutination ability in ExPEC. Moreover, baicalin dose-dependently decreased the production of AI-2 and down-regulated the expression level of luxS in PCN033. These results suggest that baicalin can weaken the virulence of PCN033 by inhibiting the LuxS/AI-2 system. After the gene luxS was deleted, AI-2 production in PCN033 was almost completely eliminated, similar to the effect of baicalin on the production of AI-2 in PCN033. This indicates that baicalin reduced the production of AI-2 by inhibiting the expression level of luxS in ExPEC. In addition, the animal experiment further showed the potential of baicalin as a LuxS/AI-2 system inhibitor to prevent ExPEC infection. This study highlights the potential of baicalin as a natural quorum-sensing inhibitor for therapeutic applications in preventing ExPEC infection by targeting the LuxS/AI-2 system.

Unveiling the High Prevalence of Antibiotic Resistance and Quorum Sensing Genes in Uropathogenic <i>Escherichia coli</i>

Escherichia coli is considered one of the uropathogenic bacteria with different infection symptoms representing mild illness to acute sepsis. This study aims to detect E. coli in patients with urinary infection and investigate quorum sensing genes (lux S and motA) in multi-drug resistant isolates of E. coli. 200 urine samples were collected from patients with urinary tract infections from several hospitals in Baghdad. The antibiotics sensitivity test showed high resistance of isolates for Ampicillin (100%), Cefazolin (97%), Trimethoprim/ Sulfamethoxazole (83%), Ceftriaxone (77%), Ceftazidime and Ciprofloxacin (70% each of them), and moderate resistance of isolates for Levofloxacin (50%), Gentamicin (47%), Cefepime (40%), while low resistance Piperacillin/ Tazobactam (33%), Cefoxitin (30%), Nitrofurantoin (17%), Imipenem (10%), Ertapenem and Amikacin (7% each of them), and Tigecycline (3%). The results showed an increase percentage of infection in females was 30% in the ages 30-44 years, whereas in ages 15-29 and more than 45 years was 17%. There was a high percentage (57.11%) of resistant isolates in females which are ages 30-44 years. While the ages more than 45 years were 66.4% and ages 15-29 were 34%. While, in males, the percentage was high in ages more than 45 years (35.25%) followed by age groups 30-44 years (31.5%) and 15-29 years (31%). The prevalence percentage for luxS and motA genes in E. coli was 100%. In conclusion, E. coli isolates were multi-drug resistant due to all isolates had quorum sensing genes. Moreover, uropathogenic of E. coli in females was more frequent than in males due to the resistance of bacteria to antibiotics.

Growth, biofilm formation, and motility of Listeria monocytogenes strains isolated from food and clinical samples located in Shanghai (China)

Listeria monocytogenes is a common foodborne pathogen that frequently causes global outbreaks. In this study, the growth characteristics, biofilm formation ability, motility ability and whole genome of 26 L. monocytogenes strains isolated from food and clinical samples in Shanghai (China) from 2020 to 2022 were analyzed. There are significant differences among isolates in terms of growth, biofilm formation, motility, and gene expression. Compared with other sequence type (ST) types, ST1930 type exhibited a significantly higher maximum growth rate, the ST8 type demonstrated a stronger biofilm formation ability, and the ST121 type displayed greater motility ability. Furthermore, ST121 exhibited significantly high mRNA expression levels compared with other ST types in virulence genes mpl, fbpA and fbpB, the quorum sensing gene luxS, starvation response regulation gene relA, and biofilm adhesion related gene bapL. Whole-genome sequencing (WGS) analyses indicated the isolates of lineage I were mostly derived from clinical, and the isolates of lineage II were mostly derived from food. The motility ability, along with the expression of genes associated with motility (motA and motB), exhibited a significantly higher level in lineage II compared with lineage I. The isolates from food exhibited significantly higher motility ability compared with isolates from clinical. By integrating growth, biofilm formation, motility phenotype with molecular and genotyping information, it is possible to enhance comprehension of the association between genes associated with these characteristics in L. monocytogenes.

Bactericidal efficacy of plasma-activated water against Vibrio parahaemolyticus on Litopenaeus vannamei.

In this study, the antimicrobial mechanism of plasma-activated water (PAW) against Vibrio parahaemolyticus and the effectiveness of PAW in artificially contaminated Litopenaeus vannamei were investigated. The results demonstrated a significant reduction (p < 0.05) in viable counts of V. parahaemolyticus with increasing plasma discharge time (5, 10, 20, and 30 min) and PAW immersion time (3, 5, 10, 20, and 30 s). Specifically, the count of V. parahaemolyticus decreased by 2.1, 2.7, 3.3, and 4.4 log CFU/mL after exposed to PAW 5, PAW 10, PAW 20, and PAW 30 for 30 s, respectively. Significant cell surface wrinkling, accompanied by notable nucleic acid and protein leakage were observed after treatment with PAW. The permeability of the inner and outer cell membranes was significantly increased (p < 0.05), along with an increase in electrical conductivity (p < 0.05). The reactive oxygen species (ROS) within V. parahaemolyticus cells were significantly increased (p < 0.05), while superoxide dismutase (SOD) activity, and the relative expression of the ompW, emrD, and luxS genes were significantly decreased (p < 0.05). A reduction number of 1.3, 1.8, 2.1, and 2.2 log CFU/g of V. parahaemolyticus in artificially contaminated L. vannamei was obtained with PAW for 5 min. The study elucidated that PAW could destroy cell membranes, leading to cell death. The findings would strengthen strategies for V. parahaemolyticus control and provide a potential application of PAW for preserving aquatic products.