Anti-bacterial activity of baicalin against APEC through inhibition of quorum sensing and inflammatory responses

Baicalein inhibits biofilm formation of avian pathogenic Escherichia coli in vitro mainly by affecting adhesion

Avian pathogenic Escherichia coli (APEC) is a widespread bacterium that causes significant economic losses to the poultry industry. APEC biofilm formation may result in chronic, persistent, and recurrent infections in clinics, making treatment challenging. Baicalein is a natural product that exhibits antimicrobial and antibiofilm activities. This study investigates the inhibitory effect of baicalein on APEC biofilm formation at different stages. The minimum inhibitory concentration (MIC) of baicalein on APEC was determined, and the growth curve of APEC biofilm formation was determined. The effects of baicalein on APEC biofilm adhesion, accumulation, and maturation were observed using optical microscopy, confocal laser scanning microscopy, and scanning electron microscopy. The biofilm inhibition rate of baicalein was calculated at different stages. The MIC of baicalein against APEC was 256 μg/mL. The process of APEC biofilm maturation takes approximately 48 h after incubation, with initial adhesion completed at 12 h, and cell accumulation finished at 24 h. Baicalein had a significant inhibitory effect on APEC biofilm formation at concentrations above 1 μg/mL (p < 0.01). Notably, baicalein had the highest rate of biofilm formation inhibition when added at the adhesion stage. Therefore, it can be concluded that baicalein is a potent inhibitor of APEC biofilm formation in vitro and acts, primarily by inhibiting cell adhesion. These findings suggests that baicalein has a potential application for inhibiting APEC biofilm formation and provides a novel approach for the prevention and control APEC-related diseases.

Baicalin nanodelivery system based on functionalized metal-organic framework for targeted therapy of osteoarthritis by modulating macrophage polarization

Intra-articular drugs used to treat osteoarthritis (OA) often suffer from poor pharmacokinetics and stability. Nano-platforms as drug delivery systems for drug delivery are promising for OA therapy. In this study, we reported an M1 macrophage-targeted delivery system Bai@FA-UIO-66-NH2 based on folic acid (FA) -modified metal-organic framework (MOF) loaded with baicalin (Bai) as antioxidant agent for OA therapy. With outstanding biocompatibility and high drug loading efficiency, Bai@FA-UIO-66-NH2 could be specifically uptaken by LPS-induced macrophages to serve as a potent ROS scavenger, gradually releasing Bai at the subcellular level to reduce ROS production, modulate macrophage polarization to M2, leading to alleviation of synovial inflammation in OA joints. The synergistic effect of Bai@FA-UIO-66-NH2 on macrophage polarization and ROS scavenging significantly improved the therapeutic efficacy of OA, which may provide a new insight into the design of OA precision therapy.

Preparation, characterisation and in vitro anti-inflammatory activity of Baicalin microsponges

Baicalin, a flavonoid extracted from traditional Chinese medicine, Scutellaria baicalensis has significant anti-inflammatory effects. Microsponges are drug delivery systems that improve drug stability and slow the release rate. The combination of baicalin and the microsponges produced a new and stable system for its delivery, resulting in a novel formulation of baicalin. Baicalin microsponges (BM) were prepared using the quasi-emulsion solvent diffusion method. Effects of the mass ratio of the polymer (ethylcellulose) to baicalin, the concentration of the emulsifier polyvinyl alcohol (PVA), the stirring speed on the encapsulation efficiency (EE), and yield of the microsponges were investigated by combining the one-factor test and Box-Behnken design (BBD). The preparation process was standardised using 2.61:1 mass ratio of ethyl cellulose to baicalin, 2.17% concentration of PVA, with stirring at 794 rpm. Optimised BM formulations were evaluated for the parameters of EE (54.06 ± 3.02)% and yield of (70.37 ± 2.41)%, transmission electron microscopy (TEM), and in vitro cell evaluation. Results of the in vitro anti-inflammatory assay showed that baicalin microsponges-pretreated-lipopolysaccharide (LPS)-induced RAW264.7, mouse macrophages showed reduced inflammatory response, similar to that seen in baicalin-treated macrophages.

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.

Biofilm-mediated infections by multidrug-resistant microbes: a comprehensive exploration and forward perspectives

A biofilm is a collection of microorganisms organized in a matrix of extracellular polymeric material. Biofilms consist of microbial cells that attach to both surfaces and each other, whether they are living or non-living. These microbial biofilms can lead to hospital-acquired infections and are generally detrimental. They possess the ability to resist the human immune system and antibiotics. The National Institute of Health (NIH) states that biofilm formation is associated with 65% of all microbial illnesses and 80% of chronic illnesses. Additionally, non-device-related microbial biofilm infections include conditions like cystic fibrosis, otitis media, infective endocarditis, and chronic inflammatory disorders. This review aims to provide an overview of research on chronic infections caused by microbial biofilms, methods used for biofilm detection, recent approaches to combat biofilms, and future perspectives, including the development of innovative antimicrobial strategies such as antimicrobial peptides, bacteriophages, and agents that disrupt biofilms.

Development of an amoxicillin-radix scutellaria extract formulation and evaluation of its pharmacokinetics in pigs

BACKGROUND

A new antibacterial compound powder of amoxicillin (AMO)/Radix Scutellaria extract (RSE) was developed, and its pharmacokinetics were determined in pigs following oral administration.

RESULTS

The MIC ranges of AMO against Escherichia coli, Staphylococcus aureus and Streptococcus were 1-8 μg/mL, 0.5-4 μg/mL and 0.5-64 μg/mL, respectively. The MIC ranges of RSE against E. coli, S. aureus, and Streptococcus were greater than 2.5 mg/mL, 0.156-2.5 mg/mL, and greater than 2.5 mg/mL, respectively. For S. aureus, the combined drug susceptibility test showed that AMO and RSE had an additive or synergistic effect. The results of compatibility test, the excipient screening test and the drug quality control test showed that the formulation had stable quality and uniform properties under the test conditions. Two studies were conducted to investigate the pharmacokinetics of the compound product in pigs. First, the pharmacokinetics of the AMO-RSE powder were compared with those of their respective single products. The results showed no significant change in the main pharmacokinetic parameters when either component was removed from the compound formulation; thus, AMO and RSE have no pharmacokinetic interaction in pigs. Second, pigs were orally administered three different doses of AMO-RSE powder. The Cmax and AUC increased proportionally with increasing p.o. dose; thus, the λz, t1/2λ, MRT, and Tmax were unchanged for the doses of 10, 20, and 30 mg/kg AMO and the doses of 5, 10, and 15 mg/kg BCL, showing that AMO/baicalin in AMO-RSE powder showed linear pharmacokinetic characteristics in pigs.

CONCLUSIONS

The combined drug sensitivity test of AMO and RSE against S. aureus showed that the combination was additive or synergistic. Pharmacokinetic studies indicated that AMO and BCL do not interfere with each other in pigs when used in a compound formulation. The pharmacokinetic parameters remained unchanged regardless of the dose for p.o. administration, indicating linear pharmacokinetic properties over the tested dose range. The quality of the AMO-RSE powder was good and stable, providing a foundation for its clinical application in veterinary medicine. Further bioavailability, PK/PD and clinical trials are still needed to determine the final dosage regimen.

Baicalin Weakens the Porcine ExPEC-Induced Inflammatory Response in 3D4/21 Cells by Inhibiting the Expression of NF-κB/MAPK Signaling Pathways and Reducing NLRP3 Inflammasome Activation

Porcine extraintestinal pathogenic Escherichia coli (ExPEC) is a leading cause of death in pigs and has led to considerable economic losses for the pig industry. Porcine ExPEC infections often cause systemic inflammatory responses in pigs, characterized by meningitis, arthritis, pneumonia, and septicemia. Baicalin has been reported to possess potent anti-inflammatory activity, but its function in porcine ExPEC remains unknown. The aim of this study was to explore the protective effect and mechanism of baicalin against the porcine ExPEC-induced inflammatory responses in 3D4/21 cells. After treatment with baicalin, the effects on cell damage, the level of pro-inflammatory cytokines, the expression of nuclear factor-κB (NF-κB)/mitogen-activated protein kinase (MAPK) signaling pathways, and the activation of NOD-like receptor protein 3 (NLRP3) inflammasomes were examined. Our results show that baicalin significantly reduced the damage to 3D4/21 cells infected with porcine ExPEC PCN033. Further study showed that baicalin significantly reduced the transcription and expression of pro-inflammatory cytokines such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and interleukin-8 (IL-8). Furthermore, baicalin inhibited the phosphorylation of proteins such as P65, nuclear factor κB inhibitor α (IκBα), extracellular regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and P38 and reduced the expression levels of proteins such as NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), and caspase-1. These results reveal that baicalin reduced the damage to 3D4/21 cells by inhibiting the expression of NF-κB/MAPK signaling pathways and blocking NLRP3 inflammasome activation in 3D4/21 cells infected with porcine ExPEC. Taken together, these results suggest that baicalin may have potential as a medicine for the treatment of porcine ExPEC-infected pigs by regulating inflammatory responses. This study provides a novel potential pharmaco-therapeutic approach to preventing porcine ExPEC infection.

Detection of Antibiotic Resistance in Feline-Origin ESBL Escherichia coli from Different Areas of China and the Resistance Elimination of Garlic Oil to Cefquinome on ESBL E. coli

The development of drug-resistance in the opportunistic pathogen Escherichia coli has become a global public health concern. Due to the share of similar flora between pets and their owners, the detection of pet-origin antibiotic-resistant E. coli is necessary. This study aimed to detect the prevalence of feline-origin ESBL E. coli in China and to explore the resistance elimination effect of garlic oil to cefquinome on ESBL E. coli. Cat fecal samples were collected from animal hospitals. The E. coli isolates were separated and purified by indicator media and polymerase chain reaction (PCR). ESBL genes were detected by PCR and Sanger sequencing. The MICs were determined. The synergistic effect of garlic oil and cefquinome against ESBL E. coli was investigated by checkerboard assays, time-kill and growth curves, drug-resistance curves, PI and NPN staining, and a scanning electronic microscope. A total of 80 E. coli strains were isolated from 101 fecal samples. The rate of ESBL E. coli was 52.5% (42/80). The prevailing ESBL genotypes in China were CTX-M-1, CTX-M-14, and TEM-116. In ESBL E. coli, garlic oil increased the susceptibility to cefquinome with FICIs from 0.2 to 0.7 and enhanced the killing effect of cefquinome with membrane destruction. Resistance to cefquinome decreased with treatment of garlic oil after 15 generations. Our study indicates that ESBL E. coli has been detected in cats kept as pets. The sensitivity of ESBL E. coli to cefquinome was enhanced by garlic oil, indicating that garlic oil may be a potential antibiotic enhancer.

Detection of antibiotic-resistant canine origin Escherichia coli and the synergistic effect of magnolol in reducing the resistance of multidrug-resistant Escherichia coli

Background

The development of antimicrobial resistance in the opportunistic pathogen Escherichia coli has become a global public health concern. Due to daily close contact, dogs kept as pets share the same E. coli with their owners. Therefore, the detection of antimicrobial resistance in canine E. coli is important, as the results could provide guidance for the future use of antibiotics. This study aimed to detect the prevalence of antibiotic-resistance of canine origin E. coli in Shaanxi province and to explore the inhibition effect of magnolol combined with cefquinome on MDR E. coli, so as to provide evidence for the use of antibiotics.

Methods

Canine fecal samples were collected from animal hospitals. The E. coli isolates were separated and purified using various indicator media and polymerase chain reaction (PCR). Drug-resistance genes [aacC2, ant(3')-I, aph(3')-II, aac(6')-Ib-cr, aac(3')-IIe, blaKPC, blaIMP−4, blaOXA, blaCMY, blaTEM−1, blaSHV, blaCTX−M−1, blaCTX−M−9, Qnra, Qnrb, Qnrs, TetA, TetB, TetM, Ermb] were also detected by PCR. The minimum inhibitory concentration (MIC) was determined for 10 antibiotics using the broth-microdilution method. Synergistic activity of magnolol and cefquinome against multidrug-resistant (MDR) E. coli strains was investigated using checkerboard assays, time-kill curves, and drug-resistance curves.

Results

A total of 101 E. coli strains were isolated from 158 fecal samples collected from animal hospitals. MIC determinations showed that 75.25% (76/101) of the E. coli strains were MDR. A total of 22 drug-resistance genes were detected among the 101 strains. The blaTEM−1gene exhibited the highest detection rate (89.77%). The TetA and Sul gene also exhibited high detection rate (66.34 and 53.47%, respectively). Carbapenem-resistant E. coli strains were found in Shangluo and Yan'an. Additionally, in MDR E. coli initially resistant to cefquinome, magnolol increased the susceptibility to cefquinome, with an FICI (Fractional Inhibitory Concentration Index) between 0.125 and 0.5, indicating stable synergy. Furthermore, magnolol enhanced the killing effect of cefquinome against MDR E. coli. Resistance of MDR E. coli to cefquinome decreased markedly after treatment with magnolol for 15 generations.

Conclusion

Our study indicates that antibiotic-resistance E. coli has been found in domestic dogs. After treatment with magnolol extracted from the Chinese herb Houpo (Magnolia officinalis), the sensitivity of MDR E. coli to cefquinome was enhanced, indicating that magnolol reverses the resistance of MDR E. coli. The results of this study thus provide reference for the control of E. coli resistance.

Promising Role of the Scutellaria baicalensis Root Hydroxyflavone-Baicalein in the Prevention and Treatment of Human Diseases

Plant roots, due to a high content of natural antioxidants for many years, have been used in herbal medicine. It has been documented that the extract of Baikal skullcap (Scutellaria baicalensis) has hepatoprotective, calming, antiallergic, and anti-inflammatory properties. Flavonoid compounds found in the extract, including baicalein, have strong antiradical activity, which improves overall health and increases feelings of well-being. Plant-derived bioactive compounds with antioxidant activity have for a long time been used as an alternative source of medicines to treat oxidative stress-related diseases. In this review, we summarized the latest reports on one of the most important aglycones with respect to the pharmacological activity and high content in Baikal skullcap, which is 5,6,7-trihydroxyflavone (baicalein).

Baicalein Inhibits the Staphylococcus aureus Biofilm and the LuxS/AI-2 System in vitro

Introduction

Staphylococcus aureus (S. aureus) is a common cause of mastitis in dairy cows, a condition that has a significant economic impact. S. aureus displays quorum sensing (QS) system-controlled virulence characteristics, like biofilm formation, that make therapy challenging. In order to effectively combat S. aureus, one potential technique is to interfere with quorum sensing.

Methods

This study evaluated the effects of different Baicalin (BAI) concentrations on the growth and the biofilm of S. aureus isolates, including the biofilm formation and mature biofilm clearance. The binding activity of BAI to LuxS was verified by molecular docking and kinetic simulations. The secondary structure of LuxS in the formulations was characterized using fluorescence quenching and Fourier transform infrared (FTIR) spectroscopy. Additionally, using fluorescence quantitative PCR, the impact of BAI on the transcript levels of the luxS and biofilm-related genes was investigated. The impact of BAI on LuxS at the level of protein expression was also confirmed by a Western blotting investigation.

Results

According to the docking experiments, they were able to engage with the amino acid residues in LuxS and BAI through hydrogen bonding. The results of molecular dynamics simulations and the binding free energy also confirmed the stability of the complex and supported the experimental results. BAI showed weak inhibitory activity against S. aureus but significantly reduced biofilm formation and disrupted mature biofilms. BAI also downregulated luxS and biofilm-associated genes' mRNA expression. Successful binding was confirmed using fluorescence quenching and FTIR.

Discussion

We thus report that BAI inhibits the S. aureus LuxS/AI-2 system for the first time, which raises the possibility that BAI could be employed as a possible antimicrobial drug to treat S. aureus strain-caused biofilms.

Luteolin Attenuates APEC-Induced Oxidative Stress and Inflammation via Inhibiting the HMGB1/TLR4/NF-κB Signal Axis in the Ileum of Chicks

Avian pathogenic E. coli (APEC) is typically the cause of avian colibacillosis, which can result in oxidative stress, inflammation, and intestinal damage (APEC). Luteolin, in the form of glycosylation flavone, has potent anti-inflammatory and anti-oxidative properties. However, its effects on APEC-induced intestinal oxidative stress and NF-κB-mediated inflammation in chicks remains poorly understood. After hatching, one-day-old chicks were stochastically assigned to four groups: a control group (basic diet), an E. coli group (basic diet) and L10 and L20 groups (with a dry matter of luteolin diet 10 mg/kg and 20 mg/kg, respectively), with fifteen chicks in each group and one repeat per group. They were pretreated for thirteen days. The body weight, mortality, histopathological changes in the ileum, antioxidant status, and the mRNA and protein-expression levels of factors associated with the HMGB1/TLR4/NF-κB signal axis of the chicks were measured. The results showed that luteolin treatment decreased the mRNA and protein-expression level of the related factors of HMGB1/TLR4/NF-κB signal axis in the ileum, reduced inflammation, increased antioxidant enzyme activity, and reduced intestinal injury. Collectively, luteolin alleviated APEC-induced intestinal damage by means of hindering the HMGB1/TLR4/NF-κB signal axis, which suggests that luteolin could be a good method for the prevention and treatment of avian colibacillosis.

Recent advances on the regulation of bacterial biofilm formation by herbal medicines

Biofilm formation is a fundamental part of life cycles of bacteria which affects various aspects of bacterial-host interactions including the development of drug resistance and chronic infections. In clinical settings, biofilm-related infections are becoming increasingly difficult to treat due to tolerance to antibiotics. Bacterial biofilm formation is regulated by different external and internal factors, among which quorum sensing (QS) signals and nucleotide-based second messengers play important roles. In recent years, different kinds of anti-biofilm agents have been discovered, among which are the Chinese herbal medicines (CHMs). CHMs or traditional Chinese medicines have long been utilized to combat various diseases around the world and many of them have the ability to inhibit, impair or decrease bacterial biofilm formation either through regulation of bacterial QS system or nucleotide-based second messengers. In this review, we describe the research progresses of different chemical classes of CHMs on the regulation of bacterial biofilm formation. Though the molecular mechanisms on the regulation of bacterial biofilm formation by CHMs have not been fully understood and there are still a lot of work that need to be performed, these studies contribute to the development of effective biofilm inhibitors and will provide a novel treatment strategy to control biofilm-related infections.

1,8-Cineole inhibits biofilm formation and bacterial pathogenicity by suppressing luxS gene expression in Escherichia coli

In recent years, with frequent reports of multi-drug resistant strains, bacteria antibiotic resistance has become an increasingly serious health problem worldwide. One of the most promising ways for combating bacterial infections and antibiotic resistance is development of quorum-sensing (QS) interfering drugs. In this study, the results show that 1,8-cineole inhibited the expression of QS as well as the virulence genes in Escherichia coli O101 (E. coli O101) with a 65% inhibition rate against luxS gene. Therefore, we hypothesized that 1,8-cineole may inhibit the biofilm formation and reduce the pathogenicity of E. coli O101 by inhibiting the expression of luxS gene. To confirm our hypotheses, a luxS gene deleted E. coli O101 was constructed. The results show that the biofilm formation, motility, structure and pathogenicity of E. coli O101 were significantly inhibited following deletion of the luxS gene. In addition, the transcript levels of QS and virulence genes of E. coli O101 were also significantly down-regulated. Interestingly, 1,8-cineole no longer had a significant inhibitory effect on the related phenotype and gene expression of E. coli O101 without luxS gene. In conclusion, the results show that 1,8-cineole can affect bacterial biofilm formation and pathogenicity by suppressing the expression of luxS gene in E. coli O101, which could provide a new perspective for dealing with the biofilm problem of pathogenic bacteria.

Auranofin and Baicalin Inhibit Clostridioides difficile Growth and Sporulation: An In vitro Study

Clostridioides difficile is a principal cause of hospital-acquired gastrointestinal infections, with sporulation and toxin production being key determinants in the disease pathogenesis. Although infections have been escalating and the complications can be life-threatening, the narrow pipeline of approved therapeutics has not witnessed an equivalent surge. With the unfolding of worrisome mutations and antimicrobial resistance, attention has been drawn to either discovering new therapeutics, or even better, repurposing already available ones. Consequently, this study was undertaken to assess the anti-clostridial activity of auranofin, an anti-rheumatic FDA-approved therapeutic; and baicalin, a natural flavone glycoside with reported anti-microbial potential. In comparison with vancomycin, the in vitro efficacy of auranofin and baicalin was tested against hypervirulent C. difficile (BAA-1870TM). Broth suspensions were prepared with and without the three agents and anaerobically incubated. At 24- and 48-hours post-incubation, serial dilutions were prepared and inoculated onto agar plates. Viable cell counts and viable spore counts were then quantified. Meanwhile, toxin production was assessed via ELISA. At a concentration as low as 3 μg/mL, auranofin demonstrated a potent anti-clostridial activity. Both auranofin and baicalin exhibited a remarkable reduction in C. difficile viable cell counts (P-value 0.03 for each) and spore counts (P-values 0.023 and 0.045 respectively). While auranofin and baicalin proved to be non-inferior to vancomycin as inhibitors of C. difficile growth, both drugs proved to be superior to vancomycin in decreasing the spore counts 48-hours post inoculation. Additionally, auranofin markedly reduced C. difficile toxin production (P-value 0.021); a feature that was deficient in both baicalin and vancomycin. To enrich the currently limited repertoire of anti-clostridial drugs, further research is encouraging to compare between the in vivo efficacy of auranofin and that of baicalin. Both agents represent promising approaches that could address the unfulfilled needs in controlling C. difficile infection.

Escherichia coli O88 induces intestinal damage and inflammatory response through the oxidative phosphorylation and ribosome pathway in Pekin ducks

Colibacillosis is one of the major health threats in the poultry industry worldwide. Understanding the pathogenic mechanisms involved in Escherichia coli-induced inflammatory response may lead to the development of new therapies to combat the disease. To address this, a total of 96 1-day-old male lean Pekin ducklings were employed and randomly allocated to two treatments, each with six replicates of eight ducks. Ducks in the experiment group (EG) and the control group (CG) were separately orally administered with 0.2 ml of pathogenic E. coli O88 (3 × 109 CFU/ml) or equivalent volumes of 0.9% sterile saline solution on day 7, two times with an 8-h interval. Serum and intestinal samples were collected on days 9, 14, and 28. Results showed that ducks challenged with E. coli had lower average daily gain and higher feed intake/weight gain during days 9–14 and overall (P &lt; 0.05). Histopathological examination showed that E. coli decreased the villus height and the ratio of villus height/crypt depth in the jejunum (P &lt; 0.05) on days 9 and 14. The intestinal barrier was disrupted, presenting in E. coli ducks having higher serum DAO and D-LA on days 9 and 14 (P &lt; 0.05) and greater content of serum LPS on day 9 (P &lt; 0.05). Escherichia coli infection also triggered a systemic inflammatory response including the decrease of the serum IgA, IgM, and jejunal sIgA on day 14 (P &lt; 0.05). In addition to these, 1,062 differentially expressed genes were detected in the jejunum tissues of ducks by RNA-seq, consisting of 491 upregulated and 571 downregulated genes. Based on the KEGG database, oxidative phosphorylation and the ribosome pathway were the most enriched. These findings reveal the candidate pathways and genes that may be involved in E. coli infection, allow a better understanding of the molecular mechanisms of inflammation progression and may facilitate the genetic improvement of ducks, and provide further insights to tackle the drug sensitivity and animal welfare issues.

Novel Antibiofilm Inhibitor Ginkgetin as an Antibacterial Synergist against Escherichia coli

As an opportunistic pathogen, Escherichia coli (E. coli) forms biofilm that increases the virulence of bacteria and antibiotic resistance, posing a serious threat to human and animal health. Recently, ginkgetin (Gin) has been discovered to have antiinflammatory, antioxidant, and antitumor properties. In the present study, we evaluated the antibiofilm and antibacterial synergist of Gin against E. coli. Additionally, Alamar Blue assay combined with confocal laser scanning microscope (CLSM) and crystal violet (CV) staining was used to evaluate the effect of antibiofilm and antibacterial synergist against E. coli. Results showed that Gin reduces biofilm formation, exopolysaccharide (EPS) production, and motility against E. coli without limiting its growth and metabolic activity. Furthermore, we identified the inhibitory effect of Gin on AI-2 signaling molecule production, which showed apparent anti-quorum sensing (QS) properties. The qRT-PCR also indicated that Gin reduced the transcription of curli-related genes (csgA, csgD), flagella-formation genes (flhC, flhD, fliC, fliM), and QS-related genes (luxS, lsrB, lsrK, lsrR). Moreover, Gin showed obvious antibacterial synergism to overcome antibiotic resistance in E. coli with marketed antibiotics, including gentamicin, colistin B, and colistin E. These results suggested the potent antibiofilm and novel antibacterial synergist effect of Gin for treating E. coli infections.

Small Carbohydrate Derivatives as Potent Antibiofilm Agents

Biofilm formation by most pathogenic bacteria is considered as one of the key mechanisms associated with virulence and antibiotic resistance. Biofilm-forming bacteria adhere to the surfaces of biological or implant medical devices and create communities within their self-produced extracellular matrix that are difficult to treat by existing antibiotics. There is an urgent need to synthesize and screen structurally diverse molecules for their antibiofilm activity that can remove or minimize the bacterial biofilm. The development of carbohydrate-based small molecules as antibiofilm agents holds a great promise in addressing the problem of the eradication of biofilm-related infections. Owing to their structural diversity and specificity, the sugar scaffolds are valuable entities for developing antibiofilm agents. In this perspective, we discuss the literature pertaining to carbohydrate-based natural antibiofilm agents and provide an overview of the design, activity, and mode of action of potent synthetic carbohydrate-based molecules.

Targeting the Holy Triangle of Quorum Sensing, Biofilm Formation, and Antibiotic Resistance in Pathogenic Bacteria

Chronic and recurrent bacterial infections are frequently associated with the formation of biofilms on biotic or abiotic materials that are composed of mono- or multi-species cultures of bacteria/fungi embedded in an extracellular matrix produced by the microorganisms. Biofilm formation is, among others, regulated by quorum sensing (QS) which is an interbacterial communication system usually composed of two-component systems (TCSs) of secreted autoinducer compounds that activate signal transduction pathways through interaction with their respective receptors. Embedded in the biofilms, the bacteria are protected from environmental stress stimuli, and they often show reduced responses to antibiotics, making it difficult to eradicate the bacterial infection. Besides reduced penetration of antibiotics through the intricate structure of the biofilms, the sessile biofilm-embedded bacteria show reduced metabolic activity making them intrinsically less sensitive to antibiotics. Moreover, they frequently express elevated levels of efflux pumps that extrude antibiotics, thereby reducing their intracellular levels. Some efflux pumps are involved in the secretion of QS compounds and biofilm-related materials, besides being important for removing toxic substances from the bacteria. Some efflux pump inhibitors (EPIs) have been shown to both prevent biofilm formation and sensitize the bacteria to antibiotics, suggesting a relationship between these processes. Additionally, QS inhibitors or quenchers may affect antibiotic susceptibility. Thus, targeting elements that regulate QS and biofilm formation might be a promising approach to combat antibiotic-resistant biofilm-related bacterial infections.

San-Wu-Huang-Qin decoction attenuates tumorigenesis and mucosal barrier impairment in the AOM/DSS model by targeting gut microbiome

BACKGROUND

A classic herbal formula San-Wu-Huang-Qin (SWHQ) decoction has been widely used in clinical practices to prevent and treat colorectal cancer (CRC) for years, but its anti-tumorigenic properties and the underlying mechanisms remain undetermined.

PURPOSE

The present study used a CRC mouse model to clarify whether and how SWHQ suppresses tumorigenesis.

METHODS

Different doses of SWHQ were gavaged to the AOM/DSS model mice to examine its anti-tumor efficacy in comparison with the positive control drug Aspirin. The underlying microbiota-driven anti-tumor action of SWHQ was proven with bacterial manipulations by fecal microbial transplantation (FMT) in vivo and anaerobic culturing in vitro.

RESULTS

SWHQ decoction dose-dependently reduced colonic tumor numbers/loads of AOM/DSS models and suppressed their disease activity index scores. SWHQ also recovered epithelial MUC2 secretion and colonic tight junction protein (ZO-1 and claudin1) expression in the mouse model. Such inhibitory impact on tumorigenesis and mucosal barrier impairment was found to be associated with modulation of gut dysbiosis, particularly for suppressing lipopolysaccharide (LPS) producers. The FMT experiment confirmed the substantial contribution of SWHQ-reshaped microbiota to anti-tumor function and mucosal barrier protection. Moreover, LPS-activated TLR4/NF-κB signaling and its downstream pro-inflammatory factors were significantly suppressed in the colon of SWHQ-treated models and SWHQ-reshaped microbiota recipients.

CONCLUSIONS

We demonstrated that the SWHQ effectively inhibited tumorigenesis and protect mucosal barrier in CRC at least partially by targeting gut microbiota. This study provides scientific basis for the clinical usage of SWHQ in CRC intervention and prevention.

Evaluation of Toxicity, Bacteriostatic, Analgesic, Anti-Inflammatory, and Antipyretic Activities of Huangqin-Honghua-Pugongying-Jinyinhua Extract

The extensive use of antibiotics has caused the global spread of multidrug-resistant bacteria and genes, seriously reducing antibiotic efficacy and threatening animal and human health. As an alternative, traditional Chinese veterinary medicine (TCVM) was used in this study for its lack of drug resistance and low toxicity. Huangqin-honghua-pugongying-jinyinhua extract (HHPJE), a novel TCVM, consists of the extracts of Huangqin (Scutellaria baicalensis), Honghua (Carthami Flos), Pugongying (Taraxacum) and Jinyinhua (Lonicerae Japonicae Flos), and was developed to treat bovine mastitis. In this study, we evaluated the toxicity, bacteriostatic, analgesic, anti-inflammatory, and antipyretic activities of HHPJE. Our results show that HHPJE did not show any acute oral toxicity and can be considered safe for oral administration. Additionally, HHPJE possessed a dose-dependent antibacterial effect on Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae and Streptococcus dysgalactiae. HHPJE (60, 30 and 15 g/kg) can reduce the abdominal pain by 44.83 ± 7.69%, 43.15 ± 9.50% and 26.14 ± 4.17%, respectively. The percentages of anti-inflammation inhibition (60, 30 and 15 g/kg) were 35.34 ± 2.17%, 22.29 ± 2.74% and 12.06 ± 3.61%, respectively. The inhibition rates (60, 30 and 15 g/kg) of antipyretic activity were 82.05%, 65.71% and 52.80%, respectively. The evaluation of pharmacodynamics and toxicity indicate that HHPJE possesses significant bacteriostatic, analgesic, anti-inflammatory and antipyretic potential, and also that it is safe for acute oral toxicity, which means it has potential value for treating bovine mastitis in future and alleviating clinical symptoms with no drug resistance or side effects.

Baicalin ameliorates APEC-induced intestinal injury in chicks by inhibiting the PI3K/AKT-mediated NF-κB signaling pathway

Avian pathogenic Escherichia coli (APEC) is the causative agent of avian colibacillosis. Baicalin (BA) possesses multiple pharmacological effects, but the mechanism underlying its activity in APEC-induced intestinal injury remains unknown. This study aims to investigate the protective effects and possible mechanism of BA against APEC-induced intestinal injury. Sixty 1-day-old chicks were randomly divided into 4 groups: the control group (basal diet), E. coli group (basal diet), BAI10 group (10 mg/kg BA), and BAI20 group (20 mg/kg BA). After pretreatment with BA for 15 d and subsequent induction of APEC infection by pectoralis injection, the ileum was collected and analyzed. The results showed that BA-pretreatment demonstrated an alleviation of chicks in diarrhea rate, mortality, and histopathological changes in intestinal tissues after APEC infection. Additionally, following APEC infection, BA improved the intestinal barrier by elevating zona occludens (ZO)s (ZO-1, 2, 3), Claudins (Claudin1, 2, 3), Occludin, avian β-defensin (AvBD)s (AvBD1, 2, 4), lysozyme (Lyz) mRNA levels and ZO-1, Claudin1, and Occludin protein levels. Besides, the activities of total superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and the SOD-1 and CAT mRNA levels and SOD-1 protein level were elevated by BA pretreatment. BA pretreatment also decreased the malondialdehyde (MDA) content, heme oxygenase-1 (HO-1) and NADH quinone oxidoreductase 1 (NQO1) mRNA levels, and HO-1 protein level after APEC infection. BA alleviated the APEC-induced inflammatory response, including downregulating the mRNA levels of proinflammatory cytokines (tumor necrosis factor-α (TNF-α), interleukin [IL]-1β, IL-6, IL-8) and upregulating the mRNA levels of anti-inflammatory cytokines (IL-4, IL-10, IL-13, transforming growth factor-β [TGF-β]). Furthermore, BA decreased the mRNA and protein levels of phosphatidylinositol 3 kinase (PI3K), protein kinase B (AKT), and nuclear factor kappa-B (NF-κB) as well as the expression of the phosphorylated forms of these proteins after APEC infection. Collectively, our findings indicate that BA exerts a protective effect against APEC-induced intestinal injury in chicks by inhibiting the PI3K/AKT-mediated NF-κB pathway, suggesting that BA may be a potential therapeutic approach for avian colibacillosis.

Repurposing phytochemicals as anti-virulent agents to attenuate quorum sensing-regulated virulence factors and biofilm formation in Pseudomonas aeruginosa

Unregulated consumption and overexploitation of antibiotics have paved the way for emergence of antibiotic‐resistant strains and ‘superbugs’. Pseudomonas aeruginosa is among the opportunistic nosocomial pathogens causing devastating infections in clinical set‐ups globally. Its artillery equipped with diversified virulence elements, extensive antibiotic resistance and biofilms has made it a ‘hard‐to‐treat’ pathogen. The pathogenicity of P. aeruginosa is modulated by an intricate cell density‐dependent mechanism called quorum sensing (QS). The virulence artillery of P. aeruginosa is firmly controlled by QS genes, and their expression drives the aggressiveness of the infection. Attempts to identify and develop novel antimicrobials have seen a sharp rise in the past decade. Among different proposed mechanisms, a novel anti‐virulence approach to target pseudomonal infections by virtue of anti‐QS and anti‐biofilm drugs appears to occupy the centre stage. In this respect, bioactive phytochemicals have gained prominence among the scientific community owing to their significant quorum quenching (QQ) properties. Recent studies have shed light on the QQ activities of various phytochemicals and other drugs in perturbing the QS‐dependent virulence in P. aeruginosa. This review highlights the recent evidences that reinforce the application of plant bioactives for combating pseudomonal infections, their advantages and shortcomings in anti‐virulence therapy.

The bird's immune response to avian pathogenic Escherichia coli

Avian pathogenic Escherichia coli (APEC) cause colibacillosis in birds, a syndrome of severe respiratory and systemic disease that constitutes a major threat due to early mortality, condemnation of carcasses and reduced productivity. APEC can infect different types of birds in all commercial settings, and birds of all ages, although disease tends to be more severe in younger birds likely a consequence of an immature immune system. APEC can act as both primary and secondary pathogens, with predisposing factors for secondary infections including poor housing conditions, respiratory viral and Mycoplasma spp. infections or vaccinations. Controlled studies with APEC as primary pathogens have been used to study the bird's immune response to APEC, although it may not always be representative of natural infections which may be more complex due to the presence of secondary agents, stress and environmental factors. Under controlled experimental conditions, a strong early innate immune response is induced which includes host defence peptides in mucus and a cellular response driven by heterophils and macrophages. Both antibody and T-cell mediated adaptive responses have been demonstrated after vaccination. In this review we will discuss the bird's immune response to APEC as primary pathogen with a bias towards the innate immune response, as mechanistic adaptive studies clearly form a much more limited body of work despite numerous vaccine trials.

A review: antimicrobial properties of several medicinal plants widely used in Traditional Chinese Medicine

Due to the dramatic increase in the use of antibiotics and growing health threat of bacterial resistance to many commonly used antibiotics, many studies have been directed at developing new and effective antibacterial compounds, among which many new, natural, and effective antibacterial compounds discovered from medicinal plants have drawn great interest and raised new hope for treating the challenges of antibiotic resistance. This review aimed to summarize the most important and widely used medicinal plants that were reported to have antibacterial activities. A general literature search from 2010 to 2020 was conducted using different databases, including Science Direct, Web of Science, and PubMed. According to the literature, three medicinal plants with outstanding antibacterial activities, Taraxacum officinale, Coptis Rhizome, and Scutellaria baicalensis, were screened and reviewed by prioritization. The extraction methods, antibacterial activities of different parts of plants or the plant-derived compounds, spectra of antibacterial activities, and toxicity were described, respectively. However, the antibacterial activities of the extracts or pure compounds as reported in the reviewed literature were mostly based on in vitro assays, and moreover, the deeper antibacterial mechanisms have not been elucidated clearly. Therefore, further studies are required in the fields of purification and identification of the antibacterial compounds, its mechanisms of action, and synergistic effects in combination with other antibacterial drugs, which may be helpful in the development of new antibacterial drugs.

Natural DNA Intercalators as Promising Therapeutics for Cancer and Infectious Diseases

Cancer and infectious diseases are one of the greatest challenges of modern medicine. An unhealthy lifestyle, the improper use of drugs, or their abuse are conducive to the increase of morbidity and mortality caused by these diseases. The imperfections of drugs currently used in therapy for these diseases and the increasing problem of drug resistance have forced a search for new substances with therapeutic potential. Throughout history, plants, animals, fungi and microorganisms have been rich sources of biologically active compounds. Even today, despite the development of chemistry and the introduction of many synthetic chemotherapeutics, a substantial part of the new compounds being tested for treatment are still of natural origin. Natural compounds exhibit a great diversity of chemical structures, and thus possess diverse mechanisms of action and molecular targets. Nucleic acids seem to be a good molecular target for substances with anticancer potential in particular, but they may also be a target for antimicrobial compounds. There are many types of interactions of small-molecule ligands with DNA. This publication focuses on the intercalation process. Intercalators are compounds that usually have planar aromatic moieties and can insert themselves between adjacent base pairs in the DNA helix. These types of interactions change the structure of DNA, leading to various types of disorders in the functioning of cells and the cell cycle. This article presents the most promising intercalators of natural origin, which have aroused interest in recent years due to their therapeutic potential.

Exploring the anti-caries properties of baicalin against Streptococcus mutans: an in vitro study

Plant-derived molecules are excellent alternatives to antibiotics as anti-infective agents owing to their minimal cytotoxicity. Herein, the anti-infective property of the hydroxyflavone baicalin, was investigated against biofilms of the key dental caries pathogen Streptococcus mutans. Baicalin inhibited sucrose-dependent biofilm formation at a concentration of 500 µg ml^-1 without affecting bacterial growth. It significantly inhibited acid production for an extended period of 8 h. Microscopic analysis revealed a 6-fold reduction in the number of adhered cells with baicalin treatment. Transcriptomic analysis of the mid-log phase and biofilm cells showed marked downregulation of the virulence genes required for biofilm formation and acid production. This study sheds significant new light on the potential for baicalin to be developed into an anti-caries agent.

Protective Effects of Baicalin on Peritoneal Tight Junctions in Piglets Challenged with Glaesserella parasuis

Glaesserella parasuis (G. parasuis) causes inflammation and damage to piglets. Whether polyserositis caused by G. parasuis is due to tight junctions damage and the protective effect of baicalin on it have not been examined. Therefore, this study aims to investigate the effects of baicalin on peritoneal tight junctions of piglets challenged with G. parasuis and its underlying molecular mechanisms. Piglets were challenged with G. parasuis and treated with or without baicalin. RT-PCR was performed to examine the expression of peritoneal tight junctions genes. Immunofluorescence was carried out to detect the distribution patterns of tight junctions proteins. Western blot assays were carried out to determine the involved signaling pathways. Our data showed that G. parasuis infection can down-regulate the tight junctions expression and disrupt the distribution of tight junctions proteins. Baicalin can alleviate the down-regulation of tight junctions mRNA in peritoneum, prevent the abnormalities and maintain the continuous organization of tight junctions. Our results provide novel evidence to support that baicalin has the capacity to protect peritoneal tight junctions from G. parasuis-induced inflammation. The protective mechanisms of baicalin could be associated with inhibition of the activation of PKC and MLCK/MLC signaling pathway. Taken together, these data demonstrated that baicalin is a promising natural agent for the prevention and treatment of G. parasuis infection.

Baicalein Inhibits Streptococcus mutans Biofilms and Dental Caries-Related Virulence Phenotypes

Dental caries, the most common oral disease, is a major public healthcare burden and affects more than three billion people worldwide. The contemporary understanding of the need for a healthy microbiome and the emergence of antimicrobial resistance has resulted in an urgent need to identify compounds that curb the virulence of pathobionts without microbial killing. Through this study, we have demonstrated for the first time that 5,6,7-trihydroxyflavone (Baicalein) significantly downregulates crucial caries-related virulence phenotypes in Streptococcus mutans. Baicalein significantly inhibited biofilm formation by Streptococcus mutans UA159 (MBIC50 = 200 μM), without significant growth inhibition. Notably, these concentrations of baicalein did not affect the commensal S. gordonii. Strikingly, baicalein significantly reduced cell surface hydrophobicity, autoaggregation and acid production by S. mutans. Mechanistic studies (qRT-PCR) showed downregulation of various genes regulating biofilm formation, surface attachment, quorum sensing, acid production and competence. Finally, we demonstrate the potential translational value of baicalein by reporting synergistic interaction with fluoride against S. mutans biofilms.

Redox Homeostasis in Poultry: Regulatory Roles of NF-κB

Redox biology is a very quickly developing area of modern biological sciences, and roles of redox homeostasis in health and disease have recently received tremendous attention. There are a range of redox pairs in the cells/tissues responsible for redox homeostasis maintenance/regulation. In general, all redox elements are interconnected and regulated by various means, including antioxidant and vitagene networks. The redox status is responsible for maintenance of cell signaling and cell stress adaptation. Physiological roles of redox homeostasis maintenance in avian species, including poultry, have received limited attention and are poorly characterized. However, for the last 5 years, this topic attracted much attention, and a range of publications covered some related aspects. In fact, transcription factor Nrf2 was shown to be a master regulator of antioxidant defenses via activation of various vitagenes and other protective molecules to maintain redox homeostasis in cells/tissues. It was shown that Nrf2 is closely related to another transcription factor, namely, NF-κB, responsible for control of inflammation; however, its roles in poultry have not yet been characterized. Therefore, the aim of this review is to describe a current view on NF-κB functioning in poultry with a specific emphasis to its nutritional modulation under various stress conditions. In particular, on the one hand, it has been shown that, in many stress conditions in poultry, NF-κB activation can lead to increased synthesis of proinflammatory cytokines leading to systemic inflammation. On the other hand, there are a range of nutrients/supplements that can downregulate NF-κB and decrease the negative consequences of stress-related disturbances in redox homeostasis. In general, vitagene-NF-κB interactions in relation to redox balance homeostasis, immunity, and gut health in poultry production await further research.

Baicalin ameliorates Mycoplasma gallisepticum-induced lung inflammation in chicken by inhibiting TLR6-mediated NF-κB signalling

1. Mycoplasma gallisepticum (MG) causes severe lung inflammation and cell damage by activating toll-like receptor (TLR) signalling, the nuclear factor-kappaB (NF-κB) pathway and pro-inflammatory cytokine gene expression. Baicalin (BA) is a flavonoid extracted from Scutellaria baicalensis, which possesses anti-inflammatory and anti-bacterial properties. This study investigated the effect of BA in MG-induced lung inflammation and its potential mechanism in MG-infected chicken embryo lungs and DF-1 cells.2. The histopathological examination result showed that BA treatment alleviated MG-induced lung pathological changes. In addition, CCK-8 and cell cycle assays showed that BA treatment inhibited MG-induced cell proliferation and cell cycle progression in DF-1 cells.3. The ELISA and RT-qPCR results demonstrated that BA treatment decreased the expression of interleukin-1beta (IL-1β), IL-6, and tumour necrosis factor-alpha (TNF-α) both in MG-infected chicken embryo lungs and DF-1 cells.4. The results revealed that BA inhibited mRNA expression levels of toll-like receptor-6 (TLR6), myeloid differentiation primary response gene-88 (MyD88) and nuclear factor-κB (NF-κB), and the nuclear translocation of NF-κB-p655. In conclusion, the results showed that BA has a protective effect against MG-induced lung inflammation in chicken by inhibiting the TLR6-mediated NF-κB signalling.

High-throughput metabolomic method based on liquid chromatography: high resolution mass spectrometry with chemometrics for metabolic biomarkers and pathway analysis to reveal the protective effects of baicalin on thyroid cancer

Cell metabonomics focuses on discovering metabolic biomarkers and pathway changes in cells from biological systems to obtain the cell properties and functional information under different conditions. Baicalin possesses various pharmacological activities, and plays a vital role in the oncology research field. However, the detailed mechanism of its action is still unclear. In this work, we employed ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) based non-targeted metabolomics method associated with chemometrics analysis to explore metabolic pathways and biomarkers for investigating the efficacy and pharmacological targets of baicalin against thyroid cancer cells. In addition, morphological observation, parameter calculation of cell proliferation and apoptosis were carried out, which assisted in elucidation of pharmacological activity of baicalin on the human thyroid cancer cells. The results showed that baicalin possesses an intense stimulative apoptosis and inhibits proliferation activity on SW579 human thyroid cancer cells, and partially reversed the cell metabolite abnormalities. A total of nineteen differentiated metabolites in SW579 cells were identified and deemed as potential biomarkers after the baicalin treatment, involving nine metabolic pathways, such as taurine and hypotaurine metabolism, pyrimidine metabolism, fructose and mannose metabolism, steroid hormone biosynthesis and sphingolipid metabolism. High-throughput non-targeted metabolomics provide an insight into specialized mechanism of baicalin against thyroid cancer and contributes to novel drug discovery and thyroid cancer management in clinical practice.

The effects of baicalin on piglets challenged with Glaesserella parasuis

Glaesserella parasuis (G. parasuis) causes porcine vascular inflammation and damage. Baicalin is reported to have antioxidant and anti-inflammatory functions. However, whether baicalin protects piglets against G. parasuis challenge and the potential protective mechanism have not been investigated. Therefore, in this study, we comprehensively examined the protective efficacy of baicalin in piglets challenged with G. parasuis and the possible protective mechanism. Our results show that baicalin attenuated the release of the inflammation-related cytokines interleukin (IL) 1β, IL6, IL8, IL10, and tumour necrosis factor α (TNF-α) and reduced high mobility group box 1 (HMGB1) production and cell apoptosis in piglets infected with G. parasuis. Baicalin also inhibited the activation of the mitogen-activated protein kinase (MAPK) signalling pathway and protected piglets against G. parasuis challenge. Taken together, our data suggest that baicalin could protect piglets from G. parasuis by reducing HMGB1 release, attenuating cell apoptosis, and inhibiting MAPK signalling activation, thereby alleviating the inflammatory response induced by the bacteria. Our results suggest that baicalin has utility as a novel therapeutic drug to control G. parasuis infection.