Emodin affects biofilm formation and expression of virulence factors in Streptococcus suis ATCC700794

Rethinking the control of Streptococcus suis infection: Biofilm formation

Streptococcus suis is an emerging zoonotic pathogen that is widespread in swine populations. The control of S. suis infection and its associated diseases is a daunting challenge worldwide. Biofilm formation appears to be the main reason for the persistence of S. suis. In this review we gather existing knowledge on S. suis biofilm, describing the role of biofilm formation in S. suis virulence and drug resistance, the regulatory factors of S. suis biofilm formation, and the research progress of inhibiting S. suis biofilm formation, with the aim of providing guidance for future studies related to the field of S. suis biofilms.

In vitro effects of antimicrobial properties and shear bond strength of different concentrations of Emodin nanoparticles incorporated orthodontic composites

OBJECTIVE

Fixed appliances used in orthodontic treatment are accompanied by some drawbacks, including the development of white spots or enamel demineralization in the vicinity of the brackets and bonding failures. This study aims to evaluate the effect of combining different wt.% of Emodin nanoparticles (ENPs) with orthodontic adhesives to attain adhesives with improved antimicrobial and mechanical properties.

METHODS

ENPs were synthesized and added to orthodontic composite at different concentrations (0.5%, 1%, and 2%). The distribution of ENPs within the composite was evaluated using a field emission scanning electron microscope (FESEM). A total of 216 disks were prepared, with 144 subjected to an eluted components test, 36 used for disk agar diffusion (DAD) test, and 36 for biofilm inhibition test. These tests aimed to assess the antimicrobial activity of the composites against Streptococcus mutans, Lactobacillus acidophilus, and Candida albicans. Additionally, the bond strength between stainless-steel brackets and teeth was evaluated using the shear bond strength (SBS) test, and the adhesive remnant index (ARI) score was determined. One-way analysis of variance and Kruskal-Wallis test were used to analyse the SBS and ARI, respectively. For pairwise group comparison concerning the biofilm inhibition, DAD, and eluted components tests, the Tamhane and Games-Howell tests for data with unequal variances and the post-hoc Tukey's HSD and Scheffe tests for data with equal variances were used.

RESULTS

The FESEM results confirmed the synthesis and even distribution of ENPs in the composite. Only the 2% group showed significant biofilm inhibition against all microorganisms studied (P<0.05). The DAD test revealed that a 1% concentration of ENPs is sufficient to inhibit growth for all microorganisms. The eluted components test demonstrated that the 2% concentration of ENPs performed significantly better against S. mutans compared to the control group (P<0.05). The highest mean SBS was observed with the 0.5% ENP concentration, while no significant differences in SBS and ARI were found among the groups (P>0.05).

CONCLUSIONS

This in vitro study showed that the 2% concentration of ENP produced significantly improved antimicrobial activity without adversely affecting SBS and ARI score. This would support the addition of 2% ENP to orthodontic adhesives.

Ultrasound-assisted extraction of emodin from Rheum officinale Baill and its antibacterial mechanism against Streptococcus suis based on CcpA

Emodin was extracted from Rheum officinale Baill by ultrasound-assisted extraction (UAE), and ethanol was chosen as the suitable solvent through SEM and molecular dynamic simulation. Under the optimum conditions (power 541 W, time 23 min, liquid to material ratio 13:1 mL/g, ethanol concentration 83 %) predicted by RSM, the yield of emodin was 2.18 ± 0.11 mg/g. Moreover, ultrasound power and time displayed the significant effects on the extraction process. Extracting dynamics analysis indicated that the extraction process of emodin by UAE conformed to Fick's second diffusion law. The results of antibacterial experiments suggested that emodin can damage cell membrane and inhibit the expression of cps2A, sao, mrp, epf, neu and the hemolytic activity of S. suis. Biolayer interferometry and FT-IR multi-peak fitting assays demonstrated that emodin induced a secondary conformational shift in CcpA. Molecular docking and molecular dynamics confirmed that emodin bound to CcpA through hydrogen bonding (ALA248, GLU249, GLY129 and ASN196) and π-π T-shaped interaction (TYR225 and TYR130), and the mutation of amino acid residues affected the affinity of CcpA to emodin. Therefore, emodin inhibited the sugar utilization of S. suis through binding to CcpA, and CcpA may be a potential target to inhibit the growth of S. suis.

Subcutaneous Streptococcus dysgalactiae GAPDH vaccine in mice induces a proficient innate immune response

BACKGROUND

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) on the surface of Streptococcus dysgalactiae, coded with gapC, is a glycolytic enzyme that was reported to be a moonlighting protein and virulence factor.

OBJECTIVE

This study assessed GAPDH as a potential immunization candidate protein to prevent streptococcus infections.

METHODS

Mice were vaccinated subcutaneously with recombinant GAPDH and challenged with S. dysgalactiae in vivo. They were then evaluated using histological methods. rGAPDH of mouse bone marrow-derived dendritic cells (BMDCs) was evaluated using immunoblotting, reverse transcription quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay methods.

RESULTS

Vaccination with rGAPDH improved the survival rates and decreased the bacterial burdens in the mammary glands compared to the control group. The mechanism by which rGAPDH vaccination protects against S. dysgalactiae was investigated. In vitro experiments showed that rGAPDH boosted the generation of interleukin-10 and tumor necrosis factor-α. Treatment of BMDCs with TAK-242, a toll-like receptor 4 inhibitor, or C29, a toll-like receptor 2 inhibitor, reduced cytokines substantially, suggesting that rGAPDH may be a potential ligand for both TLR2 and TLR4. Subsequent investigations showed that rGAPDH may activate the phosphorylation of MAPKs and nuclear factor-κB.

CONCLUSIONS

GAPDH is a promising immunization candidate protein for targeting virulence and enhancing immune-mediated protection. Further investigations are warranted to understand the mechanisms underlying the activation of BMDCs by rGAPDH in a TLR2- and TLR4-dependent manner and the regulation of inflammatory cytokines contributing to mastitis pathogenesis.

Antibacterial activities of anthraquinones: structure-activity relationships and action mechanisms

With the increasing prevalence of untreatable infections caused by antibiotic-resistant bacteria, the discovery of new drugs from natural products has become a hot research topic. The antibacterial activity of anthraquinones widely distributed in traditional Chinese medicine has attracted much attention. Herein, the structure and activity relationships (SARs) of anthraquinones as bacteriostatic agents are reviewed and elucidated. The substituents of anthraquinone and its derivatives are closely related to their antibacterial activities. The stronger the polarity of anthraquinone substituents is, the more potent the antibacterial effects appear. The presence of hydroxyl groups is not necessary for the antibacterial activity of hydroxyanthraquinone derivatives. Substitution of di-isopentenyl groups can improve the antibacterial activity of anthraquinone derivatives. The rigid plane structure of anthraquinone lowers its water solubility and results in the reduced activity. Meanwhile, the antibacterial mechanisms of anthraquinone and its analogs are explored, mainly including biofilm formation inhibition, destruction of the cell wall, endotoxin inhibition, inhibition of nucleic acid and protein synthesis, and blockage of energy metabolism and other substances.

Bringing Antimicrobial Strategies to a New Level: The Quorum Sensing System as a Target to Control Streptococcus suis

Streptococcus suis (S. suis) is an important zoonotic pathogen. It mainly uses quorum sensing (QS) to adapt to complex and changeable environments. QS is a universal cell-to-cell communication system that has been widely studied for its physiological functions, including the regulation of bacterial adhesion, virulence, and biofilm formation. Quorum sensing inhibitors (QSIs) are highly effective at interfering with the QS system and bacteria have trouble developing resistance to them. We review the current research status of the S. suis LuxS/AI-2 QS system and QSIs. Studies showed that by inhibiting the formation of AI-2, targeting the LuxS protein, inhibiting the expression of luxs gene can control the LuxS/AI-2 QS system of S. suis. Other potential QSIs targets are summarized, which may be preventing and treating S. suis infections, including AI-2 production, transmission, LuxS protein, blockage of AI-2 binding to receptors, AI-2-mediated QS. Since antibiotics are becoming increasingly ineffective due to the emergence of resistant bacteria, including S. suis, it is thus critical to find new antibacterial drugs with different mechanisms of action. QSIs provide hope for the development of such drugs.

Quinones as an Efficient Molecular Scaffold in the Antibacterial/Antifungal or Antitumoral Arsenal

Quinone-based compounds constitute several general classes of antibiotics that have long shown unwavering efficiency against both Gram-positive and Gram-negative microbial infections. These quinone-based antibiotics are increasingly popular due to their natural origins and are used in natural beverages from herbs or plants in African, Chinese and Indian traditional medicines to treat and prevent various diseases. Quinone-based antibiotics display different bioactive profiles depending on their structures and exert specific biocidal and anti-biofilm properties, and based on recent literature, will be discussed herein.

Tylosin Inhibits Streptococcus suis Biofilm Formation by Interacting With the O-acetylserine (thiol)-lyase B CysM

Streptococcus suis (S. suis) can decrease its virulence or modify local conditions through biofilm formation, which promotes infection persistence in vivo. Biofilm formation is an important cause of chronic drug-resistant S. suis infection. The aim of this study was to evaluate whether tylosin effectively inhibits S. suis biofilm formation by interacting with O-acetylserine (thiol)-lyase B (CysM), a key enzymatic regulator of cysteine synthesis. Biofilm formation of the mutant (ΔcysM) strain was significantly lower compared to the wild-type ATCC 700794 strain. Tylosin inhibited cysM gene expression, decreased extracellular matrix contents, and reduced cysteine, homocysteine, and S-adenosylmethionine levels, indicating its potential value as an effective inhibitor of S. suis biofilm formation. Furthermore, using biolayer interferometry technology and fourier-transform infrared spectroscopy, we found that tylosin and CysM could be combined directly. Overall, these results provide evidence that tylosin inhibits S. suis biofilm formation by interacting with CysM.

Paeoniflorin reduce luxS/AI-2 system-controlled biofilm formation and virulence in Streptococcus suis

Streptococcus suis (S. suis), more specifically serotype 2, is a bacterial pathogen that threatens the lives of pigs and humans. Like many other pathogens, S. suis exhibits quorum sensing (QS) system-controlled virulence factors, such as biofilm formation that complicates treatment. Therefore, impairing the QS involving LuxS/AI-2 cycle in S. suis, may be a promising alternative strategy for overcoming S. suis infections. In this study, we investigated paeoniflorin (PF), a monoterpenoid glycoside compound extracted from peony, as an inhibitor of S. suis LuxS/AI-2 system. At a sub-minimal inhibitory concentration (MIC) (1/16 MIC; 25 μg/ml), PF significantly reduced biofilm formation by S. suis through inhibition of extracellular polysaccharide (EPS) production, without affecting bacterial growth. Moreover, evidence was brought that PF reduces AI-2 activity in S. suis biofilm. Molecular docking indicated that LuxS may be the target of PF. Monitoring LuxS enzymatic activity confirmed that PF had a partial inhibitory effect. Finally, we showed that the use of PF in a mouse model can relieve S. suis infections. This study highlighted the anti-biofilm potential of PF against S. suis, and brought evidence that it may as an inhibitor of the LuxS/AI-2 system to prevent S. suis biofilm-related infections. PF can thus be used as a new type of natural biofilm inhibitor for clinical application.

Elucidating the antibiofilm activity of Frangula emodin against Staphylococcus aureus biofilms

AIMS

Because the Staphylococcus aureus is one of the most well-known pathogens associated with medical devices and nosocomial infections, the aim of the study was to examine antibiofilm potential of emodin against it.

METHODS AND RESULTS

Antibacterial activity was examined through microdilution assay. Antibiofilm testing included crystal violet staining of biofilm biomass and morphology analysis by Atomic force microscopy (AFM). Furthermore, aerobic respiration was monitored using the Micro-Oxymax respirometer. For investigation of gene expression qRT-PCR was performed. Emodin demonstrated strong antibacterial activity and ability to inhibit biofilm formation of all tested strains. The effect on preformed biofilms was spotted in few strains. AFM revealed that emodin affects biofilm structure and roughness. Monitoring of respiration under emodin treatment in planktonic and biofilm form revealed that emodin influenced aerobic respiration. Moreover, qRT-PCR showed that emodin modulates expression of icaA, icaD, srrA and srrB genes, as well as RNAIII, and that this activity was strain-specific.

CONCLUSION

The results obtained in this study indicate the novel antibiofilm activity of emodin and its multiple pathways of action.

SIGNIFICANCE AND IMPACT OF STUDY

This is the first study that examined pathways through which emodin expressed its antibiofilm activity.

Advances in the study of emodin: an update on pharmacological properties and mechanistic basis

Rhei Radix et Rhizoma, also known as rhubarb or Da Huang, has been widely used as a spice and as traditional herbal medicine for centuries, and is currently marketed in China as the principal herbs in various prescriptions, such as Da-Huang-Zhe-Chong pills and Da-Huang-Qing-Wei pills. Emodin, a major bioactive anthraquinone derivative extracted from rhubarb, represents multiple health benefits in the treatment of a host of diseases, such as immune-inflammatory abnormality, tumor progression, bacterial or viral infections, and metabolic syndrome. Emerging evidence has made great strides in clarifying the multi-targeting therapeutic mechanisms underlying the efficacious therapeutic potential of emodin, including anti-inflammatory, immunomodulatory, anti-fibrosis, anti-tumor, anti-viral, anti-bacterial, and anti-diabetic properties. This comprehensive review aims to provide an updated summary of recent developments on these pharmacological efficacies and molecular mechanisms of emodin, with a focus on the underlying molecular targets and signaling networks. We also reviewed recent attempts to improve the pharmacokinetic properties and biological activities of emodin by structural modification and novel material-based targeted delivery. In conclusion, emodin still has great potential to become promising therapeutic options to immune and inflammation abnormality, organ fibrosis, common malignancy, pathogenic bacteria or virus infections, and endocrine disease or disorder. Scientifically addressing concerns regarding the poor bioavailability and vague molecular targets would significantly contribute to the widespread acceptance of rhubarb not only as a dietary supplement in food flavorings and colorings but also as a health-promoting TCM in the coming years.

The anti-biofilm capability of nano-emodin-mediated sonodynamic therapy on multi-species biofilms produced by burn wound bacterial strains

BACKGROUND

Management of burn wound infections (BWIs) is difficult due to the emergence of multidrug-resistant microorganisms. This study aimed to explore the anti-biofilm efficacy of sonodynamic therapy (SDT) using nano-emodin (N-EMO) against multi-species bacterial biofilms containing Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii.

METHODS

Following synthesis and confirmation of N-EMO as a sonosensitizer, the anti-biofilm efficacy of SDT against multi-species bacterial biofilms was determined using minimum inhibitory concentrations (MIC), minimum biofilm inhibitory concentration (MBIC), and minimal biofilm eradication concentration (MBEC) of N-EMO. The reduction of multi-species bacterial biofilms was then evaluated following the treatments using Log reduction and crystal violet (CV) assays. In addition, the expression profiling of abaI, agrA, and lasI genes using SDT with sub-MIC, sub-MBIC, and sub-MBEC of N-EMO was assessed.

RESULTS

Successful synthesis of N-EMO was confirmed through several characterization tests. As the results demonstrated, the MIC value of N-EMO for the multi-species bacterial suspension was 0.15 × 10^-4 g/L, as well as, the MBEC value of N-EMO was 2.5 × 10^-4 g/L, approximately 4-fold higher than that of MBIC (0.62 × 10^-4 g/L). According to the CV assay, there were 57.8 %, 71.0 %, and 81.5 % reduction in the biofilm of multi-species bacterial growth following SDT using 1/128 MBEC, 1/16 MBIC, and 1/2 MIC of N-EMO, respectively. Log reductions analysis demonstrated that 1/2 MIC of N-EMO was more potent in inhibiting the biofilm growth of multi-species test bacteria by 5.725 ± 0.12 (99.9993 %). In this study, N-EMO-mediated SDT could obviously downregulate the gene expression of virulence factors (P < 0.05). The gene expression of lasI, agrA, and abaI were downregulated about 2.5-, 3.6-, and 5.5-fold; and 3.0-, 5.2-, and 7.4-fold following SDT with sub-MBIC and sub-MBEC of N-EMO, respectively.

CONCLUSION

These results highlight the potential of N-EMO-mediated SDT in inhibition of biofilm formation, degradation of formed biofilms, and reduction of virulence factor associated with biofilms of multi-species bacterial biofilms in BWIs.

Effect of Syringopicroside Extracted from Syringa oblata Lindl on the Biofilm Formation of Streptococcus suis

Syringopicroside is a natural drug with antibacterial activity, which is the main ingredient of Syringa oblata Lindl (S. oblata). In order to further develop the application of S. oblata and evaluate the ability of syringopicroside against Streptococcus suis (S. suis), this investigation first applied an ultrasonic-assisted method to extract syringopicroside, and then response surface methodology (RSM) was performed to get the optimum condition. Based on RSM analysis, a second-order polynomial equation about the syringopicroside yield and four variables, including ultrasonic power, time, temperature, and liquid-to-solid ratio, was purposed. Through RSM prediction and model verification experiments, the optimum conditions were determined, as follows: ultrasonic time was 63 min, temperature was 60 °C, a liquid-to-solid ratio was set to 63 mL/g, and ultrasonic power was 835 W. Under this condition, a high syringopicroside yield was obtained (3.07 ± 0.13 mg/g), which was not significantly different with a predicated value. After separation and purification by HPD 500 microporous resin, then mass spectrum was applied to identify the main ingredient in aqueous extract. A minimal inhibitory concentration (MIC) assay revealed the value against S. suis of syringopicroside was 2.56 µg/µL and syringopicroside with sub-inhibitory concentrations that could effectively inhibit biofilm formation of S. suis. Besides, scanning electron microscopy analysis indicated syringopicroside could destroy the multi-layered aggregation structure of S. suis. Finally, molecular docking analysis confirmed that syringopicroside was combined with Orfy protein of S. suis through hydrogen bonds, hydrophobic interaction, and π-π stacking.

Natural Anti-biofilm Agents: Strategies to Control Biofilm-Forming Pathogens

Pathogenic microorganisms and their chronic pathogenicity are significant concerns in biomedical research. Biofilm-linked persistent infections are not easy to treat due to resident multidrug-resistant microbes. Low efficiency of various treatments and in vivo toxicity of available antibiotics drive the researchers toward the discovery of many effective natural anti-biofilm agents. Natural extracts and natural product-based anti-biofilm agents are more efficient than the chemically synthesized counterparts with lesser side effects. The present review primarily focuses on various natural anti-biofilm agents, i.e., phytochemicals, biosurfactants, antimicrobial peptides, and microbial enzymes along with their sources, mechanism of action via interfering in the quorum-sensing pathways, disruption of extracellular polymeric substance, adhesion mechanism, and their inhibitory concentrations existing in literature so far. This study provides a better understanding that a particular natural anti-biofilm molecule exhibits a different mode of actions and biofilm inhibitory activity against more than one pathogenic species. This information can be exploited further to improve the therapeutic strategy by a combination of more than one natural anti-biofilm compounds from diverse sources.

In vitro activity and In vivo efficacy of Isoliquiritigenin against Staphylococcus xylosus ATCC 700404 by IGPD target

Staphylococcus xylosus (S. xylosus) is a type of coagulase-negative Staphylococcus, which was previously considered as non-pathogenic. However, recent studies have linked it with cases of mastitis in cows. Isoliquiritigenin (ISL) is a bioactive compound with pharmacological functions including antibacterial activity. In this study, we evaluated the effect of ISL on S. xylosus in vitro and in vivo. The MIC of ISL against S. xylosus was 80 μg/mL. It was observed that sub-MICs of ISL (1/2MIC, 1/4MIC, 1/8MIC) significantly inhibited the formation of S. xylosus biofilm in vitro. Previous studies have observed that inhibiting imidazole glycerol phosphate dehydratase (IGPD) concomitantly inhibited biofilm formation in S. xylosus. So, we designed experiments to target the formation of IGPD or inhibits its activities in S. xylosus ATCC 700404. The results indicated that the activity of IGPD and its histidine content decreased significantly under 1/2 MIC (40 μg/mL) ISL, and the expression of IGPD gene (hisB) and IGPD protein was significantly down-regulated. Furthermore, Bio-layer interferometry experiments showed that ISL directly interacted with IGPD protein (with strong affinity; KD = 234 μM). In addition, molecular docking was used to predict the binding mode of ISL and IGPD. In vivo tests revealed that, ISL significantly reduced TNF-α and IL-6 levels, mitigated the destruction of the mammary glands and reversed the production of inflammatory cells in mice. The results of the study suggest that, ISL may inhibit S. xylosus growth by acting on IGPD, which can be used as a target protein to treat infections caused by S. xylosus.

Transcriptomic analysis reveals flavonoid biosynthesis of Syringa oblata Lindl. in response to different light intensity

BACKGROUND

Hazy weather significantly increase air pollution and affect light intensity which may also affect medicinal plants growth. Syringa oblata Lindl. (S. oblata), an effective anti-biofilm medicinal plants, is also vulnerable to changes in plant photoperiods and other abiotic stress responses. Rutin, one of the flavonoids, is the main bioactive ingredient in S. oblata that inhibits Streptococcus suis biofilm formation. Thus, the present study aims to explore the biosynthesis and molecular basis of flavonoids in S. oblata in response to different light intensity.

RESULTS

In this study, it was shown that compared with natural (Z0) and 25% ~ 35% (Z2) light intensities, the rutin content of S. oblata under 50% ~ 60% (Z1) light intensity increased significantly. In addition, an integrated analysis of metabolome and transcriptome was performed using light intensity stress conditions from two kinds of light intensities which S. oblata was subjected to: Z0 and Z1. The results revealed that differential metabolites and genes were mainly related to the flavonoid biosynthetic pathway. We found out that 13 putative structural genes and a transcription factor bHLH were significantly up-regulated in Z1. Among them, integration analysis showed that 3 putative structural genes including 4CL1, CYP73A and CYP75B1 significantly up-regulated the rutin biosynthesis, suggesting that these putative genes may be involved in regulating the flavonoid biosynthetic pathway, thereby making them key target genes in the whole metabolic process.

CONCLUSIONS

The present study provided helpful information to search for the novel putative genes that are potential targets for S. oblata in response to light intensity.

Inhibition Activity of Compounds and Bacteriophages against Flavobacterium psychrophilum Biofilms In Vitro

Flavobacterium psychrophilum produces biofilms under laboratory conditions, and it has been inconclusively suggested that F. psychrophilum biofilms can be a potential reservoir for transmission of the pathogen to a fish population under fish farming conditions. Therefore, there is a need for anti-biofilm compounds. The main aim of this study was to determine the anti-biofilm properties of certain compounds and bacteriophages on F. psychrophilum biofilms under static conditions using a standard 96-well microtiter plate biofilm assay in vitro. Eight compounds (A-type proanthocyanidins, D-leucine, EDTA, emodin, fucoidan, L-alliin, parthenolide, and 2-aminoimidazole) at three sub-minimum inhibitory concentrations (sub-MICs), four bacteriophages (Fpv-3, Fpv-9, Fpv-10, and Fpv-21), and a phage combination (Fpv-9 + Fpv-10) were tested for inhibition of biofilm formation and reduction of the biomass of mature biofilms formed by two smooth isolates (P7-9/10 and P1-10B/10) and two rough isolates (P7-9/2R/10 and P1-10B/2R/10) of F. psychrophilum. The crystal violet staining method was used to stain the biofilms. Most of the compounds at sub-MICs inhibited the biofilm formation of mainly smooth isolates, attaining up to 80% inhibition. Additionally, the same reduction trend was also observed for 2-aminoimidazole, emodin, parthenolide, and D-leucine on the biomass of mature biofilms in a concentration-dependent manner. The anti-biofilm properties of the compounds are believed to lie in their ability to disturb the cellular interactions during biofilm formation and probably to cause cell dispersal in already formed biofilms. Lytic bacteriophages efficiently inhibited biofilm formation of F. psychrophilum, while they partially reduced the biomass of mature biofilms. However, the phage combination (Fpv-9 + Fpv-10) showed a successful reduction in the biomass of F. psychrophilum mature biofilms. We conclude that inhibiting compounds together with bacteriophages may supplement the use of disinfectants against bacterial biofilms (e.g., F. psychrophilum biofilms), leading to a reduced occurrence of bacterial coldwater disease outbreaks at fish farms.

Chitosan Grafted With β-Cyclodextrin: Synthesis, Characterization, Antimicrobial Activity, and Role as Absorbefacient and Solubilizer

We synthesized chitosan grafted with β-cyclodextrin (CD-g-CS) from mono-6-deoxy-6-(p-toluenesulfonyl)-β-cyclodextrin and chitosan. Two different amounts of immobilized β-cyclodextrin (β-CD) on CD-g-CS (Q_CD: 0.643 × 10³ and 0.6 × 10² μmol/g) were investigated. The results showed that the amino contents of CD-g-CS with Q_CD = 0.643 × 10³ and 0.6 × 10² μmol/g were 6.34 ± 0.072 and 9.41 ± 0.055%, respectively. Agar diffusion bioassay revealed that CD-g-CS (Q_CD = 0.6 × 10² μmol/g) was more active against Staphylococcus xylosus and Escherichia coli than CD-g-CS (Q_CD = 0.643 × 10³ μmol/g). Cell membrane integrity tests and scanning electron microscopy observation revealed that the antimicrobial activity of CD-g-CS was attributed to membrane disruption and cell lysis. Uptake tests showed that CD-g-CS promoted the uptake of doxorubicin hydrochloride by S. xylosus, particularly for CD-g-CS with Q_CD = 0.6 × 10² μmol/g, and the effect was concentration dependent. CD-g-CS (Q_CD = 0.6 × 10² and 0.643 × 10³ μmol/g) also improved the aqueous solubilities of sulfadiazine, sulfamonomethoxine, and sulfamethoxazole. These findings provide a clear understanding of CD-g-CS and are of great importance for reducing the dosage of antibiotics and antibiotic residues in animal-derived foods. The results also provide a reliable, direct, and scientific theoretical basis for its wide application in the livestock industry.

Combination of berberine and ciprofloxacin reduces multi-resistant Salmonella strain biofilm formation by depressing mRNA expressions of luxS, rpoE, and ompR

Bacterial biofilms have been demonstrated to be closely related to clinical infections and contribute to drug resistance. Berberine, which is the main component of Coptis chinensis, has been reported to have efficient antibacterial activity. This study aimed to investigate the potential effect of a combination of berberine with ciprofloxacin (CIP) to inhibit Salmonella biofilm formation and its effect on expressions of related genes (rpoE, luxS, and ompR). The fractional inhibitory concentration (FIC) index of the combination of berberine with CIP is 0.75 showing a synergistic antibacterial effect. The biofilm's adhesion rate and growth curve showed that the multi-resistant Salmonella strain had the potential to form a biofilm relative to that of strain CVCC528, and the antibiofilm effects were in a dose-dependent manner. Biofilm microstructures were rarely observed at 1/2 × MIC/FIC concentrations (MIC, minimal inhibition concentration), and the combination had a stronger antibiofilm effect than each of the antimicrobial agents used alone at 1/4 × FIC concentration. LuxS, rpoE, and ompR mRNA expressions were significantly repressed (p ＜ 0.01) at 1/2 × MIC/FIC concentrations, and the berberine and CIP combination repressed mRNA expressions more strongly at the 1/4 × FIC concentration. The results indicate that the combination of berberine and CIP has a synergistic effect and is effective in inhibiting Salmonella biofilm formation via repression of luxS, rpoE, and ompR mRNA expressions.

Spectrum-Effect Relationships Between the Bioactive Ingredient of Syringa oblata Lindl. Leaves and Its Role in Inhibiting the Biofilm Formation of Streptococcus suis

Syringa oblata Lindl. (S. oblata) has been used in herbal medicines for treating bacterial diseases. It is also thought to inhibit Streptococcus suis (S. suis) biofilm formation. However, due to the inherent nature of the complexity in its chemical properties, it is difficult to understand the possible bioactive ingredients of S. oblata. The spectrum-effect relationships method was applied to screen the main active ingredients in S. oblata obtained from Heilongjiang Province based on gray relational analysis. The results revealed that Sub-MICs obtained from 10 batches of S. oblata could inhibit biofilm formation by S. suis. Gray relational analysis revealed variations in the contents of 15 main peaks and rutin was discovered to be the main active ingredient. Then, the function of rutin was further verified by inhibiting S. suis biofilm formation using crystal violet staining. Computational studies revealed that rutin may target the chloramphenicol acetyltransferase protein in the biofilm formation of S. suis. In conclusion, this study revealed that the spectrum-effect relationships and computational studies are useful tools to associate the active ingredient with the potential anti-biofilm effects of S. oblata. Here, our findings would provide foundation for the further understanding of the mechanism of S. oblata intervention in biofilm formation.

Inhibition of Streptococcus suis Adhesion and Biofilm Formation in Vitro by Water Extracts of Rhizoma Coptidis

Streptococcus suis is difficult to treat and responsible for various infections in humans and pigs. It can also form biofilms and induce persistent infections. Rhizoma Coptidis is a medicinal plant widely used in Traditional Chinese Medicine. Although the inhibitory effects of Rhizoma Coptidis on biofilm formation have been investigated in several studies, the ability of Rhizoma Coptidis to inhibit S. suis biofilm formation and the underlying mechanisms have not yet been reported. In this study, we showed that sub-minimal inhibitory concentrations (25 and 50 μg mL^-1) of water extracts of Rhizoma Coptidis (Coptis deltoidea C.Y.Cheng & P.K.Hsiao, obtained from Sichuan Province) were sufficient to inhibit biofilm formation, as shown in the tissue culture plate (TCP) method and scanning electron microscopy. Real-time PCR and iTRAQ were used to measure gene and protein expression in S. suis. Sub-minimum inhibitory concentrations (25 and 50 μg mL^-1) of Rhizoma Coptidis water extracts inhibited S. suis adhesion significantly in an anti-adherence assay. Some genes, such as gapdh, sly, and mrp, and proteins, such as antigen-like protein, CPS16V, and methyltransferase H, involved in adhesion were significantly modulated in cells treated with 50 μg mL^-1 of Rhizoma Coptidis water extracts compared to untreated cells. The results from this study suggest that compounds in Rhizoma Coptidis water extracts play an important role in inhibiting adhesion of S. suis cells and, therefore, biofilm formation.

The Influence of Shuttle-Shape Emodin Nanoparticles on the Streptococcus suis Biofilm

Biofilm is one of the most important physiological protective barriers of the Streptococcus suis (S. suis), and it is also one of the primary causes of hindrance to drug infiltration, reduction of bactericidal effects, and the development of antibiotic resistance. In order to intervene or eliminate S. suis biofilm, shuttle-shape emodin-loaded nanoparticles were developed in our study. The emodin nanoparticles were prepared by emodin and gelatin-cyclodextrin which was synthesized as drug carrier, and the nanoparticles were 174 nm in size, -4.64 mv in zeta potential, and exhibited a sustained emodin release. Moreover, the delivery kinetics of nanoparticles were also explored in our study. The confocal laser scanning microscopy and colony forming unit enumeration experiment indicated that nanoparticles could increase drug infiltration and uptake by biofilm. The flow cytometry system analysis showed that nanoparticles could be up taken by 99% of the bacteria cells. TCP assay and scanning electron microscopy showed that the nanoparticles had better effect on biofilm inhibition and elimination when compared with emodin solution. These results revealed that the emodin nanoparticles had a better therapeutic effect on the S. suis biofilm in vitro.

Antimicrobial peptide GH12 suppresses cariogenic virulence factors of Streptococcus mutans

Cariogenic virulence factors of Streptococcus mutans include acidogenicity, aciduricity, and extracellular polysaccharides (EPS) synthesis. The de novo designed antimicrobial peptide GH12 has shown bactericidal effects on S. mutans, but its interaction with virulence and regulatory systems of S. mutans remains to be elucidated. The objectives were to investigate the effects of GH12 on virulence factors of S. mutans, and further explore the function mechanisms at enzymatic and transcriptional levels. To avoid decrease in bacterial viability, we limited GH12 to subinhibitory levels. We evaluated effects of GH12 on acidogenicity of S. mutans by pH drop, lactic acid measurement and lactate dehydrogenase (LDH) assay, on aciduricity through survival rate at pH 5.0 and F₁F₀-ATPase assay, and on EPS synthesis using quantitative measurement, morphology observation, vertical distribution analyses and biomass calculation. Afterwards, we conducted quantitative real-time PCR to acquire the expression profile of related genes. GH12 at 1/2 MIC (4 mg/L) inhibited acid production, survival rate, EPS synthesis, and biofilm formation. The enzymatic activity of LDH and F₁F₀-ATPase was inhibited, and ldh, gtfBCD, vicR, liaR, and comDE genes were significantly downregulated. In conclusion, GH12 inhibited virulence factors of S. mutans, through reducing the activity of related enzymes, downregulating virulence genes, and inactivating specific regulatory systems.

Homology Modeling and Virtual Screening to Discover Potent Inhibitors Targeting the Imidazole Glycerophosphate Dehydratase Protein in Staphylococcus xylosus

The imidazole glycerophosphate dehydratase (IGPD) protein is a therapeutic target for herbicide discovery. It is also regarded as a possible target in Staphylococcus xylosus (S. xylosus) for solving mastitis in the dairy cow. The 3D structure of IGPD protein is essential for discovering novel inhibitors during high-throughput virtual screening. However, to date, the 3D structure of IGPD protein of S. xylosus has not been solved. In this study, a series of computational techniques including homology modeling, Ramachandran Plots, and Verify 3D were performed in order to construct an appropriate 3D model of IGPD protein of S. xylosus. Nine hits were identified from 2,500 compounds by docking studies. Then, these nine compounds were first tested in vitro in S. xylosus biofilm formation using crystal violet staining. One of the potential compounds, baicalin was shown to significantly inhibit S. xylosus biofilm formation. Finally, the baicalin was further evaluated, which showed better inhibition of biofilm formation capability in S. xylosus by scanning electron microscopy. Hence, we have predicted the structure of IGPD protein of S. xylosus using computational techniques. We further discovered the IGPD protein was targeted by baicalin compound which inhibited the biofilm formation in S. xylosus. Our findings here would provide implications for the further development of novel IGPD inhibitors for the treatment of dairy mastitis.

iTRAQ-based quantitative proteomic analysis reveals multiple effects of Emodin to Haemophilus parasuis

Haemophilus parasuis, a symbiotic bacteria of upper respiratory tract of swine, is the etiological agent of Glässer's disease, which is characterized by fibrinous polyserositis. Emodin, exhibits antibacterial activity against H. parasuis, yet the action mode has not been fully understood. In present study, isobaric tag for relative and absolute quantification (iTRAQ) method was applied to analyze the global protein alteration of H. parasuis in response to 16μg/mL Emodin. In total, 338 proteins exhibiting significant differential expressions were identified. It was speculated that, through application of bioinformatics analysis to theses differentially expressed proteins, Emodin mainly inhibited some key proteins expression of ABC transport system, carbohydrate metabolism pathway and bacterial cell division by inhibiting the ribosome synthesis, resulting in the growth inhibition of H. parasuis. Remarkably, nine virulence-associated proteins were detected differently expressed, further experiments revealed that after treatment with Emodin, H. parasuis could be inhibited to adhere to and invade into porcine kidney epithelial cells (PK-15 line) and exhibited increased sensitivity to serum complement in a concentration-dependent manner. Phagocytosis assay showed Emodin also could enhance phagocytic activity of porcine alveolar macrophages PAM to H. parasuis. These results indicated that Emodin also can attenuate virulence of H. parasuis and reduce infection.

BIOLOGICAL SIGNIFICANCE

The Glässer's disease caused by H. parasuis has become a typical bacterial disease and cause serious economic loss to the swine industry around the world. Antibiotics are extensively used to control the infection, but increasing antibiotic resistance has been a severe problem. Hence, novel treatment agents are needed. So far, few antibacterial agents were reported that could control H. parasuis infection. In the present study, the state-of-the-art quantitative proteomic technology was applied to uncover underlying action mechanism of Emodin. This study extends understanding of antibacterial effect of Emodin to H. parasuis at molecular level and provides useful information for further investigations. Moreover, our results provide theoretical foundation for the practical application of Emodin.

Comparative Proteomic Analysis Provides insight into the Key Proteins as Possible Targets Involved in Aspirin Inhibiting Biofilm Formation of Staphylococcus xylosus

Staphylococcus xylosus is an opportunistic pathogen that causes infection in humans and cow mastitis. And S. xylosus possesses a strong ability to form biofilms in vitro. As biofilm formation facilitates resistance to antimicrobial agents, the discovery of new medicinal properties for classic drugs is highly desired. Aspirin, which is the most common active component of non-steroidal anti-inflammatory compounds, affects the biofilm-forming capacity of various bacterial species. We have found that aspirin effectively inhibits biofilm formation of S. xylosus by Crystal violet (CV) staining and scanning electron microscopy analyses. The present study sought to elucidate possible targets of aspirin in suppressing S. xylosus biofilm formation. Based on an isobaric tag for relative and absolute quantitation (iTRAQ) fold-change of >1.2 or <0.8 (P-value < 0.05), 178 differentially expressed proteins, 111 down-regulated and 67 up-regulated, were identified after application of aspirin to cells at a 1/2 minimal inhibitory concentration. Gene ontology analysis indicated enrichment in metabolic processes for the majority of the differentially expressed proteins. We then used the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database to analyze a large number of differentially expressed proteins and identified genes involved in biosynthesis of amino acids pathway, carbon metabolism (pentose phosphate and glycolytic pathways, tricarboxylic acid cycle) and nitrogen metabolism (histidine metabolism). These novel proteins represent candidate targets in aspirin-mediated inhibition of S. xylosus biofilm formation at sub-MIC levels. The findings lay the foundation for further studies to identify potential aspirin targets.

Rutin Inhibits Streptococcus suis Biofilm Formation by Affecting CPS Biosynthesis

Streptococcus suis (S. suis) form biofilms and causes severe diseases in humans and pigs. Biofilms are communities of microbes embedded in a matrix of extracellular polymeric substances. Eradicating biofilms with the use of antibiotics or biocides is often ineffective and needs replacement with other potential agents. Compared to conventional agents, promising and potential alternatives are biofilm-inhibiting compounds without impairing growth. Here, we screened a S. suis adhesion inhibitor, rutin, derived from Syringa. Rutin, a kind of flavonoids, shows efficient biofilm inhibition of S. suis without impairing its growth. Capsular polysaccharides(CPS) are reported to be involved in its adherence to influence bacterial biofilm formation. We investigated the effect of rutin on S. suis CPS content and structure. The results showed that rutin was beneficial to improve the CPS content of S. suis without changing its structure. We further provided evidence that rutin specifically affected S. suis biofilm susceptibility by affecting CPS biosynthesis in vitro. The study explores the antibiofilm potential of rutin against S. suis which can be used as an adhesion inhibitor for the prevention of S. suis biofilm-related infections. Nevertheless, rutin could be used as a novel natural inhibitor of biolfilm and its molecular mechanism provide basis for its pharmacological and clinical applications.

The effect of emodin on Staphylococcus aureus strains in planktonic form and biofilm formation in vitro

Staphylococcus aureus (S. aureus) is a Gram-positive pathogen and forms biofilm easily. Bacteria inside biofilms display an increased resistance to antibiotics and disinfectants. The objective of the current study was to assess the antimicrobial activities of emodin, 1,2,8-trihydroxy-6-methylanthraquinone, an anthraquinone derivative isolated from Polygonum cuspidatum and Rheum palmatum, against S. aureus CMCC26003 grown in planktonic and biofilm cultures in vitro. In addition, a possible synergistic effect between emodin and berberine chloride was evaluated. As quantified by crystal violet method, emodin significantly decreased S. aureus biofilm growth in a dose-dependent manner. The above findings were further supported by scanning electron microscopy. Moreover, the present study demonstrated that sub-MICs emodin obviously intervened the release of extracellular DNA and inhibited expression of the biofilm-related genes (cidA, icaA, dltB, agrA, sortaseA and sarA) by real-time RT-PCR. These results revealed a promising application for emodin as a therapeutic agent and an effective strategy to prevent S. aureus biofilm-related infections.

Syringa oblata Lindl. Aqueous Extract Is a Potential Biofilm Inhibitor in S. suis

Streptococcus suis (S. suis) is a zoonotic pathogen that causes severe disease symptoms in pigs and humans. Syringa oblata Lindl. distributed in the middle latitudes of Eurasia and North America were proved as the most development potential of Chinese Medicine. In this study, biofilm formation by S. suis decreased after growth with 1/2 MIC, 1/4 MIC, or 1/8 MIC of Syringa oblata Lindl. aqueous extract and rutin. Scanning electron microscopy analysis revealed the potential effect of Syringa oblata Lindl. aqueous extract and rutin against biofilm formation by S. suis. Using iTRAQ technology, comparative proteomic analyses was performed at two conditions: 1/2 MIC of Syringa oblata Lindl. aqueous extract treated and non-treated cells. The results revealed the existence of 28 proteins of varying amounts. We found that the majority of the proteins were related to cell growth and metabolism. We also found that Syringa oblata Lindl. Aqueous extract affected the synthesis enzymes. In summary, Syringa oblata Lindl. aqueous extract might be used to inhibit the biofilm formation effectively by S. suis, and the active ingredients of the Syringa oblate Lindl. aqueous extract is rutin. The content of rutin is 9.9 ± 0.089 mg/g dry weight.

Sub-MICs of Azithromycin Decrease Biofilm Formation of Streptococcus suis and Increase Capsular Polysaccharide Content of S. suis

Streptococcus suis (S. suis) caused serious disease symptoms in humans and pigs. S. suis is able to form thick biofilms and this increases the difficulty of treatment. After growth with 1/2 minimal inhibitory concentration (MIC) of azithromycin, 1/4 MIC of azithromycin, or 1/8 MIC of azithromycin, biofilm formation of S. suis dose-dependently decreased in the present study. Furthermore, scanning electron microscopy analysis revealed the obvious effect of azithromycin against biofilm formation of S. suis. Especially, at two different conditions (1/2 MIC of azithromycin non-treated cells and treated cells), we carried out comparative proteomic analyses of cells by using iTRAQ technology. Finally, the results revealed the existence of 19 proteins of varying amounts. Interestingly, several cell surface proteins (such as ATP-binding cassette superfamily ATP-binding cassette transporter (G7SD52), CpsR (K0FG35), Cps1/2H (G8DTL7), CPS16F (E9NQ13), putative uncharacterized protein (G7SER0), NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (G5L259), putative uncharacterized protein (G7S2D6), amino acid permease (B0M0G6), and NsuB (G5L351)) were found to be implicated in biofilm formation. More importantly, we also found that azithromycin affected expression of the genes cps1/2H, cpsR and cps16F. Especially, after growth with 1/2 MIC of azithromycin and 1/4 MIC of azithromycin, the capsular polysaccharide content of S. suis was significantly higher.

Sub-MIC Tylosin Inhibits Streptococcus suis Biofilm Formation and Results in Differential Protein Expression

Streptococcus suis (S.suis) is an important zoonotic pathogen that causes severe diseases in humans and pigs. Biofilms of S. suis can induce persistent infections that are difficult to treat. In this study, the effect of tylosin on biofilm formation of S. suis was investigated. 1/2 minimal inhibitory concentration (MIC) and 1/4 MIC of tylosin were shown to inhibit S. suis biofilm formation in vitro. By using the iTRAQ strategy, we compared the protein expression profiles of S. suis grown with sub-MIC tylosin treatment and with no treatment. A total of 1501 proteins were identified by iTRAQ. Ninety-six differentially expressed proteins were identified (Ratio > ±1.5, p < 0.05). Several metabolism proteins (such as phosphoglycerate kinase) and surface proteins (such as ABC transporter proteins) were found to be involved in biofilm formation. Our results indicated that S. suis metabolic regulation, cell surface proteins, and virulence proteins appear to be of importance in biofilm growth with sub-MIC tylosin treatment. Thus, our data revealed the rough regulation of biofilm formation that may provide a foundation for future research into mechanisms and targets.