Effect of Subinhibitory Concentrations of Chlorogenic Acid on Reducing the Virulence Factor Production byStaphylococcus aureus

Pharmacological Significance of Boraginaceae with Special Insights into Shikonin and Its Potential in the Food Industry

Shikonin is a naphthoquinone pigment present in the hairy roots of the plant species from the Boraginaceae family. The compound has been well investigated for its highly efficient medicinal, antioxidant, and antimicrobial properties. Various extraction methodologies have been employed to maximise yield while minimising waste production of shikonin and its derivatives. Despite substantial research on shikonin and Boraginaceae plants, a research gap persists in the food industry and extraction technologies. This review addresses crucial aspects of shikonin deserving of further exploration. It begins by elucidating the attributes of the Boraginaceae plants and their medicinal traits in folklore. It proceeds to focus on the roots of the plant and its medicinal properties, followed by extraction procedures explored in the last fifteen years, emphasising the novel technologies that have been chosen to improve the yield extract while minimising extraction times. Furthermore, this review briefly outlines studies employing cell culture techniques to enhance in vitro shikonin production. Lastly, attention is directed towards research in the food industry, particularly on shikonin-loaded biodegradable films and the antioxidant activity of shikonin. This review concludes by summarising the future potential in food science and prominent research gaps in this field.

Antibacterial activities of coumarin-3-carboxylic acid against Acidovorax citrulli

Coumarin-3-carboxylic acid (3-CCA), previously screened from natural coumarins, was found to possess strong antibacterial activity against Acidovorax citrulli (Ac). In order to further evaluate the activity of this compound against plant bacterial pathogens and explore its potential value as a bactericidal lead compound, the activity of 3-CCA against 14 plant pathogenic bacteria in vitro and in vivo was tested. Results showed that 3-CCA exhibited strong in vitro activities against Ac, Ralstonia solanacearum, Xanthomonas axonopodis pv. manihotis, X. oryzae pv. oryzae, and Dickeya zeae with EC50 values ranging from 26.64 μg/mL to 40.73 μg/mL. Pot experiment results showed that 3-CCA had powerful protective and curative effects against Ac. In addition, the protective efficiency of 3-CCA was almost equivalent to that of thiodiazole copper at the same concentration. The results of SEM and TEM observation and conductivity tests showed that 3-CCA disrupted the integrity of the cell membrane and inhibited polar flagella growth. Furthermore, 3-CCA resulted in reductions in motility and extracellular exopolysaccharide (EPS) production of Ac while inhibiting the biofilm formation of Ac. These findings indicate that 3-CCA could be a promising natural lead compound against plant bacterial pathogens to explore novel antibacterial agents.

Chlorogenic acid exerts antibacterial effects by affecting lipid metabolism and scavenging ROS in Streptococcus pyogenes

Chlorogenic acid (CGA), one of the most abundant polyphenols in the human diet, exhibits many biological properties, including antibacterial properties. Numerous studies have investigated the antibacterial effects of CGA, however, the molecular mechanisms governing its effects against Streptococcus pyogenes have not been fully elucidated. Streptococcus pyogenes is a Gram-positive pathogen that causes a wide range of human infections and postinfectious immune-mediated disorders. In this study, we used an isobaric tagging for relative and absolute quantitation (iTRAQ)-based proteomic technique to investigate the underlying mode of action of CGA against S. pyogenes. KEGG and GO analyses indicated that CGA affected the expression of protein alterations involved in multiple pathways, downregulating the expression of ribosomal proteins, and upregulating the expression of proteins associated with fatty acid metabolism, pyruvate metabolism, and propanoate metabolism, while activating the expression of oxidation-reduction-related proteins. Moreover, further cell-based experiments verified that CGA scavenges intracellular ROS in S. pyogenes. These results suggest that CGA may exert its antibacterial action through several actions, such as downregulating ribosomal subunits, affecting lipid metabolism, and scavenging intracellular ROS. The results of this study may help to elucidate the molecular mechanisms by which CGA combats pathogens.

Evaluation of the antifungal effect of chlorogenic acid against strains of Candida spp. resistant to fluconazole: apoptosis induction and in silico analysis of the possible mechanisms of action

Introduction. Candida spp. are commensal fungal pathogens of humans, but when there is an imbalance in the microbiota, or weak host immunity, these yeasts can become pathogenic, generating high medical costs.Gap Statement. With the increase in resistance to conventional antifungals, the development of new therapeutic strategies is necessary. This study evaluated the in vitro antifungal activity of chlorogenic acid against fluconazole-resistant strains of Candida spp. Mechanism of action through flow cytometry and in silico analyses, as well as molecular docking assays with ALS3 and SAP5, important proteins in the pathogenesis of Candida albicans associated with the adhesion process and biofilm formation.Results. The chlorogenic acid showed in vitro antifungal activity against the strains tested, causing reduced cell viability, increased potential for mitochondrial depolarization and production of reactive oxygen species, DNA fragmentation and phosphatidylserine externalization, indicating an apoptotic process. Concerning the analysis through docking, the complexes formed between chlorogenic acid and the targets Thymidylate Kinase, CYP51, 1Yeast Cytochrome BC1 Complex e Exo-B-(1,3)-glucanase demonstrated more favourable binding energy. In addition, chlorogenic acid presented significant interactions with the ALS3 active site residues of C. albicans, important in the adhesion process and resistance to fluconazole. Regarding molecular docking with SAP5, no significant interactions were found between chlorogenic acid and the active site of the enzyme.Conclusion. We concluded that chlorogenic acid has potential use as an adjuvant in antifungal therapies, due to its anti-Candida activity and ability to interact with important drug targets.

Thinned-Young Apple Polyphenols Inhibit Halitosis-Related Bacteria Through Damage to the Cell Membrane

The thinned young apple is a by-product and is generally discarded in the orchard during fruit thinning. The polyphenol content of thinned young apples is about 10 times more than that of ripe apples. In our study, the antibacterial effect of thinned young apple polyphenols (YAP) on the halitosis-related bacteria including Porphyromonas gingivalis, Prevotella intermedius, and Fusobacterium nucleatum was investigated. The minimum inhibitory concentrations of YAP against P. gingivalis, P. intermedia, and F. nucleatum were 8.0, 8.0, and 12.0 mg/ml, while the minimum bactericidal concentrations were 10.0, 10.0, and 14.0 mg/ml, respectively. The scanning electron microscopy and transmission electron microscopy analyses showed that after YAP treatment, the membrane surface of halitosis-related bacterial cells was coarse and the cell wall and membrane were separated and eventually ruptured. The integrity of the cell membrane was determined by flow cytometry, indicating that the cells with the integrity membrane significantly reduced as the YAP concentration treatment increased. The release of proteins and nucleic acids into the cell suspension significantly increased, and the membrane potential reduced after the YAP treatment. This research illustrated the antibacterial mechanism of YAP against halitosis-related bacteria and provided a scientific basis of utilizing the polyphenols from the discarded thinned young apples.

Hazard of Staphylococcal Enterotoxins in Food and Promising Strategies for Natural Products against Virulence

Staphylococcal enterotoxins (SEs) secreted by Staphylococcus aureus frequently contaminate food and cause serious foodborne diseases but are ignored during food processing and even cold-chain storage. Notably, SEs are stable and resistant to harsh sterilization environments, which can induce more serious hazards to public health than the bacterium itself. Therefore, it is necessary to develop promising strategies to control SE contamination in food and improve food safety. Natural products not only have various pharmaceutical properties, such as antimicrobial and antitoxin activities, but they are also eco-friendly, safe, nutritive, and barely drug-resistant. Here, the hazards of SEs and the promising natural compounds with different inhibitory mechanisms are summarized and classified. The key points of future research and applications for natural products against bacterial toxin contamination in food are also prospected. Overall, this review may provide enlightening insights for screening effective natural compounds to prevent foodborne diseases caused by bacterial toxins.

Chemical composition, antioxidant and antibacterial activity of Adiantum capillus-veneris L. extract from Algeria

The present study evaluates the antioxidant and antibacterial activities as well as the chemical composition of the aerial part of Adiantum capillus-veneris L., which are endemic to the flora of Algeria. The total phenolic amount of the hydromethanolic extract, as measured by the Folin-Ciocalteu reagent procedure, was found to be about 23.44 ± 0.14 mg GAE/g DW, while the flavonoid content value was 4.66 ± 0.01 mg CE/g DW, as measured by aluminum chloride colorimetric method. The antioxidant power of the extract was analyzed using the DPPH method. DPPH radicals were scavenged with an IC50 value of 65.85 µg/mL. The antibacterial activity of hydromethanolic extract against five bacterial strains of Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 25853), Staphylococcus aureus (ATCC 25923), Streptococcus pneumoniae and Bacillus cereus (ATCC 10876) were carried out using the disc diffusion test and the microdilution method. Streptococcus pneumoniae is the most sensitive bacterium with inhibition zone of 9.0 ± 1.1 cm and MIC=10 mg/mL. Based on HPLC analysis, we find that quercetin 3-O-glucoside was the most abundant compound in the plant extract. This study demonstrates that Adiantum capillus-veneris could be a potential natural source of antibacterial and antioxidant compounds.

Control of Foodborne Staphylococcus aureus by Shikonin, a Natural Extract

Foodborne Staphylococcus aureus (S. aureus) has attracted widespread attention due to its foodborne infection and food poisoning in human. Shikonin exhibits antibacterial activity against a variety of microorganisms, but there are few studies on its antibacterial activity against S. aureus. This study aims to explore the antibacterial activity and mechanism of shikonin against foodborne S. aureus. The results show that the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of shikonin were equal for all tested strains ranging from 35 μg/mL to 70 μg/mL. Shikonin inhibited the growth of S. aureus by reducing intracellular ATP concentrations, hyperpolarizing cell membrane, destroying the integrity of cell membrane, and changing cell morphology. At the non-inhibitory concentrations (NICs), shikonin significantly inhibited biofilm formation of S. aureus, which was attributed to inhibiting the expression of cidA and sarA genes. Moreover, shikonin also markedly inhibited the transcription and expression of virulence genes (sea and hla) in S. aureus. In addition, shikonin has exhibited antibacterial ability against both planktonic and biofilm forms of S. aureus. Importantly, in vivo results show that shikonin has excellent biocompatibility. Moreover, both the heat stability of shikonin and the antimicrobial activity of shikonin against S. aureus were excellent in food. Our findings suggest that shikonin are promising for use as a natural food additive, and it also has great potential in effectively controlling the contamination of S. aureus in food and reducing the number of illnesses associated with S. aureus.

Honey in wound healing: An updated review

Wound healing is a complex process with many interdependent pathophysiological and immunological mediators to restore the cellular integrity of damaged tissue. Cutaneous wound healing is the repair response to a multitude of pathologies induced by trauma, surgery, and burn leading to the restoration and functionality of the compromised cells. Many different methods have been employed to treat acute and chronic wounds, such as antimicrobial therapy, as most wounds are susceptible to infection from microbes and are difficult to treat. However, many antimicrobial agents have become ineffective in wound treatment due to the emergence of multiple drug-resistant bacteria, and failures in current wound treatment methods have been widely reported. For this reason, alternative therapies have been sought, one of which is the use of honey as a wound treatment agent. The use of honey has recently gained clinical popularity for possible use in wound treatment and regenerative medicine. With this high demand, a better delivery and application procedure is required, as well as research aiming at its bioactivity. Honey is a safe natural substance, effective in the inhibition of bacterial growth and the treatment of a broad range of wound types, including burns, scratches, diabetic boils (Skin abscesses associated with diabetic), malignancies, leprosy, fistulas, leg ulcers, traumatic boils, cervical and varicose ulcers, amputation, burst abdominal wounds, septic and surgical wounds, cracked nipples, and wounds in the abdominal wall. Honey comprises a wide variety of active compounds, including flavonoids, phenolic acid, organic acids, enzymes, and vitamins, that may act to improve the wound healing process. Tissue-engineered scaffolds have recently attracted a great deal of attention, and various scaffold fabrication techniques are being researched. Some incorporate honey to improve their delivery during wound treatment. Hence, the aim of this review is to summarize recent studies on the wound healing properties of honey.

Virulence alterations in staphylococcus aureus upon treatment with the sub-inhibitory concentrations of antibiotics

Background

The treatment of patients with Staphylococcus aureus infections mainly relies on antistaphylococcal regimens that are established with effective antibiotics. In antibiotic therapy or while living in nature, pathogens often face the sub-inhibitory concentrations (sub-MICs) of antibiotics due to drug pharmacokinetics, diffusion barriers, waste emission, resistant organism formation, and farming application. Different categories of antibiotics at sub-MICs have diverse effects on the physiological and chemical properties of microorganisms. These effects can result in virulence alterations. However, the mechanisms underlying the actions of antibiotics at sub-MICs on S. aureus virulence are obscure.

Aim of review

In this review, we focus on the effects of sub-MICs of antibiotics on S. aureus virulence from the aspects of cell morphological change, virulence factor expression, bacterial adherence and invasion, staphylococcal biofilm formation, and small-colony variant (SCV) production. The possible mechanisms of antibiotic-induced S. aureus virulence alterations are also addressed.

Key scientific concepts of review

Five main aspects of bacterial virulence can be changed in S. aureus exposure to the sub-MIC levels of antibiotics, resulting in deformed bacterial cells to stimulate abnormal host immune responses, abnormally expressed virulence factors to alter disease development, changed bacterial adhesion and invasion abilities to affect colonization and diffusion, altered biofilm formation to potentate material-related infections, and increased SCV formation to achieve persistent infection and recurrence. These advanced findings expand our knowledge to rethink the molecular signaling roles of antibiotics beyond their actions as antimicrobial agents.

Molecular interaction between methicillin-resistant Staphylococcus aureus (MRSA) and chicken breast reveals enhancement of pathogenesis and toxicity for food-borne outbreak

To study pathogenesis and toxicity of Staphylococcus aureus in foods, FORC_062 was isolated from a human blood sample and complete genome sequence has a type II SCCmec gene cluster and a type II toxin-antitoxin system, indicating an MRSA strain. Its mobile gene elements has many pathogenic genes involved in host infection, biofilm formation, and various enterotoxin and hemolysin genes. Clinical MRSA is often found in animal foods and ingestion of MRSA-contaminated foods causes human infection. Therefore, it is very important to understand the role of contaminated foods. To elucidate the interaction between clinical MRSA FORC_062 and raw chicken breast, transcriptome analysis was conducted, showing that gene expressions of amino acid biosynthesis and metabolism were specifically down-regulated, suggesting that the strain may import and utilize amino acids from the chicken breast, but not able to synthesize them. However, toxin gene expressions were up-regulated, suggesting that human infection of S. aureus via contaminated food may be more fatal. In addition, the contaminated foods enhance multiple-antibiotic resistance activities and virulence factors in this clinical MRSA. Consequently, MRSA-contaminated food may play a role as a nutritional reservoir as well as in enhancing factor for pathogenesis and toxicity of clinical MRSA for severe food-borne outbreaks.

Antibacterial Mechanism of Vanillic Acid on Physiological, Morphological, and Biofilm Properties of Carbapenem-Resistant Enterobacter hormaechei

ABSTRACT

Many studies have evaluated the antimicrobial activity of natural products against various microorganisms, but to our knowledge there have been no studies of the possible use of natural products for their antimicrobial activity against Enterobacter hormaechei. In this study, we investigated vanillic acid (VA) for its antimicrobial activities and its modes of action against carbapenem-resistant E. hormaechei (CREH). The MIC of VA against CREH was determined by the agar diffusion method. The antibacterial action of VA against CREH was elucidated by measuring variations in intracellular ATP concentration, intracellular pH, membrane potential, and cell morphology. Moreover, the efficacy of VA against biofilm formation and VA damage to CREH cells embedded in biofilms were further explored. Our results show that VA was effective against CREH with a MIC of 0.8 mg/mL. VA could rupture the cell membrane integrity of CREH, as measured by a decrease of intracellular ATP, pH, and membrane potential, along with distinctive alternations in cell morphology. In addition, VA exerted a remarkable inhibitory effect on the biofilm formation of CREH and also killed CREH cells within biofilms. These findings show that VA has a potent antibacterial and antibiofilm activity against CREH and, hence, has the potential to be used clinically as a novel candidate agent to treat CREH infections and in the food industry as a food preservative and surface disinfectant.

HIGHLIGHTS

Antibacterial activity and action mode of chlorogenic acid against Salmonella Enteritidis, a foodborne pathogen in chilled fresh chicken

The study evaluated the antibacterial activity of chlorogenic acid (CA) against Salmonella Enteritidis S1, a foodborne pathogen in chilled fresh chicken. Its minimum inhibitory concentration for S. Enteritidis S1 was 2 mM. 1 MIC CA treatment reduced the viable count of S. Enteritidis S1 by 3 log cfu/g in chilled fresh chicken. Scanning electron microscopy examination indicated that CA induced the cell envelope damage of S. Enteritidis S1. Following this, 1-N-Phenylnaphthylamine assay and LPS content analysis indicated that CA induced the permeability of outer membrane (OM). Confocal laser scanning microscopy examination further demonstrated that CA acted on the inner membrane (IM). To support this, the release of intracellular protein and ATP after CA treatment was also observed. CA also suppressed the activities of malate dehydrogenase and succinate dehydrogenase, two main metabolic enzymes in TCA cycle and electron transport chain. Thus, damage of intracelluar and outer membranes as well as disruption of cell metabolism resulted in cell death eventually. The finding suggested that CA has the potential to be developed as a preservative to control S. Enteritidis associated foodborne diseases.

Strengthened and Thermally Resistant Poly(lactic acid)-Based Composite Nanofibers Prepared via Easy Stereocomplexation with Antibacterial Effects

Strengthened poly(lactic acid) (PLA)-based materials with improved mechanical performance and improved thermal resistance, notably, are prepared by introducing stereocomplex crystallite (SC), an ideal filler, into the materials. Owing to the intermolecular hydrogen bond among the stereoisomer chains, the melting point of the special crystallite is up to 200 °C, which is 50 °C higher than the isostatic crystallite. The modulus of the PLA-based materials can be enhanced to several 100 MPa because of the integrated polymer chain arrangement. In this study, we electrospun hybrid nanofibers consisted of PLA stereoisomers and induced the stereocomplex crystallization under a mild condition (65 °C for 1 h). The mild warming is favorable for the protection of chlorogenic acid (CA) that was selected as the antibacterial agent. Both of Gram-positive and Gram-negative bacteria were efficiently cleared away using the warmed nanofibers that released CA rapidly within just a few hours. Used as filters, the SC electrospinning membrane also presented a potent filtering effect, leaving no bacteria retained in the filtrates. Attributing to SC, the PLA-based nanofibers showed extremely increased melting temperature over 200 °C and improved Young's modulus up to 270.0 MPa. The durable nanofibers prepared in present study are meaningful for enlarging the application of PLA-based materials, for example, as filters, masks, and packages.

In vitro antibacterial effects of Tanreqing injection combined with vancomycin or linezolid against methicillin-resistant Staphylococcus aureus

BACKGROUND

Combining conventional drugs and traditional medicine may represent a useful approach to combating antibiotic resistance, which has become a serious threat to global public health. This study aimed to evaluate the potential synergistic interactions between Tanreqing (TRQ) injection, a commercial traditional Chinese medicine formula used for the treatment of upper respiratory tract infection, and selected antibiotics used against methicillin-resistant Staphylococcus aureus (MRSA).

METHODS

The minimum inhibitory concentrations (MICs) of TRQ, vancomycin and linezolid against planktonic MRSA strain were determined by the broth microdilution method. The combined effects of TRQ and antibiotics were studied by the checkerboard method and the time-kill curve assay. The 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay was employed to determine the inhibitory effect of the test compounds alone and in combination against MRSA embedded in biofilms.

RESULTS

MRSA strain was found to be susceptible to TRQ formula with MIC value 4125 μg/ml, while the MIC values for antibiotics, vancomycin and linezolid, were 2.5 μg/ml. The checkerboard analysis revealed that TRQ markedly enhanced activities of the tested antibiotics by reducing their MICs. In the time-kill analysis, TRQ at 1/2 × MIC in combination with vancomycin at 1/2 × MIC, as well as TRQ at 1/8 × MIC in combination with linezolid at 1/2 × MIC decreased the viable colonies by ≥2log10 CFU/ml, resulting in a potent synergistic effect against planktonic MRSA. In contrast to the tested antibiotics, which did not affect mature MRSA biofilms at subinhibitory concentrations, TRQ alone showed strong ability to disrupt preformed biofilms and induce biofilm cell death. The combination of TRQ with vancomycin or linezolid at sub-MIC concentrations resulted in a synergistic antibiofilm effect significantly higher than for each single agent.

CONCLUSIONS

This study provides the first in vitro evidence on the synergistic effects of TRQ and vancomycin or linezolid against planktonic and biofilm MRSA, and revealed their optimal combination doses, thereby providing a rational basis for the combination therapies against MRSA.

Influence of subinhibitory concentrations of NH125 on biofilm formation & virulence factors of Staphylococcus aureus

AIM

l-benzyl-3-cetyl-2-methylimidazolium iodide (NH125) can inhibit Staphylococcus aureus growth. We investigated the effects of sub-MIC concentrations of NH125 on S. aureus biofilm and virulence. Methodology & results: Three strains of S. aureus were tested. Sub-lethal concentrations of NH125 repressed biofilm formation. At partial sub-MICs, NH125 downregulated the expression of most virulence, while strain-dependent effects were found in the production of α-hemolysin, δ-hemolysin, coagulase and nuclease. In Galleria mellonella model, methicillin-resistant S. aureus pre-exposed to NH125 demonstrated significantly lower killing (p = 0.032 for 1/16 and 1/8 MICs; 0.008 for 1/4 MIC; and 0.001 for 1/2 MIC).

CONCLUSION

Sub-MIC concentrations of NH125 inhibited biofilm formation and virulence of S. aureus. These findings provide further support for evaluating the clinical efficacy of NH125 in staphylococcal infection.

Sub-Inhibitory Concentrations of Mupirocin Strongly Inhibit Alpha-Toxin Production in High-Level Mupirocin-Resistant MRSA by Down-Regulating agr, saeRS, and sarA

Mupirocin, a topical antibiotic, has been utilized for decades to treat Staphylococcus aureus skin infections, as well as to decolonize patients at risk of methicillin-resistant S. aureus (MRSA) infection. The aims of this study were to investigate the expression of α-toxin (encoded by the hla gene) in ten clinical MRSA strains (MIC = 1024 μg/ml) in response to a sub-inhibitory concentration of mupirocin (1/32 minimum inhibitory concentration [MIC]) (32 μg/ml) by using α-toxin activity determination and enzyme-linked immune sorbent assay (ELISA). Subsequently, real-time polymerase chain reaction (RT-PCR) was used to examine the expression of saeR, agrA, RNAIII, and sarA genes under sub-inhibitory concentration of mupirocin in order to investigate the mechanism of action of this treatment regarding its strong inhibition of α-toxin expression. For all the strains tested, mupirocin dramatically reduced mRNA levels of α-toxin. The results indicated that α-toxin activity in mupirocin-treated groups was significantly lower than that in untreated groups. The results show that the levels of agrA, RNAIII, saeR, and sarA expression significantly decrease by 11.82- to 2.23-fold (P < 0.01). Moreover, we speculate that mupirocin-induced inhibition of α-toxin expression may be related to the inhibition of regulatory loci, such as agr, sarA and saeRS. More specifically, we found that the mechanism involves inhibiting the expression of agrA and RNAIII. In conclusion, sub-inhibitory concentrations of mupirocin strongly inhibit alpha-toxin production in high-level mupirocin-resistant MRSA by down-regulating agr, saeRS and sarA, which could potentially be developed as a supplemental treatment to control high-level mupirocin-resistant MRSA infection and reduce the risk of infection and colonization.

Plant Natural Products Targeting Bacterial Virulence Factors

Decreased antimicrobial efficiency has become a global public health issue. The paucity of new antibacterial drugs is evident, and the arsenal against infectious diseases needs to be improved urgently. The selection of plants as a source of prototype compounds is appropriate, since plant species naturally produce a wide range of secondary metabolites that act as a chemical line of defense against microorganisms in the environment. Although traditional approaches to combat microbial infections remain effective, targeting microbial virulence rather than survival seems to be an exciting strategy, since the modulation of virulence factors might lead to a milder evolutionary pressure for the development of resistance. Additionally, anti-infective chemotherapies may be successfully achieved by combining antivirulence and conventional antimicrobials, extending the lifespan of these drugs. This review presents an updated discussion of natural compounds isolated from plants with chemically characterized structures and activity against the major bacterial virulence factors: quorum sensing, bacterial biofilms, bacterial motility, bacterial toxins, bacterial pigments, bacterial enzymes, and bacterial surfactants. Moreover, a critical analysis of the most promising virulence factors is presented, highlighting their potential as targets to attenuate bacterial virulence. The ongoing progress in the field of antivirulence therapy may therefore help to translate this promising concept into real intervention strategies in clinical areas.

The therapeutic effect of chlorogenic acid against Staphylococcus aureus infection through sortase A inhibition

The emergence and wide spread of multi-drug resistant Staphylococcus aureus (S. aureus) requires the development of new therapeutic agents with alternative modes of action. Anti-virulence strategies are hoped to meet that need. Sortase A (SrtA) has attracted great interest as a potential drug target to treat infections caused by S. aureus, as many of the surface proteins displayed by SrtA function as virulence factors by mediating bacterial adhesion to specific organ tissues, invasion of host cells, and evasion of the host-immune responses. It has been suggested that inhibitors of SrtA might be promising candidates for the treatment and/or prevention of S. aureus infections. In this study, we report that chlorogenic acid (CHA), a natural compound that lacks significant anti-S. aureus activity, inhibit the activity of SrtA in vitro (IC50 = 33.86 ± 5.55 μg/ml) and the binding of S. aureus to fibrinogen (Fg). Using molecular dynamics simulations and mutagenesis assays, we further demonstrate that CHA binds to the binding sites of C184 and G192 in the SrtA. In vivo studies demonstrated that CHA prevent mice from S. aureus-induced renal abscess, resulting in a significant survival advantage. These findings indicate that CHA is a promising therapeutic compound against SrtA during S. aureus infections.

Therapeutic Potential of Dietary Phenolic Acids

Although modern lifestyle has eased the quality of human life, this lifestyle's related patterns have imparted negative effects on health to acquire multiple diseases. Many synthetic drugs are invented during the last millennium but most if not all of them possess several side effects and proved to be costly. Convincing evidences have established the premise that the phytotherapeutic potential of natural compounds and need of search for novel drugs from natural sources are of high priority. Phenolic acids (PAs) are a class of secondary metabolites spread throughout the plant kingdom and generally involved in plethora of cellular processes involved in plant growth and reproduction and also produced as defense mechanism to sustain various environmental stresses. Extensive research on PAs strongly suggests that consumption of these compounds hold promise to offer protection against various ailments in humans. This paper focuses on the naturally derived PAs and summarizes the action mechanisms of these compounds during disease conditions. Based on the available information in the literature, it is suggested that use of PAs as drugs is very promising; however more research and clinical trials are necessary before these bioactive molecules can be made for treatment. Finally this review provides greater awareness of the promise that natural PAs hold for use in the disease prevention and therapy.