Allicin reduces the production of α-toxin by Staphylococcus aureus

Plant-derived virulence arresting drugs as novel antimicrobial agents: Discovery, perspective, and challenges in clinical use

Antimicrobial resistance (AMR) emerges as a severe crisis to public health and requires global action. The occurrence of bacterial pathogens with multi-drug resistance appeals to exploring alternative therapeutic strategies. Antivirulence treatment has been a positive substitute in seeking to circumvent AMR, which aims to target virulence factors directly to combat bacterial infections. Accumulated evidence suggests that plant-derived natural products, which have been utilized to treat infectious diseases for centuries, can be abundant sources for screening potential virulence-arresting drugs (VADs) to develop advanced therapeutics for infectious diseases. This review sums up some virulence factors and their actions in various species of bacteria, as well as recent advances pertaining to plant-derived natural products as VAD candidates. Furthermore, we also discuss natural VAD-related clinical trials and patents, the perspective of VAD-based advanced therapeutics for infectious diseases and critical challenges hampering clinical use of VADs, and genomics-guided identification for VAD therapeutic. These newly discovered natural VADs will be encouraging and optimistic candidates that may sustainably combat AMR.

Secondary metabolites of plants and their possible role in the "age of superbugs"

Bacterial infections are a serious cause of high morbidity and mortality worldwide. Over the past decades, the drug resistance of bacterial pathogens has been steadily increasing, while the rate of development of new effective antibacterial drugs remains consistently low. The plant kingdom is sometimes called a bottomless well for the search for new antimicrobial therapies. This is due to the fact that plants are easily accessible and cheap to process, while extracts and components of plant origin often demonstrate a high level of biological activity with minor side effects. The variety of compounds obtained from plant raw materials can provide a wide choice of various chemical structures for interaction with various targets inside bacterial cells, while the rapid development of modern biotechnological tools opens the way to the targeted production of bioactive components with desired properties. The objective of this review is to answer the question, whether antimicrobials of plant origin have a chance to play the role of a panacea in the fight against infectious diseases in the "post-antibiotic era".

Antibacterial and immunological properties of piperine evidenced by preclinical studies: a systematic review

Aim: To review in vitro, in vivo, and in silico studies examining the antibacterial and immunomodulatory properties of piperine (PPN). Methods: This systematic review followed PRISMA guidelines, and five databases were searched. Results: A total of 40 articles were included in this study. Six aspects of PPN activity were identified, including antibacterial spectrum, association with antibiotics, efflux pump inhibition, biofilm effects, protein target binding, and modulation of immune functions/virulence factors. Most studies focused on Mycobacterium spp. and Staphylococcus aureus. Cell lineages and in vivo models were employed to study PPN antibacterial effects. Conclusion: We highlight PPN as a potential adjuvant in the treatment of bacterial infections. PPN possesses several antibacterial properties that need further exploration to determine the mechanisms behind its pharmacological activity.

An Assessment of the In Vitro Models and Clinical Trials Related to the Antimicrobial Activities of Phytochemicals

An increased number antibiotic-resistant bacteria have emerged with the rise in antibiotic use worldwide. As such, there has been a growing interest in investigating novel antibiotics against antibiotic-resistant bacteria. Due to the extensive history of using plants for medicinal purposes, scientists and medical professionals have turned to plants as potential alternatives to common antibiotic treatments. Unlike other antibiotics in use, plant-based antibiotics have the innate ability to eliminate a broad spectrum of microorganisms through phytochemical defenses, including compounds such as alkaloids, organosulfur compounds, phenols, coumarins, and terpenes. In recent years, these antimicrobial compounds have been refined through extraction methods and tested against antibiotic-resistant strains of Gram-negative and Gram-positive bacteria. The results of the experiments demonstrated that plant extracts successfully inhibited bacteria independently or in combination with other antimicrobial products. In this review, we examine the use of plant-based antibiotics for their utilization against antibiotic-resistant bacterial infections. In addition, we examine recent clinical trials utilizing phytochemicals for the treatment of several microbial infections.

Recent advances to combat ESKAPE pathogens with special reference to essential oils

Biofilm-associated bacteria, especially ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.), are a serious challenge worldwide. Due to the lack of discovery of novel antibiotics, in the past two decades, it has become necessary to search for new antibiotics or to study synergy with the existing antibiotics so as to counter life-threatening infections. Nature-derived compounds/based products are more efficient than the chemically synthesized ones with less resistance and lower side effects. In this descriptive review, we discuss the most promising therapeutics for the treatment of ESKAPE-related biofilms. The first aspect includes different types of natural agents [botanical drugs, essential oils (EOs), antimicrobial peptides, bacteriophages, and endolysins] effective against ESKAPE pathogens. The second part of the review deals with special references to EOs/essential oil components (EOCs) (with some exclusive examples), mode of action (via interfering in the quorum-sensing pathways, disruption of biofilm and their inhibitory concentrations, expression of genes that are involved, other virulence factors), existing in literature so far. Moreover, different essential oils and their major constituents were critically discussed using in vivo models to target ESKAPE pathogens along with the studies involving existing antibiotics.

A Comprehensive Review of Natural Compounds for Wound Healing: Targeting Bioactivity Perspective

Wound healing is a recovering process of damaged tissues by replacing dysfunctional injured cellular structures. Natural compounds for wound treatment have been widely used for centuries. Numerous published works provided reviews of natural compounds for wound healing applications, which separated the approaches based on different categories such as characteristics, bioactivities, and modes of action. However, current studies provide reviews of natural compounds that originated from only plants or animals. In this work, we provide a comprehensive review of natural compounds sourced from both plants and animals that target the different bioactivities of healing to promote wound resolution. The compounds were classified into four main groups (i.e., anti-inflammation, anti-oxidant, anti-bacterial, and collagen promotion), mostly studied in current literature from 1992 to 2022. Those compounds are listed in tables for readers to search for their origin, bioactivity, and targeting phases in wound healing. We also reviewed the trend in using natural compounds for wound healing.

Allicin in Digestive System Cancer: From Biological Effects to Clinical Treatment

Allicin is the main active ingredient in freshly-crushed garlic and some other allium plants, and its anticancer effect on cancers of digestive system has been confirmed in many studies. The aim of this review is to summarize epidemiological studies and in vitro and in vivo investigations on the anticancer effects of allicin and its secondary metabolites, as well as their biological functions. In epidemiological studies of esophageal cancer, liver cancer, pancreatic cancer, and biliary tract cancer, the anticancer effect of garlic has been confirmed consistently. However, the results obtained from epidemiological studies in gastric cancer and colon cancer are inconsistent. In vitro studies demonstrated that allicin and its secondary metabolites play an antitumor role by inhibiting tumor cell proliferation, inducing apoptosis, controlling tumor invasion and metastasis, decreasing angiogenesis, suppressing Helicobacter pylori, enhancing the efficacy of chemotherapeutic drugs, and reducing the damage caused by chemotherapeutic drugs. In vivo studies further demonstrate that allicin and its secondary metabolites inhibit cancers of the digestive system. This review describes the mechanisms against cancers of digestive system and therapeutic potential of allicin and its secondary metabolites.

Current studies and potential future research directions on biological effects and related mechanisms of allicin

Allicin, a thiosulfonate extract from freshly minced garlic, has been reported to have various biological effects on different organs and systems of animals and human. It can reduce oxidative stress, inhibit inflammatory response, resist pathogen infection and regulate intestinal flora. In addition, dozens of studies also demonstrated allicin could reduce blood glucose level, protect cardiovascular system and nervous system, and fight against cancers. Allicin was widely used in disease prevention and health care. However, more investigations on human cohort study are needed to verify the biological or clinical effects of allicin in the future. In this review, we summarized the biological effects of allicin from previous outstanding and valuable studies and provided useful information for future studies on the health effects of allicin.

Sub-growth-inhibitory concentrations of omadacycline inhibit Staphylococcus aureus haemolytic activity in vitro

Objectives

To evaluate the effect of sub-growth-inhibitory concentrations of omadacycline on Staphylococcus aureus ATCC 10832 haemolytic activity in vitro.

Methods

Following determination of the MICs of omadacycline and comparator antibiotics, the strain was grown in the presence of individual antibiotics and the percentage of haemolysis assayed; ‘washout’ experiments were performed with omadacycline only.

Results

Omadacycline inhibited S. aureus haemolytic activity in vitro at sub-growth-inhibitory concentrations. Inhibition was maintained at least 4 h after removal of extracellular drug.

Conclusions

Omadacycline’s in vitro potency and suppression of virulence factors might contribute to its efficacy in the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia caused by virulent strains of S. aureus. This finding could be relevant for other organisms and virulence factors that depend on new protein synthesis.

Immunomodulatory effects of Allium Sativum L. and its constituents against viral infections and metabolic diseases

BACKGROUND

Allium sativum L., or garlic, is one of the most studied plants worldwide within the field of traditional medicine. Current interests lie in the potential use of garlic as a preventive measure and adjuvant treatment for viral infections, e.g., SARS-CoV-2. Even though it cannot be presented as a single treatment, its beneficial effects are beyond doubt. The World Health Organization has deemed it an essential part of any balanced diet with immunomodulatory properties.

OBJECTIVE

The aim of the study was to review the literature on the effects of garlic compounds and preparations on immunomodulation and viral infection management, with emphasis on SARS-CoV-2.

METHOD

Exhaustive literature search has been carried out on electronic databases.

CONCLUSION

Garlic is a fundamental part of a well-balanced diet which helps maintain general good health. The reported information regarding garlic's ability to beneficially modulate inflammation and the immune system is encouraging. Nonetheless, more efforts must be made to understand the actual medicinal properties and mechanisms of action of the compounds found in this plant to inhibit or diminish viral infections, particularly SARS-CoV-2. Based on our findings, we propose a series of innovative strategies to achieve such a challenge in the near future.

Antibacterial Properties of Organosulfur Compounds of Garlic (Allium sativum)

Garlic (Allium sativum), a popular food spice and flavoring agent, has also been used traditionally to treat various ailments especially bacterial infections for centuries in various cultures around the world. The principal phytochemicals that exhibit antibacterial activity are oil-soluble organosulfur compounds that include allicin, ajoenes, and allyl sulfides. The organosulfur compounds of garlic exhibit a range of antibacterial properties such as bactericidal, antibiofilm, antitoxin, and anti-quorum sensing activity against a wide range of bacteria including multi-drug resistant (MDR) strains. The reactive organosulfur compounds form disulfide bonds with free sulfhydryl groups of enzymes and compromise the integrity of the bacterial membrane. The World Health Organization (WHO) has recognized the development of antibiotic resistance as a global health concern and emphasizes antibiotic stewardship along with the urgent need to develop novel antibiotics. Multiple antibacterial effects of organosulfur compounds provide an excellent framework to develop them into novel antibiotics. The review provides a focused and comprehensive portrait of the status of garlic and its compounds as antibacterial agents. In addition, the emerging role of new technologies to harness the potential of garlic as a novel antibacterial agent is discussed.

Comparison of Antivirulence Activities of Black Ginseng against Methicillin-Resistant Staphylococcus aureus According to the Number of Repeated Steaming and Drying Cycles

Korean ginseng has been widely used in Eastern medicine for thousands of years. The contents of the compounds in ginseng roots change depending on the amount of steaming and drying, and the drying method used. Black ginseng (BG) is the Korean ginseng processed by repeated steaming and drying. In this study, 5-year-old fresh Korean ginseng roots were steamed and dried 3 or 5 times, and we investigated how many cycles of steaming and drying are preferable for antivirulence activities against methicillin-resistant Staphylococcus aureus (MRSA). As a result, the antivirulence activities was increased by the treatment of BG that was steamed and dried three times, and the effect was further increased by five-time processed BG. Moreover, an ELISA showed that the TNF-α production of RAW264.7 cells stimulated by MRSA supernatants was inhibited by subinhibitory concentrations of BG extract. The expression of Hla, staphylococcal enterotoxin A (SEA), and staphylococcal enterotoxin B (SEB), an important virulence factor in the pathogenicity of MRSA, was found to decrease when bacterial cells were treated with BG extract. The antivirulence activities of BG were not simply due to pathogen growth inhibition; the BG extract was shown to decrease agrA, hla, sea, and seb expression in MRSA. Therefore, BG strongly reduces the secretion of the virulence factors produced by Staphylococcus aureus, suggesting that a BG-based structure may be used for the development of drugs aimed at staphylococcal virulence-related exoproteins. This study suggests that BG could be used as a promising natural compound in the food and pharmaceutical industry.

Thioredoxin Reductase Is a Valid Target for Antimicrobial Therapeutic Development Against Gram-Positive Bacteria

There is a drought of new antibacterial compounds that exploit novel targets. Thioredoxin reductase (TrxR) from the Gram-positive bacterial antioxidant thioredoxin system has emerged from multiple screening efforts as a potential target for auranofin, ebselen, shikonin, and allicin. Auranofin serves as the most encouraging proof of concept drug, demonstrating TrxR inhibition can result in bactericidal effects and inhibit Gram-positive bacteria in both planktonic and biofilm states. Minimal inhibitory concentrations are on par or lower than gold standard medications, even among drug resistant isolates. Importantly, existing drug resistance mechanisms that challenge treatment of infections like Staphylococcus aureus do not confer resistance to TrxR targeting compounds. The observed inhibition by multiple compounds and inability to generate a bacterial genetic mutant demonstrate TrxR appears to play an essential role in Gram-positive bacteria. These findings suggest TrxR can be exploited further for drug development. Examining the interaction between TrxR and these proof of concept compounds illustrates that compounds representing a new antimicrobial class can be developed to directly interact and inhibit the validated target.

Novel Treatments and Preventative Strategies Against Food-Poisoning Caused by Staphylococcal Species

Staphylococcal infections are a widespread cause of disease in humans. In particular, S. aureus is a major causative agent of infection in clinical medicine. In addition, these bacteria can produce a high number of staphylococcal enterotoxins (SE) that may cause food intoxications. Apart from S. aureus, many coagulase-negative Staphylococcus spp. could be the source of food contamination. Thus, there is an active research work focused on developing novel preventative interventions based on food supplements to reduce the impact of staphylococcal food poisoning. Interestingly, many plant-derived compounds, such as polyphenols, flavonoids, or terpenoids, show significant antimicrobial activity against staphylococci, and therefore these compounds could be crucial to reduce the incidence of food intoxication in humans. Here, we reviewed the most promising strategies developed to prevent staphylococcal food poisoning.

Plant Secondary Metabolites in the Battle of Drugs and Drug-Resistant Bacteria: New Heroes or Worse Clones of Antibiotics?

Infectious diseases that are caused by bacteria are an important cause of mortality and morbidity in all regions of the world. Bacterial drug resistance has grown in the last decades, but the rate of discovery of new antibiotics has steadily decreased. Therefore, the search for new effective antibacterial agents has become a top priority. The plant kingdom seems to be a deep well for searching for novel antimicrobial agents. This is due to the many attractive features of plants: they are readily available and cheap, extracts or compounds from plant sources often demonstrate high-level activity against pathogens, and they rarely have severe side effects. The huge variety of plant-derived compounds provides very diverse chemical structures that may supply both the novel mechanisms of antimicrobial action and provide us with new targets within the bacterial cell. In addition, the rapid development of modern biotechnologies opens up the way for obtaining bioactive compounds in environmentally friendly and low-toxic conditions. In this short review, we ask the question: do antibacterial agents derived from plants have a chance to become a panacea against infectious diseases in the "post-antibiotics era".

Antivirulence properties and related mechanisms of spice essential oils: A comprehensive review

In recent decades, reduced antimicrobial effectiveness, increased bacterial infection, and newly emerged microbial resistance have become global public issues, leading to an urgent need to find effective strategies to counteract these problems. Strategies targeting bacterial virulence factors rather than bacterial survival have attracted increasing interest, since the modulation of virulence factors may prevent the development of drug resistance in bacteria. Spices are promising natural sources of antivirulence compounds owing to their wide availability, diverse antivirulence phytochemical constituents, and generally favorable safety profiles. Essential oils are the predominant and most important antivirulence components of spices. This review addresses the recent efforts of using spice essential oils to inhibit main bacterial virulence traits, including the quorum sensing system, biofilm formation, motility, and toxin production, with an intensive discussion of related mechanisms. We hope that this review can provide a better understanding of the antivirulence properties of spice essential oils, which have the potential to be used as antibiotic alternatives by targeting bacterial virulence.

Mechanism of Action of Topical Garlic on Wound Healing

BACKGROUND

Allicin, the active component of garlic, has been shown to have antimicrobial and anti-inflammatory properties. Garlic has also been used historically by many cultures to heal wounds. Several animal studies have shown that garlic extracts increase the rate of wound healing and decrease the rate of infection.

OBJECTIVE

Fibroblasts play a key role in wound healing. Here we hypothesize that fibroblasts are being activated by allicin, leading to more organized and rapid wound repair.

MATERIALS AND METHODS

Six rats were each given 2 surgical wounds. One side was treated with a 30% garlic ointment while the other was treated with Vaseline for two weeks. A biopsy was taken from each scar site and histopathology with Immunohistochemistry was performed to quantify the number of fibroblasts and proliferating fibroblasts in each site.

RESULTS

The wound biopsies had more proliferating fibroblasts in the scars treated with the 30% garlic ointment than in the scars treated with Vaseline with a p-value of 0.0175 at two weeks post op and 0.081 at 6 week post op.

CONCLUSION

This data tells us that allicin is acting on fibroblasts as there were more proliferating fibroblasts in the garlic treated sites than in the other sites.

Antibacterial Effect of (2E,2E)-4,4-Trisulfanediylbis(but-2-enoic acid) against Staphylococcus aureus

A new highly active molecule, (2E, 2E)-4,4-trisulfanediylbis(but-2-enoic acid) (TSDB), was designed and synthesized through comparative molecular field analysis with the diallyl trisulfide structure of garlic. TSDB exerted a strong inhibitory effect against Staphylococcus aureus, with minimal inhibitory and minimal bactericidal concentrations of 16 and 128 μg/mL, respectively. TSDB destructed the integrity of the S. aureus cell membrane but weakly damaged the bacterial cell wall. TSDB also increased the conductivity and protein expression in microbial broth but minimally influenced the level of extracellular alkaline phosphatase. TSDB could be a novel food preservative.

Evaluation of phytochemicals from medicinal plants of Myrtaceae family on virulence factor production by Pseudomonas aeruginosa

Virulence factors regulated by quorum sensing (QS) play a critical role in the pathogenesis of an opportunistic human pathogen, Pseudomonas aeruginosa in causing infections to the host. Hence, in the present work, the anti-virulence potential of the medicinal plant extracts and their derived phytochemicals from Myrtaceae family was evaluated against P. aeruginosa. In the preliminary screening of the tested medicinal plant extracts, Syzygium jambos and Syzygium antisepticum demonstrated a maximum inhibition in QS-dependent violacein pigment production by Chromobacterium violaceum DMST 21761. These extracts demonstrated an inhibitory activity over a virulence factor, pyoverdin, production by P. aeruginosa ATCC 27853. Gas chromatography-mass spectrometric (GC-MS) analysis revealed the presence of 23 and 12 phytochemicals from the extracts of S. jambos and S. antisepticum respectively. Three top-ranking phytochemicals, including phytol, ethyl linoleate and methyl linolenate, selected on the basis of docking score in molecular docking studies lowered virulence factors such as pyoverdin production, protease and haemolytic activities of P. aeruginosa to a significant level. In addition, the phytochemicals reduced rhamnolipid production by the organism. The work demonstrated an importance of plant-derived compounds as anti-virulence drugs to conquer P. aeruginosa virulence towards the host.

Phytochemicals for human disease: An update on plant-derived compounds antibacterial activity

In recent years, many studies have shown that phytochemicals exert their antibacterial activity through different mechanisms of action, such as damage to the bacterial membrane and suppression of virulence factors, including inhibition of the activity of enzymes and toxins, and bacterial biofilm formation. In this review, we summarise data from the available literature regarding the antibacterial effects of the main phytochemicals belonging to different chemical classes, alkaloids, sulfur-containing phytochemicals, terpenoids, and polyphenols. Some phytochemicals, besides having direct antimicrobial activity, showed an in vitro synergistic effect when tested in combination with conventional antibiotics, modifying antibiotic resistance. Review of the literature showed that phytochemicals represent a possible source of effective, cheap and safe antimicrobial agents, though much work must still be carried out, especially in in vivo conditions to ensure the selection of effective antimicrobial substances with low side and adverse effects.

Subinhibitory concentrations of punicalagin reduces expression of virulence-related exoproteins by Staphylococcus aureus

Staphylococcus aureus produces a number of virulence factors. The major virulence factors exhibited by S aureus include various antigens, enzymes, cytotoxins and exotoxins (e.g. hemolysins, enterotoxins and toxic shock syndrome toxin). In this report, we show the influence of punicalagin on the secretion of exoprotein from S aureus by western blotting, tumor necrosis factor (TNF) release assay and quantitative RT-PCR. When added to S aureus cultures at an OD600 of 0.9, graded subinhibitory concentrations of punicalagin reduced the production of α-toxin, SEA and SEB in methicillin-resistant Staphylococcus aureus in a dose-dependent manner. Consistently, punicalagin reduced TNF-inducing activity by S aureus culture supernatants. Here, the transcriptional level of agr (accessory gene regulator) in S aureus was inhibited by punicalagin, suggesting that the reduced transcription may affect the secretion of exotoxins. These findings suggest that the expression of α-toxin and enterotoxins in S aureus is sensitive to the action of punicalagin, which may be an advantageous candidate in the treatment of toxigenic staphylococcal disease.

Allicin-inspired thiolated fluoroquinolones as antibacterials against ESKAPE pathogens

Thiolated fluoroquinolones were synthesized from ciprofloxacin and evaluated for antimicrobial activity against a panel of pathogenic bacteria. Gram-positive species including methicillin-resistant Staphylococcus aureus (MRSA) exhibited the highest level of increased sensitivity toward ciprofloxacin bound with a N-propylthio substituent. Evidence was found that the antibiotics form disulfides with low molecular weight thiols in bacteria and potentiate generation of cytosolic reactive oxygen species (ROS). In final analysis, the enhanced anti-MRSA activity of thiolated fluoroquinolones was attributed to increased cell permeability and reaction with cytosolic thiols that yields an inactive disulfide metabolite and the parent drug ciprofloxacin as an inhibitor of DNA synthesis.

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.

Modulatory role of garlicin in migration and invasion of intrahepatic cholangiocarcinoma via PI3K/AKT pathway

Increasing evidences have indicated the role of garlicin in inhibiting the progression of various tumors including glioma, pulmonary carcinoma and pancreatic carcinoma, via mediating cell apoptosis or cell cycle. The regulatory effect and related molecular mechanism of garlicin in intrahepatic cholangiocarcinoma, however, remained unknown. This study thus aimed to investigate this scientific issue. HCCC-9810 cell line was treated with serially diluted garlicin, followed by cell proliferation assay using MTT approach. Transwell migration and invasion assays were further employed the regulatory effect of garlicin. The expression level of p-AKT and AKT proteins in tumor cells was quantified by Western blot. The growth of tumor cells was significantly inhibited by high concentration of garlicin (> 1.5 μM). Lower concentration of garlicin showed dose-dependent inhibition of tumor cell invasion and migration. After using specific agonist IGF-1 (50 ng/mL) of PI3K/AKT signaling pathway, such facilitating effects of garlicin were depressed (P < 0.05). Western blotting showed significantly decreased phosphorylation level of AKT after treated with gradient concentrations of garlicin, while leaving the total AKT protein level unchanged. Garlicin may inhibit the invasion and migration of intrahepatic cholangiocarcinoma cells via inhibiting PI3K/AKT signaling pathway.

Allicin from garlic inhibits the biofilm formation and urease activity of Proteus mirabilis in vitro

Several virulence factors contribute to the pathogenesis of Proteus mirabilis. This study determined the inhibitory effects of allicin on urease, hemolysin and biofilm of P. mirabilis ATCC 12453 and its antimicrobial activity against 20 clinical isolates of P. mirabilis. Allicin did not inhibit hemolysin, whereas it did inhibit relative urease activity in both pre-lysed (half-maximum inhibitory concentration, IC50 = 4.15 μg) and intact cells (IC50 = 21 μg) in a concentration-dependent manner. Allicin at sub-minimum inhibitory concentrations (2-32 μg mL(-1)) showed no significant effects on the growth of the bacteria (P > 0.05), but it reduced biofilm development in a concentration-dependent manner (P < 0.001). A higher concentration of allicin was needed to inhibit the established biofilms. Using the microdilution technique, the MIC90 and MBC90 values of allicin against P. mirabilis isolates were determined to be 128 and 512 μg mL(-1), respectively. The results suggest that allicin could have clinical applications in controlling P. mirabilis infections.

Subinhibitory concentrations of pinocembrin exert anti-Staphylococcus aureus activity by reducing α-toxin expression

AIMS

Natural products have been used as potentially important sources of novel antibacterials in combating pathogenic Staphylococcus aureus isolates, a major problem around the world. In this study, we aimed to investigate the antibacterial effects of pinocembrin (PNCB) against Staph. aureus pneumonia in a murine model and its influence on the production of Staph. aureus α-haemolysin (Hla).

METHODS AND RESULTS

The in vitro activities of PNCB on α-haemolysin production were determined using haemolysis, Western blot and real-time RT-PCR assays. The viability and cytotoxicity assays were performed to evaluate the influence of PNCB on α-toxin-mediated injury of human alveolar epithelial cells. Moreover, through histopathologic analysis, we further determined the in vivo effects of PNCB on Staph. aureus pneumonia in a mouse model. In vitro, PNCB at low concentrations exhibited inhibitory activity against α-haemolysin production and attenuated α-haemolysin-mediated cell injury. Furthermore, the in vivo findings demonstrated that PNCB protected mice from Staph. aureus pneumonia.

CONCLUSIONS

We have provided new evidence of the effects of PNCB, which suggest that PNCB attenuated α-haemolysin-mediated cell injury and protected mice from Staph. aureus pneumonia.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings indicate that PNCB may be used as a basis for anti-Staphylococcus agent.

Apigenin alleviates the symptoms of Staphylococcus aureus pneumonia by inhibiting the production of alpha-hemolysin

Staphylococcus aureus is a common human pathogenic bacteria that can cause serious infections, including lethal staphylococcal pneumonia. The development of antimicrobial resistance has limited treatment options for this pathogen; consequently, novel antibiotics and strategies are urgently desired to combat these infections. In recent years, virulence factors secreted by pathogenic microorganisms have been developed as targets for drug discovery. Alpha-hemolysin, a pore-forming cytotoxin that is secreted by most S. aureus strains, is essential for the pathogenesis of S. aureus pneumonia. In this study, we report that apigenin, a compound extracted from parsley that has no antimicrobial activity vs. S. aureus in vitro, can remarkably decrease the production of α-hemolysin at low concentrations. When added to the A549 cells and S. aureus co-culture system, apigenin protected A549 cells from α-hemolysin-mediated injury. Furthermore, in vivo tests indicated that apigenin alleviated injury of the lung tissue and decreased cytokine levels in the bronchoalveolar lavage fluid in the mouse model of S. aureus pneumonia.