Potential effect of Allium sativum bulb for the treatment of biofilm forming clinical pathogens recovered from periodontal and dental caries

Biofilm producing clinical bacterial isolates were isolated from periodontal and dental caries samples and identified as, Lactobacillus acidophilus, Streptococcus sanguis, S. salivarius, S. mutansand Staphylococcus aureus. Among the identified bacterial species, S. aureus and S. mutansshowed strong biofilm producing capacity. The other isolated bacteria, Streptococcus sanguis, S. salivarius showed moderate biofilm formation. These pathogens were subjected for the production of extracellular polysaccharides (EPS) in nutrient broth medium and the strain S. aureus synthesized more amounts of EPS (610 ± 11.2 µg/ml) than S. sanguis (480 ± 5.8 µg/ml).EPS production was found to be less in S. salivarius (52 ± 3.8 µg/ml).The solvent extract of A. sativum bulb showed the phytochemicals such as, carbohydrate, total protein, alkaloids, saponins, flavonoids, tannins and sterioids. The solvent extract of A. sativum bulb showed wide ranges of activity against the selected dental pathogens. The difference in antibacterial activity of the solvent extract revealed differences in solubility of phytochemicals in organic solvents. Ethanol extract was highly active againstS. aureus (25 ± 2 mm). The Minimum Inhibitory Concentration (MIC) of crude garlic bulb varied widely and this clearly showed that bacteria exhibits different level of susceptibility to secondary metabolites. MIC value ranged between 20 ± 2 mg/ml and 120 ± 6 mg/ml and Minimum Bactericidal Concentration (MBC) value ranged from 60 ± 5 mg/l to 215 ± 7 mg/ml. To conclude, A. sativum bulb can be effectively used to treat periodontal and dental caries infections.     

Non-toxic plant metabolites regulate Staphylococcus viability and biofilm formation: a natural therapeutic strategy useful in the treatment and prevention of skin infections

In the present study, the efficacy of generally recognised as safe (GRAS) antimicrobial plant metabolites in regulating the growth of Staphylococcus aureus and S. epidermidis was investigated. Thymol, carvacrol and eugenol showed the strongest antibacterial action against these microorganisms, at a subinhibitory concentration (SIC) of ≤ 50 μg ml^?1. Genistein, hydroquinone and resveratrol showed antimicrobial effects but with a wide concentration range (SIC = 50–1,000 μg ml^?1), while catechin, gallic acid, protocatechuic acid, p-hydroxybenzoic acid and cranberry extract were the most biologically compatible molecules (SIC ≥ 1000 μg ml^?1). Genistein, protocatechuic acid, cranberry extract, p-hydroxybenzoic acid and resveratrol also showed anti-biofilm activity against S. aureus, but not against S. epidermidis in which, surprisingly, these metabolites stimulated biofilm formation (between 35% and 1,200%). Binary combinations of cranberry extract and resveratrol with genistein, protocatechuic or p-hydroxibenzoic acid enhanced the stimulatory effect on S. epidermidis biofilm formation and maintained or even increased S. aureus anti-biofilm activity.     

A novel series of enoyl reductase inhibitors targeting the ESKAPE pathogens, Staphylococcus aureus and Acinetobacter baumannii

S. aureus and A. baumannii are among the ESKAPE pathogens that are increasingly difficult to treat due to the rise in the number of drug resistant strains. Novel therapeutics targeting these pathogens are much needed. The bacterial enoyl reductase (FabI) is as potentially significant drug target for developing pathogen-specific antibiotics due to the presence of alternate FabI isoforms in many other bacterial species. We report the identification and development of a novel N-carboxy pyrrolidine scaffold targeting FabI in S. aureus and A. baumannii, two pathogens for which FabI essentiality has been established. This scaffold is unrelated to other known antibiotic families, and FabI is not targeted by any currently approved antibiotic. Our data shows that this scaffold displays promising enzyme inhibitory activity against FabI from both S. aureus and A. baumannii, as well as encouraging antibacterial activity in S. aureus. Compounds also display excellent synergy when combined with colistin and tested against A. baumannii. In this combination the MIC of colistin is reduced by 10-fold. Our first generation compound displays promising enzyme inhibition, targets FabI in S. aureus with a favorable selectivity index (ratio of cytotoxicity to MIC), and has excellent synergy with colistin against A. baumannii, including a multidrug resistant strain.     

Antimicrobial and antibiofilm activity of polyurethane/Hypericum perforatum extract (PHPE) composite

Microbial accumulation in materials used in sectors such as medical, textile and food can lead to serious diseases, infections and uncontrollable problems. Many of the materials used in the above-mentioned industries have highly sensitive surfaces for microorganisms and cause colonization and biofilm formation. Colonization and biofilm formation threaten human health and they cause many diseases that result in death every year. Antimicrobial materials have an important role in combating pathogens. This article is about a new material with antibiofilm and antimicrobial properties combining polyurethane and Hypericum perforatum extract (PHPE) together. Antimicrobial effect of H. perforatum extract was determined against three clinical pathogens; C. albicans, E. coli and S. aureus. The highest antimicrobial activity of H. perforatum extract was found against S. aureus strain. Antibiofilm analysis results revealed that H. perforatum was also inhibited by the biofilm formation of S. aureus by 56.85%. The combination of polyurethane material and H. perforatum extract (PHPE) resulted in 92.85% decrease in S. aureus biofilm compared to control group. The reduction of S. aureus after H. perforatum incorporation was revealed by Scanning Electron Microscopy (SEM) study. The results show that the polyurethane material combined with H. perforatum extract inhibits the formation of S. aureus biofilm.     

Antimicrobial efficacy of extracts of Saudi Arabian desert Terfezia claveryi truffles

BackgroundTerfezia claveryi truffles are known for their nutritional value and have been considered among traditional treatments for ophthalmic infections and ailments.ObjectivesWe sought to investigate the in vitro antimicrobial efficacy of several T. claveryi extracts from Saudi Arabia. Certain pathogenic fungi and gram-negative and gram-positive bacteria were included.MethodsDry extracts were prepared using methanol, ethyl acetate, and distilled water, while the latter was used for preparing fresh extracts. The extracts were microbiologically evaluated through the disc-diffusion agar method; the zones of inhibition of microbial growth were measured post-incubation. The minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) were determined in Müller-Hinton Broth through the microdilution susceptibility method. anti-biofilm activity was assessed for potent extracts.ResultsDry extracts showed potent activity (>16-mm inhibition zones) against gram-positive (Bacillus subtilis IFO3007 and Staphylococcus aureus IFO3060) and gram-negative (Pseudomonas aeruginosa IFO3448 and Escherichia coli IFO3301) bacteria. The activity against fungi was moderate (12–16-mm inhibition zones) for both Aspergillus oryzae IFO4177 and Candida albicans IFO0583; there was no activity against Aspergillus niger IFO4414 growth. Methanolic extract had the lowest MIC and MBC, exhibiting remarkable activity against B. subtilis growth. Fresh extract showed moderate activity against bacterial growth and inactivity against fungal growth. Methanolic extract showed potent anti-biofilm activity (IC₅₀, 2.0 ± 0.18 mg/mL) against S. aureus.ConclusionsT. claveryi extracts showed antibacterial effects potentially suitable for clinical application, which warrants further in-depth analysis of their individual isolated compounds.     

Andrographolide: antibacterial activity against common bacteria of human health concern and possible mechanism of action

Increasing bacterial resistance to common drugs is a major public health concern for the treatment of infectious diseases. Certain naturally occurring compounds of plant sources have long been reported to possess potential antimicrobial activity. This study was aimed to investigate the antibacterial activity and possible mechanism of action of andrographolide (Andro), a diterpenoid lactone from a traditional medicinal herb Andrographis paniculata. Extent of antibacterial action was assessed by minimal bactericidal concentration method. Radiolabeled N-acetyl glucosamine, leucine, thymidine, and uridine were used to determine the effect of Andro on the biosyntheses of cell wall, protein, DNA, and RNA, respectively. In addition, anti-biofilm potential of this compound was also tested. Andro showed potential antibacterial activity against most of the tested Gram-positive bacteria. Among those, Staphylococcus aureus was found to be most sensitive with a minimal inhibitory concentration value of 100 μg/mL. It was found to be bacteriostatic. Specific inhibition of intracellular DNA biosynthesis was observed in a dose-dependent manner in S. aureus. Andro mediated inhibition of biofilm formation by S. aureus was also found. Considering its antimicrobial potency, Andro might be accounted as a promising lead for new antibacterial drug development.     

Screening and identification of novel isolate Streptomyces sp., NLKPB45 from Nellore costal region for its biomedical applications

Actinobacteria, which are the prolific producers of antibiotics and significant suppliers to the pharmaceutical industry, can produce a wide variety of bioactive metabolites. An actinomycete strain designated NLKPB45 was isolated from mangrove soils samples of Nellore coastal regions Andhra Pradesh and assessed for antibiotic production and activity against pathogenic bacteria. From a total of 9 mangrove soil samples, 143 acinomycetes were isolated. Among the isolated them 6 actinomycetes strains showed potential antibacterial activity against at two tested pathogens gram positive and gram negative bacteria E. coli and S. aureus. The potent strain NLKPB45 was identified by 16S gene isolation and sequencing to the Streptomyces genus. The ethyl acetate extracts also as shown excellent antimicrobial activity against Salmonella sp., staphylococcus aureus, E. coli, and B. subtilus were detected in both the supernatant extract samples from fermentations of culture NLKPB45. The anticancer activity of extracts in the HeLa with IC₅₀ value of 37.1924 μg/ml, MCF-7 IC₅₀ value of 40.9177 μg/ml and HT 29 IC₅₀ value of 43.3758 μg/ml.     

Quercetin Influences Quorum Sensing in Food Borne Bacteria: In-Vitro and In-Silico Evidence

Quorum sensing (QS) plays a vital role in regulating the virulence factor of many food borne pathogens, which causes severe public health risk. Therefore, interrupting the QS signaling pathway may be an attractive strategy to combat microbial infections. In the current study QS inhibitory activity of quercetin and its anti-biofilm property was assessed against food-borne pathogens using a bio-sensor strain. In addition in-silico techniques like molecular docking and molecular dynamics simulation studies were applied to screen the quercetin’s potentiality as QS inhibitor. Quercetin (80μg/ml) showed the significant reduction in QS-dependent phenotypes like violacein production, biofilm formation, exopolysaccharide (EPS) production, motility and alginate production in a concentration-dependent manner. Synergistic activity of conventional antibiotics with quercetin enhanced the susceptibility of all tested pathogens. Furthermore, Molecular docking analysis revealed that quercetin binds more rigidly with LasR receptor protein than the signaling compound with docking score of -9.17Kcal/mol. Molecular dynamics simulation predicted that QS inhibitory activity of quercetin occurs through the conformational changes between the receptor and quercetin complex. Above findings suggest that quercetin can act as a competitive inhibitor for signaling compound towards LasR receptor pathway and can serve as a novel QS-based antibacterial/anti-biofilm drug to manage food-borne pathogens.     

Development of ebsulfur analogues as potent antibacterials against methicillin-resistant Staphylococcus aureus

Antibiotic resistance is a worldwide problem that needs to be addressed. Staphylococcus aureus is one of the dangerous “ESKAPE” pathogens that rapidly evolve and evade many current FDA-approved antibiotics. Thus, there is an urgent need for new anti-MRSA compounds. Ebselen (also known as 2-phenyl-1,2-benzisoselenazol-3(2H)-one) has shown promising activity in clinical trials for cerebral ischemia, bipolar disorder, and noise-induced hearing loss. Recently, there has been a renewed interest in exploring the antibacterial properties of ebselen. In this study, we synthesized an ebselen-inspired library of 33 compounds where the selenium atom has been replaced by sulfur (ebsulfur derivatives) and evaluated them against a panel of drug-sensitive and drug-resistant S. aureus and non-S. aureus strains. Within our library, we identified three outstanding analogues with potent activity against all S. aureus strains tested (MIC values mostly ⩽2 μg/mL), and numerous additional ones with overall very good to good antibacterial activity (1–7.8 μg/mL). We also characterized the time-kill analysis, anti-biofilm ability, hemolytic activity, mammalian cytotoxicity, membrane-disruption ability, and reactive oxygen species (ROS) production of some of these analogues.     

Antimicrobial Activity of Artemisia absinthium Against Surgical Wounds Infected by Staphylococcus aureus in a Rat Model

The wound infection is one of the frequent complications in patients undergoing surgical operations. Staphylococcus aureus is the most common cause of surgical wounds. Artemisia absinthium has been shown to bear strong antimicrobial activity, especially against Gram-positive pathogens. This study was designed to investigate the antimicrobial effects of A. absinthium against surgical wounds infected by S. aureus in a rat model. Twenty male Sprague–Dawley rats were divided randomly into two equal groups of treated and control rats. A circular incision was created on the dorsal inter-scapular region of each rat. After skin wounding, rats were inoculated locally with 1 × 10⁴ CFU of S. aureus at sites of skin wounds. The extract was applied topically twice a day throughout the experiment. Animals of the control group were left untreated. Results have revealed that topical application of A. absinthium extract on the infected wound sites produced significant antibacterial activity against S. aureus.     

Control of Staphylococcus aureus methicillin resistant isolated from auricular infections using aqueous and methanolic extracts of Ephedra alata

In the current study the potential use of aqueous and methanolic extracts of Ephedra alata aerial parts as biological control agent against pathogenic bacteria and especially Staphylococcus aureus methicillin resistant isolated from auricular infections was evaluated. Chemical tests and spectrophotometric methods were used for screening and quantification of phytochemicals. The assessment of the antioxidant activity was accomplished by DPPH and ABTS radicals scavenging assays. Extracts were evaluated for their antibacterial efficacy by diffusion and microdilution methods. Biofilm inhibition was tested using XTT assay and the cytotoxicity of extracts was carried out on Vero cell line. The GC-FID analysis revealed that E. alata was rich in unsatured fatty acids. In addition, the aqueous extract had the highest flavonoid and protein contents (30.82 mg QE /g dry extract and 98.92 mg BSAE/g dry extract respectively). However, the methanolic extract had the highest phenolic, sugars and tannins. The antioxidant activity demonstrated that the aqueous extract exhibited the strong potency (IC50 ranged between 0.001 and 0.002 mg/mL).Both extracts displayed antimicrobial activity on Gram negative and positive strains. They were effective against S. aureus isolated from auricular infections. The tested extracts were able to inhibit biofilm formation with concentration-dependent manner.Moreover, no cytotoxic effect on Vero cells line was demonstrated for the extracts. Overall, our findings highlight the potential use of E. alata extract as a novel source of bioactive molecules with antioxidant, antibacterial and antiobiofilm effects for the control of infectious disease especially those associated to S. aureus methicillin resistant.     

Synthesis and antibacterial evaluation of novel oxazolidinone derivatives containing a piperidinyl moiety

In this article, a series of novel oxazolidinone derivatives containing a piperidinyl moiety was designed and synthesized. Their antibacterial activities were measured against S. aureus, MRSA, MSSA, LREF and VRE by MIC assay. Most of them exhibited potent activity against Gram-positive pathogens comparable to linezolid. Among them, compound 9h exhibited comparable activity with linezolid against human MAO-A for safety evaluation and showed moderate metabolism in human liver microsome. The most promising compound 9h, which showed remarkable antibacterial activity against S. aureus, MRSA, MSSA, LREF and VRE pathogens with MIC value of 0.25–1 μg/mL, was an interesting candidate for further investigation.     

A Clinical Trial to Evaluate the Efficacy of α-Viniferin in Staphylococcus aureus – Specific Decolonization without Depleting the Normal Microbiota of Nares

Staphylococcus aureus is currently a significant multidrug-resistant bacterium, causing severe healthcare-associated and community-acquired infections worldwide. The current antibiotic regimen against this pathogen is becoming ineffective due to resistance, in addition, they disrupt the normal microbiota. It highlights the urgent need for a pathogen-specific drug with high antibacterial efficacy against S. aureus. α-Viniferin, a bioactive phytochemical compound, has been reported to have excellent anti-Staphylococcus efficacy as a topical agent. However, so far, there were no clinical trials that have been conducted to elucidate its efficacy. The present study aimed to investigate the antibacterial efficacy of α-viniferin against S. aureus in a ten-day clinical trial. Based on the results, α-viniferin showed 50% minimum inhibitory concentrations (MIC₅₀ values) of 7.8 μg/ml in culture broth medium. α-Viniferin was administered in the nares three times a day for ten days using a sterile cotton swab stick. Nasal swab specimens were collected before (0 days) and after finishing the trial (10^th day), and then analyzed. In the culture and RT-PCR-based analysis, S. ureus was reduced significantly: 0.01. In addition, 16S ribosomal RNA-based amplicon sequencing analysis showed that S. aureus reduced from 51.03% to 23.99% at the genus level. RNA-seq analysis was also done to gain insights into molecular mechanisms of α-viniferin against S. aureus, which revealed that some gene groups were reduced in 5-fold FC cutoff at two times MIC conditions. The study results demonstrate α-viniferin as a potential S. aureus-specific drug candidate.     

The synthesis and antistaphylococcal activity of N-sulfonaminoethyloxime derivatives of dehydroabietic acid

A series of N-sulfonaminoethyloxime derivatives of dehydroabietic acid were synthesized and investigated for their antibacterial activity against Staphylococcus aureus Newman strain and multidrug-resistant strains (NRS-1, NRS-70, NRS-100, NRS-108 and NRS-271). Most of the target compounds having chloro, bromo, trifluoromethyl phenyl moiety exhibited potent in vitro antistaphylococcal activity. The meta-CF₃ phenyl derivative T23 showed the highest activity with MIC of 0.39–0.78?μg/mL against S. aureus Newman, while several analogues showed similar potent antibacterial activity with MIC values between 0.78 and 1.56?μg/mL against five multidrug-resistant S. aureus. The stability of T35 in plasma of SD rat and the cellular cytotoxicity were also evaluated.     

Extraction and bioautographic-guided separation of antibacterial compounds from Ulva lactuca

This study aimed to optimize an extraction and separation procedure to obtain a concentrated fraction with antibacterial activity from the macroalga Ulva lactuca. Antibacterial compounds were extracted using eight solvents, and consistent activity against Staphylococcus aureus, Bacillus subtilis and methicillin-resistant (MR) S. aureus was observed from a dilute (1:100, w/v) ethyl acetate extract. Seasonal analysis revealed that antibacterial activity was the lowest in spring/summer and the highest in autumn/winter. Bioautography was found to be a more appropriate assay compared to disc diffusion when screening crude extracts, as it separates the masking compounds from the antibacterial compounds and a direct assessment of the bands responsible for the antibacterial effect could be made. The antibacterial compounds were first separated from the crude extract using preparative thin-layer chromatography, followed by column chromatography to obtain a semi-pure sub-fraction. Using this approach, the antibacterial compounds were successfully concentrated from a crude extract (300 μg) to semi-pure fractions (6 μg) in which antibacterial activities were greatly enhanced. This study also revealed that prolonged storage (9 months) under a nitrogen atmosphere at ?20°C resulted in a considerable increase in antibacterial activity. This is the first report of seasonal assessment of antibacterial compounds from seaweeds collected in Ireland. In addition, an antibacterial fraction was successfully isolated from U. lactuca which exhibited potent anti-MR S. aureus activity.     

Design and synthesis of biaryloxazolidinone derivatives containing amide or acrylamide moiety as novel antibacterial agents against Gram-positive bacteria

A series of novel biaryloxazolidinone derivatives containing amide and acrylamide structure were designed, synthesized and evaluated for their antibacterial activity. Most compounds generally exhibited potent antibacterial activity with MIC values of 1 μg/mL against S. aureus, MRSA, MSSA, LREF and VRE pathogens, using linezolid and radezolid as positive controls. Compound 17 exhibited good antibacterial activity with MIC values of 0.5 μg/mL against S. aureus, MRSA, MSSA and VRE and 0.25 μg/mL against LREF. The results indicated that compound 17 might serve as a potential hit-compound for further investigation.     

Identification of a Napin-Like Peptide from Eugenia malaccensis L. Seeds with Inhibitory Activity Toward Staphylococcus aureus and Salmonella Enteritidis

This study aimed to purify and characterize peptides from the seeds of Eugenia malaccensis, L. (jambo) with inhibitory activity against the foodborne pathogens Staphylococcus aureus and Salmonella Enteritidis. Crude extract (CE), precipitate fraction 30–60 % and molecules between 3.5 and 10 kDa obtained from precipitate fraction 30–60 % (Em2) showed inhibitory activity against the tested bacterial strains. The highest antibacterial activity was observed for Em2 against S. aureus. The major peak eluted at approximately 30 % in an acetonitrile gradient in reverse-phase chromatography of Em2 (Em2-F1 to Em2-F19), and it showed the highest antibacterial activity, which was twofold higher against S. aureus than against S. Enteritidis. MALDI-ToF spectra of Em2-F18 revealed a molecular mass of 1,231.1 Da and the amino acid sequence showed high identity to the napin family. These findings report for the first time a napin-like peptide from E. malaccensis L. seeds with potential to be applied as a new anti-Staphylococcus molecule.     

Antibacterial activities of viriditoxin congeners and synthetic analogues against fish pathogens

Viriditoxin is a fungal secondary metabolite of the fungus Paecilomyces variotii derived from the inner tissues of the giant jellyfish Nemopilema nomurai. Viriditoxin exhibits antibacterial activity against Streptococcus iniae and Streptococcus parauberis, which are major pathogens of aqua cultured fish. Viriditoxin induced abnormal cell morphologies in the fish pathogens S. iniae and S. parauberis, presumably by inhibiting FtsZ polymerization as was previously observed in Escherichia coli. Synthetic analogues of viriditoxin, designed based on docking simulation results to FtsZ of Staphylococcus aureus, were prepared and compared with viriditoxin for antibacterial activity. Reconstitution of free hydroxyl or carboxyl groups of the methoxyl or methyl ester groups of viriditoxin led to significant reduction of antibacterial activity, implying that the natural molecule is optimized for antibacterial activity to deter bacteria potentially harmful to Paecilomyces.     

Antibacterial activity of an epoxidised prenylated cinnamaldehdye derivative from Vepris glomerata

A prenylated cinnamaldehyde (glomeral), together with the known p-hydroxycinnamic acid, caffeic acid, methyl cinnamate, hesperetin, scoparone, skimmianine, syringaresinol and two limonoids (limonin and limonyl acetate) were isolated from the roots and stem bark of Vepris glomerata. The antibacterial assay of the isolated compounds indicated an inhibition zone, ranging from 8 to 16 mm, against standard strains of Staphylococcus aureus (ATCC 29213, 25923) and Shigella dysentrieae. Glomeral inhibited the growth of S. aureus and S. dysentrieae at low concentrations (MIC of 2 μg/mL and 0.4 μg/mL respectively). Of the other compounds tested, hesperetin displayed good antibacterial activity, the limonoids, scoparone and skimmianine displayed moderate antibacterial activity and the cinnamic acid derivatives were inactive against the test pathogens. This study provides a rationale for the use of V. glomerata in its treatment of bacterial infections.     

Broad-spectrum In vitro antimicrobial activities of Streptomyces sp. strain BCNU 1001

Streptomyces sp. strain BCNU 1001 was isolated from forest soil samples. Cultural, morphological, and physiological characteristics as well as 16S rDNA analysis revealed that the isolate, BCNU 1001, belonged to the genus Streptomyces. The antimicrobial activity of the ethyl acetate extract was confirmed using the broth microdilution technique. The minimum inhibitory concentration (MIC) of the BCNU 1001 ethyl acetate extract was 0.25 mg/mL for Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa, and 0.125 mg/mL for Micrococcus luteus, Staphylococcus aureus, and Pseudomonas fluorescens. The MIC of the BCNU 1001 ethyl acetate extract for Aspergillus niger, Candida albicans, and Saccharomyces cerevisiae was 0.5, 0.125, and 0.25 mg/mL, respectively. BCNU 1001 was also active against dermatophytic fungi such as Trichophyton mentagrophytes and T. rubrum. Furthermore, BCNU 1001 was also found to be effective against Methicillin-resistant Staphylococcus aureus (MRSA), and its ethyl acetate extract showed MIC = 0.5 mg/mL against MRSA. The most abundant antimicrobial compound was identified as a 2-hydroxybenzyl alcohol through analysis utilizing a nuclear magnetic resonance spectroscopy. This compound was seen to be very effective against some kinds of bacteria and fungi.