Insight into the antibacterial activity of lauric arginate against Escherichia coli O157:H7: Membrane disruption and oxidative stress

Effects of UV/H2O2 Degradation on the Physicochemical and Antibacterial Properties of Fucoidan

The applications of fucoidan in the food industry were limited due to its high molecular weight and low solubility. Moderate degradation was required to depolymerize fucoidan. A few studies have reported that fucoidan has potential antibacterial activity, but its antibacterial mechanism needs further investigation. In this study, the degraded fucoidans were obtained after ultraviolet/hydrogen peroxide treatment (UV/H2O2) at different times. Their physicochemical properties and antibacterial activities against Staphylococcus aureus and Escherichia coli were investigated. The results showed that the average molecular weights of degraded fucoidans were significantly decreased (up to 22.04 times). They were mainly composed of fucose, galactose, and some glucuronic acid. Fucoidan degraded for 90 min (DFuc-90) showed the strongest antibacterial activities against Staphylococcus aureus and Escherichia coli, with inhibition zones of 27.70 + 0.84 mm and 9.25 + 0.61 mm, respectively. The minimum inhibitory concentrations (MIC) were 8 mg/mL and 4 mg/mL, respectively. DFuc-90 could inhibit the bacteria by damaging the cell wall, accumulating intracellular reactive oxygen species, reducing adenosine triphosphate synthesis, and inhibiting bacterial metabolic activity. Therefore, UV/H2O2 treatment could effectively degrade fucoidan and enhance its antibacterial activity.

Synergistic bactericidal effect and mechanism of ultrasound combined with Lauroyl Arginate Ethyl against Salmonella Typhimurium and its application in the preservation of onions

In the present study, the synergistic bactericidal effect and mechanism of ultrasound (US) combined with Lauroyl Arginate Ethyl (LAE) against Salmonella Typhimurium were investigated. On this basis, the effect of US+LAE treatment on the washing of S. Typhimurium on the surface of onions and on the physical and chemical properties of onion during fresh-cutting and storage were studied. The results showed that treatment with US+LAE could significantly (P < 0.05) reduce the number of S. Typhimurium compared to US and LAE treatments alone, especially the treatment of US+LAE (230 W/cm2, 8 min, 71 μM) reduced S. Typhimurium by 8.82 log CFU/mL. Confocal laser scanning microscopy (CLSM), flow cytometry (FCM), protein and nucleic acid release and N-phenyl-l-naphthylamine (NPN) assays demonstrated that US+LAE disrupted the integrity and permeability of S. Typhimurium cell membranes. Reactive oxygen species (ROS) and malondialdehyde (MDA) assays indicated that US+LAE exacerbated oxidative stress and lipid peroxidation in cell membranes. Field emission scanning electron microscopy (FESEM) demonstrated that US+LAE treatment caused loss of cellular contents and led to cell crumpling and even lost the original cell morphology. US+LAE treatment caused a significant (P < 0.05) decrease in the number of S. Typhimurium on onions, but there was no significant (P > 0.05) effect on the color, hardness, weight and ascorbic acid content of onions. This study elucidated the synergistic antibacterial mechanism of US+LAE and verified the feasibility of bactericidal effect on the surface of onions, providing a theoretical basis for improving the safety of fresh produce in the food industry and to propose a new way to achieve the desired results.

Sporadic regional re-emergent cholera: a 19th century problem in the 21st century

Cholera, caused by Vibrio cholerae, is a severe diarrheal disease that necessitates prompt diagnosis and effective treatment. This review comprehensively examines various diagnostic methods, from traditional microscopy and culture to advanced nucleic acid testing like polymerase spiral reaction and rapid diagnostic tests, highlighting their advantages and limitations. Additionally, we explore evolving treatment strategies, with a focus on the challenges posed by antibiotic resistance due to the activation of the SOS response pathway in V. cholerae. We discuss promising alternative treatments, including low-pressure plasma sterilization, bacteriophages, and selenium nanoparticles. The paper emphasizes the importance of multidisciplinary approaches combining novel diagnostics and treatments in managing and preventing cholera, a persistent global health challenge. The current re-emergent 7th pandemic of cholera commenced in 1961 and shows no signs of abeyance. This is probably due to the changing genetic profile of V. cholerae concerning bacterial pathogenic toxins. Given this factor, we argue that the disease is effectively re-emergent, particularly in Eastern Mediterranean countries such as Lebanon, Syria, etc. This review considers the history of the current pandemic, the genetics of the causal agent, and current treatment regimes. In conclusion, cholera remains a significant global health challenge that requires prompt diagnosis and effective treatment. Understanding the history, genetics, and current treatments is crucial in effectively addressing this persistent and re-emergent disease.

Antibacterial activity of a polysaccharide isolated from Artemisia argyi leaf against Staphylococcus aureus and mechanism investigation

Abuse of antibiotics has led to excessive amounts of antibiotic residues in food and environment, thus enhancing pathogenic bacterium resistance and threatening human health. Therefore, searching and developing safe and green antibiotic alternatives are necessary. In this study, an Artemisia argyi leaf polysaccharide (AALP) fraction was extracted and analyzed. Chemical composition analysis showed that the carbohydrate, uronic acid, protein, and polyphenol content in AALP were 68.3 % ± 4.13 %, 9.4 % ± 0.86 %, 1.79 % ± 0.27 %, and 0.16 % ± 0.035 %, respectively. Chromatographic results suggested that AALP contained rhamnose, arabinose, glucosamine, galactose, glucose, xylose, mannose, galacturonic acid, and glucuronic acid in a molar ratio of 9.26, 1.35, 1.18, 3.04, 48.51, 2.33, 31.26, 3.93, and 9.08; the weight average molecular weight, number average molecular weight, and polydispersity of AALP were 5.41 kDa, 4.63 kDa, and 1.168, respectively. Fourier transform infrared spectroscopy indicated that AALP constituted the polysaccharide-specific groups of CH, CO, and OH. Meanwhile, AALP showed a dose-dependent inhibitory effect on Staphylococcus aureus in the inhibition zone assay, and the minimal inhibitory concentration was 1.25 mg/mL. Furthermore, AALP disrupted the cell wall, depolarized the inner membrane potential, and inhibited the activities of succinate dehydrogenase and malate dehydrogenase in S. aureus.

Investigation of the Suitability of a Combination of Ethyl-Να-dodecanyl-L-arginat_HCl (LAE) and Starter Culture Bacteria for the Reduction of Bacteria from Fresh Meat of Different Animal Species

Meat can be contaminated with (pathogenic) microorganisms during slaughter, dissection and packaging. Therefore, preservation technologies are frequently used to reduce the risk of (fatal) human infections due to the consumption of meat. In this study, we first investigated, if the application of ethyl-Nα-dodecanyl-L-arginate hydrochloride (LAE) and the starter culture bacteria Staphylococcus carnosus and Lactobacillus sakei, either single or in combination, influences the bacteria number on pork, chicken meat and beef, inoculated with Brochothrix (Br.) thermosphacta (all meat species) or Salmonella (S.) Typhimurium (pork), Campylobacter (C.) jejuni (chicken) and Listeria (L.) monocytogenes (beef), before packaging under modified atmosphere and on days 7 and 14 of storage. To evaluate effects of the treatment on the appearance during storage, additionally, the physicochemical parameters color and myoglobin redox form percentages were analyzed. LAE regularly resulted in a significant reduction of the number of all bacteria species on day 1 of storage, whereas up to day 14 of storage, the preservation effect did not persist in nearly all samples, except in the beef with Br. thermosphacta. However, with the starter culture bacteria on day 1, only L. monocytogenes on beef was significantly reduced. Interestingly, on day 7 of storage, this reducing effect was also found with S. Typhimurium on pork. Br. thermosphacta, which was principally not influenced by the starter culture bacteria. The combinatory treatment mainly resulted in no additional effects, except for the S. Typhimurium and Br. thermosphacta results on pork on day 7 and the Br. thermosphacta results on beef on day 14. The physicochemical parameters were not influenced by the single and combinatory treatment. The results indicate that LAE was mainly responsible for the antimicrobial effects and that a combination with starter culture bacteria should be individually evaluated for the meat species.

The use of chitosan-based composites for environmental remediation: A review

The presence of hazardous pollutants in water sources as a result of industrial activities is a major environmental challenge that impedes the availability of safe drinking water. Adsorptive and photocatalytic degradative removal of various pollutants in wastewater have been recognized as cost-effective and energy-efficient strategies. In addition to its biological activity, chitosan and its derivatives are considered as promising materials for the removal of various pollutants. The abundance of hydroxyl and amino groups in the chitosan macromolecular structure results in a variety of concurrent pollutant's adsorption mechanisms. Furthermore, adding chitosan to photocatalysts increases the mass transfer while decreasing both the band gap energy and the amount of intermediates produced during photocatalytic processes, improving the overall photocatalytic efficiency. Herein, we have reviewed the current design and preparation of chitosan and its composites, as well as their applications for the removal of various pollutants by adsorption and photocatalysis processes. Effects of operating variables such as the pH, catalyst mass, contact time, light wavelength, initial pollutant's concentration, and catalyst recyclability, are discussed. Various kinetic and isotherm models are presented to elucidate the rates, and mechanisms of pollutant's removal, onto chitosan-based composites, and several case studies are presented. Additionally, the antibacterial activity of chitosan-based composites has been discussed. This review aims to provide a comprehensive and up-to-date overview of the applications of chitosan-based composites in wastewater treatment and put forward new insights for the development of highly effective chitosan-based adsorbents and photocatalysts. Finally, the main challenges and future directions in the field are discussed.

Oxidative stress induced by sub-lethal exposure to copper as a mediator in development of bacterial resistance to antibiotics

Limited information exists on how bacterial resistance to antibiotics is acquired and altered in response to short-term metal stress, and what the prevailing pathways are. Here the precursor mechanisms of development of bacterial antibiotic resistance mediated by oxidative stress induce under sub-lethal Cu²⁺ exposure were explored. The results showed that the overall level of antibiotic resistance in wild-type Escherichia coli and antibiotic-resistant E. coli was enhanced under 4 and 20 mg/L Cu²⁺ exposure, as demonstrated by the 2- to 8-fold increase in minimum inhibitory concentration (MIC). The MIC correlated with the increase of the cellular ROS generation and the enhancement of the antioxidant enzyme activity (p < 0.05), suggesting that changes in antibiotic resistance under sub-lethal Cu²⁺ exposure could be associated with oxidative stress. Likewise, enhanced cell membrane permeability and an increase in the number of bacteria entering the viable but non culturable (VBNC) state contributed to bacterial resistance to antibiotics. Moreover, the variance partitioning analysis demonstrated that the alterations of the antibiotic resistance phenotype of wild-type E. coli was mainly caused by oxidative stress-mediated increase in cell membrane permeability and entry into the VBNC state. The development of antibiotic resistance in resistant E. coli was primarily attributed to changes in the abundance and horizontal transfer ability of its antibiotic resistance genes, both of which contributed up to 20 %. Taken together the results allowed to propose a conseptual scheme on developing bacterial antibiotic resistance mediated by oxidative stress under sub-lethal Cu²⁺ exposure. This result provided a strong basis for reduction of early bacterial resistance.

The synergy of thanatin and cathelicidin-BF-15a3 combats Escherichia coli O157:H7

Escherichia coli O157:H7 is a pathogen that commonly causes foodborne illness and represents a health hazard to consumers. The combined use of synergistic antimicrobial peptides (AMPs) is a promising way to improve the microbiological safety of foods. In this study, we detected the synergistic interactions between thanatin and BF-15a3 to reduce their usage and obtain more efficient antibacterial activity. The minimal inhibitory concentrations (MICs) of thanatin and BF-15a3 against 49 E. coli O157:H7 strains were ranged from 2 to 8 μg/mL and 4-32 μg/mL, showed a general inhibitory effect on E. coli O157:H7 strains, respectively, even multidrug-resistant strains. Their fractional inhibitory concentration index (FICI) was 0.375, which suggested that their combination presented synergistic antibacterial effect against E. coli O157:H7. The killing kinetic curves indicated that the 0.25 × MIC combination had equivalent bactericidal effects to 1 × MIC thanatin or BF-15a3. When AMP combinations were used to treat eukaryotic cells to evaluate the hemolytic characteristics against rabbit erythrocytes and cytotoxicity against human embryonic kidney 293T (HEK-293T) cells and intestinal porcine enterocyte J2 (IPEC-J2) cells, no magnified adverse effects were observed, exhibiting higher specificity to bacteria and lower toxicity to eukaryotic cells. Compared with bacteriostasis of thanatin or BF-15a3 alone, the proportion of membrane-damaged bacteria treated with the synergetic combination did not appear a significant rise, interestingly the Zeta potential of them greatly decreased and their cell membrane permeability significantly increased. Besides, more release of ions and cytoplasm were detected, confirming a more severe loss of membrane integrity. These results suggested that the synergistic action mode of thanatin and BF-15a3 is likely attributed to damage aggravation to E. coli membrane. When applying in fresh-cut lettuce and cucumber, their combination allowed for 2.5 log CFU/piece reductions of E. coli O157:H7 in 24 h. In conclusion, the combination of thanatin and BF-15a3 showed excellent synthetic efficacy to kill E. coli O157:H7 in vitro under lower MICs than single use of them.

Eco-friendly synthesis of Ag-NPs using Endostemon viscosus (Lamiaceae): Antibacterial, antioxidant, larvicidal, photocatalytic dye degradation activity and toxicity in zebrafish embryos

Nanotechnology is a multidisciplinary area of study that has grown significantly in serving many functions and impacting human society. New fields of science have been facilitated by the clean, non-toxic, and biocompatible nature of plant-derived nanoparticles. The present study deals with the first green synthesis of silver nanoparticles (Ag-NPs) using Endostemon viscosus, and their synthesized Ag NPs were characterized by different spectral methods (UV-vis Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction Spectroscopy (XRD), Transmission Electron Microscopy (TEM) and Energy dispersive X-ray Spectroscopy (EDAX). The change initially observed the production of Ag-NPs in color from green to ash and then confirmed by SPR band at 435 nm in UV-vis spectral analysis. The FTIR findings indicate that many functional groups belong to the pharmaceutically useful phytochemicals, which interact as reducing, capping, and stabilizing agents in synthesizing silver nanoparticles. The predominant peaks in the XRD pattern belong to the planes 210°, 111°, 200°, 241°, and 311° and thus demonstrated the Ag-NPs FCC crystal structure. TEM analysis exhibited spherical-shaped particles with an average size of 13 nm, and the EDAX band showed a distinctive metallic silver peak at 3.0 keV. The antibacterial activity of Ag-NPs tested to show a maximum zone of inhibition of 19 mm for Staphylococcus aureus and 15 mm for Escherichia coli at 100 μg/mL, respectively. Bio-fabricated Ag-NPs were assessed for antioxidant activity (DPPH with % inhibition 57.54% and FRAP with % inhibition 70.89%). The biosynthesized Ag-NPs demonstrated potential larvicidal efficacy against Aedes aegypti with more than 90% at 250 μg/mL. Histological profiles were altered while treating with Ag-NPs at 250 μg/mL. The photocatalytic activity of synthesized E. viscosus Ag-NPs was tested against methylene blue (MB) and crystal violet (CV), and the maximum degradation efficiency was found as 90 and 94%, respectively. Furthermore, the toxicity test on zebrafish embryos demonstrated that aberrations have only been induced at concentrations higher than 500 μg/mL. We conclude that the greenly produced Ag-NPs may find use in biomedical applications based on bacteria and cost-effective industrial wastewater treatment.

Lauric arginate ethyl ester: An update on the antimicrobial potential and application in the food systems

Lauric arginate ethyl ester (LAE), a cationic surfactant with low toxicity, displays excellent antimicrobial activity against a broad range of microorganisms. LAE has been approved as generally recognized as safe (GRAS) for widespread application in certain foods at a maximum concentration of 200 ppm. In this context, extensive research has been carried out on the application of LAE in food preservation for improving the microbiological safety and quality characteristics of various food products. This study aims to present a general review of recent research progress on the antimicrobial efficacy of LAE and its application in the food industry. It covers the physicochemical properties, antimicrobial efficacy of LAE, and the underlying mechanism of its action. This review also summarizes the application of LAE in various foods products as well as its influence on the nutritional and sensory properties of such foods. Additionally, the main factors influencing the antimicrobial efficacy of LAE are reviewed in this work, and combination strategies are provided to enhance the antimicrobial potency of LAE. Finally, the concluding remarks and possible recommendations for the future research are also presented in this review. In summary, LAE has the great potential application in the food industry. Overall, the present review intends to improve the application of LAE in food preservation.

Investigation of d-Amino Acid-Based Surfactants and Nanocomposites with Gold and Silica Nanoparticles as against Multidrug-Resistant Bacteria Agents

d-amino acid-based surfactants (d-AASs) were synthesized and their antimicrobial activity was evaluated. N-α-lauroyl-d-arginine ethyl ester hydrochloride (d-LAE), d-proline dodecyl ester (d-PD), and d-alanine dodecyl ester (d-AD) were found to have antibacterial activity against both Gram-positive and -negative bacteria, but less efficacy against Gram-negative bacteria. For these reasons, combining antimicrobial agents with nanoparticles is a promising technique for improving their antibacterial properties to eliminate drug-resistant pathogens. d-LAE coated on gold (AuNP) and silica (SiNP) nanoparticles has more efficient antibacterial activity than that of d-LAE alone. However, unlike d-LAE, d-PD has enhanced antibacterial activity upon being coated on AuNP. The antibacterial d-AASs and their nanocomposites with nanoparticles were synthesized in an environmentally friendly manner and are expected to be valuable new antimicrobial agents against multidrug-resistant (MDR) pathogens.

Membrane damage mechanism of protocatechualdehyde against Micrococcus luteus and its effect on pork quality characteristics

This study investigated the mechanism of membrane damage by protocatechualdehyde (PCA) against Micrococcus luteus and assessed effects of PCA on the sensory and physicochemical properties of pork. The mechanism of PCA inhibition on M. luteus was studied by determining the minimum inhibitory concentration (MIC) based on membrane potential, intracellular ATP concentration, intracellular pH, confocal laser scanning microscopy (CLSM), and field emission gun scanning electron microscopy (FEG-SEM). The results showed that the MIC of PCA against M. luteus was 1.25 mg/mL. Hyperpolarization of the bacterial cell membrane, a decrease in the intracellular ATP concentration, and intracellular pH indicated that PCA damaged the cell membrane of M. luteus. FEG-SEM observation revealed that PCA could cause surface collapse, cell membrane rupture, and content outflow of M. luteus. Additionally, PCA was found to inhibit increases in the total number of colonies, the thiobarbituric acid reactive substances (TBARS) value growth rate, and moisture mobility in raw pork. Additionally, it improved the color and texture of raw pork, all of which effectively prolonged its shelf life. This study will encourage the application of PCA as a natural antibacterial agent in the food industry.