LcCCL28-25, Derived from Piscine Chemokine, Exhibits Antimicrobial Activity against Gram-Negative and Gram-Positive Bacteria In Vitro and In Vivo

A novel antimicrobial peptide Larimicin78-102 from large yellow croaker (Larimichthys crocea) shows potent antibacterial activity in vitro and enhances resistance to vibrio fluvialis infection in vivo

Antimicrobial peptides (AMPs) are considered a key component of innate immunity, playing a vital role in host defense. In the study, a novel functional gene, named Larimicin, was identified from large yellow croaker Larimichthys crocea. The Larimicin gene was widely distributed in multiple tissues of healthy L. crocea and was significantly induced in the liver after Vibrio alginolyticus or Vibrio parahaemolyticus infection. Larimicin78-102, a truncated peptide derived from Larimicin, showed broad-spectrum antimicrobial activity and a binding affinity with LPS. It exhibited effective bactericidal activity against the common aquatic pathogens Vibrio fluvialis, Pseudomonas fluorescens, and Pseudomonas putida. It also showed anti-biofilm activity against three aquatic pathogens. Moreover, Larimicin78-102 disrupted the integrity of the outer and inner membranes, resulting in ATP leakage and intracellular ROS accumulation, which ultimately led to bacterial cell death. Larimicin78-102 exhibited good thermal stability and cation tolerance, with no obvious cytotoxicity or hemolytic activity. Notably, Larimicin78-102 significantly improved the survival rate of L. crocea infected with V. fluvialis, raising it to 95 %, indicating its anti-infective role in vivo. In addition, Larimicin78-102 significantly reduced the expression of the pro-inflammatory cytokines TNF-α and IL-1β, while up-regulating the anti-inflammatory factor IL-4 mRNA level. It also elevated the expression levels of piscidin, hepcidin, and lysozyme, as well as enhanced the enzymatic activity of lysozyme. Taken together, Larimicin78-102 is a potential antibacterial agent for use in aquaculture to combat V. fluvialis infection diseases in the future.

Rationally designed antimicrobial peptides with high selectivity and efficiency against phytopathogenic Ralstonia solanecearum

Ralstonia solanacearum, the causative agent of bacterial wilt, poses a global threat to agriculture, necessitating urgent and sustainable solutions as traditional methods lose efficacy. This study developed WRF-13, a synthetic antimicrobial peptide (AMP) designed to mimic natural AMPs, exhibiting potent antibacterial and anti-biofilm activity with high specificity against R. solanacearum. Mechanistic studies, including microscopy and computational analyses, demonstrated that WRF-13 disrupts the bacterial membrane. WRF-13 remained stable across a wide pH (5-8) and temperature (25-50 °C) range, essential for field applications, and showed no detectable toxicity to mammalian or plant cells at elevated concentrations. Greenhouse trials confirmed its efficacy in reducing bacterial wilt severity up to 65 %, highlighting its potential to protect crops from R. solanacearum infection. Overall, this study highlights WRF-13 as a targeted solution for managing bacterial wilt and advancing sustainable agriculture.

Therapeutic potential of isoallolithocholic acid in methicillin-resistant Staphylococcus Aureus peritoneal infection

A significant increase in multidrug-resistant Methicillin-resistant Staphylococcus aureus (MRSA) infections has made it crucial to explore new antimicrobial drugs and strategies. Emerging evidence suggests that the bile acid metabolite isoallolithocholic acid (isoallo-LCA) may contribute to reducing the risk of infection among centenarians. However, its precise role remains somewhat ambiguous and necessitates further investigation. This study aims to investigate the roles of isoallo-LCA in MRSA-associated peritoneal infection. The effects of isoallo-LCA on peritoneal infection are examined in a MRSA-induced peritoneal infected model. Antibacterial activity, biofilm formation assay, and bacterial membrane permeability experiments are conducted to explore the mechanisms involved. Our findings demonstrate that isoallo-LCA effectively suppresses the replication of MRSA with minimal adverse effects on mammalian cells. Furthermore, isoallo-LCA significantly inhibits the formation of bacterial biofilms and eradicates existing bacterial biofilms of MRSA. Administration of isoallo-LCA reduces MRSA colonization in peritoneal organs and alleviates peritonitis-related inflammation and damage in a MRSA-infected peritonitis mice. Mechanistically, isoallo-LCA exhibits potent bactericidal activity against MRSA by disrupting the integrity and permeability of bacterial cells. In addition, isoallo-LCA also enhances the macrophage phagocytosis. In conclusion, our results suggest that isoallo-LCA could be an effective treatment for infections caused by MRSA.

Larimichthys crocea (large yellow croaker): A bibliometric study

Larimichthys crocea is an important economic fish of East Asia, and numerous studies have been conducted on its breeding, aquaculture, preservation and processing; however, there is no systematic review of the literature on the research of Larimichthys crocea. Derwent Data Analyzer (DDA) was used to analyze 1192 Larimichthys crocea research papers indexed by SCI-E, CSCD and KCI from 2001 to 2023. The number of research publications on Larimichthys crocea has rapidly increased, and institutions and scholars from China, the United States, South Korea, Japan, and Norway have conducted the majority of Larimichthys crocea research. The immune response, Pseudomonas plecoglossicida, gene expression, lipid immune response, transcriptomics and other areas have attracted the most attention. To increase the immunity and disease resistance of Larimichthys crocea and improve its survival, growth, storage and transport, researchers have carried out a large amount of research, which has promoted not only the culture of Larimichthys crocea but also the restoration of wild Larimichthys crocea and the rehabilitation of the ecological environment.

Inhibition of the Growth of Escherichia coli and Staphylococcus aureus Microorganisms in Aesthetic Orthodontic Brackets through the In Situ Synthesis of Ag, TiO2 and Ag/TiO2 Nanoparticles

Plaque control is especially important during orthodontic treatment because areas of the teeth near brackets and wires are difficult to clean with a toothbrush, resulting in debris buildup of food or dental plaque, thus causing caries and periodontal disease. The objective of this study was to evaluate the antimicrobial properties of silver nanoparticles (AgNPs), titanium dioxide nanoparticles (TiO2NPs), and silver/titanium dioxide nanoparticles (Ag/TiO2NPs), synthesized on the surface of α-alumina ceramic brackets. The AgNPs and TiO2NPs were synthesized by a simple chemical method, and these were characterized by XRD, SEM, and XPS TEM; the antimicrobial activity was tested against Staphylococcus aureus and Escherichia coli by diffusion test. The results of this study demonstrated that by this simple chemical method, silver and titanium dioxide nanoparticles can be synthesized on the surface of α-alumina esthetic brackets, and these NPs possess good antimicrobial activity and the possibility of reducing dental caries, periodontal disease, and white spot generated during orthodontic treatment.

Chemokines Kill Bacteria by Binding Anionic Phospholipids without Triggering Antimicrobial Resistance

Classically, chemokines coordinate leukocyte trafficking during immune responses; however, many chemokines have also been reported to possess direct antibacterial activity in vitro. Yet, the bacterial killing mechanism of chemokines and the biochemical properties that define which members of the chemokine superfamily are antimicrobial remain poorly understood. Here we report that the antimicrobial activity of chemokines is defined by their ability to bind phosphatidylglycerol and cardiolipin, two anionic phospholipids commonly found in the bacterial plasma membrane. We show that only chemokines able to bind these two phospholipids kill Escherichia coli and Staphylococcus aureus and that they exert rapid bacteriostatic and bactericidal effects against E. coli with a higher potency than the antimicrobial peptide beta-defensin 3. Furthermore, our data support that bacterial membrane cardiolipin facilitates the antimicrobial action of chemokines. Both biochemical and genetic interference with the chemokine-cardiolipin interaction impaired microbial growth arrest, bacterial killing, and membrane disruption by chemokines. Moreover, unlike conventional antibiotics, E. coli failed to develop resistance when placed under increasing antimicrobial chemokine pressure in vitro. Thus, we have identified cardiolipin and phosphatidylglycerol as novel binding partners for chemokines responsible for chemokine antimicrobial action. Our results provide proof of principle for developing chemokines as novel antibiotics resistant to bacterial antimicrobial resistance mechanisms.

Centrosomal protein of 192 kDa (Cep192) fragment possesses bactericidal and parasiticidal activities in Larimichthys crocea

A novel AMP Lc1773, derived from centrosomal protein of 192 kDa (Cep192), was isolated from Larimichthys crocea using a Bacillus subtilis system. After cDNA libraries construction, repeating selection of B. subtilis system, extraction of extracellular protein, and expression of recombinant protein, we found that B. subtilis 1773, extracellular protein, and rLc1773 had a strong potential to kill Vibrio. parahaemolyticus and V. vulnificus. Further analysis of the antibacterial mechanism revealed that rLc1773 not only disrupted the integrity of bacterial membrane (as confirmed by SEM, TEM, and confocal microscopy observation, and flow cytometry assays), resulting in bacterial cell membrane pore conformation, bacterial rupture, and leakage of cellular contents, but also targeted to block protein synthesis rather than damage nucleic acids (as confirmed by SDS-PAGE, enzyme expression, and gel retardation assays). In addition, rLc1773 had the ability to kill parasite Scuticociliatida in a high rate and low concentration. Critically, the antibacterial activity of rLc1773 had good thermal stability and UV radiation tolerance, but it was affected by pH 9-11 and diverse enzyme to some extent. Lc1773 had neither hemolysis on fish, shrimp, and rabbit erythrocytes，nor significant cytotoxicity. To our knowledge, Cep192 fragment was first demonstrated to possess bactericidal and parasiticidal activities.

Identification and Functional Analysis of ToBPI1/LBP and ToBPI2/LBP in Anti-Bacterial Infection of Trachinotus ovatus

Bactericidal/permeability-increasing protein (BPI) and lipopolysaccharide-binding protein (LBP) are a group of antibacterial proteins that play an important role in the host's innate immune defense against pathogen infection. In this study, two BPI/LBPs, named ToBPI1/LBP (1434 bp in length, 478 amino acids) and ToBPI2/LBP (1422 bp in length, 474 amino acids), were identified from the golden pompano. ToBPI1/LBP and ToBPI2/LBP were significantly expressed in immune-related tissues after being challenged with Streptococcus agalactiae and Vibrio alginolyticus. The two BPI/LBPs showed significant antibacterial activity against Gram-negative Escherichia coli and Gram-positive S. agalactiae and Streptococcus iniae. In contrast, the antibacterial activity against Staphylococcus aureus, Corynebacterium glutamicum, Vibrio parahaemolyticus, V. alginolyticus and Vibrio harveyi was low and decreased with time. The membrane permeability of bacteria treated with recombinant ToBPI1/LBP and ToBPI2/LBP was significantly enhanced. These results suggest that ToBPI1/LBP and ToBPI2/LBP may play important immunological roles in the immune response of the golden pompano to bacteria. This study will provide basic information and new insights into the immune response mechanism of the golden pompano to bacteria and the function of BPI/LBP.

Temporin-GHb-Derived Peptides Exhibit Potent Antibacterial and Antibiofilm Activities against Staphylococcus aureus In Vitro and Protect Mice from Acute Infectious Pneumonia

With the continuous development of drug resistance in bacteria to traditional antibiotics, the demand for novel antibacterial agents is urgent. Antimicrobial peptides (AMPs) are promising candidates because of their unique mechanism of action and low tendency to induce drug resistance. Previously, we cloned temporin-GHb (hereafter referred to simply as "GHb") from Hylarana guentheri. In this study, a series of derived peptides were designed, namely, GHbR, GHbK, GHb3K, GHb11K, and GHbK4R. The five derived peptides had stronger antibacterial activities against Staphylococcus aureus than the parent peptide GHb and could effectively inhibit the formation of biofilms and eradicate mature biofilms in vitro. GHbR, GHbK, GHb3K, and GHbK4R exerted bactericidal effects by disrupting membrane integrity. However, GHb11K exhibited bacteriostatic efficacy with toroidal pore formation on the cell membrane. In comparison to GHbK4R, GHb3K showed much lower cytotoxicity against A549 alveolar epithelial cells, with an IC₅₀ > 200 μM, which was much higher than its minimal inhibitory concentration (MIC = 3.1 μM) against S. aureus. The anti-infection potential of GHbK4R and GHb3K was investigated in vivo. Compared with vancomycin, the two peptides displayed significant efficacy in a mouse model of acute pneumonia infected with S. aureus. Both GHbK4R and GHb3K also had no obvious toxicity to normal mice after intraperitoneal administration (15 mg/kg) for 8 days. Our results indicate that GHb3K and GHbK4R might be promising candidates for the treatment of bacterial pneumonia infected with S. aureus.

Antibacterial and Antibiofilm Efficacy of Repurposing Drug Hexestrol against Methicillin-resistant Staphylococcus aureus

There has been an explosion in the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) because of the indiscriminate use of antibiotics. In this study, we repurposed hexestrol (HXS) as an antibacterial agent to fight planktonic and biofilm-related MRSA infections. HXS is a nonsteroidal synthetic estrogen that targets estrogen receptors (ERα and ERβ) and has been used as a hormonal antineoplastic agent. In our work, the minimum inhibitory concentrations (MICs) were determined using the antimicrobial susceptibility of MSSA and MRSA strains. Anti-biofilm activity was evaluated using biofilm inhibition and eradication assays. Biofilm-related genes were analyzed with or without HXS treatment using RTqPCR analysis of S. aureus. HXS was tested using the checkerboard dilution assay to identify antibiotics that may have synergistic effects. Measurement of ATP and detection of ATPase allowed the determination of bacterial energy metabolism. As shown in the results, HXS showed effective antimicrobial activity against S. aureus, including both type strains and clinical isolations, with MICs of 16 µg/mL. Sub-HXS strongly inhibited the adhesion of S. aureus. The content of extracellular polymeric substances (EPS) and the relative transcription levels of eno, sacC, clfA, pls and fnbpB were reduced after HXS treatment. HXS showed antibacterial effects against S. aureus and synergistic activity with aminoglycosides by directly interfering with cellular energy metabolism. HXS inhibits adhesion and biofilm formation and eradicates biofilms formed by MRSA by reducing the expression of related genes. Furthermore, HXS increases the susceptibility of aminoglycosides against MRSA. In conclusion, HXS is a repurposed drug that may be a promising therapeutic option for MRSA infection.