Broad-spectrum Antibacterial Activity Research Articles

Exploring in vitro efficacy of rCHAPk with antibiotic combinations, and promising findings of its therapeutic potential for clinical-originated MRSA wound infection.

The increasing threat of antimicrobial-resistant bacteria, particularly Staphylococcus aureus, which rapidly develops multidrug resistance and commonly colonizes wound surfaces, demands innovative strategies. Phage-encoded endolysins offer a dual-purpose approach as topical therapies for infectious skin wounds and synergistic agents to reduce high-dose antibiotic dependence. This study explores recombinant CHAPk (rCHAPk), efficiently synthesized within 3 h, displaying broad-spectrum antibacterial activity against 11 Gram-positive strains, including resistant variants, with rapid bactericidal kinetics. Application of 10 μg of rCHAPk reduced OD600 by 0.4 within 5 min against a clinical methicillin-resistant S. aureus (MRSA) strain. Combining rCHAPk (1.875 μg/mL) with oxacillin/vancomycin lowered their minimum bactericidal concentrations to 1 μg/mL from initial values over 64 μg/mL and 32 μg/mL, respectively, with a fractional inhibitory concentration index below 0.1. rCHAPk retained efficacy after one year of refrigerated storage. In in vivo experiments, rCHAPk outperformed commercial fucidin therapy in MRSA-induced murine wound models over two weeks, enhancing wound healing by modulating pro-inflammatory cytokine responses and the proliferative phase. This study, for the first time, investigates rCHAPk's in vitro combination with antibiotics and wound healing parameters, highlighting its potential as a potent antibacterial agent synergizing with antibiotics to address antibiotic-resistant bacterial wound infections.

Efficient Genetic Transformation and Suicide Plasmid-mediated Genome Editing System for Non-model Microorganism Erwinia persicina.

Erwinia persicina is a gram-negative bacterium that causes diseases in plants. Recently, E. persicina BST187 was shown to exhibit broad-spectrum antibacterial activity due to its inhibitory effects on bacterial acetyl-CoA carboxylase, demonstrating promising potential as a biological control agent. However, the lack of suitable genetic manipulation techniques limits its exploitation and industrial application. Here, we developed an efficient transformation system for E. persicina. Using pET28a as the starting vector, the expression cassette of the red fluorescent protein-encoding gene with the strong promoter J23119 was constructed and transformed into BST187 competent cells to verify the overexpression system. Moreover, suicide plasmid-mediated genome editing systems was developed, and lacZ was knocked out of BST187 genome by parental conjugation transfer using the recombinant suicide vector pKNOCK-sacB-km-lacZ. Therefore, both the transformation and suicide plasmid-mediated genome editing system will greatly facilitate genetic manipulations in E. persicina and promote its development and application. Key features • Our studies establish a genetic manipulation system for Erwinia persicina, providing a versatile tool for studying the gene function of non-model microorganisms. • Requires approximately 6-10 days to complete modification of a chromosome locus.

Screening and identification of antimicrobial peptides from the gut microbiome of cockroach Blattella germanica

BackgroundThe overuse of antibiotics has led to lethal multi-antibiotic-resistant microorganisms around the globe, with restricted availability of novel antibiotics. Compared to conventional antibiotics, evolutionarily originated antimicrobial peptides (AMPs) are promising alternatives to address these issues. The gut microbiome of Blattella germanica represents a previously untapped resource of naturally evolving AMPs for developing antimicrobial agents.ResultsUsing the in-house designed tool “AMPidentifier,” AMP candidates were mined from the gut microbiome of B. germanica, and their activities were validated both in vitro and in vivo. Among filtered candidates, AMP1, derived from the symbiotic microorganism Blattabacterium cuenoti, demonstrated broad-spectrum antibacterial activity, low cytotoxicity towards mammalian cells, and a lack of hemolytic effects. Mechanistic studies revealed that AMP1 rapidly permeates the bacterial cell and accumulates intracellularly, resulting in a gradual and mild depolarization of the cell membrane during the initial incubation period, suggesting minimal direct impact on membrane integrity. Furthermore, observations from fluorescence microscopy and scanning electron microscopy indicated abnormalities in bacterial binary fission and compromised cell structure. These findings led to the hypothesis that AMP1 may inhibit bacterial cell wall synthesis. Furthermore, AMP1 showed potent antibacterial and wound healing effects in mice, with comparable performances of vancomycin.ConclusionsThis study exemplifies an interdisciplinary approach to screening safe and effective AMPs from natural biological tissues, and our identified AMP 1 holds promising potential for clinical application.Graphical Bfzw53yZZxeQJxRuWThBYFVideo

Whole genome sequence and LC-Mass for identifying antimicrobial metabolites of Bacillus licheniformis endophyte

Antimicrobial resistance (AMR) represents a critical public health issue that requiring immediate action. Wild halophytic plants can be the solution for the AMR crisis because they harbor unique endophytes capable of producing potent antimicrobial metabolites. This study aimed at identifying promising and antimicrobial metabolites produced by endophytic/epiphytic bacteria recovered from the wild Bassia scoparia plant. Standard methods were employed for the isolation of endophytes/epiphytes. Whole genome sequence (WGS) using Oxford Nanopore technology followed by antiSMASH analysis coupled with advanced LC-MS spectroscopic analysis were used for identification of the active antimicrobial metabolites. This study identified Bacillus licheniformis strain CCASU-B18 as a promising endophytic bacterium from the Bassia scoparia plant. In addition, the strain showed broad-spectrum antibacterial activity against three standard and five MDR clinical Gram-positive and Gram-negative isolates, and antifungal activity against the standard C. albicans strain. Six main antimicrobial metabolites—thermoactinoamide A, bacillibactins, lichenysins, lichenicidins, fengycin, and bacillomycin—were verified to exist by whole genome sequencing for identifying the respective conserved biosynthetic gene clusters in conjunction with LC/MS-MS analysis. The complete genomic DNA (4125835) and associated plasmid (205548 bp) of the promising endophytic isolate were sequenced, assembled, annotated, and submitted into the NCBI GenBank database under the accession codes, CP157373. In conclusion, Bacillus licheniformis strain CCASU-B18, a promising endophytic bacterium exhibiting broad-spectrum antimicrobial activities, was isolated. Future research is highly recommended to optimize the culture conditions that will be employed to enhance the production of respective antimicrobial metabolites, as well as testing these compounds against a broader range of MDR-resistant pathogens.

Evolutionary dynamics and regulatory site analysis of AMP family genes in cattle and sheep.

Ruminants possess a rich repository of natural antimicrobial peptides(AMPs) within their bodies, surpassing those found in humans and mice. These peptides, including Defensin, Cathelicidin, and Lysozyme, are integral to the body's innate and adaptive immune responses and represent promising alternatives to antibiotics with significant application potential. In the present study, we conducted a systematic analysis of 40 Defensins, 38 Cathelicidins, and 61 Lysozymes in cattle and sheep. Our findings revealed that these peptides have retained functional integrity through the evolutionary history of these species. However, they exhibit unique gene duplication and expansion events when compared to humans and mice, indicating their potent roles in cattle and sheep. Notably, the Cathelicidin gene family experienced the most substantial expansion in these ruminants. The newly expanded genes were highly expressed in tissues and organs such as the tongue surface, intestine, mammary gland, and others, exhibiting tissue-specific preferences. This expression pattern is associated with the unique behaviors and high lactation capacity of ruminants. An in vitro bacterial inhibition assay demonstrated that EBD, LALBA, LYSB, and CATHL4 exhibited significant broad-spectrum antibacterial activity. Additionally, loci dB1, dB5, cB2, cB3, and yB1 were pinpointed as key co-regulatory elements in the antimicrobial peptide motifs within cattle mammary epithelial cells. This research illuminates the structure-function relationship and antimicrobial potency of natural AMP genes in cattle and sheep, providing a theoretical foundation for the development of novel veterinary drugs to treat common bacterial diseases in ruminants and for enhancing animal health care. The identified transcriptional regulatory sites offer a new perspective on the molecular regulation of AMP genes expression, which can be leveraged to improve the disease resistance of domestic animals. This work contributes to a broader understanding of the evolution and regulation of AMP genes, with potential applications for animal health and breeding programs.

Ultrashort Peptide Hydrogels Biomaterials with Potent Antibacterial Activity.

For the past few decades, ultrashort peptide hydrogels have been at the forefront of biomaterials due to their unique properties like biocompatibility, tunable mechanical properties, and potent antibacterial activity. These ultrashort peptides self-assemble into a hydrogel matrix with nanofibrous networks. In this minireview, we have explored the design and self-assembly of these ultrashort peptide hydrogels by focusing on their antibacterial properties. Cationic and hydrophobic residues are incorporated to engineer the peptides, facilitating interaction with bacterial membranes and leading to membrane disruption and cell death. The hydrogels exhibit broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria. Overall, this minireview highlights the potential of ultrashort peptide hydrogels as versatile and practical antibacterial biomaterials, providing a novel approach to combating bacterial infections and addressing the growing challenge of antibiotic resistance.

FM-568: A Promising Phenyl-Hydrazonomalononitrile Antibacterial Agent for the Sustainable Management of Citrus Canker.

Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), poses a significant threat to citrus production worldwide. To develop effective and eco-friendly antibacterial agents, we designed and synthesized phenyl-hydrazonomalononitrile derivatives using a scaffold-hopping strategy. Among these, FM-568 emerged as a potent candidate, exhibiting broad-spectrum antibacterial activity in vitro against various phytopathogenic bacteria, including Xcc. Greenhouse experiments demonstrated that FM-568 achieved a control efficacy of 88.36% against citrus canker at 400 μg/mL, with an EC50 of 26.68 μg/mL. Field trials in two major citrus-producing regions in China confirmed its effectiveness, yielding control efficacies of 86.60 and 77.87% at 400 μg/mL, outperforming conventional agents like zinc thiazole and thiadiazole copper. Density functional theory calculations suggested that FM-568's optimized scaffold and electronic properties contribute to its enhanced antibacterial activity. These findings indicate that FM-568 is a promising eco-friendly alternative for managing citrus canker. Further studies on its mechanism of action, safety profile, and formulation optimization are warranted to advance its development for sustainable citrus production.

Screening for antibacterial and cytotoxic potential of marine fungi isolated from samples collected in Ly Son Island, Quang Ngai Province

The ocean covers almost three-quarters of our planet’s surface. Marine fungi are fungi that live in marine habitats, most of them are microscopic, either microfungi or yeasts, but many marine species that inhabit the world’s oceans are not known yet. They are well recognized as a source of many novel compounds that possess valuable pharmacological properties. In the present study, we isolated and assessed the antimicrobial and cytotoxic activities of marine fungi isolated from samples collected in Ly Son Island. From 20 samples, a total of 44 marine fungi were isolated. As a result, 33/44 strains were resistant to at least 1 tested microorganisms. Among them, there were 2 isolates VM10 and VM25 showed a broad spectrum of antibacterial activity against five to six tested pathogenic ATCC strains with low MIC values. Moreover, 4/44 extracts (VM10, VM15, VM25, and VM39) showed remarkable cytotoxic effects against HepG2 human hepatoma, MCF-7 breast cancer, and A549 lung cancer cell lines with the recorded viability of tested cancer cells ranging more than 50%. The two candidate strains were subsequently identified as Aspergillus versicolor VM10, Metarhizium sp. VM25 by using 18S rRNA sequence analysis. The promising candidate isolates were analyzed in a phylogenetic tree based on MegaX software.

High-Efficiency Broad-Spectrum Antibacterial Activity of Chitosan/Zinc Ion/Polyoxometalate Composite Films for Water Treatment.

The development of multifunctional films with rapidly killing microorganisms and adsorbing residual antibiotics in wastewater remains a challenging endeavor. In this work, the chitosan/zinc ion/polyoxometalate (CS/Zn2+/POM) multifunctional films were prepared by the freeze-drying method using chitosan, ZnO, and POM. Notably, the CS/Zn2+/POM films exhibited excellent bactericidal properties against Gram-positive/negative bacterial strains including Staphylococcus aureus (S. aureus, 99.80%), Escherichia coli (E. coli, 99.82%), and drug-resistant E. coli bacterial strains (kanamycin-resistant E. coli, 87.76% and ampicillin-resistant E. coli, 99.71%). This may be due to the chelation of Zn2+ with CS disrupting the cell membrane and bringing POM into direct contact with bacteria, leading to bacterial death. In addition, the CS/Zn2+/POM films showed good adsorption performance to a tetracycline (TC) solution (adsorption rate 75.2%). Further studies showed that the main process of tetracycline removal by CS/Zn2+/POM films was controlled by a physical adsorption. This POM-based film material has an important potential for the synthesis of broad-spectrum antimicrobial materials for the removal of residual antibiotics from water pollutants such as tetracycline.

Gatifloxacin hydrochloride confers broad-spectrum antibacterial activity against phytopathogenic bacteria.

Bacterial diseases pose significant threats to agriculture and natural ecosystems, causing substantial crop losses and impacting food security. Until now, there has been a less efficient control strategy against some bacterial diseases such as bacterial wilt, caused by Ralstonia solanacearum. In this study, we screened a library of 58 microorganism-derived natural products for their antibacterial activity against R. solanacearum. Gatifloxacin hydrochloride exhibited the best inhibitory effect with an inhibition rate of 95% at 0.0625 mg/L. Further experiments demonstrate that gatifloxacin hydrochloride inhibits R. solanacearum growth in a concentration-dependent manner, with the minimum inhibitory concentration of 0.125 mg/L. Treatment with 0.5 mg/L of gatifloxacin hydrochloride killed more than 95% of bacteria. Gatifloxacin hydrochloride significantly inhibited biofilm formation by R. solanacearum. Gatifloxacin hydrochloride also shows good antibacterial activity against Pseudomonas syringae pv. tomato DC3000 and Xanthomonas campestris pv. vesicatoria. Exogenous application of gatifloxacin hydrochloride suppressed disease development caused by R. solanacearum and P. syringae. In summary, our results demonstrate the great potential of microorganism-derived compounds as broad-spectrum antibacterial compounds, providing alternative ways for the efficient control of bacterial plant diseases.

Bacteriocin Mining in Lactiplantibacillus pentosus PCZ4 with Broad-Spectrum Antibacterial Activity and Its Biopreservative Effects on Snakehead Fish.

Some lactic acid bacteria (LAB) produce antibacterial substances such as bacteriocins, making them promising candidates for food preservation. In our study, Lactiplantibacillus pentosus PCZ4-a strain with broad-spectrum antibacterial activity-was isolated from traditional fermented kimchi in Sichuan. Whole-genome sequencing of PCZ4 revealed one chromosome and three plasmids. Through BAGEL4 mining, classes IIa and IIb bacteriocin plantaricin S were identified. Additionally, two new antibacterial peptides, Bac1109 and Bac2485, were predicted from scratch by limiting open reading frames. Furthermore, during refrigerated storage of snakehead fish, PCZ4 crude extract reduced the total bacterial count, slowed the increase in TVB-N and pH values, improved the sensory quality of the snakehead, and extended its shelf life by 2 days. Meanwhile, PCZ4 effectively inhibited the growth of artificially contaminated Aeromonas hydrophila in snakehead fish. These findings indicate that Lp. pentosus PCZ4 can produce multiple antibacterial substances with strong potential for food preservation applications.

Enhancing the solubility and antibacterial activity of novel molecular salts of enrofloxacin drug with isomeric pyridinedicarboxylic acids

Enrofloxacin (EFX) is a third-generation synthetic fluoroquinolone with a broad spectrum of antibacterial activity but suffers from low water solubility, affecting its bioavailability. This study attempts to enhance the physicochemical and biological properties of enrofloxacin by converting it into multicomponent forms using crystal engineering concepts. Cocrystallization of enrofloxacin with isomeric pyridine-2,n-dicarboxylic acids (n = 3,4,5,6) resulted in four new crystalline salts (1:1): EFX·Py2,3DCA, EFX·Py2,4DCA, EFX·Py2,5DCA·H2O and EFX·Py2,6DCA·H2O; two of these are monohydrates. The protonation of the nitrogen atom of the piperazine moiety and the presence of crystallization water molecules were confirmed by single-crystal X-ray diffraction and Fourier transform infrared spectroscopy. Thermogravimetric analysis provided information on the thermal behaviour of multicomponent forms. The biological studies showed that the obtained salts are characterized by high antibacterial activity against Gram-positive and Gram-negative bacteria, and their haemolytic activity is low. The new salts demonstrate significantly greater solubility in water compared to the parent drug, along with enhanced antibacterial activity; hence, pyridinedicarboxylic acids appear to be efficient cocrystallizing agents for improving the efficacy of pharmaceutical ingredients.

Identification and characterization of a novel bacteriocin PCM7-4 and its antimicrobial activity against Listeria monocytogenes

Listeria monocytogenes, a pathogenic bacterium causing zoonotic diseases, necessitates the urgent search for novel anti-Listeria monocytogenes drugs due to the continuous emergence of drug-resistant bacteria. In this study, we isolated and identified a bacteriocin-producing strain CM7–4 from seawater as Bacillus velezensis through 16S rRNA sequence analysis. Moreover, we successfully purified a novel bacteriocin named PCM7–4 from Bacillus velezensis CM7–4. The molecular weight of PCM7–4 was determined to be 40,228.99 Da. Notably, PCM7–4 exhibited broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria with a minimum inhibitory concentration (MIC) of 5.625 μg/mL against Listeria monocytogenes specifically. It demonstrated heat resistance and high stability within the pH range of 2–12 while being sensitive to proteinase K degradation without any observed hemolytic activity. Furthermore, SEM analysis revealed that PCM7–4 effectively inhibited biofilm formation and disrupted cell membranes in Listeria monocytogenes cells. Transcriptome analysis revealed that PCM7–4 exerts an impact on genes associated with crucial metabolic pathways, encompassing the biosynthesis of secondary metabolites, phosphotransferase systems (PTS), and starch/sucrose metabolism. These findings highlight the significant potential of bacteriocin PCM7–4 for the development of effective antimicrobial interventions targeting food-borne pathogenic bacteria.

Bacillus velezensis HBXN2020 alleviates Salmonella Typhimurium infection in mice by improving intestinal barrier integrity and reducing inflammation

Bacillus velezensis is a species of Bacillus that has been widely investigated because of its broad-spectrum antimicrobial activity. However, most studies on B. velezensis have focused on the biocontrol of plant diseases, with few reports on antagonizing Salmonella Typhimurium infections. In this investigation, it was discovered that B. velezensis HBXN2020, which was isolated from healthy black pigs, possessed strong anti-stress and broad-spectrum antibacterial activity. Importantly, B. velezensis HBXN2020 did not cause any adverse side effects in mice when administered at various doses (1×107, 1×108, and 1×109 CFU) for 14 days. Supplementing B. velezensis HBXN2020 spores, either as a curative or preventive measure, dramatically reduced the levels of S. Typhimurium ATCC14028 in the mice’s feces, ileum, cecum, and colon, as well as the disease activity index (DAI), in a model of infection caused by this pathogen in mice. Additionally, supplementing B. velezensis HBXN2020 spores significantly regulated cytokine levels (Tnfa, Il1b, Il6, and Il10) and maintained the expression of tight junction proteins and mucin protein. Most importantly, adding B. velezensis HBXN2020 spores to the colonic microbiota improved its stability and increased the amount of beneficial bacteria (Lactobacillus and Akkermansia). All together, B. velezensis HBXN2020 can improve intestinal microbiota stability and barrier integrity and reduce inflammation to help treat infection by S. Typhimurium.

Bacillus velezensis HBXN2020 alleviates Salmonella Typhimurium infection in mice by improving intestinal barrier integrity and reducing inflammation.

Bacillus velezensis is a species of Bacillus that has been widely investigated because of its broad-spectrum antimicrobial activity. However, most studies on B. velezensis have focused on the biocontrol of plant diseases, with few reports on antagonizing Salmonella Typhimurium infections. In this investigation, it was discovered that B. velezensis HBXN2020, which was isolated from healthy black pigs, possessed strong anti-stress and broad-spectrum antibacterial activity. Importantly, B. velezensis HBXN2020 did not cause any adverse side effects in mice when administered at various doses (1×107, 1×108, and 1×109 CFU) for 14 days. Supplementing B. velezensis HBXN2020 spores, either as a curative or preventive measure, dramatically reduced the levels of S. Typhimurium ATCC14028 in the mice's feces, ileum, cecum, and colon, as well as the disease activity index (DAI), in a model of infection caused by this pathogen in mice. Additionally, supplementing B. velezensis HBXN2020 spores significantly regulated cytokine levels (Tnfa, Il1b, Il6, and Il10) and maintained the expression of tight junction proteins and mucin protein. Most importantly, adding B. velezensis HBXN2020 spores to the colonic microbiota improved its stability and increased the amount of beneficial bacteria (Lactobacillus and Akkermansia). All together, B. velezensis HBXN2020 can improve intestinal microbiota stability and barrier integrity and reduce inflammation to help treat infection by S. Typhimurium.

Nanozymes as Antibacterial Agents: New Concerns in Design and Enhancement Strategies.

Nanozymes exhibiting natural enzyme-mimicking catalytic activities as antibacterial agents present several advantages, including high stability, low cost, broad-spectrum antibacterial activity, ease of preparation and storage, and minimal bacterial resistance. Consequently, they have attracted significant attention in recent years. However, the rapid expansion of antimicrobial nanozyme research has resulted in pioneering reviews that do not comprehensively address emerging concerns and enhancement strategies within this field. This paper first summarizes the factors influencing the intrinsic activity of nanozymes; subsequently, we outline new research considerations for designing antibacterial nanozymes with enhanced functionality and biosafety features such as degradable, imageable, targeted, and bacterial-binding nanozymes as well as those capable of selectively targeting pathogenic bacteria while sparing normal cells and probiotics. Furthermore, we review novel enhancement strategies involving external physical stimuli (light or ultrasound), the introduction of extrinsic small molecules, and self-supplying H2O2 to enhance the activity of antibacterial nanozymes under physiological conditions characterized by low concentrations of H2O2 and O2. Additionally, we present non-redox nanozymes that operate independently of highly toxic reactive oxygen species (ROS) alongside those designed to combat less common pathogenic bacteria. Finally, we discuss current issues, challenges faced in the field, and future prospects for antibacterial nanozymes.

In Situ Crosslinked Biodegradable Hydrogels Based on Poly(Ethylene Glycol) and Poly(ε-Lysine) for Medical Application.

Hydrogels have emerged as promising biomaterials due to their excellent performance; however, their biocompatibility, biodegradability, and absorbability still require improvement to support a broader range of medical applications. This paper presents a new biofunctionalized hydrogel based on in situ crosslinking between maleimide-terminated four-arm-poly(ethylene glycol) (4-arm-PEG-Mal) and poly(ε-lysine) (ε-PL). The PEG/ε-PL hydrogels, named LG-n, were rapidly formed via amine/maleimide reaction by mixing 4-arm-PEG-Mal and ε-PL under physiological conditions. The corresponding dry gels (DLG-n) were obtained through a freeze-drying technique. 1H NMR, FT-IR, and SEM were utilized to confirm the structures of 4-arm-PEG-Mal and LG-n (or DLG-n), and the effects of solid content on the physicochemical properties of the hydrogels were investigated. Although high solid content could increase the swelling ratio, all LG-n samples exhibited a low equilibrium swelling ratio of less than 30%. LG-7, which contained moderate solid content, exhibited optimal compression properties characterized by a compressive fracture strength of 45.2 kPa and a deformation of 69.5%. Compression cycle tests revealed that LG-n demonstrated good anti-fatigue performance. In vitro degradation studies confirmed the biodegradability of LG-n, with the degradation rate primarily governing the drug (ceftibuten) release efficiency, leading to a sustained release duration of four weeks. Cytotoxicity tests, cell survival morphology observation, live/dead assays, and hemolysis tests indicated that LG-n exhibited excellent cytocompatibility and low hemolysis rates (<5%). Furthermore, the broad-spectrum antibacterial activity of LG-n was verified by an inhibition zone method. In conclusion, the developed LG-n hydrogels hold promising applications in the medical field, particularly as drug sustained-release carriers and wound dressings.

In vitro activities of eravacycline against clinical bacterial isolates: a multicenter study in Guangdong, China.

Eravacycline (ERV), a novel tetracycline derivative, exhibits broad-spectrum antibacterial activity, but data on the bacterial activity against Chinese bacterial isolates are very scarce. This study aims to evaluate the activity of eravacycline against the common Gram-positive and Gram-negative bacteria isolates in Guangdong, China. The clinical isolates were collected from four centers between 1 November 2023 and 31 January 2024, and the susceptibility of eravacycline (MIC50, MIC90, and MIC) was determined using broth microdilution as a reference method and E-TEST strips to evaluate their consistency. A total of 594 strains were collected from the four centers, including Staphylococcus aureus (n = 126), Enterococcus faecalis (n = 58), Enterococcus faecium (n = 29), Klebsiella pneumoniae (n = 136), Escherichia coli (n = 187), and Acinetobacter baumannii (n = 58). The MIC50 and MIC90 (mg/L) of eravacycline were 0.12 and 1 for S. aureus, 0.06 and 0.12 for E. faecalis, 0.06 and 0.5 for E. faecium, 0.25 and 0.5 for E. coli, 0.5 and 2 for K. pneumoniae, and 0.25 and 2 for A. baumannii. Based on the FDA and EUCAST breakpoints, the susceptibility of eravacycline against S. aureus was 46.03% vs. 83.33%, 56.90% vs. 94.93% against E. faecalis, and 62.07% vs. 79.31% in E. faecium. The susceptibility rates of E. coli and K. pneumoniae were 90.37% and 58.09, respectively. To evaluate the performance between the broth microdilution test (BMD) and ETEST methods, we compared essential agreement (EA), categorical agreement (CA), very major error (VME), and major error (ME). The results demonstrated that compared with BMD, eravacycline measured by ETEST had higher VME and ME referring to FDA breakpoints than EUCAST breakpoints in the Gram-positive isolates. Since there were no intermediate breakpoints for the eravacycline, the MIC values measured by the ETEST method might result in lower CA and higher VME and ME. This study provides MIC values of eravacycline against Gram-positive and Gram-negative pathogens in four hospitals in Guangdong Province, and eravacycline is an effective therapeutic candidate for common bacteria.

A novel antimicrobial peptide CpAMP identified from Chinese horseshoe crab, Tachypleus tridentatus

Antibacterial peptide (AMP) is a crucial component of the innate immune system in most organism, play an important role in host defense processes. Many of these peptides have broad antimicrobial activity against Gram-negative, -positive bacteria and fungi. In the present study, a novel AMP named CpAMP was identified using transcriptome analysis in Chinese horseshoe crab. The preprotein of CpAMP consists of a signal peptide (21 aa) and a mature peptide (47 aa) enriched by cysteine. And the putative mature peptide CpAMP was 4.95 kDa with a theoretical isoelectric point (pI) of 8.73. The mature CpAMP showed α-helix and irregularly curled structure in the cys-stabilized region. CpAMP exhibited a broad spectrum of antimicrobial activity against Gram-negative, -positive bacteria and antibiotic-resistant strains. In addition, CpAMP can significantly increase the survival rate of zebrafish infected with bacteria. Due to its broad-spectrum antibacterial activity and the sensitivity of drug-resistant strains, CpAMP could be used as a new type of drug for inhibition of pathogenic microorganisms or as an immune enhancer in animals.

Development of α-Helical Antimicrobial Peptides with Imperfect Amphipathicity for Superior Activity and Selectivity.

The advancement of antimicrobial peptides (AMPs) as therapeutic agents is hindered by their poor selectivity. Recent evidence indicates that controlled disruption of the amphipathicity of α-helical AMPs may increase the selectivity. This study investigated the role of imperfect amphipathicity in optimizing AMPs with varied sequences to enhance their activity and selectivity. Among these, the lead peptide RI-18, characterized by an imperfectly amphipathic α-helical structure, demonstrated potent and broad-spectrum antibacterial activity without inducing hemolytic or cytotoxic effects. RI-18 effectively eliminated planktonic and biofilm-associated bacteria as well as persister cells and exhibited high bacterial plasma membrane affinity, inducing rapid membrane permeabilization and rupture. Notably, RI-18 significantly reduced bacterial loads without promoting bacterial resistance, highlighting its therapeutic potential. Overall, this study identified RI-18 as a promising antimicrobial candidate. The rational strategy of tuning imperfect amphipathicity to enhance the AMP activity and selectivity may facilitate the design and development of AMPs.