Inappropriate use of antibiotics exacerbates inflammation through OMV-induced pyroptosis in MDR Klebsiella pneumoniae infection

Bacterial extracellular vesicles in the initiation, progression and treatment of atherosclerosis

Atherosclerosis is the primary cause of cardiovascular and cerebrovascular diseases. However, current anti-atherosclerosis drugs have shown conflicting therapeutic outcomes, thereby spurring the search for novel and effective treatments. Recent research indicates the crucial involvement of oral and gastrointestinal microbiota in atherosclerosis. While gut microbiota metabolites, such as choline derivatives, have been extensively studied and reviewed, emerging evidence suggests that bacterial extracellular vesicles (BEVs), which are membrane-derived lipid bilayers secreted by bacteria, also play a significant role in this process. However, the role of BEVs in host-microbiota interactions remains insufficiently explored. This review aims to elucidate the complex communication mediated by BEVs along the gut-heart axis. In this review, we summarize current knowledge on BEVs, with a specific focus on how pathogen-derived BEVs contribute to the promotion of atherosclerosis, as well as how BEVs from gut symbionts and probiotics may mitigate its progression. We also explore the potential and challenges associated with engineered BEVs in the prevention and treatment of atherosclerosis. Finally, we discuss the benefits and challenges of using BEVs in atherosclerosis diagnosis and treatment, and propose future research directions to address these issues.

Klebsiella pneumoniae derived outer membrane vesicles mediated bacterial virulence, antibiotic resistance, host immune responses and clinical applications

Klebsiella pneumoniae is a gram-negative pathogen that can cause multiple diseases including sepsis, urinary tract infections, and pneumonia. The escalating detections of hypervirulent and antibiotic-resistant isolates are giving rise to growing public concerns. Outer membrane vesicles (OMVs) are spherical vesicles containing bioactive substances including lipopolysaccharides, peptidoglycans, periplasmic and cytoplasmic proteins, and nucleic acids. Emerging studies have reported various roles of OMVs in bacterial virulence, antibiotic resistance, stress adaptation, and host interactions, whereas knowledge on their roles in K. pneumoniae is currently unclear. In this review, we summarized recent progress on the biogenesis, components, and biological function of K. pneumoniae OMVs, the impact and action mechanism in virulence, antibiotic resistance, and host immune response. We also deliberated on the potential of K. pneumoniae OMVs in vaccine development, as diagnostic biomarkers, and as drug nanocarriers. In conclusion, K. pneumoniae OMVs hold great promise in the prevention and control of infectious diseases, which merits further investigation.

The mechanism of outer membrane vesicle-mediated resistance to carbapenem antibiotics

The escalating prevalence of carbapenem resistance in Gram-negative bacteria presents a critical therapeutic challenge, demanding urgent elucidation of novel resistance mechanisms. This review systematically examines the emerging role of outer membrane vesicles (OMVs) as multifunctional mediators of carbapenem resistance, synthesizing recent advances in understanding their biological properties and mechanistic contributions. Through comprehensive analysis of β-lactamase dissemination pathways, we demonstrate that OMVs are extracellular vectors facilitating antibiotic degradation through enzymatic cargo delivery while concurrently acting as genetic transmission vehicles for resistance determinants. Crucially, OMVs exhibit functional versatility in enhancing bacterial survival via dual mechanisms: structurally, by promoting biofilm matrix formation that establishes antibiotic-protected niches, and immunologically, through modulation of host-pathogen interactions that impair microbial clearance. The review further identifies OMV-mediated antibiotic sequestration and competitive binding as underappreciated resistance amplifiers. These insights refine our understanding of resistance evolution and reveal OMV biogenesis pathways as promising therapeutic targets. This synthesis establishes OMVs as central players in carbapenem resistance architecture, providing a strategic framework for developing countermeasures against multidrug-resistant infections.

Beta-Lactam Antibiotics Promote Extracellular Vesicle Production of Staphylococcus aureus Through ROS-Mediated Lipid Metabolic Reprogramming

Bacterial extracellular vesicles (EVs) are natural reservoirs of biological active substances. They exhibit promising application in developing bioproducts such as vaccine, drug-delivery system and anticancer agent. However, the low yield of naturally secreted EVs during bacterial growth is a bottleneck factor that restricts EV applications. In this study, we showed that sub-minimum inhibitory concentration (MIC) of β-lactams boosted EV production in various Staphylococcus aureus strains. The expression of penicillin-binding protein (PBP) genes increased after β-lactam treatment, and the inactivation of alternative PBPs promoted EV secretion of S. aureus. We also demonstrated that sub-MIC β-lactams promoted EV production via a reactive oxygen species (ROS)-dependent pathway. Deletion of redundant pbp genes enhanced oxacillin (OXA)-stimulated ROS levels. Transcriptomic and lipidomic analyses revealed that OXA-induced ROS triggered lipid metabolic reprogramming in S. aureus. Particularly, ROS promoted lipid peroxidation (LPO) and increased the biosynthesis of phosphatidic acid (PA) and lipoteichoic acid (LTA) that contributed to EV generation. Furthermore, OXA treatment altered the diversity of EV-loaded proteins. OXA-treated ∆ agr /OXAEVs induced stronger Dengue EDIII-specific antibodies in BALB/c mice than did ∆ agrEVs. Overall, this study provided mechanic insights into β-lactam-promoted EV production in S. aureus, and highlighted the potential strategies to prepare EVs for various applications.

Chlorogenic acid inhibits virulence and resistance gene transfer in outer membrane vesicles of carbapenem-resistant Klebsiella pneumoniae

Introduction

Carbapenem-resistant Klebsiella pneumoniae (CRKp) infection poses a significant global public health challenge, with the misuse of antibiotics further contributing to the development of resistance and triggering harmful inflammatory responses. Outer membrane vesicles (OMVs) released by CRKp under sub-lethal concentration of MEM pressure (KOMV-MEM) exhibit enhanced virulence and greater efficiency in transferring resistance genes.

Methods

We investigated the inhibitory effects of chlorogenic acid (CA) on KOMV-MEM characteristics and its protective role in KOMV-MEM infected mice. Based on LC-MS proteomic analysis of vesicles, we screened for potential targets of KOMV-MEM in promoting macrophage (MØ) pyroptosis pathways and inducing resistance gene transfer. Subsequently, computational predictions and experimental validation were performed to determine how CA regulates these mechanisms.

Results

This study confirmed that, under MEM pressure, the exacerbated infection levels in CRKp-inoculated mice are attributable to the high virulence of KOMV-MEM. Computational and experimental results demonstrated that CA inhibits pyroptosis by reducing MØ capture of KOMV-MEM through blocking the interaction between GroEL and LOX-1. Furthermore, CA prevents the spread of resistance genes by disrupting the conjugation and transfer processes between KOMV-MEM and recipient bacteria. Finally, in vitro and in vivo assays showed that CA inhibits KOMV-MEM resistance enzymes, thereby preventing the hydrolysis of MEM in the environment and depriving susceptible bacteria of protection.

Discussion

These findings provide the first confirmation that CA can inhibit both the virulence and the transmission of drug resistance in KOMV-MEM. This underscores the potential of CA treatment as a promising antimicrobial strategy against CRKp infection.

Plant based enteral nutrition outperforms artificial nutrition in mitigating consequences of antibiotic-induced dysbiosis in mice and humans

Malnutrition, gut inflammation, and antibiotic induced dysbiosis (AID) are omnipresent risk factors for poor clinical outcomes among critically ill patients. We previously showed that commercially available plant-based enteral nutrition (PBEN) preserves a commensal microbiome when compared to commonly used forms of commercially available artificial enteral nutrition (AEN). This study reveals that PBEN is superior to artificial enteral nutrition (AEN) in recovering from antibiotic-induced dysbiosis (AID) in mice and humans. PBEN effectively mitigates anemia, leukopenia, restores naïve lymphocyte populations, and reduces bone marrow myeloid cell expansion. Animals randomized to PBEN also fared better in response to infectious challenges after antibiotics. A pilot clinical study validated these findings, showing increased gut commensals, reduced pathogens, and improved leukocyte balance in critically ill patients receiving PBEN compared to AEN. These results suggest PBEN offers a practical dietary approach to mitigate antibiotic-associated complications and improve clinical outcomes among hospitalized patients requiring supplemental nutrition.

Capsular polysaccharide enables Klebsiella pneumoniae to evade phagocytosis by blocking host-bacteria interactions

Capsule polysaccharide (CPS) is among the most important virulence factors of Klebsiella pneumoniae. Previous studies demonstrated that CPS plays multiple functional roles, but the mechanism by which this virulence factor enhances the survival fitness of K. pneumoniae remains unclear. In this work, we demonstrate that CPS is the main cellular component that not only elicits the host immune response to K. pneumoniae but also enables this pathogen to survive for a prolonged period under adverse environmental conditions. Consistently, our in vitro experiments suggest that CPS prevents K. pneumoniae from phagocytosis, rendering the encapsulated strain more difficult to be eradicated by the host. We also found that phagocytosis of K. pneumoniae is partially mediated by LOX-1, a scavenger receptor of the host, and that CPS may impede interaction between LOX-1 and this pathogenic bacteria, therefore reducing the phagocytosis process. These findings provide insights into the pathogenic mechanisms of this important clinical pathogen and should facilitate the design of new strategies to combat K. pneumoniae infections.

IMPORTANCE

Klebsiella pneumoniae has become one of the most important clinical bacterial pathogens due to its evolution into hyperresistant and hypervirulent phenotypes. The mechanism of virulence of this pathogen is not well understood, particularly because it differs from other Enterobacteriaceae pathogens such as Escherichia coli and Salmonella. The capsule polysaccharide (CPS) of this pathogen is well recognized for contributing to the virulence of K. pneumoniae, but the exact mechanisms underlying its contribution are unclear. In this study, we demonstrated that CPS does not directly contribute to the host response; rather, it forms an external coat that blocks host recognition and prevents immune cells from binding to receptor proteins on K. pneumoniae, thus inhibiting phagocytosis, which makes it more challenging for the body to fight off infections. Understanding these mechanisms is vital for developing new treatments against K. pneumoniae infections, ultimately improving patient outcomes and public health.

Outer membrane vesicle contributes to the Pseudomonas aeruginosa resistance to antimicrobial peptides in the acidic airway of bronchiectasis patients

Pseudomonas aeruginosa is the predominant pathogen causing chronic infection in the airway of patients with bronchiectasis (BE), a chronic respiratory disease with high prevalence worldwide. Environmental factors are vital for bacterial successful colonization. Here, with sputa and bronchoalveolar lavage fluids, we determined that the concentration of airway antimicrobial peptide LL-37 and lactate was elevated in BE patients, especially in those infected with P. aeruginosa. The in vitro antibacterial assay revealed the bactericidal activity of LL-37 against the clinical P. aeruginosa isolates, which were dampened in the acidic condition. P. aeruginosa production of outer membrane vesicles (OMVs) enhanced in the lactate-adjusted acidic condition. Transcriptomic analysis suggested that OMVs induce the hyperproduction of the chemical compound 2-heptyl-4-quinolone (HHQ) in the bacterial population, which was verified by high-performance liquid chromatography. The positively charged HHQ interfered with the binding of LL-37 to bacterial cell membrane, potentiating the P. aeruginosa resistance to LL-37. To our knowledge, this is a new resistance mechanism of P. aeruginosa against antimicrobial peptides and may provide theoretical support for the development of new antibacterial therapies.

An improvised one-step OptiPrep cushion ultracentrifugation method for outer membrane vesicles isolation of Klebsiella pneumoniae

BACKGROUND

Extracellular vesicles (EVs) play a crucial role in intraspecies and interspecies communication, significantly influencing physiological and pathological processes. Outer membrane vesicles (OMVs) secreted by Gram-negative bacteria are rich in components from the parent cells and are important for bacterial communication, immune evasion, and pathogenic mechanisms. However, the extraction and purification of OMVs face numerous challenges due to their small size and heterogeneity.

RESULTS

This study proposes an innovative strategy that combines traditional differential centrifugation (DC) with one-step ultracentrifugation (ODG) to develop a dual differential gradient centrifugation (DDGC) method for extracting outer membrane vesicles from Klebsiella pneumoniae. By comparing the DC and DDGC extraction methods, we found that OMVs extracted by DDGC exhibited more typical morphology, clearer backgrounds, and more uniform particle size distribution. The lipid polysaccharide (LPS) content in OMVs extracted by DDGC was significantly higher than that obtained by DC, and the outer membrane protein content was also greater, demonstrating enhanced biological activity. Biological activity assays indicated that OMVs extracted by DDGC showed stronger cytotoxicity to A549 lung epithelial cells, a significant decrease in cell viability, and higher levels of inflammatory factor expression(IL-6, TNF-α, IL-1β, and IL-8).

CONCLUSION

Our study demonstrates the advantages of the DDGC method in extracting K. pneumoniae OMVs, showing improvements in morphology, particle size distribution, protein content, and biological activity. This provides a solid foundation for further exploration of the biological functions of OMVs and their potential applications in the biomedical field.

Fatty Acid Uptake in Klebsiella pneumoniae and the Landscape of Its Infectious Niches

Klebsiella pneumoniae is consistently ranked among the most problematic multidrug-resistant bacterial pathogens in healthcare systems. Developing novel treatments requires a better understanding of its interaction with the host environment. Although bacteria can synthesize fatty acids, emerging findings suggest a potential preference for their acquisition from the host. Fatty acid profiling of mice revealed a dramatic increase in the level of hepatic lipids during K. pneumoniae infection. The K. pneumoniae fatty acid composition and uptake capabilities were found to be largely clonally conserved. Correlations between fatty acid uptake, outer membrane vesicle production, and cell permeability were observed, but this did not translate to alterations in cell morphology, capsule production, or antimicrobial susceptibility. Importantly, hyper-capsulation did not prevent the uptake of hydrophobic fatty acids. The uptake of a saturated fatty acid by hypervirulent K. pneumoniae isolate may provide insights into the clinical association of K. pneumoniae infections with hyperlipidemic and/or obese individuals.

Photocatalytic Degradation of Bacterial Lipopolysaccharides by Peptide-Coated TiO2 Nanoparticles

In this study, we report the degradation of smooth and rough lipopolysaccharides (LPS) from Gram-negative bacteria and of lipoteichoic acid (LTA) from Gram-positive bacteria by peptide-coated TiO2 nanoparticles (TiO2 NPs). While bare TiO2 NPs displayed minor binding to both LPS and LTA, coating TiO2 NPs with the antimicrobial peptide LL-37 dramatically increased the level of binding to both LPS and LTA, decorating these uniformly. Importantly, peptide coating did not suppress reactive oxygen species generation of TiO2 NPs; hence, UV illumination triggered pronounced degradation of LPS and LTA by peptide-coated TiO2 NPs. Structural consequences of oxidative degradation were examined by neutron reflectometry for smooth LPS, showing that degradation occurred preferentially in its outer O-antigen tails. Furthermore, cryo-TEM and light scattering showed lipopolysaccharide fragments resulting from degradation to be captured by the NP/lipopolysaccharide coaggregates. The capacity of LL-37-TiO2 NPs to capture and degrade LPS and LTA was demonstrated to be of importance for their ability to suppress lipopolysaccharide-induced activation in human monocytes at simultaneously low toxicity. Together, these results suggest that peptide-coated photocatalytic NPs offer opportunities for the confinement of infection and inflammation.

Hypervirulent and carbapenem-resistant Klebsiella pneumoniae: A global public health threat

The evolution of hypervirulent and carbapenem-resistant Klebsiella pneumoniae can be categorized into three main patterns: the evolution of KL1/KL2-hvKp strains into CR-hvKp, the evolution of carbapenem-resistant K. pneumoniae (CRKp) strains into hv-CRKp, and the acquisition of hybrid plasmids carrying carbapenem resistance and virulence genes by classical K. pneumoniae (cKp). These strains are characterized by multi-drug resistance, high virulence, and high infectivity. Currently, there are no effective methods for treating and surveillance this pathogen. In addition, the continuous horizontal transfer and clonal spread of these bacteria under the pressure of hospital antibiotics have led to the emergence of more drug-resistant strains. This review discusses the evolution and distribution characteristics of hypervirulent and carbapenem-resistant K. pneumoniae, the mechanisms of carbapenem resistance and hypervirulence, risk factors for susceptibility, infection syndromes, treatment regimens, real-time surveillance and preventive control measures. It also outlines the resistance mechanisms of antimicrobial drugs used to treat this pathogen, providing insights for developing new drugs, combination therapies, and a "One Health" approach. Narrowing the scope of surveillance but intensifying implementation efforts is a viable solution. Monitoring of strains can be focused primarily on hospitals and urban wastewater treatment plants.

Bovine Neutrophil β-Defensin-5 Provides Protection against Multidrug-Resistant Klebsiella pneumoniae via Regulating Pulmonary Inflammatory Response and Metabolic Response

Klebsiella pneumoniae (K. pneumoniae), a kind of zoonotic bacteria, is among the most common antibiotic-resistant pathogens, and it causes nosocomial infections that pose a threat to public health. In this study, the roles of synthetic bovine neutrophil β-defensin-5 (B5) in regulating inflammatory response and metabolic response against multidrug-resistant K. pneumoniae infection in a mouse model were investigated. Mice were administrated intranasally with 20 μg of B5 twice and challenged with K. pneumoniae three days after B5 pretreatment. Results showed that B5 failed to directly kill K. pneumoniae in vitro, but it provided effective protection against multidrug-resistant K. pneumoniae via decreasing the bacterial load in the lungs and spleen, and by alleviating K. pneumoniae-induced histopathological damage in the lungs. Furthermore, B5 significantly enhanced the mRNA expression of TNF-α, IL-1β, Cxcl1, Cxcl5, Ccl17, and Ccl22 and obviously enhanced the rapid recruitment of macrophages and dendritic cells in the lungs in the early infection phase, but significantly down-regulated the levels of TNF-α, IL-1β, and IL-17 in the lungs in the later infection phase. Moreover, RNA-seq results showed that K. pneumoniae infection activated signaling pathways related to natural killer cell-mediated cytotoxicity, IL-17 signaling pathway, inflammatory response, apoptosis, and necroptosis in the lungs, while B5 inhibited these signaling pathways. Additionally, K. pneumoniae challenge led to the suppression of glycerophospholipid metabolism, the phosphotransferase system, the activation of microbial metabolism in diverse environments, and metabolic pathways in the lungs. However, B5 significantly reversed these metabolic responses. Collectively, B5 can effectively regulate the inflammatory response caused by K. pneumoniae and offer protection against K. pneumoniae. B5 may be applied as an adjuvant to the existing antimicrobial therapy to control multidrug-resistant K. pneumoniae infection. Our study highlights the potential of B5 in enhancing pulmonary bacterial clearance and alleviating K. pneumoniae-caused inflammatory damage.

The aryl hydrocarbon receptor and FOS mediate cytotoxicity induced by Acinetobacter baumannii

Acinetobacter baumannii is a pathogenic and multidrug-resistant Gram-negative bacterium that causes severe nosocomial infections. To better understand the mechanism of pathogenesis, we compare the proteomes of uninfected and infected human cells, revealing that transcription factor FOS is the host protein most strongly induced by A. baumannii infection. Pharmacological inhibition of FOS reduces the cytotoxicity of A. baumannii in cell-based models, and similar results are also observed in a mouse infection model. A. baumannii outer membrane vesicles (OMVs) are shown to activate the aryl hydrocarbon receptor (AHR) of host cells by inducing the host enzyme tryptophan-2,3-dioxygenase (TDO), producing the ligand kynurenine, which binds AHR. Following ligand binding, AHR is a direct transcriptional activator of the FOS gene. We propose that A. baumannii infection impacts the host tryptophan metabolism and promotes AHR- and FOS-mediated cytotoxicity of infected cells.

The role of extracellular vesicles in pyroptosis-mediated infectious and non-infectious diseases

Pyroptosis, a lytic and pro-inflammatory cell death, is important in various pathophysiological processes. Host- and bacteria-derived extracellular vesicles (EVs), as natural nanocarriers messengers, are versatile mediators of intercellular communication between different types of cells. Recently, emerging research has suggested that EVs exhibit multifaceted roles in disease progression by manipulating pyroptosis. This review focuses on new findings concerning how EVs shape disease progression in infectious and non-infectious diseases by regulating pyroptosis. Understanding the characteristics and activity of EVs-mediated pyroptotic death may conducive to the discovery of novel mechanisms and more efficient therapeutic targets in infectious and non-infectious diseases.

TrxR1 is involved in the activation of Caspase-11 by regulating the oxidative-reductive status of Trx-1

Sepsis is a common complication of infections that significantly impacts the survival of critically patients. Currently, effective pharmacological treatment strategies are lacking. Auranofin, known as an inhibitor of Thioredoxin reductase (TrxR), exhibits anti-inflammatory activity, but its role in sepsis is not well understood. Here, we demonstrate the significant inhibitory effect of Auranofin on sepsis in a cecal ligation and puncture (CLP) mouse model. In vitro, Auranofin inhibits pyroptosis triggered by Caspase-11 activation. Further investigations reveal that inhibiting TrxR1 suppresses macrophage pyroptosis induced by E. coli, while TrxR2 does not exhibit this effect. TrxR1, functioning as a reductase, regulates the oxidative-reductive status of Thioredoxin-1 (Trx-1). Mechanistically, the modulation of Trx-1's reductive activity by TrxR1 may be involved in Caspase-11 activation-induced pyroptosis. Additionally, inhibiting TrxR1 maintains Trx-1 in its oxidized state. The oxidized form of Trx-1 interacts with Caveolin-1 (CAV1), regulating outer membrane vesicle (OMV) internalization. In summary, our study suggests that inhibiting TrxR1 suppresses OMV internalization by maintaining the oxidized form of Trx-1, thereby restricting Caspase-11 activation and alleviating sepsis.

Cross-talk of MLST and transcriptome unveiling antibiotic resistance mechanism of carbapenem resistance Acinetobacter baumannii clinical strains isolated in Guiyang, China

Introduction

Acinetobacter baumannii (A. baumannii) is an important opportunistic pathogen causing nosocomial infection in the clinic. The occurrence rate of antibiotic resistance is increasing year by year, resulting in a highly serious situation of bacterial resistance.

Methods

To better understand the local epidemiology of multidrug-resistant A. baumannii, an investigation was conducted on the antibiotic resistance of different types of A. baumannii and its relationship with the genes of A. baumannii. Furthermore, the molecular mechanism underlying antibiotic resistance in A. baumannii was investigated through transcriptome analysis.

Results

These results showed that a total of 9 STs were detected. It was found that 99% of the strains isolated in the hospital belonged to the same STs, and the clone complex CC208 was widely distributed in various departments and all kinds of samples. Furthermore, these A. baumannii strains showed high resistance to ertapenem, biapenem, meropenem, and imipenem, among which the resistance to ertapenem was the strongest. The detection rate of bla OXA-51 gene in these carbapenem resistance A. baumannii (CRAB) reached 100%; Additionally, the transcriptome results showed that the resistance genes were up-regulated in resistance strains, and these genes involved in biofilm formation, efflux pumps, peptidoglycan biosynthesis, and chaperonin synthesis.

Discussion

These results suggest that the CC208 STs were the main clonal complex, and showed high carbapenem antibiotic resistance. All these resistant strains were distributed in various departments, but most of them were distributed in intensive care units (ICU). The bla OXA-23 was the main antibiotic resistance genotype; In summary, the epidemic trend of clinical A. baumannii in Guiyang, China was analyzed from the molecular level, and the resistance mechanism of A. baumannii to carbapenem antibiotics was analyzed with transcriptome, which provided a theoretical basis for better control of A. baumannii.

Influences of bacterial extracellular vesicles on macrophage immune functions

Bacterial extracellular vesicles (EVs) are crucial mediators of information transfer between bacteria and host cells. Macrophages, as key effector cells in the innate immune system, have garnered widespread attention for their interactions with bacterial EVs. Increasing evidence indicates that bacterial EVs can be internalized by macrophages through multiple pathways, thereby influencing their immune functions. These functions include inflammatory responses, antimicrobial activity, antigen presentation, and programmed cell death. Therefore, this review summarizes current research on the interactions between bacterial EVs and macrophages. This will aid in the deeper understanding of immune modulation mediated by pathogenic microorganisms and provide a basis for developing novel antibacterial therapeutic strategies.

Recent advances in cell membrane camouflaged nanotherapeutics for the treatment of bacterial infection

Infectious diseases caused by bacterial infections are common in clinical practice. Cell membrane coating nanotechnology represents a pioneering approach for the delivery of therapeutic agents without being cleared by the immune system in the meantime. And the mechanism of infection treatment should be divided into two parts: suppression of pathogenic bacteria and suppression of excessive immune response. The membrane-coated nanoparticles exert anti-bacterial function by neutralizing exotoxins and endotoxins, and some other bacterial proteins. Inflammation, the second procedure of bacterial infection, can also be suppressed through targeting the inflamed site, neutralization of toxins, and the suppression of pro-inflammatory cytokines. And platelet membrane can affect the complement process to suppress inflammation. Membrane-coated nanoparticles treat bacterial infections through the combined action of membranes and nanoparticles, and diagnose by imaging, forming a theranostic system. Several strategies have been discovered to enhance the anti-bacterial/anti-inflammatory capability, such as synthesizing the material through electroporation, pretreating with the corresponding pathogen, membrane hybridization, or incorporating with genetic modification, lipid insertion, and click chemistry. Here we aim to provide a comprehensive overview of the current knowledge regarding the application of membrane-coated nanoparticles in preventing bacterial infections as well as addressing existing uncertainties and misconceptions.

Extracellular Vesicles From Mycoplasma gallisepticum: Modulators of Macrophage Activation and Virulence

Extracellular vesicles (EVs) mediate intercellular communication by transporting proteins. To investigate the pathogenesis of Mycoplasma gallisepticum, a major threat to the poultry industry, we isolated and characterized M. gallisepticum-produced EVs. Our study highlights the significant impact of M. gallisepticum-derived EVs on immune function and macrophage apoptosis, setting them apart from other M. gallisepticum metabolites. These EVs dose-dependently enhance M. gallisepticum adhesion and proliferation, simultaneously modulating Toll-like receptor 2 and interferon γ pathways and thereby inhibiting macrophage activation. A comprehensive protein analysis revealed 117 proteins in M. gallisepticum-derived EVs, including established virulence factors, such as GapA, CrmA, VlhA, and CrmB. Crucially, these EV-associated proteins significantly contribute to M. gallisepticum infection. Our findings advance our comprehension of M. gallisepticum pathogenesis, offering insights for preventive strategies and emphasizing the pivotal role of M. gallisepticum-derived EVs and their associated proteins. This research sheds light on the composition and crucial role of M. gallisepticum-derived EVs in M. gallisepticum pathogenesis, aiding our fight against M. gallisepticum infections.

Use of Transcriptional Signatures to Differentiate Pathogen-Specific and Treatment-Specific Host Responses in Patients With Bacterial Bloodstream Infections

BACKGROUND

Clinical outcomes in bacterial bloodstream infections (BSIs) are influenced by bacterial species, host immunity, and antibiotic therapy. The mechanisms by which such factors influence outcomes are poorly understood. We aimed to identify bacterial- and antibiotic-specific host transcriptional signatures in patients with bacterial BSI.

METHODS

RNA sequencing was performed on blood samples from patients with BSI due to gram-negative (GN) versus gram-positive (GP) pathogens: Escherichia coli (n = 30) or Klebsiella pneumoniae (n = 28) versus methicillin-susceptible Staphylococcus aureus (MSSA) (n = 24) or methicillin-resistant S. aureus (MRSA) (n = 58). Patients were matched by age, sex, and race.

RESULTS

No significant host transcriptome differences were detected in patients with E. coli versus K. pneumoniae BSI, so these were considered together as GN BSI. Relative to S. aureus BSI, patients with GN BSI had increased activation of the classic complement system. However, the most significant signal was a reduction in host transcriptional signatures involving mitochondrial energy transduction and oxidative burst in MRSA versus MSSA. This attenuated host transcriptional signature remained after controlling for antibiotic therapy.

CONCLUSIONS

Given the importance of immune cellular energetics and reactive oxygen species in eliminating hematogenous or intracellular MRSA, these findings may offer insights into its persistence relative to other bacterial BSIs.

β-lactam-induced OMV release promotes polymyxin tolerance in Salmonella enterica sv. Typhi

The rise of multidrug-resistant bacteria is a global concern, leading to a renewed reliance on older antibiotics like polymyxins as a last resort. Polymyxins, cationic cyclic peptides synthesized nonribosomally, feature a hydrophobic acyl tail and positively charged residues. Their antimicrobial mechanism involves initial interaction with Gram-negative bacterial outer-membrane components through polar and hydrophobic interactions. Outer membrane vesicles (OMVs), nano-sized proteoliposomes secreted from the outer membrane of Gram-negative bacteria, play a crucial role in tolerating harmful molecules, including cationic peptides such as polymyxins. Existing literature has documented environmental changes' impact on modulating OMV properties in Salmonella Typhimurium. However, less information exists regarding OMV production and characteristics in Salmonella Typhi. A previous study in our laboratory showed that S. Typhi ΔmrcB, a mutant associated with penicillin-binding protein (PBP, a β-lactam antibiotic target), exhibited hypervesiculation. Consequently, this study investigated the potential impact of β-lactam antibiotics on promoting polymyxin tolerance via OMVs in S. Typhi. Our results demonstrated that sub-lethal doses of β-lactams increased bacterial survival against polymyxin B in S. Typhi. This phenomenon stems from β-lactam antibiotics inducing hypervesiculation of OMVs with higher affinity for polymyxin B, capturing and diminishing its biologically effective concentration. These findings suggest that β-lactam antibiotic use may inadvertently contribute to decreased polymyxin effectivity against S. Typhi or other Gram-negative bacteria, complicating the effective treatment of infections caused by these pathogens. This study emphasizes the importance of evaluating the influence of β-lactam antibiotics on the interaction between OMVs and other antimicrobial agents.

The proteome of bacterial membrane vesicles in Escherichia coli-a time course comparison study in two different media

Introduction

Bacteria inhabit the in- and outside of the human body, such as skin, gut or the oral cavity where they play an innoxious, beneficial or even pathogenic role. It is well known that bacteria can secrete membrane vesicles (MVs) like eukaryotic cells with extracellular vesicles (EVs). Several studies indicate that bacterial membrane vesicles (bMVs) play a crucial role in microbiome-host interactions. However, the composition of such bMVs and their functionality under different culture conditions are still largely unknown.

Methods

To gain a better insight into bMVs, we investigated the composition and functionality of E. coli (DSM 105380) bMVs from the culture media Lysogeny broth (LB) and RPMI 1640 throughout the different phases of growth (lag-, log- and stationary-phase). bMVs from three time points (8 h, 54 h, and 168 h) and two media (LB and RPMI 1640) were isolated by ultracentrifugation and analyzed using nanoparticle tracking analysis (NTA), cryogenic electron microscopy (Cryo-EM), conventional transmission electron microscopy (TEM) and mass spectrometry-based proteomics (LC-MS/MS). Furthermore, we examined pro-inflammatory cytokines IL-1β and IL-8 in the human monocyte cell line THP-1 upon bMV treatment.

Results

Particle numbers increased with inoculation periods. The bMV morphologies in Cryo-EM/TEM were similar at each time point and condition. Using proteomics, we identified 140 proteins, such as the common bMV markers OmpA and GroEL, present in bMVs isolated from both media and at all time points. Additionally, we were able to detect growth-condition-specific proteins. Treatment of THP-1 cells with bMVs of all six groups lead to significantly high IL-1β and IL-8 expressions.

Conclusion

Our study showed that the choice of medium and the duration of culturing significantly influence both E. coli bMV numbers and protein composition. Our TEM/Cryo-EM results demonstrated the presence of intact E. coli bMVs. Common E. coli proteins, including OmpA, GroEL, and ribosome proteins, can consistently be identified across all six tested growth conditions. Furthermore, our functional assays imply that bMVs isolated from the six groups retain their function and result in comparable cytokine induction.

Engineered Bacterial Biomimetic Vesicles Reprogram Tumor-Associated Macrophages and Remodel Tumor Microenvironment to Promote Innate and Adaptive Antitumor Immune Responses

Tumor-associated macrophages (TAMs) are among the most abundant infiltrating leukocytes in the tumor microenvironment (TME). Reprogramming TAMs from protumor M2 to antitumor M1 phenotype is a promising strategy for remodeling the TME and promoting antitumor immunity; however, the development of an efficient strategy remains challenging. Here, a genetically modified bacterial biomimetic vesicle (BBV) with IFN-γ exposed on the surface in a nanoassembling membrane pore structure was constructed. The engineered IFN-γ BBV featured a nanoscale structure of protein and lipid vesicle, the existence of rich pattern-associated molecular patterns (PAMPs), and the costimulation of introduced IFN-γ molecules. In vitro, IFN-γ BBV reprogrammed M2 macrophages to M1, possibly through NF-κB and JAK-STAT signaling pathways, releasing nitric oxide (NO) and inflammatory cytokines IL-1β, IL-6, and TNF-α and increasing the expression of IL-12 and iNOS. In tumor-bearing mice, IFN-γ BBV demonstrated a targeted enrichment in tumors and successfully reprogrammed TAMs into the M1 phenotype; notably, the response of antigen-specific cytotoxic T lymphocyte (CTL) in TME was promoted while the immunosuppressive myeloid-derived suppressor cell (MDSC) was suppressed. The tumor growth was found to be significantly inhibited in both a TC-1 tumor and a CT26 tumor. It was indicated that the antitumor effects of IFN-γ BBV were macrophage-dependent. Further, the modulation of TME by IFN-γ BBV produced synergistic effects against tumor growth and metastasis with an immune checkpoint inhibitor in an orthotopic 4T1 breast cancer model which was insensitive to anti-PD-1 mAb alone. In conclusion, IFN-γ-modified BBV demonstrated a strong capability of efficiently targeting tumor and tuning a cold tumor hot through reprogramming TAMs, providing a potent approach for tumor immunotherapy.

Proteomic analysis of meropenem-induced outer membrane vesicles released by carbapenem-resistant Klebsiella pneumoniae

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is an important multidrug resistance (MDR) pathogen that threatens human health and is the main source of hospital-acquired infection. Outer membrane vesicles (OMVs) are extracellular vesicles derived from Gram-negative bacteria and contain materials involved in bacterial survival and pathogenesis. They also contribute to cellular communication to nearby or distant recipient cells and influence their functions and phenotypes. In this study, we sought to understand the mechanism of bacterial response to meropenem pressure and explore the relationship between pathogenic proteins and the high pathogenicity of bacteria. We performed whole-genome PacBio sequencing on a clinical CRKP strain, and its OMVs were characterized using nanoparticle tracking analysis, transmission electron microscopy, and proteomic analysis. Thousands of vesicle proteins have been identified in mass spectrometry-based high-throughput proteomics analyses of K. pneumoniae OMVs. Protein functionality analysis showed that the OMVs were predominantly involved in metabolic, intracellular compartments, nucleic acid binding, survival, defense, and antibiotic resistance, such as Chromosome partition protein MukB, 3-methyl-2-oxobutanoate hydroxymethyltransferase, methionine-tRNA ligase, Heat shock protein 60 family chaperone GroEL, and Gamma-glutamyl phosphate reductase. Additionally, a protein-protein interaction network demonstrated that OMVs from meropenem-treated K. pneumoniae showed the highest connectivity in DNA polymerase I, phenylalanine-tRNA ligase beta subunit, DNA-directed RNA polymerase subunit beta, methionine-tRNA ligase, DNA-directed RNA polymerase subunit beta, and DNA-directed RNA polymerase subunit alpha. The OMVs proteome expression profile indicates increased secretion of stress proteins released from meropenem-treated K. pneumoniae, which provides clues for revealing the biogenesis and pathophysiological functions of Gram-negative bacteria OMVs. The significant differentially expressed proteins identified in this study are of great significance for exploring effective control strategies for CRKP infection.IMPORTANCEMeropenem is one of the main antibiotics used in the clinical treatment of carbapenem-resistant Klebsiella pneumoniae (CRKP). This study demonstrated that some important metabolic changes occurred in meropenem-induced CRKP-outer membrane vesicles (OMVs), The OMVs proteome expression profile indicates increased secretion of stress proteins released from meropenem-induced Klebsiella pneumoniae. Furthermore, this is the first study to discuss the protein-protein interaction network of the OMVs released by CRKP, especially under antibiotic stress.

BACTERIAL EXTRACELLULAR VESICLES IN THE REGULATION OF INFLAMMATORY RESPONSE AND HOST-MICROBE INTERACTIONS

ABSTRACT

Extracellular vesicles (EVs) are a new revelation in cross-kingdom communication, with increasing evidence showing the diverse roles of bacterial EVs (BEVs) in mammalian cells and host-microbe interactions. Bacterial EVs include outer membrane vesicles released by gram-negative bacteria and membrane vesicles generated from gram-positive bacteria. Recently, BEVs have drawn attention for their potential as biomarkers and therapeutic tools because they are nano-sized and can deliver bacterial cargo into host cells. Importantly, exposure to BEVs significantly affects various physiological and pathological responses in mammalian cells. Herein, we provide a comprehensive overview of the various effects of BEVs on host cells (i.e., immune cells, endothelial cells, and epithelial cells) and inflammatory/infectious diseases. First, the biogenesis and purification methods of BEVs are summarized. Next, the mechanisms and pathways identified by BEVs that stimulate either proinflammatory or anti-inflammatory responses are highlighted. In addition, we discuss the mechanisms by which BEVs regulate host-microbe interactions and their effects on the immune system. Finally, this review focuses on the contribution of BEVs to the pathogenesis of sepsis/septic shock and their therapeutic potential for the treatment of sepsis.

Bacterial extracellular vesicles: an emerging avenue to tackle diseases

A growing body of research, especially in recent years, has shown that bacterial extracellular vesicles (bEVs) are one of the key underlying mechanisms behind the pathogenesis of various diseases like pulmonary fibrosis, sepsis, systemic bone loss, and Alzheimer's disease. Given these new insights, bEVs are proposed as an emerging vehicle that can be used as a diagnostic tool or to tackle diseases when used as a therapeutic target. To further boost the understanding of bEVs in health and disease we thoroughly discuss the contribution of bEVs in disease pathogenesis and the underlying mechanisms. In addition, we speculate on their potential as novel diagnostic biomarkers and how bEV-related mechanisms can be exploited as therapeutic targets.

"Superbugs" with hypervirulence and carbapenem resistance in Klebsiella pneumoniae: the rise of such emerging nosocomial pathogens in China

Although hypervirulent Klebsiella pneumoniae (hvKP) can produce community-acquired infections that are fatal in young and adult hosts, such as pyogenic liver abscess, endophthalmitis, and meningitis, it has historically been susceptible to antibiotics. Carbapenem-resistant K. pneumoniae (CRKP) is usually associated with urinary tract infections acquired in hospitals, pneumonia, septicemias, and soft tissue infections. Outbreaks and quick spread of CRKP in hospitals have become a major challenge in public health due to the lack of effective antibacterial treatments. In the early stages of K. pneumoniae development, HvKP and CRKP first appear as distinct routes. However, the lines dividing the two pathotypes are vanishing currently, and the advent of carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP) is devastating as it is simultaneously multidrug-resistant, hypervirulent, and highly transmissible. Most CR-hvKP cases have been reported in Asian clinical settings, particularly in China. Typically, CR-hvKP develops when hvKP or CRKP acquires plasmids that carry either the carbapenem-resistance gene or the virulence gene. Alternatively, classic K. pneumoniae (cKP) may acquire a hybrid plasmid carrying both genes. In this review, we provide an overview of the key antimicrobial resistance mechanisms, virulence factors, clinical presentations, and outcomes associated with CR-hvKP infection. Additionally, we discuss the possible evolutionary processes and prevalence of CR-hvKP in China. Given the wide occurrence of CR-hvKP, continued surveillance and control measures of such organisms should be assigned a higher priority.

The tale of antibiotics beyond antimicrobials: Expanding horizons

Antibiotics had proved to be a godsend for mankind since their discovery. They were once the magical solution to the vexing problem of infection-related deaths. German scientist Paul Ehrlich had termed salvarsan as the silver bullet to treatsyphilis.As time passed, the magic of newly discovered silver bullets got tarnished with raging antibiotic resistance among bacteria and associated side-effects. Still, antibiotics remain the primary line of treatment for bacterial infections. Our understanding of their chemical and biological activities has increased immensely with advancement in the research field. Non-antibacterial effects of antibiotics are studied extensively to optimise their safer, broad-range use. These non-antibacterial effects could be both useful and harmful to us. Various researchers across the globe including our lab are studying the direct/indirect effects and molecular mechanisms behind these non-antibacterial effects of antibiotics. So, it is interesting for us to sum up the available literature. In this review, we have briefed the possible reason behind the non-antibacterial effects of antibiotics, owing to the endosymbiotic origin of host mitochondria. We further discuss the physiological and immunomodulatory effects of antibiotics. We then extend the review to discuss molecular mechanisms behind the plausible use of antibiotics as anticancer agents.

Correlation between bacterial extracellular vesicles and antibiotics: A potentially antibacterial strategy

Bacterial extracellular vesicles (BEVs) are proteoliposome nanoparticles that are secreted by both Gram-negative (G^-) and Gram-positive (G⁺) bacteria. BEVs have significant roles in various physiological processes of bacteria, including driving inflammatory responses, regulating bacterial pathogenesis, and promoting bacterial survival in diverse environments. Recently, there has been increasing interest in the use of BEVs as a potential solution to antibiotic resistance. BEVs have shown great promise as a new approach to antibiotics, as well as a drug-delivery tool in antimicrobial strategies. In this review, we provide a summary of recent scientific advances in BEVs and antibiotics, including BEV biogenesis, ability to kill bacteria, potential for delivering antibiotics, and their role in the development of vaccines or as immune adjuvants. We propose that BEVs provide a novel antimicrobial strategy that would be beneficial against the increasing threat of antibiotic resistance.

Bacterial extracellular vesicles and their interplay with the immune system

The mammalian intestinal tract harbors trillions of microorganisms confined within this space by mucosal barriers. Despite these barriers, bacterial components may still be found elsewhere in the body, even in healthy subjects. Bacteria can release small lipid-bound particles, also named bacterial extracellular vesicles (bEV). While bacteria themselves cannot normally penetrate the mucosal defense, bEVs may infiltrate the barrier and disseminate throughout the body. The extremely diverse cargo that bEVs can carry, depending on their parent species, strain, and growth conditions, grant them an equally broad potential to interact with host cells and influence immune functions. Herein, we review the current knowledge of processes underlying the uptake of bEVs by mammalian cells, and their effect on the immune system. Furthermore, we discuss how bEVs could be targeted and manipulated for diverse therapeutic purposes.

Outer Membrane Vesicles Transmitting blaNDM-1 Mediate the Emergence of Carbapenem-Resistant Hypervirulent Klebsiella pneumoniae

Dissemination of hypervirulent and carbapenem-resistant Klebsiella pneumoniae (CRKP) has been reported worldwide, posing a serious threat to antimicrobial therapy and public health. Outer membrane vesicles (OMVs) act as vectors for the horizontal transfer of virulence and resistance genes. However, K. pneumoniae OMVs that transfer carbapenem resistance genes into hypervirulent K. pneumoniae (hvKP) have been insufficiently investigated. Therefore, this study investigates the transmission of the bla_NDM-1 gene encoding resistance via OMVs released from CRKP and the potential mechanism responsible for the carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP) emergence. OMVs were isolated via ultracentrifugation from CRKP with or without meropenem selective pressure. OMVs were then used to transform classical K. pneumoniae (ckp) ATCC 10031, extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae ATCC 700603, and hvKP NTUH-K2044. Our results showed that meropenem treatment resulted in changes in the number and diameter of OMVs secreted by CRKP. OMVs derived from CRKP mediated the transfer of bla_NDM-1 to ckp and hvKP, thereby increasing the carbapenem MIC of transformants. Further experiments confirmed that NTUH-K2044 transformants exhibited hypervirulence. Our study demonstrates, for the first time, that OMVs derived from CRKP can carry bla_NDM-1 and deliver resistance genes to other K. pneumoniae strains, even hvKP. The transfer of carbapenem genes into hypervirulent strains may promote the emergence and dissemination of CR-hvKP. This study elucidates a new mechanism underlying the formation of CR-hvKP.

Carbapenemase-loaded outer membrane vesicles protect Pseudomonas aeruginosa by degrading imipenem and promoting mutation of antimicrobial resistance gene

AIMS

To investigate the effect of Klebsiella pneumoniae carbapenemase (KPC)-loaded outer membrane vesicles (OMVs) in protecting Pseudomonas aeruginosa against imipenem treatment and its mechanism.

METHODS

The OMVs of carbapenem-resistant Klebsiella pneumonia (CRKP) were isolated and purified from the supernatant of bacterial culture by using ultracentrifugation and Optiprep density gradient ultracentrifugation. The transmission electron microscope, bicinchoninic acid, PCR and carbapenemase colloidal gold assays were applied to characterize the OMVs. Bacterial growth and larvae infection experiments were performed to explore the protective function of KPC-loaded OMVs for P. aeruginosa under imipenem treatment. Ultra-performance liquid chromatography, antimicrobial susceptibility testing, whole-genome sequencing and bioinformatics analysis were used to investigate the mechanism of P. aeruginosa resistance phenotype mediated by OMVs.

RESULTS

CRKP secreted OMVs loaded with KPC, which protect P. aeruginosa from imipenem through hydrolysis of antibiotics in a dose- and time-dependent manner. Furthermore, carbapenem-resistant subpopulations were developed in P. aeruginosa by low concentrations of OMVs that were confirmed to inadequately hydrolyze imipenem. Interestingly, none of the carbapenem-resistant subpopulations obtained the exogenous antibiotic resistance genes, but all of them possessed OprD mutations, which was consistent with the mechanism of P. aeruginosa induced by sub-minimal inhibitory concentrations of imipenem.

CONCLUSIONS

OMVs containing KPC provide a novel route for P. aeruginosa to acquire an antibiotic-resistant phenotype in vivo.

Keeping alert to the hypervirulent K1, K2, K3, K5, K54 and K57 strains of Klebsiella pneumoniae within dairy production process

Klebsiella pneumoniae (Kp) is now recognized as an urgent threat to public health since the emergence of multidrug-resistant and hypervirulent isolates. We identified a hypervirulent K2 isolate from the milk samples possibly associated with an infection incident in children, which raised the alarm to the zoonotic potential of bovine mastitis Kp as a foodborne pathogen. Subsequently, numerous K1, K2, K3, K5, K54 and K57 strains were identified from mastitis milk samples, and showed high pathogenicity in infected mouse. Further analysis based on complete genomes found that these isolates showed closely evolutionary relationships with the human hypervirulent strains in diverse phylogenetic lineages, suggesting their potential risk to public health.

Characteristics of antibiotic resistance mechanisms and genes of Klebsiella pneumoniae

Klebsiella pneumoniae is an important multidrug-resistant (MDR) pathogen that can cause a range of infections in hospitalized patients. With the growing use of antibiotics, MDR K. pneumoniae is more prevalent, posing additional difficulties and obstacles in clinical therapy. To provide a valuable reference to deeply understand K. pneumoniae, and also to provide the theoretical basis for clinical prevention of such bacteria infections, the antibiotic resistance and mechanism of K. pneumoniae are discussed in this article. We conducted a literature review on antibiotic resistance of K. pneumoniae. We ran a thorough literature search of PubMed, Web of Science, and Scopus, among other databases. We also thoroughly searched the literature listed in the papers. We searched all antibiotic resistance mechanisms and genes of seven important antibiotics used to treat K. pneumoniae infections. Antibiotics such as β-lactams, aminoglycosides, and quinolones are used in the treatment of K. pneumoniae infection. With both chromosomal and plasmid-encoded ARGs, this pathogen has diverse resistance genes. Carbapenem resistance genes, enlarged-spectrum β-lactamase genes, and AmpC genes are the most often β-lactamase resistance genes. K. pneumoniae is a major contributor to antibiotic resistance worldwide. Understanding K. pneumoniae antibiotic resistance mechanisms and molecular characteristics will be important for the design of targeted prevention and novel control strategies against this pathogen.

Effects of Klebsiella pneumoniae Bacteriophages on IRAK3 Knockdown/Knockout THP-1 Monocyte Cell Lines

Bacterial sepsis characterised by an immunosuppressive and cytokine storm state is a challenge to treat clinically. While conventional antibiotics have been associated with exacerbating the cytokine storm, the role that bacteriophages may play in immune modulation of sepsis remains unclear. Bacteriophages are bacterial viruses that have the capacity to lyse specific bacteria and hence provide a natural alternative to antibiotics. K. pneumoniae is known to cause sepsis in humans, and in this study we isolated two lytic bacteriophages against this pathogen, one of which was a novel jumbo bacteriophage. We employed THP-1 monocyte cell lines, with different functional phenotypes for the interleukin-1 receptor associated kinase 3 (IRAK3- a cytoplasmic homeostatic mediator and prognostic marker of inflammation), to evaluate the role of the K. pneumoniae bacteriophages in modulating the immune response in-vitro. We showed for the first time that bacteriophages did not stimulate excessive production of tumour necrosis factor alpha, or interleukin-6, in THP-1 monocyte cell lines which displayed varying levels of IRAK3 expression.

Antibiotics for the Secondary Prevention of Coronary Heart Disease

It is estimated that 200 million people are living with coronary heart disease, which remains one of the leading causes of mortality and morbidity worldwide. Those living with coronary heart disease are at an increased risk of cardiovascular events such as stroke, myocardial infarction, and cardiovascular death. Pathophysiology of coronary heart disease revolves around inflammation which leads to plaque build-up. Antibiotics are known to hold anti-inflammatory and anti-oxidative properties. It is theorized that reductions in inflammation could prevent cardiovascular events which may reduce suffering, risk of death and hospital admission rates in patients with coronary heart disease. This article critically appraises a systematic review that assessed the risk of antibiotics used as secondary prevention for coronary heart disease.

Proteomic Network of Antibiotic-Induced Outer Membrane Vesicles Released by Extensively Drug-Resistant Elizabethkingia anophelis

Elizabethkingia anophelis, a nonfermenting Gram-negative bacterium, causes life-threatening health care-associated infections. E. anophelis harbors multidrug resistance (MDR) genes and is intrinsically resistant to various classes of antibiotics. Outer membrane vesicles (OMVs) are secreted by Gram-negative bacteria and contain materials involved in bacterial survival and pathogenesis. OMVs specialize and tailor their functions by carrying different components to challenging environments and allowing communication with other microorganisms or hosts. In this study, we sought to understand the characteristics of E. anophelis OMVs under different antibiotic stress conditions. An extensively drug-resistant clinical isolate, E. anophelis C08, was exposed to multiple antibiotics in vitro, and its OMVs were characterized using nanoparticle tracking analysis, transmission electron microscopy, and proteomic analysis. Protein functionality analysis showed that the OMVs were predominantly involved in metabolism, survival, defense, and antibiotic resistance processes, such as the Rag/Sus family, the chaperonin GroEL, prenyltransferase, and an HmuY family protein. Additionally, a protein-protein interaction network demonstrated that OMVs from imipenem-treated E. anophelis showed significant enrichments in the outer membrane, adenyl nucleotide binding, serine-type peptidase activity, the glycosyl compound metabolic process, and cation binding proteins. Collectively, the OMV proteome expression profile indicates that the role of OMVs is immunologically relevant and related to bacterial survival in antibiotic stress environments rather than representing a resistance point. IMPORTANCE Elizabethkingia anophelis is a bacterium often associated with nosocomial infection. This study demonstrated that imipenem-induced E. anophelis outer membrane vesicles (OMVs) are immunologically relevant and crucial for bacterial survival under antibiotic stress conditions rather than being a source of antibiotic resistance. Furthermore, this is the first study to discuss the protein-protein interaction network of the OMVs released by E. anophelis, especially under antibiotic stress. Our findings provide important insights into clinical antibiotic stewardship.

Novel insights in antimicrobial and immunomodulatory mechanisms of action of PepBiotics CR-163 and CR-172

OBJECTIVES

Recently our group developed a novel group of antimicrobial peptides termed PepBiotics, of which peptides CR-163 and CR-172 showed optimized antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus without inducing antimicrobial resistance. In this study, the antibacterial mechanism of action and the immunomodulatory activity of these two PepBiotics was explored.

METHODS

RAW264.7 cells were used to determine the ability of PepBiotics to neutralize LPS-and LTA-induced activation of macrophages. Isothermal titration calorimetry and competition assays with dansyl-labeled polymyxin B determined binding characteristics to LPS and LTA. Combined bacterial killing with subsequent macrophage activation assays was performed to determine so-called silent killing'. Finally, flow cytometry of peptide-treated genetically engineered E. coli,expressing GFP and mCherry in the cytoplasm and periplasm, respectively further established the antimicrobial mechanism of PepBiotics.

RESULTS

Both CR-163 and CR-172 were shown to have broad-spectrum activity against ESKAPE pathogens and E. coli, using a membranolytic mechanism of action. PepBiotics could exothermically bind LPS/LTA and were able to replace polymyxin B. Finally, it was demonstrated that bacteria killed by PepBiotics were less prone to stimulate immune cells, contrary to gentamicin and heat-killed bacteria that still elicited a strong immune response CONCLUSIONS: These studies highlight the multifunctional nature of the two peptide antibiotics as both broad spectrum antimicrobial and immunomodulator. Their ability to kill bacteria and reduce unwanted subsequent immune activation is a major advantage and highlights their potential for future therapeutic use.

Engineered bacterial membrane vesicles are promising carriers for vaccine design and tumor immunotherapy

Bacterial membrane vesicles (BMVs) have emerged as novel and promising platforms for the development of vaccines and immunotherapeutic strategies against infectious and noninfectious diseases. The rich microbe-associated molecular patterns (MAMPs) and nanoscale membrane vesicle structure of BMVs make them highly immunogenic. In addition, BMVs can be endowed with more functions via genetic and chemical modifications. This article reviews the immunological characteristics and effects of BMVs, techniques for BMV production and modification, and the applications of BMVs as vaccines or vaccine carriers. In summary, given their versatile characteristics and immunomodulatory properties, BMVs can be used for clinical vaccine or immunotherapy applications.

The Role of Bacterial Membrane Vesicles in Human Health and Disease

Bacterial membrane vesicles (MVs) are nanoparticles derived from the membrane components of bacteria that transport microbial derived substances. MVs are ubiquitous across a variety of terrestrial and marine environments and vary widely in their composition and function. Membrane vesicle functional diversity is staggering: MVs facilitate intercellular communication by delivering quorum signals, genetic information, and small molecules active against a variety of receptors. MVs can deliver destructive virulence factors, alter the composition of the microbiota, take part in the formation of biofilms, assist in the uptake of nutrients, and serve as a chemical waste removal system for bacteria. MVs also facilitate host-microbe interactions including communication. Released in mass, MVs overwhelm the host immune system and injure host tissues; however, there is also evidence that vesicles may take part in processes which promote host health. This review will examine the ascribed functions of MVs within the context of human health and disease.

Is the Success of Cefazolin plus Ertapenem in Methicillin-Susceptible Staphylococcus aureus Bacteremia Based on Release of Interleukin 1-beta?

Cefazolin and ertapenem has been shown to be an effective salvage regimen for refractory methicillin-susceptible Staphylococcus aureus bacteremia. Our findings suggest cefazolin plus ertapenem in vitro stimulates interleukin-1β release from peripheral blood monocytes both with and without S. aureus presence. This IL-1β augmentation was primarily driven by ertapenem. These findings support further exploration of cefazolin plus ertapenem in MSSA bacteremia and may partially explain its marked potency in vivo despite modest synergy in vitro .