Outer Membrane Vesicles Derived from Klebsiella pneumoniae Influence the miRNA Expression Profile in Human Bronchial Epithelial BEAS-2B Cells

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.

Exploring bacterial extracellular vesicles: Focus on WHO critical priority pathogens

Bacterial extracellular vesicles (EVs) are cell-derived particles with a phospholipidic bilayer structure and diameter ranging from 20 to 250 nm, comprising a varied of components, including bioactive proteins, lipids, DNA, RNA, and other metabolites. These EVs play an essential role in bacterial and host function and are recognized as essential keys in cell-to-cell communication and pathogenesis. Due to these characteristics and functions, EVs exhibit great potential for biomedical applications and are promising tools for the development of drug delivery systems and vaccines, as well as for use in disease diagnostics. An interesting focus of this review is on the clinical relevance of EVs, with a particular emphasis on two critical pathogens, Acinetobacter baumannii and Klebsiella pneumoniae. Insights into the outer membrane vesicles (OMVs) derived from these bacteria underscore their roles in antimicrobial resistance and pathogenicity. Additionally, the review explores OMV-based vaccine strategies as a promising means to mitigating these pathogens.

Efficient Isolation of Outer Membrane Vesicles (OMVs) Secreted by Gram-Negative Bacteria via a Novel Gradient Filtration Method

Bacterial extracellular vesicles (bEVs) secreted by Gram-negative bacteria are referred to as outer membrane vesicles (OMVs) because they originate in the outer membrane. OMVs are membrane-coated vesicles 20-250 nm in size. They contain lipopolysaccharide (LPS), peptidoglycan, proteins, lipids, nucleic acids, and other substances derived from their parent bacteria and participate in the transmission of information to host cells. OMVs have broad prospects in terms of potential application in the fields of adjuvants, vaccines, and drug delivery vehicles. Currently, there remains a lack of efficient and convenient methods to isolate OMVs, which greatly limits OMV-related research. In this study, we developed a fast, convenient, and low-cost gradient filtration method to separate OMVs that can achieve industrial-scale production while maintaining the biological activity of the isolated OMVs. We compared the gradient filtration method with traditional ultracentrifugation to isolate OMVs from probiotic Escherichia coli Nissle 1917 (EcN) bacteria. Then, we used RAW264.7 macrophages as an in vitro model to study the influence on the immune function of EcN-derived OMVs obtained through the gradient filtration method. Our results indicated that EcN-derived OMVs were efficiently isolated using our gradient filtration method. The level of OMV enrichment obtained via our gradient filtration method was about twice as efficient as that achieved through traditional ultracentrifugation. The EcN-derived OMVs enriched through the gradient filtration method were successfully taken up by RAW264.7 macrophages and induced them to secrete pro-inflammatory cytokines such as tumor necrosis factor α (TNF-α) and interleukins (ILs) 6 and 1β, as well as anti-inflammatory cytokine IL-10. Furthermore, EcN-derived OMVs induced more anti-inflammatory response (i.e., IL-10) than pro-inflammatory response (i.e., TNF-α, IL-6, and IL-1β). These results were consistent with those reported in the literature. The related literature reported that EcN-derived OMVs obtained through ultracentrifugation could induce stronger anti-inflammatory responses than pro-inflammatory responses in RAW264.7 macrophages. Our simple and novel separation method may therefore have promising prospects in terms of applications involving the study of OMVs.

Klebsiella pneumoniae-OMVs activate death-signaling pathways in Human Bronchial Epithelial Host Cells (BEAS-2B)

The programmed cell death pathways of apoptosis are important in mammalian cellular protection from infections. The activation of these pathways depends on the presence of membrane receptors that bind bacterial components to activate the transduction mechanism. In addition to bacteria, these mechanisms can be activated by outer membrane vesicles (OMVs). OMVs are spherical vesicles of 20-250 nm diameter, constitutively released by Gram-negative bacteria. They contain several bacterial determinants including proteins, DNA/RNA and proteins, that activate different cellular processes in host cells. This study focused on Klebsiella pneumoniae-OMVs in activating death mechanisms in human bronchial epithelial cells (BEAS-2B). Characterization of purified OMVs was achieved by scanning electron microscopy, nanoparticle tracking analysis and protein profiling. Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay while apoptotic induction was measured by flow cytometry and confirmed by western blotting. The OMVs produced showed a spherical morphology, with a diameter of 137.2 ± 41 nm and a vesicular density of 7.8 × 109 particles/mL Exposure of cell monolayers to 50 μg of K. pneumoniae-OMV for 14 h resulted in approximately 25 % cytotoxicity and 41.15-41.14 % of cells undergoing early and late apoptosis. Fluorescence microscopy revealed reduced cellular density, the presence of apoptotic bodies, chromatin condensation, and nuclear membrane blebbing in residual cells. Activation of caspases -3 and -9 and dysregulation of BAX, BIM and Bcl-xL indicated the activation of mitochondria-dependent apoptosis. Furthermore, a decrease in the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase involved endoplasmic reticulum stress with the potential formation of reactive oxygen species. These findings provide evidence for the role of OMVs in apoptosis and involvement in the pathogenesis of K. pneumoniae infections.

rs822336 binding to C/EBPβ and NFIC modulates induction of PD-L1 expression and predicts anti-PD-1/PD-L1 therapy in advanced NSCLC

Efficient predictive biomarkers are needed for immune checkpoint inhibitor (ICI)-based immunotherapy in non-small cell lung cancer (NSCLC). Testing the predictive value of single nucleotide polymorphisms (SNPs) in programmed cell death 1 (PD-1) or its ligand 1 (PD-L1) has shown contrasting results. Here, we aim to validate the predictive value of PD-L1 SNPs in advanced NSCLC patients treated with ICIs as well as to define the molecular mechanisms underlying the role of the identified SNP candidate. rs822336 efficiently predicted response to anti-PD-1/PD-L1 immunotherapy in advanced non-oncogene addicted NSCLC patients as compared to rs2282055 and rs4143815. rs822336 mapped to the promoter/enhancer region of PD-L1, differentially affecting the induction of PD-L1 expression in human NSCLC cell lines as well as their susceptibility to HLA class I antigen matched PBMCs incubated with anti-PD-1 monoclonal antibody nivolumab. The induction of PD-L1 expression by rs822336 was mediated by a competitive allele-specificity binding of two identified transcription factors: C/EBPβ and NFIC. As a result, silencing of C/EBPβ and NFIC differentially regulated the induction of PD-L1 expression in human NSCLC cell lines carrying different rs822336 genotypes. Analysis by binding microarray further validated the competitive allele-specificity binding of C/EBPβ and NFIC to PD-L1 promoter/enhancer region based on rs822336 genotype in human NSCLC cell lines. These findings have high clinical relevance since identify rs822336 and induction of PD-L1 expression as novel biomarkers for predicting anti-PD-1/PD-L1-based immunotherapy in advanced NSCLC patients.

Normospermic Patients Infected With Ureaplasma parvum: Role of Dysregulated miR-122-5p, miR-34c-5, and miR-141-3p

Background

Ureaplasma parvum (UP) is a causative agent of non-gonococcal urethritis, involved in the pathogenesis of prostatitis and epididymitis, and it could impair human fertility. Although UP infection is a frequent cause of male infertility the study evidence assessing their prevalence and the association in patients with infertility is still scarce. The molecular processes leading to defects in spermatozoa quality are not completely investigated. MicroRNAs (miRNAs) have been extensively reported as gene regulatory molecules on post-transcriptional levels involved in various biological processes such as gametogenesis, embryogenesis, and the quality of sperm, oocyte, and embryos.

Methods

Therefore, the study design was to demonstrate that miRNAs in body fluids like sperm could be utilized as non-invasive diagnostic biomarkers for pathological and physiological conditions such as infertility. A post-hoc bioinformatics analysis was carried out to predict the pathways modulated by the miRNAs dysregulated in the differently motile spermatozoa.

Results

Here it is shown that normospermic patients infected by UP had spermatozoa with increased quantity of superoxide anions, reduced expression of miR-122-5p, miR-34c-5, and increased miR-141-3p compared with non-infected normospermic patients. This corresponded to a reduction of sperm motility in normospermic infected patients compared with normospermic non-infected ones. A target gene prediction presumed that an essential role of these miRNAs resided in the regulation of lipid kinase activity, accounting for the changes in the constitution of spermatozoa membrane lipids caused by UP.

Conclusions

Altogether, the data underline the influence of UP on epigenetic mechanisms regulating spermatozoa motility.

Antibacterial and antibiofilm effects of Pseudomonas aeruginosa derived outer membrane vesicles against Streptococcus mutans

Antimicrobial resistance (AMR) is a serious and most urgent global threat to human health. AMR is one of today's biggest difficulties in the health system and has the potential to harm people at any stage of life, making it a severe public health issue. There must be fewer antimicrobial medicines available to treat diseases given the rise in antibiotic-resistant organisms. If no new drugs are created or discovered, it is predicted that there won't be any effective antibiotics accessible by 2050. In most cases, Streptococcus increased antibiotic resistance by forming biofilms, which account for around 80 % of all microbial infections in humans. This highlights the need to look for new strategies to manage diseases that are resistant to antibiotics. Therefore, development alternative, biocompatible and high efficacy new strategies are essential to overcome drug resistance. Recently, bacterial derived extracellular vesicles have been applied to tackle infection and reduce the emergence of drug resistance. Therefore, the objective of the current study was designed to assess the antibacterial and antibiofilm potential of outer membrane vesicles (OMVs) derived from Pseudomonas aeruginosa againstStreptococcus mutans. According to the findings of this investigation, the pure P. aeruginosa outer membrane vesicles (PAOMVs) display a size of 100 nm. S. mutans treated with PAOMVs showed significant antibacterial and antibiofilm activity. The mechanistic studies revealed that PAOMVs induce cell death through excessive generation of reactive oxygen species and imbalance of redox leads to lipid peroxidation, decreased level of antioxidant markers including glutathione, superoxide dismutase and catalase. Further this study confirmed that PAOMVs significantly impairs metabolic activity through inhibiting lactate dehydrogenase activity (LDH), adenosine triphosphate (ATP) production, leakage of proteins and sugars. Interestingly, combination of sub-lethal concentrations of PAOMVs and antibiotics enhances cell death and biofilm formation of S. mutans. Altogether, this work, may serve as an important basis for further evaluation of PAOMVs as novel therapeutic agents against bacterial infections.

Extracellular nanovesicles produced by Bacillus licheniformis: A potential anticancer agent for breast and lung cancer

Cancer is a major public burden and leading cause of death worldwide; furthermore, it is a significant barrier to increasing life expectancy in most countries of the world. Among various types of cancers, breast and lung cancers lead to significant mortality in both males and females annually. Bacteria-derived products have been explored for their use in cancer therapy. Although bacteria contain significant amounts of anticancer substances, attenuated bacteria may still pose a potential risk for infection owing to the variety of immunomodulatory molecules present in the parental bacteria; therefore, non-cellular bacterial extracellular vesicles (BEVs), which are naturally non-replicating, safer, and are considered to be potential anticancer agents, are preferred for cancer therapy. Gram-positive bacteria actively secrete cytoplasmic membrane vesicles that are spherical and vary between 10 and 400 nm in size. However, no studies have considered cytoplasmic membrane vesicles derived from Bacillus licheniformisin cancer treatment. In this study, we investigated the potential use of B. licheniformis extracellular nanovesicles (BENVs) as therapeutic agents to treat cancer. Purified BENVs from the culture supernatant of B. licheniformis using ultracentrifugation and ExoQuick were characterized using a series of analytical techniques. Human breast cancer cells (MDA-MB-231) and lung cancer cells (A549) were treated with different concentrations of purified BENVs, which inhibited the cell viability and proliferation, and increased cytotoxicity in a dose-dependent manner. To elucidate the mechanism underlying the anticancer activity of BENVs, the oxidative stress markers such as reactive oxygen species (ROS) and glutathione (GSH) levels were measured. The ROS levels were significantly higher in BENV-treated cells, whereas the GSH levels were markedly reduced. Cells treated with BENVs, doxorubicin (DOX), or a combination of BENVs and DOX showed significantly increased expression of p53, p21, caspase-9/3, and Bax, and concomitantly decreased expression of Bcl-2. The combination of BENVs and doxorubicin enhanced mitochondrial dysfunction, DNA damage, and apoptosis. To our knowledge, this is the first study to determine the anticancer properties of BENVs derived from industrially significant probacteria on breast and lung cancer cells.

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.

Isolation and protein MdtQ analysis of outer membrane vesicles released by carbapenem-resistant Klebsiella pneumoniae

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged as a leading public health problem, and is increasingly being reported worldwide with resistance to a wide spectrum of antibiotics. Recent reports have demonstrated that the outer membrane vesicles (OMVs) of gram-negative bacteria are potent resistance factors, but their role in the drug resistance of CRKP has not been elucidated. In order to investigate the effects of OMV components on drug resistance and to explore the mechanism of antimicrobial resistance in CRKP, we isolated the OMVs through ultracentrifugation, separated the OMV proteins through mass spectrometry (MS), and performed bioinformatics analysis. A total of 3,192 proteins were detected by nano LC-MS/MS analysis, with 108 (61.4%) cytoplasmic proteins, 50 (28.4%) cytoplasmic membrane proteins, nine (5.1%) periplasmic proteins, six (3.4%) outer membrane proteins, two (1.1%) extracellular proteins, and one (0.6%) other protein detected in the vesicles. MdtQ was detected as the only multidrug resistance outer membrane protein. Further experiments confirmed that MdtQ included the 1440 BP sequence and had a unique three-dimensional structure. To superimpose MdtQ with KPC-2 resistant proteins, I7ACB1, I7AKP2, and Q93LQ9, the root mean square deviation (RMSD) values were calculated (0.379, 0.671, and 1.35, respectively). I7ACB1 had the lowest RMSD value, indicating that it had the best superimposition effect. Furthermore, MdtQ had 20 biological pocket structures, and the four most important pockets were evenly distributed around the inner perimeter of its three-dimensional structure. These findings may provide a theoretical basis for controlling the spread of bacterial resistance in the future.

K. pneumoniae and M. smegmatis infect epithelial cells via different strategies

Background

As the first line of defense, epithelial cells play a vital role in the initiation and control of both innate and adaptive immunity, which participate in the development of disease. Despite its therapeutic significance, little is understood about the specific interaction between pathogenic microorganisms and lung epithelial cells.

Methods

In this study, we performed a head-to-head comparison of the virulence and infection mechanisms of Klebsiella pneumoniae (K. pneumoniae) and Mycobacterium smegmatis (M. smegmatis), which represent Gram-negative/positive respiratory pathogens, respectively, in lung epithelial cell models for the first time.

Results

Through scanning electron microscopy combined with bacterial infection experiments, we confirmed the ability of K. pneumoniae and M. smegmatis strains to form biofilm and cord factor out of the cell wall. M. smegmatis has stronger adhesion and intracellular retention ability, while K. pneumoniae is more likely to induce acute infection. These pathogens could stay and proliferate in lung epithelial cells and stimulate the secretion of specific cytokines and chemokines through a gene transcription regulator. M. smegmatis infection can promote crosstalk among epithelial cells and other immune cells in the lung from a very early stage by prompting the secretion of pro-inflammatory cytokines. Meanwhile, there were significant correlations between K. pneumonia infection and higher levels of interleukin-15 (IL-15), interleukin-1Rα (IL-1Rα), fibroblast growth factor (FGF) basic, and granulocyte colony-stimulating factor (G-CSF). At the same time, K. pneumonia infection also led to changes in the expression of cytoskeletal proteins in epithelial cells.

Conclusions

Our results emphasized the immunoprotection and immunomodulation of lung epithelial cells against exogenous pathogenic microorganisms, indicating that different pathogens damaged the host through different strategies and induced varying innate immune responses. At the same time, they provided important clues and key immune factors for dealing with complicated pulmonary infections.

Modulation of Klebsiella pneumoniae Outer Membrane Vesicle Protein Cargo under Antibiotic Treatment

Klebsiella pneumoniae is a nosocomial pathogen and an important propagator of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains. Like other Gram-negative bacteria, they secrete outer membrane vesicles (OMVs) that distribute virulence and resistance factors. Here, we subjected a K. pneumoniae-XDR to subinhibitory concentrations of meropenem, amikacin, polymyxin B, and a combination of these agents to evaluate changes in the protein cargo of OMVs through liquid chromatography-tandem mass spectrometry (LC-MS/MS). Genome sequencing of the clinical isolate K. pneumoniae strain HCD1 (KpHCD1) revealed the presence of 41 resistance genes and 159 virulence factors. We identified 64 proteins in KpHCD1-OMVs modulated with different antibiotic treatments involved in processing genetic information, environmental information, cell envelope formation, energy metabolism, and drug resistance. The OMV proteome expression profile suggests that OMVs may be associated with pathogenicity, survival, stress response, and resistance dissemination.

Outbreak report of polymyxin-carbapenem-resistant Klebsiella pneumoniae causing untreatable infections evidenced by synergy tests and bacterial genomes

Polymyxin-carbapenem-resistant Klebsiella pneumoniae (PCR-Kp) with pan (PDR)- or extensively drug-resistant phenotypes has been increasingly described worldwide. Here, we report a PCR-Kp outbreak causing untreatable infections descriptively correlated with bacterial genomes. Hospital-wide surveillance of PCR-Kp was initiated in December-2014, after the first detection of a K. pneumoniae phenotype initially classified as PDR, recovered from close spatiotemporal cases of a sentinel hospital in Rio de Janeiro. Whole-genome sequencing of clinical PCR-Kp was performed to investigate similarities and dissimilarities in phylogeny, resistance and virulence genes, plasmid structures and genetic polymorphisms. A target phenotypic profile was detected in 10% (12/117) of the tested K. pneumoniae complex bacteria recovered from patients (8.5%, 8/94) who had epidemiological links and were involved in intractable infections and death, with combined therapeutic drugs failing to meet synergy. Two resistant bacterial clades belong to the same transmission cluster (ST437) or might have different sources (ST11). The severity of infection was likely related to patients' comorbidities, lack of antimicrobial therapy and predicted bacterial genes related to high resistance, survival, and proliferation. This report contributes to the actual knowledge about the natural history of PCR-Kp infection, while reporting from a time when there were no licensed drugs in the world to treat some of these infections. More studies comparing clinical findings with bacterial genetic markers during clonal spread are needed.

Prevalence, Resistance Patterns and Biofilm Production Ability of Bacterial Uropathogens from Cases of Community-Acquired Urinary Tract Infections in South Italy

Community-acquired urinary tract infections represent the most common infectious diseases in the community setting. Knowing the antibiotic resistance patterns of uropathogens is crucial for establishing empirical treatment. The aim of the current study is to determine the incidence of the causative agents of UTIs and their resistance profiles. Patients of all ages and both sexes were enrolled in the study, and admitted to San Ciro Diagnostic Center in Naples between January 2019 and Jun 2020. Bacterial identification and antibiotic susceptibility testing were carried out using Vitek 2 system. Among the 2741 urine samples, 1702 (62.1%) and 1309 (37.9%) were negative and positive for bacterial growth, respectively. Of 1309 patients with infection, 760 (73.1%) were females and 279 (26.9%) were males. The greatest number of positive cases were found in the in the elderly (>61 years). Regarding uropathogens, 1000 (96.2%) were Gram-negative while 39 (3.8%) were Gram-positive strains. The three most isolated pathogenic strains were Escherichia coli (72.2%), Klebsiella pneumoniae (12.4%), and Proteus mirabilis (9.0%). Strong biofilm formation ability was observed in about 30% of the tested isolates. The low resistance rates recorded against nitrofurantoin, fosfomycin, piperacillin-tazobactam, and gentamicin could suggest them as the most appropriate therapies for CA-UTIs.

The Acinetobacter baumannii model can explain the role of small non-coding RNAs as potential mediators of host-pathogen interactions

Bacterial small RNAs (sRNAs) research has accelerated over the past decade, boosted by advances in RNA-seq technologies and methodologies for capturing both protein-RNA and RNA-RNA interactions. The emerging picture is that these regulatory sRNAs play important roles in controlling complex physiological processes and are required to survive the antimicrobial challenge. In recent years, the RNA content of OMVs/EVs has also gained increasing attention, particularly in the context of infection. Secreted RNAs from several bacterial pathogens have been characterized but the exact mechanisms promoting pathogenicity remain elusive. In this review, we briefly discuss how secreted sRNAs interact with targets in infected cells, thus representing a novel perspective of host cell manipulation during bacterial infection. During the last decade, Acinetobacter baumannii became clinically relevant emerging pathogens responsible for nosocomial and community-acquired infections. Therefore, we also summarize recent findings of regulation by sRNAs in A. baumannii and discuss how this emerging bacterium utilizes many of these sRNAs to adapt to its niche and become successful human pathogen.

Deployment of a Novel Organic Acid Compound Disinfectant against Common Foodborne Pathogens

BACKGROUND

The disinfection process represents an important activity closely linked to the removal of micro-organisms in common processing systems. Traditional disinfectants are often not sufficient to avoid the spread of food pathogens; therefore, innovative strategies for decontamination are crucial to countering microbial transmission. This study aims to assess the antimicrobial efficiency of tetrapotassium iminodisuccinic acid salt (IDSK) against the most common pathogens present on surfaces, especially in food-borne environments.

METHODS

IDSK was synthesized from maleic anhydride and characterized through nuclear magnetic resonance (NMR) spectroscopy (both ¹H-NMR and ¹³C-NMR), thermogravimetric analysis (TGA) and Fourier Transform Infrared (FTIR) spectroscopy. The antibacterial activity was performed via the broth microdilution method and time-killing assays against Escherichia coli, Staphylococcus aureus, Salmonella enterica, Enterococcus faecalis and Pseudomonas aeruginosa (IDSK concentration range: 0.5-0.002 M). The biofilm biomass eradicating activity was assessed via a crystal violet (CV) assay.

RESULTS

The minimum inhibitory concentration (MIC) of IDSK was 0.25 M for all tested strains, exerting bacteriostatic action. IDSK also reduced biofilm biomass in a dose-dependent manner, reaching rates of about 50% eradication at a dose of 0.25 M. The advantages of using this innovative compound are not limited to disinfecting efficiency but also include its high biodegradability and its sustainable synthesis.

CONCLUSIONS

IDSK could represent an innovative and advantageous disinfectant for food processing and workers' activities, leading to a better quality of food and safer working conditions for the operators.

Horizontal gene transfer via OMVs co-carrying virulence and antimicrobial-resistant genes is a novel way for the dissemination of carbapenem-resistant hypervirulent Klebsiella pneumoniae

INTRODUCTION

The rapidly increased isolation rate of CR-HvKP worldwide has brought great difficulties in controlling clinical infection. Moreover, it has been demonstrated that the transmission of drug-resistant genes among bacteria can be mediated by outer membrane vesicles (OMVs), which is a new way of horizontal gene transfer (HGT). The transmission of virulence genes among bacteria has also been well studied; however, it remains unclear whether virulence and drug-resistant genes can be co-transmitted simultaneously. Co-transmission of virulence and drug-resistant genes is essential for the formation and prevalence of CR-HvKP.

METHODS

First, we isolated OMVs from CR-HvKP by cushioned-density gradient ultracentrifugation (C-DGUC). TEM and DLS were used to examine the morphology and size of bacterial OMVs. OMV-mediated gene transfer in liquid cultures and the acquisition of the carbapenem gene and virulence gene was confirmed using colony-PCR. Antimicrobial susceptibility testing, mCIM and eCIM were conducted for the resistance of transformant. Serum killing assay, assessment of the anti-biofilm effect and galleria mellonella infection model, mucoviscosity assay, extraction and quantification of capsules were verified the virulence of transformant. Pulsed-field gel electrophoresis (PFGE), S1 nuclease-pulsed-field gel electrophoresis (S1-PFGE), Southern blotting hybridization confirmed the plasmid of transformant.

RESULTS

Firstly, OMVs were isolated from CR-HvKP NUHL30457 (K2, ST86). TEM and DLS analyses revealed the spherical morphology of the vesicles. Secondly, our study demonstrated that CR-HvKP delivered genetic material, incorporated DNA within the OMVs, and protected it from degradation by extracellular exonucleases. Thirdly, the vesicular lumen DNA was delivered to the recipient cells after determining the presence of virulence and carbapenem-resistant genes in the CR-HvKP OMVs. Importantly, S1-PFGE and Southern hybridization analysis of the 700603 transformant strain showed that the transformant contained both drug-resistant and virulence plasmids.

DISCUSSION

In the present study, we aimed to clarify the role of CRHvKP-OMVs in transmitting CR-HvKP among K. pneumoniae. Collectively, our findings provided valuable insights into the evolution of CR-HvKP.

Viral Infection and Antiviral Treatments in Ocular Pathologies

Ocular viral infections are common and widespread globally. These infectious diseases are a major cause of acute red eyes and vision loss. The eye and its nearby tissues can be infected by several viral agents, causing infections with a short course and limited ocular implications or a long clinical progression and serious consequences for the function and structure of the ocular region. Several surveillance studies underline the increased emergence of drug resistance among pathogenic viral strains, limiting treatment options for these infections. Currently, in the event of resistant infections, topical or systemic corticosteroids are useful in the management of associated immune reactions in the eye, which contribute to ocular dysfunction. Many cases of viral eye infections are misdiagnosed as being of bacterial origin. In these cases, therapy begins late and is not targeted at the actual cause of the infection, often leading to severe ocular compromises, such as corneal infiltrates, conjunctival scarring, and reduced visual acuity. The present study aims at a better understanding of the viral pathogens that cause eye infections, along with the treatment options available.

The current landscape of microRNAs (miRNAs) in bacterial pneumonia: opportunities and challenges

MicroRNAs (miRNAs), which were initially discovered in Caenorhabditis elegans, can regulate gene expression by recognizing cognate sequences and interfering with the transcriptional or translational machinery. The application of bioinformatics tools for structural analysis and target prediction has largely driven the investigation of certain miRNAs. Notably, it has been found that certain miRNAs which are widely involved in the inflammatory response and immune regulation are closely associated with the occurrence, development, and outcome of bacterial pneumonia. It has been shown that certain miRNA techniques can be used to identify related targets and explore associated signal transduction pathways. This enhances the understanding of bacterial pneumonia, notably for "refractory" or drug-resistant bacterial pneumonia. Although these miRNA-based methods may provide a basis for the clinical diagnosis and treatment of this disease, they still face various challenges, such as low sensitivity, poor specificity, low silencing efficiency, off-target effects, and toxic reactions. The opportunities and challenges of these methods have been completely reviewed, notably in bacterial pneumonia. With the continuous improvement of the current technology, the miRNA-based methods may surmount the aforementioned limitations, providing promising support for the clinical diagnosis and treatment of "refractory" or drug-resistant bacterial pneumonia.

Impact of Escherichia coli Outer Membrane Vesicles on Sperm Function

Reproductive tract infections account for approximately 15% of male infertility cases. Escherichia coli (E. coli) represents the most frequently isolated bacterial strain in the semen of infertile men. All Gram-negative bacteria constitutively produce outer membrane vesicles (OMVs). The present study proved, for the first time, the involvement of OMVs in human sperm function. E. coli OMVs were isolated by ultracentrifugation and characterized via sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis. Human sperm was exposed to OMVs (8 µg/mL) for different times (30, 45, 60 and 90 min). The vitality, motility, morphology, ROS level and DNA fragmentation of spermatozoa were evaluated. OMVs reduced the progressive motility and increased the immobile spermatozoa amount after 30 min of treatment. In addition, a significant increase in the percentage of intracellular ROS and sperm DNA fragmentation was recorded for each vesicular exposure time. These preliminary findings prove that OMVs contribute to altering human sperm function via two mechanisms: (i) impaired motility and (ii) DNA fragmentation.

Characterization and Comparison of Ocular Surface Microbiome in Newborns

The ocular microbiome is of fundamental importance for immune eye homeostasis, and its alteration would lead to an impairment of ocular functionality. Little evidence is reported on the composition of the ocular microbiota of term infants and on the impact of antibiotic prophylaxis. Methods: A total of 20 conjunctival swabs were collected from newborns at birth and after antibiotic treatment. Samples were subjected to 16S rRNA sequencing via system MiSeq Illumina. The data were processed with the MicrobAT software and statistical analysis were performed using two-way ANOVA. Results: Antibiotic prophylaxis with gentamicin altered the composition of the microbiota. In detail, a 1.5- and 2.01-fold reduction was recorded for Cutibacterium acnes (C. acnes) and Massilia timonae (M. timonae), respectively, whereas an increase in Staphylococcus spp. of 6.5 times occurred after antibiotic exposure. Conclusions: Antibiotic prophylaxis altered the ocular microbiota whose understanding could avoid adverse effects on eye health.

MALDI-TOF Mass Spectrometry Analysis and Human Post-Mortem Microbial Community: A Pilot Study

Introduction: The human post-mortem microbiome (HPM) plays a major role in the decomposition process. Successional changes in post-mortem bacterial communities have been recently demonstrated using high throughput metagenomic sequencing techniques, showing great potential as a post-mortem interval (PMI) predictor. The aim of this study is to verify the application of the mass spectrometry technique, better known as MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry), as a cheap and quick method for microbe taxonomic identification and for studying the PM microbiome. Methods: The study was carried out on 18 human bodies, ranging from 4 months to 82 years old and with a PMI range from 24 h up to 15 days. The storage time interval in the coolers was included in the final PMI estimates. Using the PMI, the sample study was divided into three main groups: seven cases with a PMI < 72 h; six cases with a PMI of 72−168 h and five cases with a PMI > 168 h. For each body, microbiological swabs were sampled from five external anatomical sites (eyes, ears, nose, mouth, and rectum) and four internal organs (brain, spleen, liver, and heart). Results: The HPM became increasingly different from the starting communities over time in the internal organs as well as at skin sites; the HPM microbiome was mostly dominated by Firmicutes and Proteobacteria phyla; and a PM microbial turnover existed during decomposition, evolving with the PMI. Conclusions: MALDI-TOF is a promising method for PMI estimation, given its sample handling, good reproducibility, and high speed and throughput. Although several intrinsic and extrinsic factors can affect the structure of the HPM, MALDI-TOF can detect the overall microbial community turnover of most prevalent phyla during decomposition. Limitations are mainly related to its sensitivity due to the culture-dependent method and bias in the identification of new isolates.

Comparative analysis of peracetic acid (PAA) and permaleic acid (PMA) in disinfection processes

The growing demand to reduce chlorine usage and control disinfection byproducts increased the development of new strategies in wastewater treatments. Organic peracids are increasingly attracting interest in disinfection activities as a promising alternative to chlorine and chlorine-based agents. In this study, we assessed the antimicrobial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) of a new organic peracid, permaleic acid (PMA) compared with the reference peracetic acid (PAA). Disinfectant properties were evaluated by i) disk diffusion agar, ii) broth microdilution, iii) antibiofilm properties. PMA demonstrated a 10- and 5-fold decrease in the microbial inhibitory concentration (MIC) value against E. coli and S. aureus respectively, compared to PAA. Results showed greater efficacy of PMA regarding wastewater (WW) and treated wastewater (TWW) disinfection at low concentrations. Furthermore, the biofilm degradation ability was only observed following PMA treatment, for both strains. Bacterial regrowth from biofilm matrix after PAA and PMA disinfection, in the absence and presence of organic matter, was evaluated. PMA was more efficient than PAA to prevent the regrowth of planktonic cells of S. aureus and E. coli. After PAA and PMA treatment, in the presence of organic matter, the bacterial regrowth inhibition was maintained up to 10 and 5 g/L, respectively. Based on these results, PMA could be used as a valid alternative to the currently used disinfection methods.

Synthesis of Chitosan-Coated Silver Nanoparticle Bioconjugates and Their Antimicrobial Activity against Multidrug-Resistant Bacteria

The increase in multidrug-resistant bacteria represents a true challenge in the pharmaceutical and biomedical fields. For this reason, research on the development of new potential antibacterial strategies is essential. Here, we describe the development of a green system for the synthesis of silver nanoparticles (AgNPs) bioconjugated with chitosan. We optimized a Prunus cerasus leaf extract as a source of silver and its conversion to chitosan–silver bioconjugates (CH-AgNPs). The AgNPs and CH-AgNPs were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–Vis), and zeta potential measurement (Z-potential). The cytotoxic activity of AgNPs and CH-AgNPs was assessed on Vero cells using the 3-[4.5-dimethylthiazol-2-yl]-2.5-diphenyltetrazolium bromide (MTT) cell proliferation assay. The antibacterial activity of AgNPs and CH-AgNPs synthesized using the green system was determined using the broth microdilution method. We evaluated the antimicrobial activity against standard ATCC and clinically isolated multisensitive (MS) and multidrug-resistant bacteria (MDR) Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), Klebsiella pneumonia (K. pneumoniae), and Staphylococcus aureus (S. aureus), using minimum inhibitory concentration (MIC) assays and the broth dilution method. The results of the antibacterial studies demonstrate that the silver chitosan bioconjugates were able to inhibit the growth of MDR strains more effectively than silver nanoparticles alone, with reduced cellular toxicity. These nanoparticles were stable in solution and had wide-spectrum antibacterial activity. The synthesis of silver and silver chitosan bioconjugates from Prunus cerasus leaf extracts may therefore serve as a simple, ecofriendly, noncytotoxic, economical, reliable, and safe method to produce antimicrobial compounds with low cytotoxicity.

Prevalence and Antibiotic Resistance Profile of Bacterial Pathogens in Aerobic Vaginitis: A Retrospective Study in Italy

Aerobic vaginitis (AV) is a vaginal infectious condition, characterized by a high inflammatory response and/or signs of epithelial atrophy, a decrease in the amount of Lactobacillus spp. and an increase in enteric origin bacteria. AV, often misdiagnosed, is difficult to treat due to the emerging spread of multi-drug resistant bacterial strains. The present study aimed to define the prevalence of AV, to detect causative bacteria and their antimicrobial resistance pattern. Women 10-95 years old, admitted to San Giovanni di Dio e Ruggi d'Aragona Hospital, Salerno, Italy (in the years 2015-2019) are included in the study. Bacterial identification and antibiotic susceptibility tests were carried out by VITEK^® 2. Among 2069 patients, 1176 tested positive for microbial growth. A higher incidence of infection was found in the 55-64 age group. Among the pathogenic strains, 50.4% were Gram-negative, and 49.6% were Gram-positive. Escherichia coli (E. coli) (32.5%) was the most representative strain, followed by Enterococcus faecalis (E. faecalis) (29.4%), Klebsiella pneumoniae (K. pneumoniae) (7.8%) and Enterococcus faecium (E. faecium) (7.7%). E. coli showed high sensitivity to carbapenems and amikacin. K. pneumoniae carbapenems resistance was fluctuating over time. Alarming resistance to vancomycin was not recorded for Enterococci. Both strains were sensitive to teicoplanin, linezolid and tigecycline. Proper diagnosis and an effective therapeutic approach are needed to improve AV management.

Outer Membrane Vesicles Derived from Klebsiella pneumoniae Are a Driving Force for Horizontal Gene Transfer

Gram-negative bacteria release Outer Membrane Vesicles (OMVs) into the extracellular environment. Recent studies recognized these vesicles as vectors to horizontal gene transfer; however, the parameters that mediate OMVs transfer within bacterial communities remain unclear. The present study highlights for the first time the transfer of plasmids containing resistance genes via OMVs derived from Klebsiella pneumoniae (K. pneumoniae). This mechanism confers DNA protection, it is plasmid copy number dependent with a ratio of 3.6 times among high copy number plasmid (pGR) versus low copy number plasmid (PRM), and the transformation efficiency was 3.6 times greater. Therefore, the DNA amount in the vesicular lumen and the efficacy of horizontal gene transfer was strictly dependent on the identity of the plasmid. Moreover, the role of K. pneumoniae-OMVs in interspecies transfer was described. The transfer ability was not related to the phylogenetic characteristics between the donor and the recipient species. K. pneumoniae-OMVs transferred plasmid to Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa and Burkholderia cepacia. These findings address the pivotal role of K. pneumoniae-OMVs as vectors for antimicrobial resistance genes spread, contributing to the development of antibiotic resistance in the microbial communities.

Postmortem interval assessment by MALDI-TOF mass spectrometry analysis in murine cadavers

Aims

This study assessed the use of matrix‐assisted laser desorption/ionization time of flight (MALDI‐TOF) mass spectrometry as an alternative method to identify species associated with the thanatomicrobiota and epinecrotic communities.

Methods and Results

The study was conducted on 10 murine cadavers, and microbiological swabs were collected from five external anatomical sites (eyes, ears, nose, mouth and rectum) and four internal organs (brain, spleen, liver, heart), during 16 and 30 days, for the thanatomicrobiota and epinecrotic communities, respectively. Our results revealed that the postmortem microbiota associated with the external cavities showed changes over time and reduced taxonomic diversity. The internal organs, initially sterile, showed signs of microbial invasion at 3 and 10 days postmortem for the liver‐spleen and heart‐brain, respectively. The postmortem microbiota was mainly dominated by Firmicutes and Proteobacteria.

Conclusions

MALDI‐TOF is a promising method for estimating postmortem interval (PMI), associated with rapid sample handling, good reproducibility and high productivity.

Significance and Impact of the Study

This study investigated microbial changes during the decomposition process and proposed a simple strategy for PMI estimation. Results introducing the application of the MALDI‐TOF method in the field of forensic.

MicroRNA Interference in Hepatic Host-Pathogen Interactions

The liver is well recognized as a non-immunological visceral organ that is involved in various metabolic activities, nutrient storage, and detoxification. Recently, many studies have demonstrated that resident immune cells in the liver drive various immunological reactions by means of several molecular modulators. Understanding the mechanistic details of interactions between hepatic host immune cells, including Kupffer cells and lymphocytes, and various hepatic pathogens, especially viruses, bacteria, and parasites, is necessary. MicroRNAs (miRNAs), over 2600 of which have been discovered, are small, endogenous, interfering, noncoding RNAs that are predicted to regulate more than 15,000 genes by degrading specific messenger RNAs. Several recent studies have demonstrated that some miRNAs are associated with the immune response to pathogens in the liver. However, the details of the underlying mechanisms of miRNA interference in hepatic host-pathogen interactions still remain elusive. In this review, we summarize the relationship between the immunological interactions of various pathogens and hepatic resident immune cells, as well as the role of miRNAs in the maintenance of liver immunity against pathogens.

Application of Dendrimers for Treating Parasitic Diseases

Despite advances in medical knowledge, parasitic diseases remain a significant global health burden and their pharmacological treatment is often hampered by drug toxicity. Therefore, drug delivery systems may provide useful advantages when used in combination with conventional therapeutic compounds. Dendrimers are three-dimensional polymeric structures, characterized by a central core, branches and terminal functional groups. These nanostructures are known for their defined structure, great water solubility, biocompatibility and high encapsulation ability against a wide range of molecules. Furthermore, the high ratio between terminal groups and molecular volume render them a hopeful vector for drug delivery. These nanostructures offer several advantages compared to conventional drugs for the treatment of parasitic infection. Dendrimers deliver drugs to target sites with reduced dosage, solving side effects that occur with accepted marketed drugs. In recent years, extensive progress has been made towards the use of dendrimers for therapeutic, prophylactic and diagnostic purposes for the management of parasitic infections. The present review highlights the potential of several dendrimers in the management of parasitic diseases.