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

Non-Canonical Aspects of Antibiotics and Antibiotic Resistance

The understanding of antibiotic resistance, one of the major health threats of our time, is mostly based on dated and incomplete notions, especially in clinical contexts. The "canonical" mechanisms of action and pharmacodynamics of antibiotics, as well as the methods used to assess their activity upon bacteria, have not changed in decades; the same applies to the definition, acquisition, selective pressures, and drivers of resistance. As a consequence, the strategies to improve antibiotic usage and overcome resistance have ultimately failed. This review gathers most of the "non-canonical" notions on antibiotics and resistance: from the alternative mechanisms of action of antibiotics and the limitations of susceptibility testing to the wide variety of selective pressures, lateral gene transfer mechanisms, ubiquity, and societal factors maintaining resistance. Only by having a "big picture" view of the problem can adequate strategies to harness resistance be devised. These strategies must be global, addressing the many aspects that drive the increasing prevalence of resistant bacteria aside from the clinical use of antibiotics.

Sporadic clone Escherichia coli ST615 as a vector and reservoir for dissemination of crucial antimicrobial resistance genes

There is scarce information concerning the role of sporadic clones in the dissemination of antimicrobial resistance genes (ARGs) within the nosocomial niche. We confirmed that the clinical Escherichia coli M19736 ST615 strain, one of the first isolates of Latin America that harbors a plasmid with an mcr-1 gene, could receive crucial ARG by transformation and conjugation using as donors critical plasmids that harbor bla CTX-M-15, bla KPC-2, bla NDM-5, bla NDM-1, or aadB genes. Escherichia coli M19736 acquired bla CTX-M-15, bla KPC-2, bla NDM-5, bla NDM-1, and aadB genes, being only blaNDM-1 maintained at 100% on the 10th day of subculture. In addition, when the evolved MDR-E. coli M19736 acquired sequentially bla CTX-M-15 and bla NDM-1 genes, the maintenance pattern of the plasmids changed. In addition, when the evolved XDR-E. coli M19736 acquired in an ulterior step the paadB plasmid, a different pattern of the plasmid's maintenance was found. Interestingly, the evolved E. coli M19736 strains disseminated simultaneously the acquired conjugative plasmids in different combinations though selection was ceftazidime in all cases. Finally, we isolated and characterized the extracellular vesicles (EVs) from the native and evolved XDR-E. coli M19736 strains. Interestingly, EVs from the evolved XDR-E. coli M19736 harbored bla CTX-M-15 though the pDCAG1-CTX-M-15 was previously lost as shown by WGS and experiments, suggesting that EV could be a relevant reservoir of ARG for susceptible bacteria. These results evidenced the genetic plasticity of a sporadic clone of E. coli such as ST615 that could play a relevant transitional link in the clinical dynamics and evolution to multidrug/extensively/pandrug-resistant phenotypes of superbugs within the nosocomial niche by acting simultaneously as a vector and reservoir of multiple ARGs which later could be disseminated.

The effect of site-specific recombinases XerCD on the removal of over-replicated chromosomal DNA through outer membrane vesicles in bacteria

Outer membrane vesicles (OMVs) are universally produced by Gram-negative bacteria and play important roles in symbiotic and pathogenic interactions. The DNA from the lumen of OMVs from the Alphaproteobacterium Dinoroseobacter shibae was previously shown to be enriched for the region around the terminus of replication ter and specifically for the recognition sequence dif of the two site-specific recombinases XerCD. These enzymes are highly conserved in bacteria and play an important role in the last phase of cell division. Here, we show that a similar enrichment of ter and dif is found in the DNA inside OMVs from Prochlorococcus marinus, Pseudomonas aeruginosa, Vibrio cholerae, and Escherichia coli. The deletion of xerC or xerD in E. coli reduced the enrichment peak directly at the dif sequence, while the enriched DNA region around ter became broader, demonstrating that either enzyme influences the DNA content inside the lumen of OMVs. We propose that the intra-vesicle DNA originated from over-replication repair and the XerCD enzymes might play a role in this process, providing them with a new function in addition to resolving chromosome dimers.IMPORTANCEImprecise termination of replication can lead to over-replicated parts of bacterial chromosomes that have to be excised and removed from the dividing cell. The underlying mechanism is poorly understood. Our data show that outer membrane vesicles (OMVs) from diverse Gram-negative bacteria are enriched for DNA around the terminus of replication ter and the site-specific XerCD recombinases influence this enrichment. Clearing the divisome from over-replicated parts of the bacterial chromosome might be a so far unrecognized and conserved function of OMVs.

Extracellular vesicles-Potential link between periodontal disease and diabetic complications

It has long been suggested that a bidirectional impact exists between periodontitis and diabetes. Periodontitis may affect diabetes glycemic control, insulin resistance, and diabetic complications. Diabetes can worsen periodontitis by delaying wound healing and increasing the chance of infection. Extracellular vesicles (EVs) are heterogeneous particles of membrane-enclosed spherical structure secreted by eukaryotes and prokaryotes and play a key role in a variety of diseases. This review will introduce the biogenesis, release, and biological function of EVs from a microbial and host cell perspective, discuss the functional properties of EVs in the development of periodontitis and diabetes, and explore their role in the pathogenesis and clinical application of these two diseases. Their clinical implication and diagnostic value are also discussed.

Analysis of the hypovirulent Klebsiella pneumoniae with the NDM-5 gene on IncN plasmids

IMPORTANCE

It is crucial to strengthen the ongoing clinical surveillance of non-highly virulent, multi-resistant Klebsiella pneumoniae.

Functional Portrait and Genomic Feature of Carbapenem-Resistant Pseudomonas mendocina Harboring blaNDM-1 and blaIMP-1 in China

The purpose of this research was to analyze the functional portraits and genomic features of carbapenem-resistant Pseudomonas mendocina carrying NDM-1 and IMP-1. The resistance mechanism of the strain was verified by in vivo experiments. Genomic data were aligned and analyzed in the NCBI database. Growth curve measurements were used to describe the growth characteristics of the bacteria. The virulence of P. mendocina strain was analyzed by serum killing assay and biofilm formation assay. Plasmid conjugation experiments were performed to verify the transferability of plasmids carrying drug-resistance genes. The P. mendocina strain was highly resistant to carbapenems. In addition, ST typing is unknown and has been submitted to Genebank. The strain carried two carbapenemase genes, including NDM-1 and IMP-1. Among them, blaNDM-1 was located on a 5.62832 Mb chromosome, and blaIMP-1 was located on a 172.851 Kb transferable plasmid, which was a very close relative of pIMP-NY7610 in China. The strain also had a variety of virulence genes, which were expressed in the siderophore, capsule, pilus, alginate, flagella, etc. The study suggests that the functional portrait and genomic features of carbapenem-resistant P. mendocina harboring blaNDM-1 and blaIMP-1 are unique to China. This outcome represents antibiotic resistance exhibited in the genus Pseudomonas by acquiring chromosomes and plasmid genes. The monitoring and supervision of antimicrobial usage must be strengthened since the multi-drug-resistant and moderately virulent P. mendocina will attract much attention in the near future.

Latest Update on Outer Membrane Vesicles and Their Role in Horizontal Gene Transfer: A Mini-Review

Outer membrane vesicles (OMVs) are spherical, lipid-based nano-structures, which are released by Gram-negative bacteria in both in vitro and in vivo conditions. The size and composition of OMVs depend on not only the producer bacterial species but also cells belonging to the same strain. The mechanism of vesicles' biogenesis has a key role in determining their cargo and the pattern of macromolecules exposed on their surface. Thus, the content of proteins, lipids, nucleic acids, and other biomolecules defines the properties of OMVs and their beneficial or harmful effects on human health. Many studies have provided evidence that OMVs can be involved in a plethora of biological processes, including cell-to-cell communication and bacteria-host interactions. Moreover, there is a growing body of literature supporting their role in horizontal gene transfer (HGT). During this process, OMVs can facilitate the spreading of genes involved in metabolic pathways, virulence, and antibiotic resistance, guaranteeing bacterial proliferation and survival. For this reason, a deeper understanding of this new mechanism of genetic transfer could improve the development of more efficient strategies to counteract infections sustained by Gram-negative bacteria. In line with this, the main aim of this mini-review is to summarize the latest evidence concerning the involvement of OMVs in HGT.

An update on our understanding of Gram-positive bacterial membrane vesicles: discovery, functions, and applications

Extracellular vesicles (EVs) are nano-sized particles released from cells into the extracellular environment, and are separated from eukaryotic cells, bacteria, and other organisms with cellular structures. EVs alter cell communication by delivering their contents and performing various functions depending on their cargo and release into certain environments or other cells. The cell walls of Gram-positive bacteria have a thick peptidoglycan layer and were previously thought to be unable to produce EVs. However, recent studies have demonstrated that Gram-positive bacterial EVs are crucial for health and disease. In this review, we have summarized the formation, composition, and characteristics of the contents, resistance to external stress, participation in immune regulation, and other functions of Gram-positive bacterial EVs, as well as their application in clinical diagnosis and treatment, to provide a new perspective to further our understanding of Gram-positive bacterial EVs.

Peptide-Based Therapeutic HPV Cancer Vaccine Synthesized via Bacterial Outer Membrane Vesicles

Background

Peptide-based vaccines have broad application prospects because of their safety, simple preparation, and effectiveness, especially in the development of personalized cancer vaccines, which have shown great advantages. However, the current peptide-based vaccines often require artificial synthesis and intricate delivery technology, which increases the cost and complexity of preparation.

Methods

Here, we developed a simple technique for combining a peptide and a delivery system using the natural secretion system of bacteria. Specifically, we biosynthesized an antigenic peptide in bacteria, which was then extracellularly released through the bacterial secretory vesicles, thus simultaneously achieving the biosynthesis and delivery of the peptide.

Results

The system utilizes the natural properties of bacterial vesicles to promote antigen uptake and dendritic cell (DC) maturation. Therefore, tumor-specific CD4+ Th1 and CD8+ cytotoxic T lymphocyte (CTL) responses were induced in TC-1 tumor-bearing mice, thereby efficiently suppressing tumor growth.

Conclusion

This research promotes innovation and extends the application of peptide-based vaccine biosynthesis technology. Importantly, it provides a new method for personalized cancer immunotherapy that uses screened peptides as antigens in the future.

Whole-Genome Sequencing Revealed the Fusion Plasmids Capable of Transmission and Acquisition of Both Antimicrobial Resistance and Hypervirulence Determinants in Multidrug-Resistant Klebsiella pneumoniae Isolates

Klebsiella pneumoniae, a member of the Enterobacteriaceae family, has become a dangerous pathogen accountable for a large fraction of the various infectious diseases in both clinical and community settings. In general, the K. pneumoniae population has been divided into the so-called classical (cKp) and hypervirulent (hvKp) lineages. The former, usually developing in hospitals, can rapidly acquire resistance to a wide spectrum of antimicrobial drugs, while the latter is associated with more aggressive but less resistant infections, mostly in healthy humans. However, a growing number of reports in the last decade have confirmed the convergence of these two distinct lineages into superpathogen clones possessing the properties of both, and thus imposing a significant threat to public health worldwide. This process is associated with horizontal gene transfer, in which plasmid conjugation plays a very important role. Therefore, the investigation of plasmid structures and the ways plasmids spread within and between bacterial species will provide benefits in developing prevention measures against these powerful pathogens. In this work, we investigated clinical multidrug-resistant K. pneumoniae isolates using long- and short-read whole-genome sequencing, which allowed us to reveal fusion IncHI1B/IncFIB plasmids in ST512 isolates capable of simultaneously carrying hypervirulence (iucABCD, iutA, _prmpA, peg-344) and resistance determinants (armA, bla_NDM-1 and others), and to obtain insights into their formation and transmission mechanisms. Comprehensive phenotypic, genotypic and phylogenetic analysis of the isolates, as well as of their plasmid repertoire, was performed. The data obtained will facilitate epidemiological surveillance of high-risk K. pneumoniae clones and the development of prevention strategies against them.