Klebsiella pneumoniae is primarily an opportunistic pathogen known for causing healthcare-associated infections in individuals with significant risk factors and comorbidities. These bacteria are typically multidrug-resistant (MDR), a phenotype conferred in part by the production of extended-spectrum beta-lactamases and/or carbapenemases. By comparison, so-called hypervirulent K. pneumoniae (hvKp) are defined by their ability to cause severe community-acquired infections in otherwise healthy individuals. Although hvKp lineages have historically not been MDR, there has been a recent emergence of strains with both hypervirulence and multidrug resistance phenotypes. Treatment of infections caused by MDR K. pneumoniae can be difficult, and new preventative measures are needed. As a step toward the development of a vaccine directed to prevent or moderate infections caused by these pathogens, we tested the ability of capsule polysaccharide (CPS) derived from eight selected K. pneumoniae capsule types (KLs) to elicit rabbit antibodies that recognize important KLs isolated from human infections. Seventy-one out of 84 (84.5%) contemporary K. pneumoniae clinical isolates tested were recognized by CPS-specific rabbit antisera. There was the unexpected binding of the antibodies to some isolates with KLs not included in the CPS-antigen cocktails. Notably, rabbit IgG purified from CPS-specific antisera promoted and/or enhanced human PMN bactericidal activity toward all but one of the selected clinical isolates that were not killed by PMNs outright (in the absence of specific antibody). These data provide support to the idea that a CPS-antigen cocktail could be developed to protect against the K. pneumoniae KLs that are the most frequent cause of human infections.IMPORTANCEKlebsiella pneumoniae is among the leading causes of death by infectious agents. Many of the prominent K. pneumoniae lineages are resistant to multiple classes of antibiotics, and options for treatment are limited. New countermeasures that prevent infections are needed. Here we tested the ability of capsule polysaccharide (CPS) antigen mixtures (or cocktails) to elicit rabbit antibodies that recognize K. pneumoniae from a large collection of extended-spectrum beta-lactamase-producing clinical isolates. Importantly, these antibodies had the ability to promote opsonophagocytic killing by human PMNs. Our results provide proof-of-concept for a CPS vaccine cocktail approach that could be developed to prevent infections caused by the most important K. pneumoniae lineages.

Community-acquired infections caused by Klebsiella pneumoniae (K. pneumoniae) have become a significant global health concern, particularly with the emergence of hypervirulent strains (hvKP). These strains are associated with severe infections, such as pyogenic liver abscesses, even in otherwise healthy individuals. Initially reported in Taiwan in the 1980s, hvKP has now spread worldwide. The pathogenicity of hvKP is attributed to an array of virulence factors that enhance its ability to colonize and evade host immune defenses. Additionally, the convergence of hypervirulence with antibiotic resistance has further complicated treatment strategies. As a member of the ESKAPE group of pathogens, K. pneumoniae exhibits high resistance to multiple antibiotics, posing a challenge for healthcare settings. This review provides a comprehensive overview of hvKP, highlighting its structural and pathogenic differences from classical K. pneumoniae strains, key virulence factors, mechanisms of antibiotic resistance, and the increasing threat of multidrug-resistant hvKP. Lastly, we discuss current treatment guidelines and emerging therapeutic strategies to combat this formidable pathogen.

Hypervirulent Klebsiella pneumoniae (hvKP) is an emerging global health threat, exhibiting increased virulence and multidrug resistance compared to classic K. pneumoniae. Understanding the research landscape surrounding hvKP is crucial for developing effective control strategies. This study aimed to comprehensively analyze the global research trends in hvKP from 2013 to 2024 using bibliometric and topic modeling techniques.

Data from 1,014 articles on hvKP, retrieved from the Web of Science Core Collection, were analyzed using Bibliometrix, CiteSpace, and VOSviewer to assess publication trends, collaborations, geographical distribution, and keyword co-occurrence. Latent Dirichlet Allocation (LDA) topic modeling was employed to identify key research themes.

The analysis revealed a steadily increasing volume of hvKP research, with China and the United States as major contributors. Four primary research themes emerged: high virulence phenotypes and mechanisms; drug resistance and treatment strategies; genetic and molecular mechanisms; and epidemiological and transmission characteristics. Research hotspots included virulence mechanisms, drug resistance, genomic detection approaches, and epidemiological features.

This bibliometric analysis provides a comprehensive overview of hvKP research, highlighting key trends and research gaps. The identified research hotspots inform future research directions and contribute to the development of effective strategies for combating hvKP infections. The increasing research volume underscores the urgent need for continued investigation into this significant public health threat.

Klebsiella pneumoniae, a Gram-negative bacterium, comprises strains with diverse virulence potentials, ranging from classical to hypervirulent variants. Understanding the genetic basis underlying the virulence disparities between hypervirulent (hvKp) and classical K. pneumoniae (cKp) strains is crucial. hvKp strains are characterized by hypermucoviscosity, attributed to the presence of specific virulence genes and the production of molecules that aid in their ability to survive, evade host immune defenses, and cause infection. In contrast, classical strains exhibit a broader array of antimicrobial resistance determinants, conferring resistance to multiple antibiotics. Although current definitions of hvKp incorporate clinical features, phenotypes, and genotypes, identifying hvKp strains in clinical settings remains challenging. Genomic studies have been pivotal and have helped to identify distinct genetic profiles in hvKp strains, including unique virulence plasmids and chromosomal variations, underscoring the genetic diversity within K. pneumoniae populations. This review examines the virulence and genetic determinants associated with hvKp. The presence of genes defining hypervirulence, alongside considerations of their utility as biomarkers and targets for therapeutic strategies, is discussed, while also providing insight into biofilm formation by hvKp and key questions that need urgent responses in understanding hvKp.

Hypervirulent Klebsiella pneumoniae (hvKP) is a recently emerging pathogen that causes severe community-acquired infections in immunocompetent patients, in contrast to classical K. pneumoniae, which is found in nosocomial settings. We report the case of a healthy 55-year-old woman who, following recent travel to Singapore, presented with diabetic ketoacidosis (DKA) and septic shock. She presented with fever, cough, myalgias, and confusion, imaging demonstrating bilateral cavitating pneumonia, hepatic and perinephric abscesses, and renal vein and inferior vena cava thrombosis. Whole-genome sequencing identified hvKP (ST420, K2 capsular type, rmpA, rmpA2). The patient required admission to the intensive care unit (ICU) for mechanical ventilation, broad-spectrum antibiotics, and anticoagulation, and, despite progress on a stepwise incline, irreversible cavitating lung necrosis necessitated prolonged ICU dependence (>35 days). This case is notable for hvKP's virulence, its relation to travel to endemic regions, and the impact of diabetes on susceptibility, underscoring the need for early diagnosis, targeted therapy, and scrupulous source control.

Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a pathogen of global concern associated with invasive community-acquired infections. The combination of hypervirulence and carbapenem resistance can result in severe and difficult-to-treat infections. This retrospective study aimed to investigate the spread of hvKp sequence type 23 (ST23) in Ireland and the convergence of hypervirulent (hv) and antimicrobial resistance genotypes. Short-read sequences (PE300) for 90 K. pneumoniae ST23 isolates were generated by the Galway Reference Laboratory Services (GRLS). Isolates were from screening swabs (n=59), invasive infections (n=18), non-invasive sites (n=12) and the hospital environment (n=1). The virulence and resistance content were assessed genomically using Kleborate (v2.2.0), ABRicate (v1.0.1) and Platon (v1.6). The in vivo virulence of the isolates was assessed using a murine model. All isolates were genotypically hv with 88/90 isolates having a maximal Kleborate virulence score of 5 including carriage of key genes. Eighty-two per cent of isolates (74/90) carried a carbapenemase gene (bla OXA-48/bla OXA-181/bla NDM-1), and 42% carried resistance genes to 3 or more antimicrobial classes. Core genomic delineation revealed the isolates to be clonal with similar resistance and virulence profiles. Two distinct clusters of Irish isolates were detected consisting of 82/90 of the isolates. Isolates associated with carriage and infection demonstrated similar in vivo virulence. An established clone of hvKp ST23 is circulating within Ireland and causing both colonization and infection of patients. The lack of reliable screening methods for hvKp makes its detection and control in the healthcare setting challenging.

Hypervirulent Klebsiella pneumoniae (hvKp) infections have principally been identified in Asia. Within a two-month period, two patients between the ages of 30 to 50 years old presented to a tertiary referral hospital in Texas with septic shock, hepatic abscess, and septic thrombophlebitis. Blood cultures were positive for Klebsiella pneumoniae (isolates 2020CK-00441 and 2021CK-00720 respectively). The first patient survived after a prolonged hospital course while the second patient expired.

Describe the clinical presentation of these two patients. Perform whole genome sequencing and bioinformatic analysis to evaluate potential outbreak of specific hvKp bacteria isolates.

Whole genome sequencing was performed using both paired-end Illumina MiSeq and nanopore sequencing to obtain a Completed genome for both isolates.

2020CK-00441 belonged to ST23 type while 2021CK-00720 was a ST65 type isolate. Kleborate analyses predicted with high confidence both isolates were hvKp. Phylogenetic analyses showed the two strains are not closely related to each other nor to any known hvKp isolates reported. Both isolates had yersiniabactin, colibactin, aerobactin and salmochelin producing loci which likely confer these isolates hvKp phenotype. 2020CK-00441 and 2021CK-00720 had a unique pK2044 like plasmid.

HvKp strains capable of causing devastating metastatic septic infections have emerged in Texas. These isolates are unique compared to other hvKp strains globally. Country-wide surveillance and whole genome sequencing of these strains is essential to prevent a major public health emergency in the USA.

Klebsiella pneumoniae (Kp) is a Gram-negative pathogen responsible for both hospital- and community-acquired infections. Kp is classified into 2 distinct pathotypes: classical K. pneumoniae (cKp) and hypervirulent K. pneumoniae (hvKp). First described in Taiwan in 1986, hvKp are highly pathogenic and characterized by unique phenotypic and genotypic traits. The hypermucoviscous (hmv) phenotype, generally marked by overproduction of the capsule, is often associated with hvKp, although recent studies show that some cKp strains may also have this characteristic. Furthermore, hvKp can cause severe community-acquired infections in healthy people and have been associated with metastatic infections such as liver abscess, meningitis, and endophthalmitis. HvKp are increasingly being reported in hospital-acquired settings, complicating treatment strategies. In particular, while hvKp have historically been antibiotic-susceptible, multidrug-resistant (MDR) strains have emerged and pose a significant public health threat. The combination of high virulence and limited antibiotic options demands further research into virulence mechanisms and rapid identification methods. This review discusses the epidemiology of hvKp and their virulence factors, highlighting the importance of phenotypic and non-phenotypic tests, including next-generation molecular diagnostics, for the early detection of hvKp.

Klebsiella pneumoniae is an important opportunistic pathogen often resistant to antibiotics. Specific phages can be useful in eliminating infection caused by K. pneumoniae. Klebsiella phage vB_KlebPS_265 (KlebP_265) and its host strain were isolated from the sputum of a patient with Klebsiella infection. KlebP_265 was specific mainly to K. pneumoniae-type K2 strains including hypermucoid strains. Most of the hypermucoid KlebP_265-susceptible strains were antibiotic-resistant. This siphophage demonstrated good lytic activity and stability. The KlebP_265 genome was 46,962 bp and contained 88 putative genes; functions were predicted for 37 of them. No genes encoding integrases, toxins, or antibiotic resistance were found in the genome. So, KlebP_265 could potentially be a therapeutic phage. Comparative analysis indicated that KlebP_265 with the most relative Klebsiella phage DP01 formed the putative Dipiunovirus genus. Genome analysis revealed a large monophyletic group of phages related to KlebP_265 and DP01. This group is divided into two monophyletic clusters of phages forming new putative subfamilies Skatevirinae and Roufvirinae. Phylogenetic analysis showed extensive gene exchange between phages from the putative subfamilies. Horizontal transfer even involved conservative genes and led to clear genomic mosaicism, indicating multiple recombination events in the ancestral phages during evolution.

Klebsiella pneumoniae (KP) accounts for high antimicrobial resistance and mortality rates of bloodstream infections (BSIs).

To investigate incidence, antimicrobial resistance and risk factors for mortality of KP BSIs in East China.

A retrospective study of patients with KP BSIs was conducted in a tertiary care hospital from 2018 to 2022. Medical records of all hospitalised patients with KP BSIs were reviewed and analysed. The incidence, antimicrobial resistance and mortality of KP BSIs were evaluated. The Kaplan-Meier method was used to plot survival curves and logistic regression was used to analyse risk factors for crude 30-day mortality.

A total of 379 inpatients with KP BSIs were enrolled. The incidence of patients with KP BSIs was fluctuating between 4.77 and 9.40 per 100,000 patient-days. The crude 30-day mortality rate of these patients was 26.39%. Of the 379 KPisolates, 197 (51.98%) were carbapenem-resistant (CR) and 252 (66.49%) were multidrug-resistant (MDR). All isolates showed the lowest resistance to tigecycline (13.77%) and polymyxin B (14.61%). Cases with MDR/CR isolates had significantly longer length of hospital stay, higher crude 30-day mortality and medical costs than non-MDR/non-CR isolates. Age, CR phenotype, paracentesis, indwelling central venous catheter (CVC), use of carbapenems, tetracyclines, polymyxins B, and irrational empiric treatment were independently associated with crude 30-day mortality.

MDR/CR KP BSIs are associated with increased mortality, healthcare costs and prolonged hospitalisation. Patients with advanced age, CR phenotype, paracentesis, CVC, exposure to some antibiotics, and irrational empirical antibiotic treatment are at higher mortality risk.

Pathobionts are commensal intestinal microbiota capable of causing systemic infections under specific conditions, such as environmental changes or aging. However, it is unclear how pathobionts are recognized by the intestinal mucosal immune system under physiological conditions. This study demonstrates that the gut pathobiont Klebsiella pneumoniae causes injury to the epithelium and translocates to the liver in specific pathogen-free mice treated with clodronate-liposomes that depleted macrophages. In the clodronate-liposome-treated mice, indigenous classical K. pneumoniae (cKp) with non-K1/K2 capsular serotypes were isolated from the liver, indicating that gut commensal cKp translocated from the gastrointestinal tract to the liver due to the depletion of intestinal macrophages. Oral inoculation of isolated cKp to clodronate-liposome-treated mice significantly reduced the survival rates compared to that of non-treated mice. Our findings demonstrate that intestinal mucosal macrophages play a pivotal role in sensing commensal cKp and suppressing their translocation to the liver. This study demonstrates that clodronate-liposome-treated mouse models are effective for screening and evaluating drugs that prevent the translocation of cKp to the liver, providing new insights into the development of preventive protocols against K. pneumoniae infection.

Klebsiella pneumoniae (K. pneumoniae) is a gram-negative conditionally pathogenic bacterium that causes disease primarily in immunocompromised individuals. Recently, highly virulent K. pneumoniae strains have caused severe disease in healthy individuals, posing significant challenges to global infection control. Capsular polysaccharide (CPS), a major virulence determinant of K. pneumoniae, protects the bacteria from being killed by the host immune system, suggesting an urgent need for the development of drugs to prevent or treat K. pneumoniae infections. In this study, BY3 compounded traditional Chinese medicine residue (TCMR) was carried out using Lactobacillus rhamnosus as a fermentation strain, and BY3 compounded TCMR fermentation broth (BY3 fermentation broth) was obtained. The transcription of K. pneumoniae CPS-related biosynthesis genes after treatment with BY3 fermentation broth was detected using quantitative real-time polymerase chain reaction. The effects of BY3 fermentation broth on K. pneumoniae serum killing, macrophage phagocytosis, complement deposition and human β-defensin transcription were investigated. The therapeutic effect of BY3 fermentation broth on K. pneumoniae-infected mice was also observed, and the major active components of BY3 fermentation broth were analysed via LC‒MS analysis, network pharmacology, and molecular docking. The results showed that BY3 fermentation broth inhibited K. pneumoniae CPS production and downregulated transcription of CPS-related biosynthesis genes, which weakened bacterial resistance to serum killing and phagocytosis, while promoting bacterial surface complement C3 deposition and human β-defensin expression. BY3 fermentation broth demonstrated safety and therapeutic effects in vivo and in vitro, restoring body weight and visceral indices, significantly reducing the organ bacterial load and serum cytokine levels, and alleviating pathological organ damage in mice. In addition, three natural compounds-oleanolic acid, quercetin, and palmitoleic acid-were identified as the major active components in the BY3 fermentation broth. Therefore, BY3 fermentation broth may be a promising strategy for the prevention or treatment of K. pneumoniae infections.

Hypervirulent Klebsiella pneumoniae (hvKp) is an emerging pathogen and causes endophthalmitis, liver abscess, osteomyelitis, meningitis, and necrotizing soft tissue infections in both immunodeficient and healthy people. The acquisition of the antibiotic resistance genes of hvKp has become an emerging concern throughout the globe. In this study, a total of 74 K. pneumoniae isolates were collected and identified by VITEK2 and blaSHV gene amplification. Out of these, 18.91% (14/74) isolates were identified as hvKp by both phenotypic string test and genotypic iucA PCR amplification. The antibiotic susceptibility revealed that 57.14% (8/14) isolates were multidrug-resistant (MDR) and 35.71% (5/14) isolates were extremely drug-resistant (XDR). All the isolates were resistant to β-lactam, β-lactamase + inhibitor groups of antibiotics, and the least resistance to colistin. Of 14 hvKp isolates, all isolates are positive for iroB (100%), followed by iutA (92.85%), peg344 (85.71%), rmpA (57.14%), and magA (21.42%) genes. Among serotypes, K1 was the most prevalent serotype 21.4% (3/14), followed by K5 14.3% (2/14). The most common carbapenemase gene was blaOXA-48 (78.57%) followed by blaNDM (14.28%) and blaKPC (14.28%) which co-carried multiple resistance genes such as blaSHV (100%), blaCTX-M (92.85%), and blaTEM (78.57%). About 92.85% (13/14) of hvKp isolates were strong biofilm producers, while one isolate (hvKp 10) was the only moderate biofilm producer. The (GTG)5-PCR molecular typing method revealed high diversity among the hvKp isolates in the tertiary care hospital. Our findings suggest that MDR-hvKp is an emerging pathogen and a challenge for clinical practice. In order to avoid hvKp strain outbreaks in hospital settings, robust infection control and effective surveillance should be implemented.

Bacterial infections pose a significant global health threat, accounting for an estimated 7.7 million deaths. Hospital outbreaks driven by multi-drug-resistant pathogens, notably Klebsiella pneumoniae (K. pneumoniae), are of grave concern. This opportunistic pathogen causes pneumonia, urinary tract infections, and bacteremia, particularly in immunocompromised individuals. The rise of hypervirulent K. pneumoniae adds complexity, as it increasingly infects healthy individuals. Recent epidemiological data suggest that asymptomatic gastrointestinal carriage serves as a reservoir for infections in the same individual and allows for host-to-host transmission via the fecal-oral route. This review focuses on K. pneumoniae's gastrointestinal colonization, delving into epidemiological evidence, current animal models, molecular colonization mechanisms, and the protective role of the resident gut microbiota. Moreover, the review sheds light on in vivo high-throughput approaches that have been crucial for identifying K. pneumoniae factors in gut colonization. This comprehensive exploration aims to enhance our understanding of K. pneumoniae gut pathogenesis, guiding future intervention and prevention strategies.

The global dissemination of critical-priority carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) via food sources represents a significant public health concern. Epidemiological data on CR-hvKp in oysters in Egypt is limited. This study aimed to investigate the potential role of oysters sold in Egypt as a source for carbapenem-resistant K. pneumoniae (CRKP), hypervirulent K. pneumoniae (hvKp), and CR-hvKp and assess associated zoonotic risks.

A sample of 330 fresh oysters was randomly purchased from various retail fish markets in Egypt and divided into 33 pools. Bacteriological examination and the identification of Klebsiella pneumoniae were performed. Carbapenem resistance in K. pneumoniae isolates was determined by phenotypic and molecular methods. Additionally, the presence of hypervirulent K. pneumoniae was identified based on virulence gene markers (peg-344, rmpA, rmpA2, iucA, and iroB), followed by a string test. The clustering of CR-hvKp strains was carried out using R with the pheatmap package.

The overall prevalence of K. pneumoniae was 48.5% (16 out of 33), with 13 isolates displaying carbapenem resistance, one intermediate resistance, and two sensitive. Both carbapenem-resistant K. pneumoniae and carbapenem-intermediate-resistant K. pneumoniae strains exhibited carbapenemase production, predominantly linked to the blaVIM gene (68.8%). HvKp strains were identified at a rate of 62.5% (10/16); notably, peg-344 was the most prevalent gene. Significantly, 10 of the 13 CRKP isolates possessed hypervirulence genes, contributing to the emergence of CR-hvKp. Moreover, cluster analysis revealed the clustering of two CR-hvKp isolates from the same retail fish market.

This study provides the first insight into the emergence of CR-hvKp among oysters in Egypt. It underscores the potential role of oysters as a source for disseminating CR-hvKp within aquatic ecosystems, presenting a possible threat to public health.

Klebsiella pneumoniae, a member of the autochthonous human gut microbiota, utilizes a variety of virulence factors for survival and pathogenesis. Consequently, it is responsible for several human infections, including urinary tract infections, respiratory tract infections, liver abscess, meningitis, bloodstream infections, and medical device-associated infections. The main studied virulence factors in K. pneumoniae are capsule-associated, fimbriae, siderophores, Klebsiella ferric iron uptake, and the ability to metabolize allantoin. They are crucial for virulence and were associated with specific infections in the mice infection model. Notably, these factors are also prevalent in strains from the same infections in humans. However, the type and quantity of virulence factors may vary between strains, which defines the degree of pathogenicity. In this review, we summarize the main virulence factors investigated in K. pneumoniae from different human infections. We also cover the specific identification genes and their prevalence in K. pneumoniae, especially in hypervirulent strains.

A distinct strain of Klebsiella pneumoniae (K. pneumoniae) referred to as hypervirulent (hvKp) is associated with invasive infections such as pyogenic liver abscess in young and healthy individuals. In South Africa, limited information about the prevalence and virulence of this hvKp strain is available. The aim of this study was to determine the prevalence of hvKp and virulence-associated factors in K. pneumoniae isolates from one of the largest tertiary hospitals in a South African province.

A total of 74 K. pneumoniae isolates were received from Pelonomi Tertiary Hospital National Health Laboratory Service (NHLS), Bloemfontein. Virulence-associated genes (rmpA, capsule serotype K1/K2, iroB and irp2) were screened using Polymerase Chain Reaction (PCR). The iutA (aerobactin transporter) gene was used as a primary biomarker of hvKp. The extracted DNAs were sequenced using the next-generation sequencing pipeline and the curated sequences were used for phylogeny analyses using appropriate bioinformatic tools. The virulence of hvKp vs. classical Klebsiella pneumoniae (cKp) was investigated using the Caenorhabditis elegans nematode model.

Nine (12.2%) isolates were identified as hvKp. Moreover, hvKp was significantly (p < 0.05) more virulent in vivo in Caenorhabditis elegans relative to cKp. The virulence-associated genes [rmpA, iroB, hypermucoviscous phenotype (hmv) phenotype and capsule K1/K2] were significantly (p < 0.05) associated with hvKp. A homology search of the curated sequences revealed a high percentage of identity between 99.8 and 100% with other homologous iutA gene sequences of other hvKp in the GenBank.

Findings from this study confirm the presence of hvKp in a large tertiary hospital in central South Africa. However, the low prevalence and mild to moderate clinical presentation of infected patients suggest a marginal threat to public health. Further studies in different settings are required to establish the true potential impact of hvKp in developing countries.

Hypervirulent Klebsiella pneumoniae (KP) is defined according to hypermucoviscosity or various virulence factors and is clinically associated with community-acquired liver abscess (CLA). In this study, we investigated the clinical and microbiological characteristics of KP and significant factors associated with hypervirulence. The clinical characteristics, antimicrobial susceptibility, hypermucoviscosity, serotypes, hypervirulence-related genes, and biofilm formation of 414 KP isolates collected from the Keimyung University Dongsan Hospital between December 2013 and November 2015 were analyzed according to CLA. Significant risk factors for hypervirulent KP (HvKP) associated with CLA were investigated using logistic regression analysis. Notably, 155 (37.4%) isolates were hypermucoviscous, and 170 (41.1%) harbored aerobactin. CLA was present in 34 cases (8.2%). Epidemiology and treatment outcomes did not differ significantly between the CLA and non-CLA groups. The CLA group had significantly higher antibiotic susceptibility, K1/K2, rmpA, magA, allS, kfu, iutA, string test-positive result, and biofilm mass. Multivariate logistic regression revealed rmpA (OR, 5.67; 95% CI, 2.09-15.33; p = 0.001), magA (OR, 2.34; 95% CI, 1.01-5.40; p = 0.047), and biofilm mass >0.80 (OR, 2.13; 95% CI, 1.00-4.56; p = 0.050) as significant risk factors for CLA. rmpA was identified as the most significant risk factor for CLA among KP strains, implying that it is an important factor associated with HvKP.

Introduction Hypermucoviscous Klebsiella pneumoniae (hvKP) is related to invasive infections; however, there have been very few comprehensive reports on the clinical features and prognosis of critically ill patients with the infection. Methods We conducted a retrospective case series in a general intensive care unit in Japan. Patients with positive blood cultures for KP between January 1, 2020 and December 31, 2022 were included. hvKP was defined by the positivity in the string test. We analyzed the patient's characteristics at baseline, including comorbidities, abscess formation, Sequential Organ Failure Assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE) II score, septic shock, duration of hospitalization, 30-day mortality, and infection site. Results A total of 24 patients had a positive blood culture for KP; nine patients (37.5%) were positive for the string test (hvKP) while 15 (62.5%) were negative (non-hvKP). In both groups, the patients were old (mean age, hvKP 80.4 vs. non-hvKP 75.7 years) and more often male (five patients (55.6%) vs. 12 patients (80.0%)). No statistically significant difference was found between the two groups in terms of comorbidities, such as diabetes mellitus, chronic obstructive pulmonary disease, chronic kidney disease, and malignancy. No statistical difference was seen in abscess formation (two patients [22.2%] vs. one patient (6.7%)), SOFA score (5.2±4.8 vs. 4.7±3.4), APACHE II score (19.6 (15.0-20.0) vs. 17.0 (11.2-20.8)), septic shock (five patients (55.6%) vs. four patient (26.7%)), duration of hospitalization (37.2 (12.0-51.0) vs. 32.3 (9.5-21.0)), and 30-day mortality (two patients (22.2%) vs. two patients (13.3%)). Two cases with hvKP died within 24 h. No significant difference was seen in the infection sources; respiratory infection (2 (22.2%) vs. 1 (6.7%)), hepatobiliary infection (2 (22.2%) vs. 7 (46.7%)), and genitourinary infection (1 (11.1%) vs. 5 (33.3%)). Conclusions Critically ill patients with hvKP infection showed characteristics similar to those reported previously. However, the disease could rapidly become severe and have a poor prognostic outcome.

Modern medicine continues to struggle against antibiotic-resistant bacterial pathogens. Among the pathogens of critical concerns are the multidrug-resistant (MDR) Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae. These pathogens are major causes of nosocomial infections among immunocompromised individuals, involving major organs such as lung, skin, spleen, kidney, liver, and bloodstream. Therefore, novel approaches are direly needed. Recently, we developed an amphiphilic dendrimer DDC18-8A exhibiting high antibacterial and antibiofilm efficacy in vitro. DDC18-8A is composed of a long hydrophobic alkyl chain and a small hydrophilic poly(amidoamine) dendron bearing amine terminals, exerting its antibacterial activity by attaching and inserting itself into bacterial membranes to trigger cell lysis. Here, we examined the pharmacokinetics and in vivo toxicity as well as the antibacterial efficacy of DDC18-8A in mouse models of human infectious diseases. Remarkably, DDC18-8A significantly reduced the bacterial burden in mouse models of acute pneumonia and bacteremia by P. aeruginosa, methicillin-resistant S. aureus (MRSA), and carbapenem-resistant K. pneumoniae and neutropenic soft tissue infection by P. aeruginosa and MRSA. Most importantly, DDC18-8A outperformed pathogen-specific antibiotics against all three pathogens by achieving a similar bacterial clearance at 10-fold lower therapeutic concentrations. In addition, it showed superior stability and biodistribution in vivo, with excellent safety profiles yet without any observable abnormalities in histopathological analysis of major organs, blood serum biochemistry, and hematology. Collectively, we provide strong evidence that DDC18-8A is a promising alternative to the currently prescribed antibiotics in addressing challenges associated with nosocomial infections by MDR pathogens.

The opportunistic pathogen Klebsiella pneumoniae (K. pneumoniae) can colonize mucosal surfaces and spread from mucosae to other tissues, causing fatal infections. Medical equipment and the healthcare setting can become colonized by Klebsiella species, which are widely distributed in nature and can be found in water, soil, and animals. Moreover, a substantial number of community-acquired illnesses are also caused by this organism worldwide. These infections are characterized by a high rate of morbidity and mortality as well as the capacity to spread metastatically. Hypervirulent Klebsiella strains are thought to be connected to these infections. Four components are critical to this bacterium's pathogenicity-the capsule, lipopolysaccharide, fimbriae, and siderophores. Siderophores are secondary metabolites that allow iron to sequester from the surrounding medium and transport it to the intracellular compartment of the bacteria. A number of variables may lead to K. pneumoniae colonization in a specific area. Risk factors for infection include local healthcare practices, antibiotic use and misuse, infection control procedures, nutrition, gender, and age.

Hypervirulence and carbapenem-resistant have emerged as two distinct evolutionary pathotypes of Klebsiella pneumoniae, with both reaching their epidemic success and posing a great threat to public health. However, as the boundaries separating these two pathotypes fade, we assist a worrisome convergence in certain high-risk clones, causing hospital outbreaks and challenging every therapeutic option available. To better understand the basic biology of these pathogens, this review aimed to describe the virulence factors and their distribution worldwide among carbapenem-resistant highly virulent or hypervirulent K. pneumoniae strains, as well as to understand the interplay of these virulence strains with the carbapenemase produced and the sequence type of such strains. As we witness a shift in healthcare settings where carbapenem-resistant highly virulent or hypervirulent K. pneumoniae are beginning to emerge and replace classical K. pneumoniae strains, a better understanding of these strains is urgently needed for immediate and appropriate response.

Klebsiella pneumoniae strains with a combination of multidrug resistance and hypervirulence genotypes (MDR hvKp) have emerged as a cause of human infections. The ability of these microbes to avoid killing by the innate immune system remains to be tested fully. To that end, we compared the ability of a global collection of hvKp and MDR hvKp clinical isolates to survive in human blood and resist phagocytic killing by human neutrophils. The two MDR hvKp clinical isolates tested (ST11 and ST147) were killed in human blood and by human neutrophils in vitro, whereas phagocytic killing of hvKp clinical isolates (ST23 and ST86) required specific antisera. Although the data were varied and often isolate specific, they are an important first step toward gaining an enhanced understanding of host defense against MDR hvKp.

The spread of antibiotic resistance genes (ARGs) in the environment exacerbates the contamination of these genes; therefore, the role plants play in the transmission of resistance genes in the food chain requires further research. Giant pandas consume different bamboo parts at different times, which provides the possibility of investigating how a single food source can affect the variation in the spread of ARGs. In this study, metagenomic analysis and the Comprehensive Antibiotic Resistance Database (CARD) database were used to annotate ARGs and the differences in gut microbiota ARGs during the consumption of bamboo shoots, leaves, and culms by captive giant pandas. These ARGs were then compared to investigate the impact of bamboo part consumption on the spread of ARGs. The results showed that the number of ARGs in the gut microbiota of the subjects was highest during the consumption of bamboo leaves, while the variety of ARGs was highest during the consumption of shoots. Escherichia coli, which poses a higher risk of ARG dissemination, was significantly higher in the leaf group, while Klebsiella, Enterobacter, and Raoultella were significantly higher in the shoot group. The ARG risk brought by bamboo shoots and leaves may originate from soil and environmental pollution. It is recommended to handle the feces of giant pandas properly and regularly monitor the antimicrobial and virulence genes in their gut microbiota to mitigate the threat of antibiotic resistance.

An extended-spectrum beta-lactamase (ESBL)-hypervirulent Klebsiella pneumoniae (HvKP) strain HKE9 was isolated from the blood in an outpatient.

The effect of the global regulatory factor RpoS on antimicrobial resistance, pathogenicity, and environmental adaptability was elucidated.

HKE9 is a novel ST3355 (K20/O2a) hypervirulent strain with a positive string test and resistant to cephems except cefotetan. It has a genome size of 5.6M, including two plasmids. CTX-M-15 was found in plasmid 2, and only ompk37 was found in the chromosome. HKE9 could produce bacterial siderophores, and genes of enterobactin, yersiniabactin, aerobactin, and salmochelin have been retrieved in the genome. As a global regulatory factor, knockout of rpoS did not change antimicrobial resistance or hemolytic phenotype while increasing the virulence to Galleria mellonella larvae and showing higher viscosity. Moreover, rpoS knockout can increase bacterial competitiveness and cell adhesion ability. Interestingly, HKE9-M-rpoS decreased resistance to acidic pH, high osmotic pressure, heat shock, and ultraviolet and became sensitive to disinfectants (H2O2, alcohol, and sodium hypochlorite). Although there were 13 Type 6 secretion system (T6SS) core genes divided into two segments with tle1 between segments in the chromosome, transcriptomic analysis showed that rpoS negatively regulated T4SS located on plasmid 2, type 1, and type 3 fimbriae and positively regulate genes responsible for acidic response, hyperosmotic pressure, heat shock, oxidative stress, alcohol and hypochlorous acid metabolism, and quorum sensing.

Here, this novel ST3355 ESBL-HvKP strain HKE9 may spread via various clonal types. The important regulation effect of rpoS is the enhanced tolerance and resistance to environmental stress and disinfectants, which may be at the cost of reducing virulence and regulated by T4SS.

Klebsiella pneumoniae is among the most common antibiotic-resistant pathogens causing nosocomial infections. Additionally, it is a leading cause of neonatal sepsis and childhood mortality across the globe. Despite its clinical importance, we are only beginning to understand how the mammalian adaptive immune system responds to this pathogen. Further, many studies investigating potential K. pneumoniae vaccine candidates or alternative therapies have been launched in recent years. Here, we review the current state of knowledge on the adaptive immune response to K. pneumoniae infections and progress towards developing vaccines and other therapies to combat these infections.

We report a case of a woman with diabetes mellitus and choledocholithiasis who had a low fever with chills and severe weakness for 7 days. The patient's abdominal tenderness was positive. Computed tomography and magnetic resonance imaging showed a giant abscess in the liver. The production of extended-spectrum β-lactamases by hypervirulent Klebsiella pneumoniae was found in the purulent fluid of the liver by nanopore-based metagenomic third-generation sequencing combined with an antibiotic susceptibility test. The patient recovered after intravenous antibiotic therapy and percutaneous drainage. Patients with a history of diabetes mellitus and choledocholithiasis should be aware of the possibility of pyogenic liver abscesses caused by hypervirulent Klebsiella pneumoniae. To rapidly control the development of this disease, nanopore-based metagenomic third-generation sequencing plays an important role not only in rapidly identifying pathogens, but also in guiding the use of antibiotics.

Bacterial infections often involve virulence factors that play a crucial role in the pathogenicity of bacteria. Accurate detection of virulence factor genes (VFGs) is essential for precise treatment and prognostic management of hypervirulent bacterial infections. However, there is a lack of rapid and accurate methods for VFG identification from the metagenomic data of clinical samples. Here, we developed a Reads-based Virulence Factors Scanner (RVFScan), an innovative user-friendly online tool that integrates a comprehensive VFG database with similarity matrix-based criteria for VFG prediction and annotation using metagenomic data without the need for assembly. RVFScan demonstrated superior performance compared to previous assembly-based and read-based VFG predictors, achieving a sensitivity of 97%, specificity of 98% and accuracy of 98%. We also conducted a large-scale analysis of 2425 clinical metagenomic datasets to investigate the utility of RVFScan, the species-specific VFG profiles and associations between VFGs and virulence phenotypes for 24 important pathogens were analyzed. By combining genomic comparisons and network analysis, we identified 53 VFGs with significantly higher abundances in hypervirulent Klebsiella pneumoniae (hvKp) than in classical K. pneumoniae. Furthermore, a cohort of 1256 samples suspected of K. pneumoniae infection demonstrated that RVFScan could identify hvKp with a sensitivity of 90%, specificity of 100% and accuracy of 98.73%, with 90% of hvKp samples consistent with clinical diagnosis (Cohen's kappa, 0.94). RVFScan has the potential to detect VFGs in low-biomass and high-complexity clinical samples using metagenomic reads without assembly. This capability facilitates the rapid identification and targeted treatment of hvKp infections and holds promise for application to other hypervirulent pathogens.

Hypervirulent Klebsiella pneumoniae (hvKP) is emerging globally and can cause various, severe infections in healthy individuals. However, the clinical manifestations of hvKP infections are nonspecific, and there is no gold standard for differentiating hvKP strains. Our objective was to develop prognostic models for estimating severity of disease and predicting 30-day all-cause mortality in patients with hvKP infections.

We enrolled 116 patients diagnosed with hvKP infections and obtained their demographic and clinical data. Taking septic shock and acute respiratory distress syndrome (ARDS) as the primary outcomes for disease severity and 30-day all-cause mortality as the primary outcome for clinical prognosis, we explored the influencing factors and constructed prognostic models.

The results showed that increased Acute Physiologic and Chronic Health Evaluation (APACHE) II score [odds ratio (OR) = 1.146; 95% confidence interval (CI), 1.059-1.240], decreased albumin (ALB) level (OR = 0.867; 95% CI, 0.758-0.990), diabetes (OR = 9.591; 95% CI, 1.766-52.075) and high procalcitonin (PCT) level (OR = 1.051; 95%CI, 1.005-1.099) were independent risk factors for septic shock. And increased APACHE II score (OR = 1.254; 95% CI, 1.110-1.147), community-acquired pneumonia (CAP) (OR = 11.880; 95% CI, 2.524-55.923), and extrahepatic lesion involved (OR = 14.718; 95% CI, 1.005-215.502) were independent risk factors for ARDS. Prognostic models were constructed for disease severity with these independent risk factors, and the models were significantly correlated with continuous renal replacement therapy (CRRT) duration, vasopressor duration, mechanical ventilator duration and length of ICU stay. The 30-day all-cause mortality rate in our study was 28.4%. Younger age [hazard ratio (HR) = 0.947; 95% CI, 0.923-0.973)], increased APACHE II score (HR = 1.157; 95% CI, 1.110-1.207), and decreased ALB level (HR = 0.924; 95% CI, 0.869-0.983) were the independent risk factors for 30-day all-cause mortality. A prediction model for 30-day mortality was constructed, which had a good validation effect.

We developed validated models containing routine clinical parameters for estimating disease severity and predicting 30-day mortality in patients with hvKP infections and confirmed their calibration. The models may assist clinicians in assessing disease severity and estimating the 30-day mortality early.

Ocular infections can be medical emergencies that result in permanent visual impairment or blindness and loss of quality of life. Bacteria are a major cause of ocular infections. Effective treatment of ocular infections requires knowledge of which bacteria are the likely cause of the infection. This survey of ocular bacterial isolates and review of ocular pathogens is based on a survey of a collection of isolates banked over a ten-year span at the Dean McGee Eye Institute in Oklahoma. These findings illustrate the diversity of bacteria isolated from the eye, ranging from common species to rare and unique species. At all sampled sites, staphylococci were the predominant bacteria isolated. Pseudomonads were the most common Gram-negative bacterial isolate, except in vitreous, where Serratia was the most common Gram-negative bacterial isolate. Here, we discuss the range of ocular infections that these species have been documented to cause and treatment options for these infections. Although a highly diverse spectrum of species has been isolated from the eye, the majority of infections are caused by Gram-positive species, and in most infections, empiric treatments are effective.

Pyogenic liver abscess (PLA) is a severe condition that significantly increases the risk of sepsis. However, there is a notable dearth of research regarding the prediction of sepsis in PLA patients. The objective of this study was to develop and validate a prognostic nomogram for predicting sepsis in PLA patients. A total of 206 PLA patients were enrolled in our study, out of which 60 individuals (29.1%) met the Sepsis-3 criteria. Independent risk factors for sepsis were identified through univariate and multivariate logistic regression analyses. Subsequently, a nomogram was developed based on age, positive blood culture, procalcitonin, alanine aminotransferase, blood urea nitrogen, and D-dimer. The nomogram demonstrated excellent calibration and discrimination, as evidenced by the area under the receiver operating characteristic curve (AUC) values of 0.946 (95% confidence interval [CI], 0.912-0.979) and 0.980 (95%CI 0.951-1.000) in the derivation and validation cohorts, respectively. Furthermore, decision-curve analysis confirmed the clinical utility of the nomogram. This study provides valuable insights for the prevention of sepsis in PLA patients and underscores the potential application of the prognostic nomogram in clinical practice.

Purpose: To describe the characteristics of Klebsiella pneumoniae endogenous endophthalmitis (KEE) encountered during the COVID-19 pandemic. Methods: This retrospective consecutive case series evaluated eyes that presented with KEE between March 2020 and July 2022. Results: Seven eyes of 5 patients developed KEE. Between January 2020 and July 2022, KEE was observed in 42% of consecutive EE cases compared with 7.8% during the preceding 13 years. COVID-19 was positive in 4 of 5 patients before they developed KEE. Only 1 patient presented with a VA better than hand motions (20/400). All eyes were treated with urgent vitrectomy and intravitreal and systemic antibiotics. No improvement in vision occurred in any patient; VA remained light perception to no light perception in 60% of eyes. Conclusions: The visual prognosis in KEE is extremely poor. The presence of a preceding COVID-19 infection in 80% of patients may signal a new risk factor for KEE. Patients with a hypervirulent Klebsiella syndrome should be routinely screened for EE.

Klebsiella pneumoniae is recognized as an urgent public health threat because of the emergence of difficult-to-treat (DTR) strains and hypervirulent clones, resulting in infections with high morbidity and mortality rates. Despite its prominence, little is known about the genomic epidemiology of K. pneumoniae in resource-limited settings like Bangladesh. We sequenced genomes of 32 K. pneumoniae strains isolated from patient samples at the International Center for Diarrhoeal Disease Research, Bangladesh (icddr,b). Genome sequences were examined for their diversity, population structure, resistome, virulome, MLST, O and K antigens and plasmids. Our results revealed the presence of two K. pneumoniae phylogroups, namely KpI (K. pneumoniae) (97%) and KpII (K. quasipneumoniae) (3%). The genomic characterization revealed that 25% (8/32) of isolates were associated with high-risk multidrug-resistant clones, including ST11, ST14, ST15, ST307, ST231 and ST147. The virulome analysis confirmed the presence of six (19%) hypervirulent K. pneumoniae (hvKp) and 26 (81%) classical K. pneumoniae (cKp) strains. The most common ESBL gene identified was bla_CTX-M-15 (50%). Around 9% (3/32) isolates exhibited a difficult-to-treat phenotype, harboring carbapenem resistance genes (2 strains harbored bla_NDM-5 plus bla_OXA-232, one isolate bla_OXA-181). The most prevalent O antigen was O1 (56%). The capsular polysaccharides K2, K20, K16 and K62 were enriched in the K. pneumoniae population. This study suggests the circulation of the major international high-risk multidrug-resistant and hypervirulent (hvKp) K. pneumoniae clones in Dhaka, Bangladesh. These findings warrant immediate appropriate interventions, which would otherwise lead to a high burden of untreatable life-threatening infections locally.

Hypervirulent Klebsiella pneumoniae (hvKp) infections confer notable morbidity and mortality. Differential diagnosis to determine whether the infections are caused by either the hvKp or classical K. pneumoniae (cKp) strain is particularly important for undertaking optimal clinical care and infection control efforts.

To identify and assess the potential predictors of hvKp infections.

PubMed, Web of Science, and Cochrane Library databases were searched for all relevant publications from January 2000 to March 2022. The search terms included a combination of the following terms: (i) Klebsiella pneumoniae or K. pneumoniae and (ii) hypervirulent or hypervirulence. A meta-analysis of factors for which risk ratio was reported in three or more studies was conducted, and at least one statistically significant association was identified.

In this systematic review of 11 observational studies, a total of 1392 patients with K. pneumoniae infection and 596 (42.8%) with hvKp strains were evaluated. In the meta-analysis, diabetes mellitus and liver abscess (pooled risk ratio: 2.61 (95% confidence interval: 1.79-3.80) and 9.04 (2.58-31.72), respectively; all P < 0.001) were predictors of hvKp infections.

For patients with a history of the abovementioned predictors, prudent management, including the search for multiple sites of infection and/or metastatic spread and the enforcement of an early and appropriate source control procedure, should be initiated in consideration of the potential presence of hvKp. We believe that this research highlights the urgent need for increasing clinical awareness of the management of hvKp infections.

Klebsiella pneumoniae, which is frequently associated with hospital- and community-acquired infections, contains multidrug-resistant (MDR), hypervirulent (hv), non-MDR/non-hv as well as convergent representatives. It is known that mostly international high-risk clonal lineages including sequence types (ST) 11, 147, 258, and 307 drive their global spread. ST395, which was first reported in the context of a carbapenemase-associated outbreak in France in 2010, is a less well-characterized, yet emerging clonal lineage.

We computationally analyzed a large collection of K. pneumoniae ST395 genomes (n = 297) both sequenced in this study and reported previously. By applying multiple bioinformatics tools, we investigated the core-genome phylogeny and evolution of ST395 as well as distribution of accessory genome elements associated with antibiotic resistance and virulence features.

Clustering of the core-SNP alignment revealed four major clades with eight smaller subclades. The subclades likely evolved through large chromosomal recombination, which involved different K. pneumoniae donors and affected, inter alia, capsule and lipopolysaccharide antigen biosynthesis regions. Most genomes contained acquired resistance genes to extended-spectrum cephalosporins, carbapenems, and other antibiotic classes carried by multiple plasmid types, and many were positive for hypervirulence markers, including the siderophore aerobactin. The detection of "hybrid" resistance and virulence plasmids suggests the occurrence of the convergent ST395 pathotype.

To the best of our knowledge, this is the first study that investigated a large international collection of K. pneumoniae ST395 genomes and elucidated phylogenetics and detailed genomic characteristics of this emerging high-risk clonal lineage.

The clinical outcomes associated with, and risk factors for, carbapenem-resistant Enterobacterales (CRE) bloodstream infections (BSIs) in solid organ transplant (SOT) recipients remain ill-defined.

A multicenter retrospective cohort study was performed, including SOT recipients with an Enterobacterales BSI between 2005 and 2018. Exposed subjects were those with a CRE BSI. Unexposed subjects were those with a non-CRE BSI. A multivariable survival analysis was performed to determine the association between CRE BSI and risk of all-cause mortality within 60 d. Multivariable logistic regression analysis was performed to determine independent risk factors for CRE BSI.

Of 897 cases of Enterobacterales BSI in SOT recipients, 70 (8%) were due to CRE. On multivariable analysis, CRE BSI was associated with a significantly increased hazard of all-cause mortality (adjusted hazard ratio, 2.85; 95% confidence interval [CI], 1.68-4.84; P < 0.001). Independent risk factors for CRE BSI included prior CRE colonization or infection (adjusted odds ratio [aOR] 9.86; 95% CI, 4.88-19.93; P < 0.001)' liver transplantation (aOR, 2.64; 95% CI, 1.23-5.65; P = 0.012)' lung transplantation (aOR, 3.76; 95% CI, 1.40-10.09; P = 0.009)' and exposure to a third-generation cephalosporin (aOR, 2.21; 95% CI, 1.17-4.17; P = 0.015) or carbapenem (aOR, 2.80; 95% CI, 1.54-5.10; P = 0.001) in the prior 6 months.

CRE BSI is associated with significantly worse outcomes than more antibiotic-susceptible Enterobacterales BSI in SOT recipients.

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.

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.

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.

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.