Hypervirulent Klebsiella pneumoniae - clinical and molecular perspectives

Characterization and genomic insights into bacteriophages Kpph1 and Kpph9 against hypervirulent carbapenem-resistant Klebsiella pneumoniae

The increasing incidence of infections attributed to hypervirulent carbapenem-resistant Klebsiella pneumoniae (Hv-CRKp) is of considerable concern. Bacteriophages, also known as phages, are viruses that specifically infect bacteria; thus, phage-based therapies offer promising alternatives to antibiotic treatments targeting Hv-CRKp infections. In this study, two isolated bacteriophages, Kpph1 and Kpph9, were characterized for their specificity against the Hv-CRKp K. pneumoniae NUHL30457 strain that possesses a K2 capsule serotype. Both phages exhibit remarkable environmental tolerance, displaying stability over a range of pH values (4-11) and temperatures (up to 50°C). The phages demonstrate potent antibacterial and antibiofilm efficacy, as indicated by their capacity to inhibit biofilm formation and to disrupt established biofilms of Hv-CRKp. Through phylogenetic analysis, it has been revealed that Kpph1 belongs to the new species of Webervirus genus, and Kpph9 to the Drulisvirus genus. Comparative genomic analysis suggests that the tail fiber protein region exhibits the greatest diversity in the genomes of phages within the same genus, which implies distinct co-evolution histories between phages and their corresponding hosts. Interestingly, both phages have been found to contain two tail fiber proteins that may exhibit potential depolymerase activities. However, the exact role of depolymerase in the interaction between phages and their hosts warrants further investigation. In summary, our findings emphasize the therapeutic promise of phages Kpph1 and Kpph9, as well as their encoded proteins, in the context of research on phage therapy targeting hypervirulent carbapenem-resistant Klebsiella pneumoniae.

Antimicrobial resistance in hypermucoviscous and non-hypermucoviscous Klebsiella pneumoniae: a systematic review and meta-analysis

Antimicrobial resistance has recently increased due to emerging carbapenem-resistant Klebsiella pneumoniae and extended-spectrum β-lactamase (ESBL)-producing strains of K. pneumoniae, especially among hypermucoviscous K. pneumoniae (hmKp) strains. To evaluate the prevalence of ESBL-producing and carbapenem-resistant strains in hmKp and non-hmKp clinical isolates through a systematic review and meta-analysis. We searched PubMed, Scopus, and Cochrane Library databases from January 2000 to June 2023. Clinical and in vivo/in vitro studies involving confirmed K. pneumoniae clinical isolates differentiated into hmKP and non-hmKP strains based on string test results. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated based on the number of individuals in each target group. Forest plots were used to visualize the effect sizes and 95% CIs of individual studies estimated using the inverse variance and DerSimonian - Laird methods with fixed - and random-effects models, respectively. Heterogeneity was assessed using Cochran's Q test (I2 ≥ 50%). Fifteen studies comprising 2049 clinical isolates of K. pneumoniae met the inclusion criteria. Meta-analysis revealed that hmKp strains were associated with a significantly lower prevalence of ESBL-producing strains (pooled OR: 0.26, 95% CI: 0.11-0.63, P = 0.003) and a slightly lower prevalence of carbapenem-resistant strains than non-hmKp strains (pooled OR: 0.63, 95% CI: 0.40-0.97, P = 0.038). hmKp strains exhibited lower and slightly lower prevalence of ESBL production and carbapenem resistance, respectively, than non-hmKp strains. However, given the rising prevalence of ESBL-producing and carbapenem-resistant hmKp strains, patients infected by string-test-positive K. pneumoniae must be managed prudently, considering the potential for highly resistant strains.

Machine learning analysis of magnetic covalent organic framework based heterostructures extracted intracellular metabolic fingerprint for direct hypervirulent Klebsiella pneumoniae prediction

Hypervirulent Klebsiella pneumoniae (hvKP), known for its high virulence and epidemic potential, has emerged as a significant global public health threat. Therefore, improving the identification of hvKP and enabling earlier and faster detection in the community to support subsequent effective treatment and prevention of hvKP is an urgent issue. In this study, we introduce a new approach utilizing magnetic covalent organic framework based heterostructures (denoted Fe3O4@COF@Au) for the analysis of intracellular metabolites from bacterial cells, facilitating the rapid diagnosis of hvKP. Importantly, intracellular metabolites were extracted from bacterial cells using cold methanol to preserve their abundance and stability, and their metabolite fingerprints were rapidly obtained by Fe3O4@COF@Au. Using this method, we effectively extracted intracellular metabolic fingerprints from 136 clinical K. pneumoniae isolates collected from patients. Machine learning analysis of these fingerprint variations successfully distinguished hypervirulent K. pneumoniae from classical strains (cKP), achieving an area under the curve (AUC) of 1.00 in both the training and testing sets based on 359 m/z features. This strategy shows great potential for the rapid diagnosis of hvKP and could significantly improve its management.

Rapid detection of Klebsiella pneumoniae based on one-tube RPA-CRISPR/Cas12a system

Klebsiella pneumoniae (KP) is a prevalent pathogen implicated in both community-acquired and nosocomial infections, often leading to severe clinical outcomes. The conventional methods for KP identification are characterized by intricacy and suboptimal efficiency. In this research, we have engineered a novel One-Tube RPA- CRISPR/Cas12a system, integrating recombinase polymerase amplification (RPA) method with the CRISPR/Cas12a diagnostic platform, to facilitate the detection of K. pneumoniae. To minimize the likelihood of aerosol-based contamination, the RPA components are positioned at the base of the tube, while the CRISPR/Cas12a components are placed at the tube's cap. The systems are combined post-RPA amplification through a brief centrifugation step, ensuring that RPA reactions are conducted independently to produce an adequate amount of target DNA before interaction with the CRISPR/Cas12a system. This method was validated using both fluorescent and lateral flow strip assays, achieving a limit of detection (LOD) of 100 copies/μL and 101 copies/μL respectively. The specificity for KP detection was found to be 100 %. Furthermore, the system demonstrated a positivity rate of 78 % (18/23) when directly extracting DNA from sputum samples, corroborated by culture and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). The simplicity and rapidity of the assay are augmented by a straightforward sample processing without extraction. The complete assay duration from specimen receipt to result is approximately 40 min, significantly reducing the turnaround time (TAT). Collectively, this system presents a streamlined, expeditious, and highly specific diagnostic approach for the detection of Klebsiella pneumoniae strains.

Dual Role for Pld1 in Klebsiella pneumoniae Virulence: Transcriptomics and Proteomics Provide Insights into Direct and Indirect Effects

Klebsiella pneumoniae is an opportunistic pathogen frequently found in healthcare settings, exhibiting resistance to carbapenems and third-generation cephalosporins. Hypervirulent community-acquired strains are also emerging. According to the World Health Organization (WHO), it is the top priority for developing new treatment strategies. A putative phospholipase D (PLD1) was linked to K. pneumoniae virulence, as a mutant strain is avirulent in a mouse model. However, the PLD1 function remains unclear. In the current study, no interaction between PLD1 and lipids was detected in a fat-blot. Lipidomic profile was not altered between strains or infected cells. To shed light on the role of PLD1, we compared the gene expression profile of a wild-type x pld1 mutant and found 330 modulated genes. Noteworthy, capsular polysaccharide genes were increased in the wild-type, while the mutant expressed higher levels of fimbriae, conjugation systems, and stress-protection proteins. Electron microscopy confirmed a loose capsule in the mutant, which also showed an enhanced adhesion to epithelial cells. A pulldown experiment using PLD1 as bait identified 48 macrophage proteins as putative ligands, including ribosomal, RNA-related, small GTPases, and cytoskeleton-related proteins. It suggests that PLD1 may modulate host cell complexes, favoring the infection. These findings provide novel clues about PLD1's role in virulence, guiding further investigations.

Genomic analysis and therapeutic efficacy evaluation of bacteriophage PK2420 for pneumonia caused by hypervirulent Klebsiella pneumoniae (K20 serotype)

Hypervirulent Klebsiella pneumoniae (hvKp) strains are increasingly recognized for their aggressive nature, which leads to severe clinical outcomes. The emergence of multidrug-resistant strains constitutes a substantial challenge for clinical management. Phage therapy offers a potential solution to the antibiotic resistance crisis. A multidrug-resistant hvKp strain, K2420 (K20 serotype), was used to isolate bacteriophages from hospital sewage. Phage morphology, biological properties, and genome characteristics were analyzed using transmission electron microscopy, plaque assays, and whole-genome sequencing. Therapeutic safety and efficacy were assessed in an acute pneumonia murine model induced by intratracheal injection of K2420. Assessment parameters included bacterial load, phage titer, body temperature, cytokine levels, histopathological findings, and other relevant indicators. Phage PK2420, a member of the Autographiviridae family and Przondovirus genus, was identified. It rapidly lyses K. pneumoniae (K20 serotype), inhibits biofilm formation, and exhibits a burst size of 37.4 plaque-forming units/cell. The phage is stable at temperatures ranging from 0°C to 40°C and pH values between 6 and 9. Its genome, 41,155 bp in length, contains 46 coding sequences. The phage has no genes associated with antibiotic resistance, virulence, or lysogeny. In vivo, PK2420 substantially reduced K. pneumoniae bacterial loads, improved survival rates, and alleviated pneumonia severity without observable side effects. Phage PK2420 exhibits lytic activity against K. pneumoniae both in vitro and in murine models, providing a promising and safe option for the treatment of hvKp infections.IMPORTANCEOur investigation provides insights into the interaction mechanism among hypervirulent Klebsiella pneumoniae (hvKp) (K20 serotype), phage, and the host in a mouse pneumonia model, offering a valuable reference for future research on phage pharmacokinetics. This study demonstrated that bacteriophage PK2420 exhibits promising biosafety and therapeutic efficacy against hvKp-induced pulmonary infections and dissemination in a murine model. These findings suggest that phage PK2420 may be a potential option for the clinical treatment of hvKp infections.

Aetiology of Adult Community-Acquired Lung Abscess in Hong Kong

BACKGROUND AND OBJECTIVE

Knowing the pattern of pathogens in community-acquired lung abscess (CALA) is important in the choice of initial empiric antibiotics. Early studies established the anaerobes as the predominant pathogen, followed by aerobic streptococci and aerobic Gram-negative bacilli. However, recent reports indicated that Klebsiella pneumoniae and aerobic streptococci predominated.

METHODS

We performed a retrospective study on CALA cases from all public hospitals in Hong Kong over a nine-year period. Only cases with uncontaminated specimens sent for bacterial culture were included. Cases caused by mycobacteria and fungi were excluded.

RESULTS

There were 606 eligible subjects-episodes. Mean age of subjects was 57.7 years and male to female ratio was 3.3:1. Two hundred and thirty-two subjects had at least one positive bacterial culture, with a total of 338 pathogens isolated. Anaerobes were the predominant pathogen group with 103 isolates (30.5% of total). This was followed by aerobic streptococci (90, 26.6%), aerobic Gram-negative bacilli (67, 19.8%), and Staphylococcus aureus (56, 16.6%). Isolation of Staphylococcus aureus was closely linked to intravenous drug abuse, while isolation of Klebsiella pneumoniae (28 cases) was related to extrapulmonary abscesses, particularly of the liver. There were 14 cases of Pseudomonas aeruginosa with underlying chronic lung disease and major organ failure being risk factors.

CONCLUSION

Anaerobes and aerobic streptococci appear to be the major pathogens for primary CALA. Secondary lung abscess caused by haematogenous spread is commonly attributable to Staphylococcus aureus or Klebsiella pneumoniae. Choice of empiric antibiotics should take these into consideration together with local patterns of antibiotic resistance.

De Novo Design of Highly Stable Binders Targeting Dihydrofolate Reductase in Klebsiella pneumoniae

The study aims to design novel therapeutic inhibitors targeting the DHFR protein of Klebsiella pneumoniae. However, challenges like bacterial resistance to peptides and the limitations of computational models in predicting in vivo behavior must be addressed to refine the design process and improve therapeutic efficacy. This study employed deep learning-based bioinformatics techniques to tackle these issues. The study involved retrieving DHFR protein sequences from Klebsiella strains, aligning them to identify conserved regions, and using deep learning models (OmegaFold, ProteinMPNN) to design de novo inhibitors. Cell-penetrating peptide (CPP) motifs were added to enhance delivery, followed by allergenicity and thermal stability assessments. Molecular docking and dynamics simulations evaluated the binding affinity and stability of the inhibitors with DHFR. A conserved 60-residue region was identified, and 60 de novo binders were generated, resulting in 7200 sequences. After allergenicity prediction and stability testing, 10 sequences with melting points near 70°C were shortlisted. Strong binding affinities were observed, especially for complexes 4OR7-1787 and 4OR7-1811, which remained stable in molecular dynamics simulations, indicating their potential as therapeutic agents. This study designed stable de novo peptides with cell-penetrating properties and strong binding affinity to DHFR. Future steps include in vitro validation to assess their effectiveness in inhibiting DHFR, followed by in vivo studies to evaluate their therapeutic potential and stability. These peptides offer a promising strategy against Klebsiella pneumoniae infections, providing potential alternatives to current antibiotics. Experimental validation will be key to assessing their clinical relevance.

The wzc mutation mediates virulence changes in K1-type Klebsiella pneumoniae within the same patient

Hypervirulent Klebsiella pneumoniae (hvKp) is a major pathogen causing community-acquired infections, particularly severe diseases such as liver abscesses. Although extensive research has been conducted on the virulence mechanisms of hvKp and the genetic properties of resistance plasmids, studies on the adaptive evolution of clinical strains within the host are still limited. This study aimed to investigate the impact of genetic mutations on phenotypic changes in high-virulence K. pneumoniae within a host environment. We isolated three strains of K. pneumoniae from the same patient, two of which had identical genetic backgrounds but exhibited distinct phenotypic traits. Comparative genomic analysis was performed to identify genetic differences. A nucleotide mutation in the wzc gene was identified as a potential factor associated with changes in the mucoid phenotype. This mutation was verified using string tests and anti-centrifugal assays. Additionally, in vivo bioassays and animal infection models were conducted to further validate the findings. The comparative genomic analysis revealed a nucleotide mutation in the wzc gene, which was associated with changes in the mucoid phenotype of the strain. This was confirmed through string tests and anti-centrifugal assays. In vivo experiments and animal infection models suggested that hvKp adapts to the host by reducing capsular polysaccharide synthesis, thereby trading off some virulence for enhanced colonization capabilities. Our findings indicate that genetic mutations in hvKp can lead to significant phenotypic changes that facilitate adaptation within the host. The observed reduction in capsular polysaccharide synthesis appears to be a trade-off between virulence and colonization ability. This study provides insights into the adaptive evolution of hvKp and highlights the importance of considering intrahost genetic changes when studying the pathogenesis of hvKp. Future research should focus on further elucidating the mechanisms underlying these adaptations and their clinical implications.

Klebsiella pneumoniae Isolates from the Intensive Care Unit at South Qunfudah Hospital in Saudi Arabia: An Emerging Antimicrobial Resistance Profile

Introduction

Klebsiella pneumoniae is a significant pathogen in healthcare settings, particularly in the Intensive Care Unit (ICU). Its antimicrobial resistance poses a serious threat to infection control and patient outcomes. This study aims to analyze the developing antimicrobial resistance profile of Klebsiella pneumoniae isolates in the ICU.

Methods

A big hospital in Qunfudah provided 137 cases of infected individuals for this retrospective analysis. It was conducted on the available data on ICU patients' records. Various types of specimens were used. The data collected includes patients' demographic data, laboratory investigation, and tests for antimicrobial susceptibility. The isolates were identified and subjected to antimicrobial susceptibility tests using the compact system identification method. Data input and analysis were done using SPSS, version 26.

Results

The outcomes of this study reflected that more than half of K. pneumoniae were isolated from males (62.4%), many of them are Patients aged 76-95 years (n;43) were the most infected, followed by individuals aged 56-75 years (n; 27), 36-55 years (n;14), 96-105 years (n;7), and 16-35 years (n;2). The high frequency of specimens, sputum, urine, blood, and endotracheal tube (37.2%, 19%,18.2%,16.1%), respectively. Sputum had the highest culture positivity (n 51; 37.2%) for pathogens, followed by urine (n 26;19%), blood (n 25;18.2%), endotracheal tube (n 22; 16.1%), wound swabs (n 8; 5.8%), central line tip (n 3; 2.2%) stool and urethral swab (n 1; 0.7% for each). K. pneumoniae demonstrated high resistance rates (100%) for Cefalotin, Cefoxitin, Ceftriaxone, Cefepime, and Ampicillin, followed by Ciprofloxacin and Trimethoprim/Sulfamethoxazole (97.8%), Nitrofurantion (94.6%), Meropenem (91.4%), Amikacin (90.3%) and Gentamicin (87.1%). The lowest resistance rate was Imipenem (30.10%).

Conclusion

In conclusion, this study examines the antimicrobial resistance of Klebsiella pneumoniae in the ICU of South Qunfudah Hospital, focusing on specific location data rather than general resistance trends.

WGS of a lytic phage targeting biofilm-forming carbapenem-resistant Klebsiella pneumoniae prevalent in a tertiary healthcare setup

Carbapenem-resistant Enterobacteriaceae (CRE) are listed as a priority-one critical pathogen category by the WHO because of their abysmal treatment outcomes owing to antibiotic inefficiency. Among CRE, Klebsiella pneumoniae is prevalent in acquiring resistance genes and withstanding the last-resort drugs. Additionally, its ability to form robust biofilms further exacerbates the treatment challenges. The escalating resistance and recalcitrance of biofilm-residing bacteria against standard antibiotic treatments demand an alternative to antibiotics. Phages, being nature-tailored, are a never-ending arsenal against the bacteria because of their capacity to lyse bacteria rapidly and co-evolve with bacteria. In our study, we isolated K. pneumoniae from patients at Madras Medical Mission Hospital (MMMH), India, and assessed their antibiogram profiles, presence of carbapenemase genes, and biofilm-forming abilities. 100 % of the strains were extended-spectrum beta-lactamase producing, multidrug-resistant (ESBL-MDR), with 95 % harbouring carbapenemase genes. Among the isolates, 65 % were strong biofilm formers, and the rest were moderate. Further, we isolated a bacteriophage, SAKp11, from the hospital sewage, which was able to lyse 62 out of 167 clinical isolates and successfully reduced 99.99 % viable bacterial cells of the 24-h-old biofilm of strong biofilm forming MDR K. pneumoniae strains. Whole genome analysis revealed that SAKp11, with a genome size of 59,338bp, belonged to the Casjensviridae family, one of the less explored bacteriophage families. Comprehensive characterization of SAKp11 indicated its suitability for therapeutic use. Our study highlights the severity of drug-resistant K. pneumoniae in Indian healthcare and the inadequacy of current antibiotics, underscoring the potential of phages as an alternative therapeutic option.

Genetic framework and evolutionary dynamics of mcr-positive Klebsiella pneumoniae from 2000 to 2023

The international transmission of the colistin resistance gene mcr in Enterobacteriaceae poses significant public health burdens, while the understanding of the population structure and evolutionary history of mcr-positive Klebsiella pneumoniae worldwide remains unclear. Here, we conducted a genomic analysis on 463 sequences of K. pneumoniae harboring mcr genes from public database between 2000 and 2023. A total of 6 mcr variants (mcr-1, -2, -3, -8 to -10) were detected, with mcr-9 (36.1%), mcr-1 (33.7%) and mcr-8 (29.2%) genes being the most common. 43.4% of total isolates (201/463) carried carbapenemase genes (blaNDM, blaKPC, blaIMP, blaOXA-48/181/232, blaVIM and blaGES) and 15.3% of isolates (71/463) contained hypervirulent genes (iucA or iroB). Correlation analysis indicated mcr-1/8/9 genes were positively correlated with specific genomic elements that were rarely described, including mcr-1 with iucABC and iutA; mcr-8 with oqxB; mcr-9 with dfrA19, ISEsa and repA (R absolute value > 0.3, p<0.01). The population of K. pneumoniae can be classified into 6 clusters, some isolates co-harboring mcr and carbapenemase genes exhibited high level of genetic similarity and dispersed in several countries, indicating the possibility of clonal transmission. mcr-9 gene was introduced into K. pneumoniae in 1978 before the time of mcr-1 gene in 1988 and mcr-8 gene in 1993. We found mcr-1/8/9 genes in K. pneumoniae evolved high-risk lineages in specific geographical location (China, Thailand and the United Kingdom) that most isolates typically contained iucA, blaNDM or blaKPC. This study highlighted that continuous surveillance for the evolution of mcr-positive K. pneumoniae harboring iucA or carbapenemase genes is essential.

Virulence characteristics and antibiotic resistance analysis of Klebsiella pneumoniae isolated from pig farms in Xinjiang, China: revealing potential zoonotic risks

BACKGROUND

This study aimed to analyze the antimicrobial resistance and pathogenicity of Klebsiella pneumoniae(K. pneumoniae) isolates from pigs, evaluate their potential threat to pig farming and public health, and provide a theoretical basis for controlling K. pneumoniae infections in pig farms.

METHODS

Nasal swabs collected from pigs were subjected to bacterial isolation, biochemical identification, species-specific PCR, and 16S rRNA sequencing to identify K. pneumoniae. Serotyping and multilocus sequence typing (MLST) were conducted using the wzi and MLST methods, respectively. Biofilm formation was assessed using crystal violet staining. Antimicrobial susceptibility was evaluated via the Kirby-Bauer disk diffusion method, and resistance and virulence genes were identified using PCR. Pathogenicity was determined through string testing and mouse infection models.

RESULTS

21 strains of K. pneumoniae were isolated and identified from 50 swabs of pig nasal cavities. The isolates were classified into serotypes wzi 19 and wzi 81 and sequence types ST37 and ST967. Ten isolates exhibited strong biofilm-forming ability, while 11 showed moderate biofilm production. Antimicrobial susceptibility testing revealed resistance to β-lactams, aminoglycosides, quinolones, tetracyclines, sulfonamides, aminoalcohols, and glycopeptides, with sensitivity restricted to imipenem and polymyxins. Ten resistance genes and eight virulence genes were detected. Pathogenicity testing in mice revealed a moderate virulence level, with a median lethal dose (LD50) of 4.0 × 10⁶ CFU/mL. Infected mice exhibited significant lesions in the liver, lungs, and small intestine.

CONCLUSION

These findings highlight a potential risk to pig farming and public health, emphasizing the need for effective control measures against K. pneumoniae infections in pig farms.

Insertion sequences accelerate genomic convergence of multidrug resistance and hypervirulence in Klebsiella pneumoniae via capsular phase variation

BACKGROUND

The convergence of resistance and hypervirulence in Klebsiella pneumoniae represents a significant public health threat, driven by the horizontal transfer of plasmids. Understanding factors affecting plasmid transfer efficiency is essential to elucidate mechanisms behind emergence of these formidable pathogens.

METHODS

Hypermucoviscous K. pneumoniae strains were serially passaged in LB medium to investigate capsule-deficient phenotypes. Capsule-deficient mutants were analyzed using genetic sequencing to identify the types and insertion sites of insertion sequences (IS). Bioinformatics and statistical analyses based on the NCBI and National Microbiology Data Center (NMDC) database were used to map the origins and locations of IS elements. Conjugation assays were performed to assess plasmid transfer efficiency between encapsulated and capsule-deficient strains. A murine intestinal colonization model was employed to evaluate virulence levels and IS excision-mediated capsule restoration.

RESULTS

Our research revealed that a hypervirulent K. pneumoniae (hvKP) strain acquired a blaNDM-1-bearing IncX3 plasmid with IS5 and ISKox3 elements. These IS elements are capable of inserting into capsular polysaccharide synthesis genes, causing a notably high frequency of capsule loss in vitro. The IS-mediated capsular phase variation, whether occurring in the donor or recipient strain, significantly increased the conjugation frequency of both the resistance plasmid and the virulence plasmid. Additionally, capsular phase variation enhanced bacterial adaptability in vitro. Experiments in mouse models demonstrated that capsule-deficient mutants exhibited reduced virulence and colonization capacity. However, during long-term intestinal colonization, IS element excision restored capsule expression, leading to the recovery of hypervirulence and enhanced colonization efficiency.

CONCLUSIONS

Our findings reveal that IS elements mediate capsular phase variation by toggling gene activity, accelerating the genomic convergence of multidrug resistance and hypervirulence in K. pneumoniae, as well as facilitating adaptive transitions in different environments.

Prevalence of hypervirulent Klebsiella pneumoniae and application of the novel Klebsiella phage vB_KpnP_D39 for biocontrol of serotypes K1, K2, and K57 in prepared food-related samples

In recent years, the contamination of Klebsiella pneumoniae has raised significant concerns about the potential risks to human health. The presence of K. pneumoniae in prepared food-related samples and efficient control is of importance for ensuring food safety. In this study, 300 samples were collected from markets in Hefei, China, and 45 K. pneumoniae isolates were isolated from aquatic products (n = 30), vegetables (n = 9), and ready-to-eat foods (n = 6), respectively. Among these isolates, the capsular serotypes K1, K2, and K57 accounted for the highest percentage, totaling 33.33 % (15/45), and the predominant sequence types were ST23, ST412, and ST11. Additionally, twenty-six isolates (26.9 %) were identified as hypervirulent K. pneumoniae (hvKp), and all were multidrug-resistant (MDR). Notably, the strains carrying iucA generate higher levels of siderophores compared to those that were negative for iucA (P < 0.01). Furthermore, a novel lytic phage vB_KpnP_D39 (D39), which specifically targets multiple hypervirulent capsular serotypes (K1, K2, and K57), was isolated from sewage samples collected from an effluent treatment plant in Hefei, China. D39 maintained highly lytic activity over a pH range of 3.0 to 11.0 and from 20 to 60 °C. Using transmission electron microscopy, a typical podovirus morphotype of D39 was observed. Genomic analysis indicated that D39 belongs to a novel species within genus Przondovirus, and genes associated with virulence and antibiotic resistance were not identified. In practical applications, D39 has been confirmed to significantly destroy biofilm formation and effectively prevent contamination by K. pneumoniae in food production. These findings provide information about the contamination of prepared food-related samples by MDR-hvKp, and a potential biocontrol agent for prevention and control.

Genome Characterization of Carbapenem-Resistant Hypervirulent Klebsiella pneumoniae Strains, Carrying Hybrid Resistance-Virulence IncHI1B/FIB Plasmids, Isolated from an Egyptian Pediatric ICU

Despite the increased reporting of Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) in Egypt, there is a paucity of information regarding the molecular characteristics of such strains. Herein, we present the genome sequence of two CR-hvKp strains, K22 and K45, which were isolated from VAP (ventilator-associated-pneumonia) patients admitted to pediatric ICU at Assiut University Children's Hospital, Egypt. K22 and K45 isolates were subjected to antimicrobial susceptibility testing and whole-genome sequencing. Genomic analysis was performed to characterize each strain, determining their plasmids, antimicrobial resistance (AMR) genes, and virulence determinants. K22 possessed an extensive drug resistance phenotype (XDR), whilst K45 exhibited a multidrug resistance phenotype (MDR), with genome sequencing revealing the presence of a diverse array of AMR genes. Both strains were resistant to the carbapenem antibiotic imipenem, carrying the OXA-48 carbapenemase, with K22 additionally possessing an NDM-1 carbapenemase. Each strain was considered high-risk, with K22 and K45 respectively belonging to sequence types ST383 and ST14 and possessing virulence genes implicated in hypervirulence (e.g., iucABCD-iutA and rmpA). Importantly, both strains carried multiple plasmid replicons, including an AMR/virulence IncHI1B/FIB hybrid plasmid and MDR IncL/M plasmids. This report highlights the critical role of plasmids in the evolution of virulent K. pneumoniae strains and suggests the circulation of an IncHI1B/FIB hybrid plasmid, simultaneously disseminating AMR and hypervirulence, amongst K. pneumoniae strains within Assiut University Children's Hospital.

Essentiality of the virulence plasmid-encoded factors in disease pathogenesis of the major lineage of hypervirulent Klebsiella pneumoniae varies in different infection niches

BACKGROUND

Hypervirulent Klebsiella pneumoniae (HvKp) can metastasise to extra-intestinal sites to cause disseminated disease such as pyogenic liver abscesses. HvKp harbours a large virulence plasmid (KpVP) that contributes to pathogenicity. We previously identified a crucial gene region that confers virulence in SGH10 (ST23, K1 capsule), spanning genes encoding the siderophores aerobactin and salmochelin, as well as the regulator of mucoidy phenotype A (iuc-rmp-iro).

METHODS

SGH10 isogenic mutants of aerobactin, rmpA, and salmochelin were generated and tested in vitro for their siderophore production, hypermucoviscosity and growth. We investigated the essentiality of these factors in different murine infection or colonisation models.

FINDINGS

In a lung pneumonia model, capsule modulation by rmpA was the primary driver of high bacterial burden in the lung. In a systemic infection setting, rmpA was still the primary driver, followed by a significant contribution by salmochelin, that conferred virulence. However, the role of aerobactin was more significant in hvKp persistence in the gut. We further examined a large collection of Kp genomes and observed that the iro loci is often co-inherited with iuc in KpVP-1, suggesting the evolutionary importance of expressing both siderophores in these lineages.

INTERPRETATION

HvKp typically colonises the intestinal niche, however, the acquisition of the KpVP plasmid has enabled it to thrive outside the gut and cause metastatic infections. While the iuc-rmp-iro region is pivotal in bestowing virulence, the encoded factors contribute differently to the success of the pathogen in various infection sites, where the microenvironment, nutrient availability and immune response can vary. Thus, our study demonstrates that possessing the iuc-rmp-iro gene region can be an evolutionary advantage by allowing for flexibility in modulating siderophore and capsule expression in order for K. pneumoniae to thrive in distinct host niches.

FUNDING

This work is funded by the National Research FoundationMOH-000925-00 to YH Gan and OFYIRG22jul-0042 by the National Medical Research Council (NMRC) to THT.

Klebsiella pneumoniae under xylose pressure: the growth adaptation, antimicrobial susceptibility, global proteomics analysis and role of XylA and XylB proteins

Klebsiella pneumoniae can be cultured in medium with xylose as the sole carbon source. However, the effect of xylose exposure on its growth adaptation, virulence, antimicrobial susceptibility, and proteomic response remain unclear. Here, we show that low concentrations of xylose (≤ 2%) promote the planktonic growth of three K. pneumoniae isolates (K2044, EKP19, and EKP108) in a concentration-dependent manner, while 8% xylose consistently inhibits their planktonic growth. Notably, the xylose-induced isolate K2044-8Xyl-60G, when exposed to various xylose concentrations, exhibited the longest logarithmic growth phase and the highest optical density (OD) after logarithmic growth, compared to K2044. In contrast, the xylose-induced isolates EKP19 and EKP108 did not successfully reshape growth adaptation under persistent xylose pressure compared to K2044. Additionally, while the growth adaptation of K2044-8Xyl-60G under xylose pressure was confirmed, no amino acid mutations were detected in the functional proteins of this xylose-induced isolate, suggesting that persistent xylose pressure does not cause nonsense mutations in the bacterial genome. Xylose exposure reduced the gentamicin minimum inhibitory concentration (MIC) in all three K. pneumoniae isolates (K2044, EKP108, and EKP19) and their xylose-induced derivatives. In a Galleria mellonella infection model, significantly decreased virulence was observed in the xylose-induced isolates of K2044 and EKP19. Proteomic analysis of K2044-8Xyl-60G treated with 8% xylose revealed upregulation of proteins involved in glycolysis, the pentose phosphate pathway, and transmembrane transport. We also constructed K2044-ΔxylA (with deletion of the xylA gene) and K2044-ΔxylB (with deletion of the xylB gene). Our data showed that K2044-ΔxylA exhibited enhanced planktonic growth compared to K2044 when exposed to xylose concentrations of ≥ 4%, while K2044-ΔxylB displayed significantly reduced growth capacity regardless of xylose exposure. The virulence of K2044-ΔxylA was also significantly reduced, as demonstrated by the increased survival rates in G. mellonella infection models. Additionally, xylose exposure strongly enhanced membrane depolarization in both K2044-ΔxylA and K2044-ΔxylB compared to the wild-type K2044. Proteomic analysis indicated that the deletion of xylA primarily affected functional proteins related to ribosomes, xylose transmembrane transporters and capsular polysaccharides, while the deletion of xylB impacted the expression of xylose metabolism-related proteins. In conclusion, xylose exposure can reshape the growth adaptation, virulence, and antimicrobial susceptibility of K. pneumoniae in an isolate-specific manner, with xylA playing a more critical role than xylB under high xylose concentrations.

Predictive factors for liver abscess liquefaction degree based on clinical, laboratory, and computed tomography data

BACKGROUND

Effective management of liver abscess depends on timely drainage, which is influenced by the liquefaction degree. Identifying predictive factors is crucial for guiding clinical decisions.

AIM

To investigate the predictive factors of liver abscess liquefaction and develop a predictive model to guide optimal timing of percutaneous drainage.

METHODS

This retrospective study included 110 patients with pyogenic liver abscesses who underwent percutaneous catheter drainage. Patients were divided into a poor liquefaction group (n = 28) and a well liquefaction group (n = 82) based on the ratio of postoperative 24-hour drainage volume to abscess volume, using a cutoff value of 0.3. Clinical characteristics, laboratory indicators, and computed tomography imaging features were compared. A predictive model was constructed using logistic regression and evaluated using receiver operating characteristic curves and five-fold cross-validation.

RESULTS

Independent predictive factors for good liquefaction included the absence of diabetes [odds ratio (OR) = 0.339, P = 0.044], absence of pneumonia (OR = 0.218, P = 0.013), left-lobe abscess location (OR = 4.293, P = 0.041), cystic features (OR = 5.104, P = 0.025), and elevated preoperative serum alanine aminotransferase (ALT) levels (OR = 1.013, P = 0.041). The logistic regression model based on these factors demonstrated an area under the curve of 0.814, with a sensitivity of 90.24% and specificity of 67.86%. Five-fold cross-validation yielded an average accuracy of 83.61% and a kappa coefficient of 0.5209.

CONCLUSION

Pneumonia, diabetes, abscess location, abscess composition, and preoperative serum ALT levels are significant predictors of liver abscess liquefaction. The model can guide clinical decision-making.

Molecular epidemiological analysis and research on resistance and virulence of carbapenem-resistant Klebsiella pneumoniae in a tertiary hospital from 2016 to 2023

PURPOSE

Carbapenem-resistant Klebsiella pneumoniae (CRKP) represents a significant global threat due to its high prevalence rates and limited therapeutic options. The primary objective of this study was to investigate the clinical distribution and molecular epidemiology of CRKP collected between 2016 and 2023 from a tertiary care hospital in northern China.

METHODS

Polymerase chain reaction (PCR) assays were used to identify resistance and virulence genes, while various assessments, including the string test and biofilm formation analysis, assessed CRKP's virulence. Multilocus sequence typing (MLST) and whole-genome sequencing were employed to elucidate strain classification and plasmid characteristics.

RESULTS

The study identified 100 unique CRKP strains, primarily isolated from neurosurgery and ICU, with sputum as the most common specimen type. The majority of strains harbored blaKPC-2 as the primary resistance mechanism. All CRKP strains harbored a minimum of four virulence genes, with entB, mrkD, fimH, and ybtS being most commonly detected across the isolates. Notably, 66 of 100 strains were classified as carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP). The prevailing sequence type (ST) observed was ST11, with serotype KL47 being most prevalent initially, subsequently supplanted by ST11-KL64. Specific strains harbored blaKPC-2 on IncFII-type plasmids, along with other resistance genes, such as blaTEM-1. KP635_PlasmidB harbors multiple antibiotic resistance genes, and the sequence identity and coverage between KP635_PlasmidA and the NTUH-K2044 virulence plasmid are 99%, which contributes to the formation of a highly virulent and multidrug-resistant strain in KP635.

CONCLUSION

The emergence of high resistance and hypervirulence in CRKP requires vigilance, enhanced surveillance, and stringent infection control measures to limit its spread.

Evidence of hypervirulent carbapenem-resistant Klebsiella pneumoniae in cats with urinary affections and associated humans in Egypt

The emergence of hypervirulent and carbapenem-resistant Klebsiella pneumoniae poses a significant threat to the public health of both cats and their owners. Therefore, conducting molecular characterization and phylogenetic analysis of K. pneumoniae strains in both cats and humans in Egypt is crucial. 108 feline and 101 human urine samples were collected and subjected to routine microbiological isolation and molecular identification of K. pneumoniae. Subsequently, phenotypic antimicrobial sensitivity patterns and molecular identification of classical virulence, hypervirulence, and carbapenem resistance genes were examined. A total of 46 K. pneumoniae isolates were recovered, comprising 43.4% (23 out of 53) from diseased humans, 4.17% (2 out of 48) from healthy humans, 22.95% (14 out of 61) from diseased felines, and 14.89% (7 out of 47) from healthy felines. The detection rates for narrow drug-resistant (NDR), multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan drug-resistant (PDR) strains were 41.30%, 54.35%, 2.17%, and 2.17%, respectively. The distribution rates for mrKD, entB, K2, Kfu, and MagA genes were 76.1%, 82.6%, 8.7%, 13.0%, and 0%, respectively. In addition, the distribution of hypervirulence genes was 41.3%, 36.9%, 13.0%, 10.9%, and 17.4% for iucA, iroB, Peg344, rmPA, and rmPA2, respectively, and 43.5%, 30.4%, 19.6%, and 52.2% for NDM, OXA-48, VIM, and KPC resistance genes, respectively. Phylogenetic analysis of the entB gene from four recovered strains revealed a relationship between feline strains and other human strains. In conclusion, this study focused on the molecular characterization and phylogenetic analysis of hypervirulent and carbapenem-resistant K. pneumoniae in companion cats and humans in Egypt.

A systematic review of hypervirulent Klebsiella pneumoniae research: bibliometric and topic modeling perspectives

Background/objective

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.

Methods

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.

Results

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.

Conclusion

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.

Genomic and functional analysis of rmp locus variants in Klebsiella pneumoniae

BACKGROUND

Klebsiella pneumoniae is an opportunistic pathogen and a leading cause of healthcare-associated infections in hospitals, which are frequently antimicrobial resistant (AMR). Exacerbating the public health threat posed by K. pneumoniae, some strains also harbour additional hypervirulence determinants typically acquired via mobile genetic elements such as the well-characterised large virulence plasmid KpVP-1. The rmpADC locus is considered a key virulence feature of K. pneumoniae and is associated with upregulated capsule expression and the hypermucoid phenotype, which can enhance virulence by contributing to serum resistance. Typically such strains have been susceptible to all antimicrobials besides ampicillin; however, the recent emergence of AMR hypermucoid strains is concerning.

METHODS

Here, we investigate the genetic diversity, evolution, mobilisation and prevalence of rmpADC, in a dataset of 14,000 genomes from isolates of the Klebsiella pneumoniae species complex, and describe the RmST virulence typing scheme for tracking rmpADC variants for the purposes of genomic surveillance. Additionally, we examine the functionality of representatives for variants of rmpADC introduced into a mutant strain lacking its native rmpADC locus.

RESULTS

The rmpADC locus was detected in 7% of the dataset, mostly from genomes of K. pneumoniae and a very small number of K. variicola and K. quasipneumoniae. Sequence variants of rmpADC grouped into five distinct lineages (rmp1, rmp2, rmp2A, rmp3 and rmp4) that corresponded to unique mobile elements, and were differentially distributed across different populations (i.e. clonal groups) of K. pneumoniae. All variants were demonstrated to produce enhanced capsule production and hypermucoviscosity.

CONCLUSIONS

These results provide an overview of the diversity and evolution of a prominent K. pneumoniae virulence factor and support the idea that screening for rmpADC in K. pneumoniae isolates and genomes is valuable to monitor the emergence and spread of hypermucoid K. pneumoniae, including AMR strains.

New insights and perspectives on the virulence of hypervirulent Klebsiella pneumoniae

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.

Probiotic cell-free supernatant as effective antimicrobials against Klebsiella pneumoniae and reduce antibiotic resistance development

This study evaluated the antimicrobial activity, resistance development, and synergistic potential of cell-free supernatant (CFSs) derived from Levilactobacillus brevis (Lb-CFS) and Lactiplantibacillus plantarum (Lp-CFS) against Klebsiella pneumoniae. Both CFSs exhibited potent growth inhibition, with minimum inhibitory concentrations (MICs) of 128 μg/mL and 64 μg/mL for Lb-CFS and Lp-CFS, respectively, and demonstrated dose-dependent bactericidal activity, achieving complete bacterial eradication at minimum bactericidal concentrations (MBC) within 6 h. The CFSs suppressed the expression of virulence genes (galF, wzi, and manC) and biofilm formation in a dose-dependent manner. Synergistic interactions were observed when combining CFSs with antibiotics, resulting in 2- to fourfold reductions in antibiotic MICs and MBCs. Notably, adaptive evolution experiments revealed significantly slower resistance development in K. pneumoniae against CFSs (twofold MIC/MBC increase) compared to antibiotics (16- to 128-fold increase) after 21 days. Furthermore, CFS-adapted strains exhibited increased antibiotic susceptibility, while antibiotic-adapted strains displayed cross-resistance to multiple antibiotics. No cross-resistance occurred between Lb-CFS and Lp-CFS, suggesting distinct adaptive mechanisms. These findings highlight the potential of probiotic-derived CFSs as effective antimicrobials with a lower propensity for inducing rapid resistance compared to conventional antibiotics, suggesting their promise in combating multidrug-resistant infections.

Summary of clinical features of 1800 cases of pyogenic liver abscess

OBJECTIVE

This study aimed to summarize the clinical and microbiological characteristics of patients with pyogenic liver abscess (PLA) and to explore the clinical features of PLA with extrahepatic migratory infection (EMI).

METHODS

A retrospective analysis was conducted on clinical data from 1800 PLA patients at Jilin University First Hospital from January 2019 to December 2023. Patients were divided into two groups based on the presence of EMI: with EMI and without EMI. Clinical features and prognoses of the two groups were compared using rank-sum tests and chi-square tests for continuous and categorical data, respectively.

RESULTS

PLA patients were predominantly male (65.56%) with an average age of 60. Abscesses were mainly located in the right lobe (64.83%) and were often single (68.17%). Klebsiella pneumoniae was the primary pathogen (68.46%), with 9.50% of strains being multidrug-resistant. The majority of patients improved with effective treatment (96.17%). Compared with the non-EMI group, patients with EMI were younger, had longer hospital stays, smaller abscesses, and a higher incidence of diabetes and cerebrovascular disease, with poorer prognoses.

CONCLUSION

PLA is most commonly observed in middle-aged and elderly males, often presenting as single abscesses in the right lobe, with diabetes as a frequent underlying condition. Most patients recover with appropriate antibiotic treatment and ultrasound-guided drainage. PLA patients with EMI generally have poorer outcomes and require special attention.

Antibody responses in Klebsiella pneumoniae bloodstream infection: a prospective cohort study

BACKGROUND

Klebsiella pneumoniae is a leading cause of infection-related deaths globally, yet little is known about human antibody responses to invasive K pneumoniae. We sought to determine whether the O-specific polysaccharide antigen is immunogenic in humans with K pneumoniae bloodstream infection. We also sought to define the cross-reactivity of human antibody responses among structurally related K pneumoniae O-specific polysaccharide subtypes and to assess the effect of capsule production on O-specific polysaccharide-targeted antibody binding and function.

METHODS

In this prospective cohort study, we compared plasma antibody responses to O-specific polysaccharide in a cohort of consecutively enrolled patients with K pneumoniae bloodstream infection with controls, specifically a cohort of healthy individuals and a cohort of individuals with Enterococcus spp bloodstream infection. Patients were enrolled at the Massachusetts General Hospital, a tertiary hospital with affiliated clinics in the USA. We excluded patients whose isolates were not confirmed to be K pneumoniae by whole-genome sequencing. The primary outcome was the measurement of plasma IgG, IgM, and IgA antibody responses. We performed flow cytometry to measure the effects of K pneumoniae capsule production on O-specific polysaccharide antibody binding and O-specific polysaccharide antibody-mediated complement deposition, using patient isolates with variable levels of capsule production and isogenic capsule-deficient strains derived from these isolates.

FINDINGS

We enrolled 129 consecutive patients with suspected K pneumoniae bloodstream infection between July 24, 2021, and August 4, 2022, of whom 69 patients (44 [64%] male and 25 [36%] female) with confirmed K pneumoniae bloodstream infection were eligible for immunological evaluation. Common O-specific polysaccharide serotypes (O1, O2, O3, and O5) accounted for 57 (83%) of 69 infections. O-specific polysaccharide was immunogenic in patients with K pneumoniae bloodstream infection, and peak O-specific polysaccharide-IgG antibody responses in patients were ten-fold to 30-fold higher than antibody responses detected in healthy controls, depending on the serotype. There was cross-reactivity among similar O-specific polysaccharide subtypes, including the O1v1 and O1v2, O2v1 and O2v2, and O3 and O3b subtypes, as well as between the O1 and O2 types. Capsule produced by both hyperencapsulated and non-hyperencapsulated K pneumoniae inhibited O-specific polysaccharide-targeted antibody binding and function.

INTERPRETATION

O-specific polysaccharide was immunogenic in patients with K pneumoniae bloodstream infection, supporting its potential as a candidate vaccine antigen. The cross-reactivity observed between similar O-specific polysaccharide subtypes in patients with K pneumoniae bloodstream infection suggests that it might not be necessary to include all subtypes in an O-specific polysaccharide-based vaccine. However, these observations are tempered by the fact that capsule production, even in non-highly encapsulated strains, has the potential to interfere with O-specific polysaccharide antibody binding. This finding could limit the effectiveness of vaccines that exclusively target O-specific polysaccharide.

FUNDING

National Institute of Allergy and Infectious Diseases at the National Institutes of Health.

Uncomplicated pharyngitis due to family transmission of hypervirulent Klebsiella pneumoniae

We describe two cases of uncomplicated pharyngitis caused by hypervirulent Klebsiella pneumoniae (hvKp) in a family, initially in an immunocompetent adolescent, followed by possible household spread resulting in similar presentations in the patient's parent. Genomic analysis confirmed hvKp from the two cases were genetically identical and typed as K2-ST3252. Nasopharyngeal carriage and respiratory secretion/droplet may play an important yet underrecognized role in the transmission of hvKp. Enhancing routine screening for hvKp in the upper respiratory culture, followed by genotyping provides an effective pathway for early diagnosis.

Multidrug-resistant hypervirulent Klebsiella pneumoniae: an evolving superbug

Multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-hvKP) combines high pathogenicity with multidrug resistance to become a new superbug. MDR-hvKP reports continue to emerge, shattering the perception that hypervirulent K. pneumoniae (hvKP) strains are antibiotic sensitive. Patients infected with MDR-hvKP strains have been reported in Asia, particularly China. Although hvKP can acquire drug resistance genes, MDR-hvKP seems to be more easily transformed from classical K. pneumoniae (cKP), which has a strong gene uptake ability. To better understand the biology of MDR-hvKP, this review discusses the virulence factors, resistance mechanisms, formation pathways, and identification of MDR-hvKP. Given their destructive and transmissible potential, continued surveillance of these organisms and enhanced control measures should be prioritized.

Disseminated Hypervirulent Klebsiella pneumoniae Infection Following Travel: A Case of Cavitating Pneumonia, Hepatic and Renal Abscesses, and Thrombosis

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.

Bacteriophage therapy: a possible alternative therapy against antibiotic-resistant strains of Klebsiella pneumoniae

Klebsiella pneumoniae is a notorious, Gram-negative pathogen and is a leading cause of healthcare settings and community-acquired infections. This is the commensal of human microbiota and can invade and cause infections in different body parts. The global emergence of antibiotic resistance in K. pneumoniae has become a major challenge in the whole medical community. Alternative paths to treat the infections caused by these MDR pathogens are needed as these bacteria become resistant to last-resort antibiotics like colistin. The lytic bacteriophages (phages) are the bacteria's natural predators and can rapidly eliminate the bacterial cells. Phages are abundant in nature and have recently been found to be effective tools in modern biotechnology. They can be used to control the bacterial infectious diseases. They can be manipulated easily and potentially used in therapeutics, biotechnology, and research. Several studies, both in vitro and in vivo, have demonstrated the possible applications of the lytic phages in treating K. pneumoniae superbug strains. Phage endolysins have drawn the scientific world's attention because of their involvement in phage adsorption and bacterial capsules digestion. These phage-encoded enzymes digest the polysaccharide components of bacterial cell walls by recognizing and binding them. Phage lysins, being strong biological agents, are capable of effectively and swiftly eliminating bacteria. This review summarizes the information on phages of K. pneumoniae and phage-based therapies to target their bacterial hosts.

Major Predominant Serotypes and Virulence Genes and Antibiotic Resistance Characteristics of Klebsiella pneumoniae Clinical Isolates in Middle and East China

Background

Klebsiella pneumoniae is a common opportunistic pathogen. Predominant serotypes, virulence genes, and resistance characteristics of K. pneumoniae isolates from patients in different regions of China require further investigation.

Methods

K. pneumoniae isolates from patients and healthy individuals in middle and east China were identified using an auto-bacterial detector. Major serotypes and virulence genes in the isolates were detected by polymerase chain reaction, while drug resistance of the isolates was determined using broth microdilution assays.

Results

Respiratory K. pneumoniae infection was observed in 70.0% of the patients. Of the K. pneumoniae isolates from patients, 42.3% were hypervirulent K (hvKp) serotypes, of which 30.1% and 37.0% belonged to K1 and K2 serotypes with 78.6-87.8% positive rates of rmpA and rmpA2 virulence genes. The isolates from healthy individuals had fewer hvKp serotypes and rmpA/rmpA2 genes (7.2% and 22.9%/26.5%). Resistance rates (38.6-79.5%) of the isolates from healthy individuals against 14 antibiotics were higher than those from patients (16.4-40.8%). The isolates from patients were sensitive to amikacin (83.6%) and polymyxin-B (93.9%) but presented 20.3% and 26.6% resistance rates to imipenem and meropenem, respectively. The isolates from patients with urinary infections exhibited higher resistances (42.1-52%) to cefoxitin, cefuroxime, ceftriaxone, ciprofloxacin, and levofloxacin than those from patients with respiratory or blood infections (22.4-39.3%). In the isolates from patients, the K47 and K64 serotypes exhibited multiple drug resistance (65-90%) against 14 antibiotics but all the hvKp serotypes displayed much lower antibiotic resistance (1.9-26.0%).

Conclusion

K1/K2 were the major predominant hvKp serotypes with rmpA/rmpA2 virulence genes and carbapenem-resistant K. pneumoniae strains were prevalent in patients from middle and east China. The hvKp serotypes have low antibiotic resistance, but K. pneumoniae isolates from patients with urinary infections resist the cephalosporin/quinolone antibiotics for treatment of bacterial urinary infections. Amikacin and polymyxin-B can be used to treat drug-resistant K. pneumoniae infections.

Genomic analysis of virulent, multidrug resistant Klebsiella pneumoniae and Klebsiella oxytoca from bloodstream infections, South Africa

The study investigated the resistome, virulome and mobilome of multidrug resistant (MDR) Klebsiella pneumoniae and Klebsiella oxytoca clinical isolates.

METHODS

A total of 46 suspected Klebsiella species (spp.) were collected from blood cultures within the uMgungundlovu District in the KwaZulu-Natal Province. Antibiotic susceptibility was determined against a panel of 19 antibiotics using the disk diffusion test. A subset of 14 MDR K. pneumoniae (n = 10) and K. oxytoca (n = 4) isolates were selected based on their antibiograms and subjected to whole genome sequencing (WGS). The sequence types (STs), resistome, virulome, mobilome, capsule loci (KLs) were analysed using relevant WGS and bioinformatics tools.

RESULTS

Of the 10 K. pneumoniae sequence types (ST) identified, the most common were ST25 (n = 3), ST101 (n = 3), and 4 K. oxytoca belonged to ST450 (n = 3). The two high-risk K. pneumoniae clones ST15, and ST17 were identified. O and K capsule types were identified, with predominance of KL2, KL17, KL29, O1/O2v2, O1/O2v1, and OL104 respectively. The majority of isolates displayed multidrug resistance predominantly carrying β-lactamase genes, including blaCTX-M-15, blaTEM-1B, blaSHV, and blaOXA-1, and blaOXY including the carbapenemase blaOXA-181 in two (14.3 %) study isolates. Other resistance genes included: aac(6')-lb-cr, aac(3), aac, aph, aad, dfr, tet(A), and tet(D), mph(A), sul1, sul2, oqx, qnr, acrR, ramR, parC, gyrA, arr-3, cat, fosA, qacE genes conferring resistance to aminoglycosides, trimethoprim, tetracycline, macrolide, sulfonamides, fluoroquinolones, rifampicin phenicols, fosfomycin, and quaternary ammonium compound disinfectant. Virulence factors related to hypervirulence: encoding aerobactin (iuc, iutA), salmochelin (iro), yersiniabactin (ybt), enterobactin (ent), type 1 and 3 (mrk and fim), and capsule synthesis (rcsA and rcsB) were identified. IncF, IncR, and Col plasmid replicon types and class I integrons were detected, with IncFIB(K) predominance. The blaCTX-M-15 and blaTEM-1 genes were bracketed by Tn3 transposons, ISEc9, recombinase and IS91 insertion sequences.

CONCLUSIONS

The convergence of multidrug resistance and hypervirulence genes in Klebsiella strains is a potential clinical concern. Carbapenemase, ESBL screening and genomic surveillance are urgently required in hospital environments.

Genomic and phylogenetic analysis of hypervirulent Klebsiella pneumoniae ST23 in Ireland

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.

Application of targeted next-generation sequencing for detecting respiratory pathogens in the sputum of patients with pulmonary infections

Targeted next-generation sequencing (tNGS) might be valuable for identifying disease-causing pathogens. Herein, we assessed the utility of tNGS in diagnosing pulmonary infections using sputum samples. We gathered complete clinical information and tested the specimens using both conventional microbiological tests (CMTs) and tNGS. The goal was to compare the effectiveness of these two methods in detecting viral, bacterial, and fungal pathogens. Notably, tNGS demonstrated a higher pathogen detection rate compared to CMTs (80.26 % [122/152] vs. 33.55 % [51/152], P = 0.029). Specifically, tNGS was more effective in detecting viruses than CMTs (90.00 % vs. 28.07 %, P = 0.003). Moreover, tNGS detected certain fungi, such as Candida albicans and Cryptococcus neoformans, although the difference between the two assays was not statistically significant (P > 0.05). Our findings reveal that tNGS offers significant advantages in detecting pathogens in patients with lung infections, particularly for bacteria and viruses, providing valuable information that complements CMTs.

Analysis of clinical characteristics and mortality risk factors in patients with community-acquired pneumonia caused by Klebsiella pneumoniae

Community-acquired pneumonia (CAP) caused by Klebsiella pneumoniae (KP) results in high mortality. 121 cases were included in this study to explore the characteristics and risk factors of CAP patients caused by hypervirulent or resistant KP strains, which were limited reported in previous studies. We found that neither hypervirulent KP nor ESBL-producing KP infections affect mortality (P > 0.05), while increased qSOFA score (odds ratio [OR] 4.50, 95% confidence interval [CI] 1.55-12.76, P = 0.005) and APACHE-II score (OR 1.30, 95% CI 1.13-1.48, P < 0.001) were independent risk factors for mortality. In addition, the areas under the curve (AUCs) of qSOFA in predicting the mortality rate of all patients, ICU patients, and non-ICU patients were 0.82, 0.74, and 0.81, respectively. Elevated qSOFA or APACHE-II scores were considered independent risk factors for 28-day mortality. The qSOFA score was a good predictor of mortality among KP CAP patients.

Exploration of a GMMA-Based Bivalent Vaccine Against Klebsiella pneumoniae

BACKGROUND

An emerging trend of mutual convergence between drug-resistant and highly virulent strains of K. pneumoniae has been identified, highlighting the urgent need for the development of novel vaccines.

METHODS

To delete the target genes and eliminate the plasmids carrying antibiotic resistance genes, CRISPR-Cas9 technology was employed to perform genome editing on a clinically isolated O2 serotype of K. pneumoniae. Subsequently, this strain was utilized as a host to express genes associated with the synthesis of O1 serotype LPSs to construct the recombinant strain capable of simultaneously expressing LPSs of both O1 and O2 serotypes. This recombinant strain was then used as the production strain for the preparation of vaccines based on GMMAs (Generalized Modules for Membrane Antigens), and its biological characteristics were characterized. Finally, the safety and immunogenicity of the vaccine were evaluated using mice as the model animals.

RESULT

a GMMA vaccine characterized by a high yield and low toxicity was gained. Importantly, the lipopolysaccharides (LPSs) of both O1 and O2 serotypes of K. pneumoniae were successfully expressed on the surface of the outer membrane vesicles. Following immunization with the GMMA vaccine, mice were capable of producing antibodies against the GMMA and demonstrated resistance to the invasion of both serotypes of clinically isolated K. pneumoniae.

CONCLUSIONS

The GMMA vaccine showed significant promise as a bivalent vaccine against K. pneumoniae.

Vascular penetration sign: dual-phase enhanced CT manifestations of atypical liver abscess caused by Klebsiella pneumoniae

OBJECTIVES

The aim of this study was to investigate the multislice spiral computed tomography (MSCT) features of atypical liver abscesses caused by Klebsiella pneumoniae (KP).

METHODS

A retrospective review was conducted on patients with atypical KP-caused liver abscesses, as verified by biopsy or surgery, from October 2019 to December 2023. All patients underwent dual-phase enhanced CT scan, and MSCT findings were analysed.

RESULTS

Seventy-two patients (58.5 ± 12.3 years, 43 males, 29 females) with atypical KP-induced liver abscess and 115 lesions were identified. Vascular penetration was detected in twelve lesions, presenting as vascular thickening, indistinct margins, and irregular invasive alterations. Among them, three lesions were initially misdiagnosed as primary hepatic lymphoma (PHL). Additionally, 50 lesions exhibited imaging patterns such as the "honeycomb", "petal", or "cluster" signs, and 40 lesions showed "lesion shrinkage" sign. Transient abnormal enhancement in hepatic parenchyma was observed in 83 lesions.

CONCLUSION

Vascular penetration with inflammatory infiltration might be a crucial sign in the diagnosis of atypical liver abscess caused by KP; correctly recognising this sign could reduce misdiagnosis.

KEY POINTS

Question Early imaging diagnosis of atypical liver abscesses caused by Klebsiella pneumoniae is significant because microbiology or blood cultures are time-consuming and may delay appropriate treatment. Findings The vascular penetration sign was noted in some Klebsiella pneumoniae atypical liver abscesses and play a vital role in the diagnosis of this disease. Clinical relevance The newly discovered vascular penetration sign in this study is an important sign for identifying atypical liver abscesses caused by Klebsiella pneumoniae. Accurate identification of this sign facilitates early clinical diagnosis and diminishes the risk of misdiagnosis.

Molecular epidemiology and genetic dynamics of carbapenem-resistant hypervirulent Klebsiella pneumoniae in China

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CRhvKP) poses a significant global health threat due to its enhanced virulence and resistance. This study analyzed 5,036 publicly available K. pneumoniae genomes from China (2005-2023), identifying 1,538 CRhvKP genomes, accounting for 44.6% of carbapenem-resistant isolates and 69.5% of hypervirulent isolates. Predominant carbapenemases included bla KPC (92.1%), with an increasing prevalence of bla NDM and bla OXA-48-like genes. Most isolates (93.6%) carried both aerobactin and yersiniabactin genes. The genetic background showed high diversity, characterized by 36 sequence types (STs) and 22 capsule types, with high-risk endemic STs such as ST11, ST15, and ST23 being predominant. ST23 demonstrated enhanced virulence, whereas ST11 carried more resistance genes but showed minimal presence of iroBCDN genes. A core genome MLST analysis revealed that 89.0% of CRhvKP isolates clustered into 131 clonal groups, indicating widespread dissemination, particularly in eastern China. CR and hv plasmids, primarily IncF, IncH, and IncR types, showed distinct community structures, with CR plasmids demonstrating higher mobility and diversity. Crucially, we identified 40 CR-hv convergent plasmids across five STs, likely resulting from plasmid fusions, which have become increasingly prevalent in eastern China over the last decade. Furthermore, chromosomal integration of hv genes and bla KPC-2 was detected, underscoring the stable inheritance of these traits. Class 1 Integrons were present in 84.5% of CRhvKP strains, most notably in ST11 and least in ST23. These integrons harbored genes that confer resistance to various antibiotics, including bla IMP and bla VIM, with their content varying across different STs. This study highlights the genetic complexity, rapid dissemination, and increasing prevalence of CRhvKP in China, emphasizing the urgent need for enhanced genomic surveillance and targeted interventions to mitigate the threat posed by these multidrug-resistant and hypervirulent strains.

Synthesis, Antimicrobial Activities, and Model of Action of Indolyl Derivatives Containing Amino-Guanidinium Moieties

The objectives of the study were to design, synthesize, and evaluate the antibacterial activity of a series of novel aminoguanidine-indole derivatives. Thirty-seven new compounds were effectively synthesized through nucleophilic substitution reaction and guanidinylation reaction. Chemical structures of all the desired compounds were identified by NMR and HR-MS spectroscopy. Most of the synthesized compounds showed significant antibacterial activity against ESKAPE pathogens and clinical resistant Klebsiella pneumoniae (K. pneumoniae) isolates. K. pneumoniae is an important opportunistic pathogen that often threatens the health of immunocompromised people such as the elderly, children, and ICU patients. The most active compound 4P showed rapid bactericidal activity against resistant K. pneumoniae 2108 with MIC and MBC values that were 4 and 8 µg/mL, respectively. The hemolytic activity of 4P was low, with an HC50 value of 123.6 µg/mL. Compound 4P induced the depolarization of the bacterial membrane and disrupted bacterial membrane integrity and was not prone to antibiotic resistance. The dihydrofolate reductase (DHFR) activity was also notably inhibited by 4P in vitro. Molecular docking revealed that the aminoguanidine moiety and indole structure of 4P played an important role in binding to the target site of the K. pneumoniae dihydrofolate reductase (DHFR) receptor. In the mouse pneumonia model caused by K. pneumoniae, 4P improved the survival rate of mice, reduced bacterial loads, and alleviated tissues' pathological injuries at a dosage of 4 mg/kg. Therefore, compound 4P may be a promising lead compound or drug candidate for antibacterial purposes against K. pneumoniae.

Microbiological Hazards in the Food Chain of Fish and Products, a Focus on Klebsiella spp

Feeding is an elementary human need from which we obtain the energy and nutrients necessary for development and survival. Health heavily depends on food, which can be a means of different microbial hazards when contaminated at any stage of the food chain, compromising food safety and consumer health. Fish are considered widely produced foods (fishing or aquaculture) and are marketed worldwide; they are also a basic element of the human diet because they are a source of proteins and lipids. On the other hand, owing to their chemical properties (neutral pH and water activity), fish are highly susceptible to contamination by saprophytic and pathogenic microorganisms related to spoilage and risk to human health. Among the contaminating microorganisms in fish are bacteria of the genus Klebsiella, which are considered important in human and animal health worldwide due to their opportunistic pathogenicity, resistance to various antimicrobials, and association with numerous infections at the community and hospital levels, where foods such as fish and other products can serve as important sources of transmission. Therefore, this document presents a bibliographic review focused on describing, in a general way, the genus Klebsiella and its relationship with human health, aquatic animal health, and the safety of fish and products, as well as laboratory analysis procedures and identification of control and prevention measures of this biological hazard in fish and products to safeguard public health.

Unique North American isolates of severe metastatic hypervirulent Klebsiella pneumoniae strain infections with hepatic abscesses seen in young patients within Texas

RATIONALE

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.

OBJECTIVES

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

METHODS

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

MAIN RESULTS

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.

CONCLUSIONS

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.

Genomic Characterization of Carbapenemase-Producing Klebsiella pneumoniae ST895 Isolates from Canine Origins Through Whole-Genome Sequencing Analysis

The widespread application of carbapenems and other broad-spectrum antibiotics has significantly escalated the threat posed by highly drug-resistant Klebsiella pneumoniae to human public health. In this research, we isolated a carbapenem-resistant K. pneumoniae strain from the feces of pet dogs at a veterinary hospital in Changchun, Jilin Province, China. To gain insights into its genetic makeup and resistance mechanisms, we conducted comprehensive whole-genome sequencing and antimicrobial susceptibility testing on the isolated strain. Our findings revealed the presence of three distinct plasmids within the strain, classified as IncFIB&IncFII, IncR, and IncX3. Notably, the blaNDM-5 gene, conferring resistance to carbapenems, was uniquely harbored on the IncX3 plasmid, which was devoid of any other resistance genes beyond blaNDM-5. In contrast, the remaining two plasmids, IncFIB&IncFII and IncR, were found to encode an array of additional drug resistance genes, contributing to the strain's broad-spectrum resistance phenotype. The IncX3 plasmid, specifically, measures 45,829 bp in length and harbors the IS5D-blaNDM-5-Ble-MBL-PRAI cassette, which has been closely linked to the dissemination of blaNDM-5 genes in K. pneumoniae strains. We reported the blaNDM-5-carrying IncX3 in K. pneumoniae isolates recovered from the pet dog and revealed the molecular characterization. Emphasis should be placed on, and continuous monitoring carried out for, the dissemination of K. pneumoniae harboring the blaNDM-5 gene among humans, companion animals, and their related environments.

The microbiome of Total Suspended Particles and its influence on the respiratory microbiome of healthy office workers

Air particulate matter (PM) is widely recognized for its potential to negatively affect human health, including changes in the upper respiratory microbiome. However, research on PM-associated microbiota remains limited and mostly focused on PM (e.g., PM2.5 and PM10). This study aims to characterize for the first time the microbiome of Total Suspended Particles (TSP) and investigate the correlations of indoor TSP with the human upper respiratory microbiome. Biological and environmental samples were collected over three collection periods lasting three weeks each, between May and July 2022 at the University of Milan and the University of Insubria Como. TSP were sampled using a filter-based technique, while respiratory samples from both anterior nares (AN) and the nasopharynx (NP) were collected using swabs. Microbiome analysis of both human (N = 145) and TSP (N = 51) samples was conducted on metagenomic sequencing data. A comparison of indoor and outdoor TSP microbiomes revealed differences in microbial diversity and taxonomic composition. The indoor samples had higher relative abundance of environmental bacteria often associated with opportunistic infections like Paracoccus sp., as well as respiratory bacteria such as Staphylococcus aureus and Klebsiella pneumoniae. Additionally, both indoor and outdoor TSP samples contained broad spectrum antibiotic resistance genes. Indoor TSP exposure was negatively associated with commensal bacteria and positively associated with Staphylococcus aureus relative abundance. Finally, a correlation between the relative abundance of respiratory bacteria identified in the indoor TSP and the upper respiratory microbiome was found, suggesting a potential interaction between TSP and the upper airways.

Hypervirulent Klebsiella pneumoniae: Epidemiology outside Asian countries, antibiotic resistance association, methods of detection and clinical management

Two main Klebsiella pneumoniae pathotypes are of public health concern, classical K. pneumoniae (cKP), with high antibiotic resistance acquisition capacity, and hypervirulent K. pneumoniae (hvKP). The emergence of hypervirulent and antibiotic-resistant K. pneumoniae, especially carbapenem resistance, is worrisome and require effective methods for detection and treatment. Different evolutionary paths contribute to the emergence of hypervirulence and antibiotic resistance, commonly via the acquisition of resistance plasmids by hvKP (CR-hvKP) or the acquisition of virulence plasmids by CRKp (hv-CRKp). ST11-KL64 together with blaKPC-2, is the most extended hv-CRKP lineage acquiring virulence plasmids with associated biomarkers, rmpA, rmpa2, iroBCDEN, iucABCDiutA, and peg344. In addition to ST11, other hv-CRKP clones have been reported in Europe such as ST101, ST147 and ST512, highlighting the association of ST147 with OXA-48 and NDM carbapenemases. Although still very rare in Spain, hvKP cases are increasing in recent years, mainly due to ST23-K1, ST380-K2 and ST86-K2. Management of hvKP infections requires active antibiotic therapy based primarily on antibiotic susceptibility patters and site of infection.

Systematic review and meta-analysis on the carbapenem-resistant hypervirulent Klebsiella pneumoniae isolates

BACKGROUND

The global dissemination of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) poses a critical threat to public health. However, comprehensive data on the prevalence and resistance rates of CR-hvKp are limited. This systematic review and meta-analysis aim to estimate the pooled prevalence of carbapenem resistance among hvKp strains and assess the distribution of carbapenemase genes.

MATERIALS AND METHODS

A systematic search of ISI Web of Science, PubMed, and Google Scholar was conducted to identify studies reporting carbapenem resistance rates in hvKp strains. The pooled prevalence of carbapenem resistance and carbapenemase genes was calculated using event rates with 95% confidence intervals.

RESULTS

A total of 36 studies encompassing 1,098 hvKp strains were included. The pooled resistance rates were 49% for imipenem, 53.2% for meropenem, and 38.2% for ertapenem. Carbapenemase gene prevalence was 19.1% for blaVIM, 22.0% for blaNDM, 43.4% for blaOXA-48, and 58.8% for blaKPC.

CONCLUSION

The high prevalence of carbapenem resistance and the widespread distribution of carbapenemase genes among hvKp strains underscore their significant threat to global health. These findings highlight the urgent need for enhanced surveillance, rapid diagnostic tools, and stringent infection control measures to mitigate the spread of CR-hvKp. Future research should focus on understanding resistance mechanisms and developing targeted therapeutic strategies to address this critical challenge.

mRNA-LNP vaccines combined with tPA signal sequence elicit strong protective immunity against Klebsiella pneumoniae

Klebsiella pneumoniae is a prominent Gram-negative and encapsulated opportunistic pathogen that causes a multitude of infections such as severe respiratory and healthcare-associated infections. Despite the widespread anti-microbial resistance and the high mortality rate, currently, no clinically vaccine is approved for battling K. pneumoniae. To date, messenger RNA (mRNA) vaccine is one of the most advancing technologies and are extensively investigated for viral infection, while infrequently applied for prevention of bacterial infections. In the present study, we aim to construct a new mRNA vaccine encoding YidR or combining with a tissue plasminogen activator signal sequence for preventing K. pneumoniae infection. Adaptive immunity was determined in mRNA vaccines-immunized mice and the protective effects of mRNA vaccines were evaluated in K. pneumoniae infected models. The results showed that lipid nanoparticle (LNP)-YidR-mRNA vaccine was produced with good morphology, high the encapsulation efficiency, and the specific antigen was highly expressed in cells in vitro. In addition, immunization with either LNP-YidR or LNP-YidR-SP elicited a Th1-biased immune response, reduced bacterial load, and provided broad protection in the lung infection models. Importantly, the LNP-YidR-SP mRNA vaccine induced strong adaptive humoral and cellular immunity and increased the survivability of mice compared to the other groups. Our findings serve as a focal point for developing a potential mRNA vaccine against K. pneumoniae, indicating the potential of mRNA vaccines for improving next-generation bacterial vaccine.IMPORTANCEK. pneumoniae is a notorious and clinical bacterium that is evolving in community-acquired and nosocomial settings. This opportunistic pathogen causes severe infectious diseases, including urinary tract infection and pneumonia, and causes a concerning global public burden. Despite efforts having been created to develop different types of K. pneumoniae vaccines, there is no licensed vaccine for preventing K. pneumoniae infection. Therefore, to develop an effective tactic is essential to combat K. pneumoniae-caused diseases. This study provides a novel vaccine strategy against K. pneumoniae and a potent platform to elicit high levels of humoral and cell-meditated immunity.

Hypervirulent Klebsiella pneumoniae (hvKp): Overview, Epidemiology, and Laboratory Detection

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.

Hypervirulent Klebsiella pneumoniae have better clinical outcomes than classical Klebsiella pneumoniae for lower respiratory tract infection patients

BACKGROUND

The clinical outcomes and microbiological features of lower respiratory tract infections (LRTIs) caused by hypervirulent Klebsiella pneumoniae (hvKp) and classical Klebsiella pneumoniae (cKp) have not been well understood.

METHODS

This study collected 287 non-repetitive Klebsiella pneumoniae isolates from 287 LRTI patients. All these strains underwent annotation for resistance and virulence factors, with 141 strains undergoing mouse infection experiments to assess their virulence. The primary clinical outcomes of these patients were evaluated, including intensive care unit (ICU) admission and in-hospital mortality rates.

RESULTS

A total of 46 capsule serotypes were identified. Among these isolates subjected to mouse infection experiments, the proportions of strains exhibiting hypervirulent phenotypes were 92.6% (25/27), 92.1% (35/38), 80% (4/5), 25% (1/4), 10.5% (2/19), and 7.1% (1/14) for K2, K1, K20, K54, K47, and K25, respectively. Therefore, K1, K2, and K20 K. pneumoniae were defined as hvKp. In addition, the rates of ICU admission and in-hospital mortality for hvKp-infected patients were significantly lower than those of cKp-infected patients (51.4% vs. 65.9%, χ2 = 4.722, p = 0.03 and 8.6% vs. 29%, χ2 = 12.133, p < 0.001). Notably, among the cKp group, the cKp-ST11 subgroup had higher rates of ICU admission (77% vs. 58.5%, χ2 = 7.981, p = 0.005) and in-hospital mortality (44.8% vs. 18.5%, χ2 = 17.585, p < 0.001) than cKp-nonST11 subgroup.

CONCLUSIONS

These findings suggest that capsule serotype is a more accurate factor for the prediction of the virulence phenotype, while hvKp have better clinical outcomes than cKp for LRTI patients. Furthermore, the cKp-ST11 subgroup has the worst prognosis than cKp-nonST11 subgroup.

Targeted Next-Generation Sequencing in Pneumonia: Applications in the Detection of Responsible Pathogens, Antimicrobial Resistance, and Virulence

Background

Targeted next-generation sequencing (tNGS) is a high-throughput and cost-effective diagnostic alternative for pneumonia, with the ability to simultaneously detect pathogens, antimicrobial resistance genes, and virulence genes. We aimed to explore the applicability of tNGS in the co-detection of the responsible pathogens, antimicrobial resistance (AMR) genes, and virulence genes in patients with pneumonia.

Methods

A prospective study was conducted among patients with suspected pneumonia at Ruijin Hospital from March 1 to May 31, 2023. Bronchoalveolar lavage fluid (BALF) or sputum samples were collected and sent for tNGS, metagenomic next-generation sequencing (mNGS), and conventional microbiological tests (CMTs).

Results

In total, 67 BALF and 11 sputum samples from 78 patients were included in the analyses. According to the composite reference standards, the accuracy of tNGS in the detection of responsible pathogens was 0.852 (95% confidence interval 0.786-0.918), which resembled that of mNGS and remarkably exceeded that of CMTs. In addition, 81 AMR genes associated with responsible pathogens were reported, and 75.8% (25/33) priority drug-resistant pathogens could be directly identified. A total of 144 virulence genes were detected for four common pathogens. And patients with virulence genes detected were of higher proportions of severe pneumonia (95.0% vs 42.9%, P = 0.009), acute respiratory distress syndrome (55.0% vs 0%, P = 0.022), and neutrophils (82.3% vs 62.2%, P = 0.026) than those not.

Conclusion

In patients with pneumonia, tNGS could detect the responsible pathogens, AMR genes, and virulence genes simultaneously, serving as an efficient and cost-effective tool for the diagnosis, treatment, and severity indication of pneumonia.