Infection with capsular genotype K1-ST23 hypervirulent Klebsiella pneumoniae isolates in Japan after a stay in East Asia: Two cases and a literature review

Molecular Characteristics of Virulence Genes in Carbapenem-Resistant and Carbapenem-Sensitive Klebsiella Pneumoniae in Relation to Different Capsule Serotypes in Ningbo, China

Background

Klebsiella pneumoniae (KP) is a common nosocomial pathogen. Capsules are an important component of KP's virulence, among which the K1, K2, K5, K20, K54, and K57 serotypes are predominant and exhibit varying degrees of virulence.

Methods

The capsule and virulence genes of 150 carbapenem-resistant Klebsiella pneumoniae (CRKP) and 213 carbapenem-sensitive Klebsiella pneumoniae (CSKP) isolates were examined by polymerase chain reaction (PCR). The isolates were tested for hypermucoviscosity by string tests. Phylogenetic relationships between KP isolates were analyzed using multilocus sequence typing (MLST) and a Galleria mellonella infection model confirmed the differences in virulence.

Results

A total of 111 of 363 isolates of KP were detected, the highest detected serotypes were K1, K5, and K2, and CSKP was detected more frequently than CRKP. There was a greater prevalence of K1 and K2 serotypes in CSKP, while in CRKP, K5 serotypes were more prevalent. K1 isolates had the highest detection rates for hypermucoviscosity Klebsiella pneumoniae (hmKP) and hypervirulent Klebsiella pneumoniae (hvKP), and carried the most virulence genes. K54 isolates had the lowest detection rate of hmKP while K5 isolates had the lowest detection rate of hvKP and carried the fewest virulence genes. MLST results for serotypes K1, K20, and K57 showed significant homogeneity, while those for serotypes K2, K5, and K54 showed diversity. The Galleria mellonella infection model showed that the K1 serotype was the most virulent and the K54 serotype was the weakest.

Conclusion

CSKP isolates were detected more frequently than CRKP isolates for capsular serotype detection. K1 isolates had the most virulence gene and strongest virulence, K5 isolates carried the fewest virulence genes, and K54 isolates had the weakest virulence. Furthermore, significant homogeneity was observed among K1, K20, and K57 isolates.

The Rapid Emergence of Hypervirulent Klebsiella Species and Burkholderia pseudomallei as Major Health Threats in Southeast Asia: The Urgent Need for Recognition as Neglected Tropical Diseases

The World Health Organization (WHO)'s list of neglected tropical diseases (NTDs) highlights conditions that are responsible for devastating health, social and economic consequences, and yet, they are overlooked and poorly resourced. The NTD list does not include conditions caused by Gram-negative bacilli (GNB). Infections due to GNB cause significant morbidity and mortality and are prevalent worldwide. Southeast Asia is a WHO region of low- and middle-income countries carrying the largest burden of NTDs. Two significant health threats in Southeast Asia are Burkholderia pseudomallei (causing melioidosis) and hypervirulent Klebsiella pneumoniae (HvKp). Both diseases have high mortality and increasing prevalence, yet both suffer from a lack of awareness, significant under-resourcing, incomplete epidemiological data, limited diagnostics, and a lack of evidence-based treatment. Emerging evidence shows that both melioidosis and HvKp are spreading globally, including in high-income countries, highlighting the potential future global threat they pose. In this article, we review both conditions, identifying current trends and challenges in Southeast Asia and areas for future research. We also argue that melioidosis and HvKp merit inclusion as NTDs, and that mandatory global surveillance and reporting systems should be established, and we make an urgent call for research to better understand, detect, and treat these neglected diseases.

Epidemiology and molecular characterization of carbapenem-resistant Klebsiella pneumoniae isolated from neonatal intensive care units in General Hospital of Ningxia Medical University, China, 2017-2021

OBJECTIVES

This study aimed to retrospectively investigate the epidemiology and molecular characteristics of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates from neonatal intensive care units (NICU) between 2017 and 2021.

METHODS

The antibacterial susceptibility of all strains was assessed using the VITEK 2 compact system. The presence of antibiotic resistance, virulence genes, sequence types (STs), capsular (K) types, and the wzi genes was determined through polymerase chain reaction (PCR). Molecular typing was performed by pulsed-field gel electrophoresis (PFGE) using the restriction enzyme XbaI. Additionally, the virulence potential of peg344-positive strains was evaluated using the string test and mouse intraperitoneal infection models. Whole-genome sequencing was conducted on the DNB system and PacBio platforms.

RESULTS

A total of 46 CRKP isolates were collected during the study period. Out of these, 93.47% (43/46) were identified as CRKP strains belonging to the ST76-K10 type carrying blaNDM-5. It was observed that CRKP infection resulted in more severe clinical symptoms compared to CRKP colonization. Among the CRKP strains, a hypervirulent CRKP strain called KP-63, belonging to the ST23 type, was identified. This strain exhibited high mortality in the mouse infection model and was found to possess virulence genes. Genomic alignment analysis revealed a significant similarity between the virulence plasmid from KP-63 strain (pKP-63) and pK2044 from the hypervirulent K. pneumoniae strain NTUH-2044.

CONCLUSIONS

There has been a potential dissemination of ST76-K10 type CRKP carrying blaNDM-5 in the NICU at Ningxia Hospital. Neonatal CRKP infection has been found to cause more severe clinical symptoms than colonization. Furthermore, we have discovered a CR-hvKP strain of ST23 with serotype K1, which exhibits a significant resemblance in its virulent plasmid to pK2044. Therefore, it is crucial to enforce effective measures to restrict the spread and hinder the evolution of CRKP within the hospital.

A case of hypervirulent K1-ST23 Klebsiella pneumoniae endocarditis and papillary muscle rupture secondary to multiple site abscesses

Hypervirulent Klebsiella pneumoniae (hvKP) causes multisite infections and abscesses. However, endocarditis is a rare presentation of hvKP infection. Herein, we report a case of K. pneumoniae native valve infective endocarditis secondary to community-acquired liver and prostate abscesses. The patient developed papillary muscle rupture, leading to mitral regurgitation, and underwent emergent mitral valve replacement. The diagnosis of endocarditis was confirmed microbiologically and histologically. The causative strain belonged to the hypermucoid K1 capsular genotype and possessed the rmpA gene. The genome sequence was deposited in GenBank under the accession number JAQZBZ000000000.

Pyogenic liver abscess caused by extended-spectrum β-lactamase-producing hypervirulent Klebsiella pneumoniae diagnosed by third-generation sequencing: a case report and literature review

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

Covert dissemination of pLVPK-like virulence plasmid in ST29-K54 Klebsiella pneumoniae: emergence of low virulence phenotype strains

This study aimed to explore the epidemic, clinical characteristics, and molecular and virulence attributes of Klebsiella pneumoniae serotype K54 (K54-Kp). A retrospective study was conducted on 328 strains of Klebsiella pneumoniae screened in a Chinese hospital from January 2016 to December 2019. The virulence genes and antibiotic resistance genes (ARGs) were detected by PCR, and a drug sensitivity test was adopted to detect drug resistance. Multilocus sequence typing (MLST) and PFGE were performed to determine the clonal correlation between isolates. Biofilm formation assay, serum complement-mediated killing, and Galleria mellonella infection were used to characterize the virulence potential. Our results showed that thirty strains of K54-Kp were screened from 328 strains of bacteria, with an annual detection rate of 2.29%. K54-Kp had a high resistance rate to antibiotics commonly used in the clinic, and patients with hepatobiliary diseases were prone to K54-Kp infection. MLST typing showed 10 sequence typing, mainly ST29 (11/30), which concentrated in the B2 cluster. K54-Kp primarily carried virulence genes of aerobactin, silS, allS, wcaG, wabG, and mrkD, among which the terW gene was closely related to ST29 (p<0.05). The strains infected by the bloodstream had strong biofilm formation ability (p<0.05). Most strains were sensitive to serum. Still, the virulence of pLVPK-like virulence plasmid in ST29-K54 Klebsiella pneumoniae was lower than that of ST11 type and NTUH-K2044 in the Galleria mellonella model. Therefore, these findings supply a foundation to roundly comprehend K54-Kp, and clinicians should strengthen supervision and attention.

Genomic characterization of a new phage BUCT541 against Klebsiella pneumoniae K1-ST23 and efficacy assessment in mouse and Galleria mellonella larvae

Over the past decades, the spread of multi-drug-resistant Klebsiella pneumoniae (MDR-KP) is becoming a new threat and new effective therapies against this pathogen are needed. Bacteriophage (phage) therapy is considered to be a promising alternative treatment for MDR-KP infections compared with antibacterial drug usage. Here, we reported a new phage BUCT541 which can lyse MDR-KP ST23. The genome of BUCT541 is a double-stranded linear 46,100-bp long DNA molecule with 48% GC content through the Next generation sequencing (NGS) data. A total of 81 open reading frames and no virulence or antimicrobial resistance genes are annotated in the BUCT541 genome. BUCT541 was able to lyse 7 of the 30 tested MDR-KP according to the host range analysis. And the seven sensitive strains belonged to the K. pneumoniae K1-ST23. BUCT541 exhibited high thermal stability (4–70°C) and broad pH tolerance (pH 3-11) in the stability test. The in vivo results showed that BUCT541 (4 × 10⁵ plaque-forming units (PFU)/each) significantly increased the survival rate of K. pneumoniae infected Galleria mellonella from 5.3% to 83.3% within 48 h. Moreover, in the mouse lung infection model, high doses of BUCT541 (2 × 10⁷ PFU/each) cured 100% of BALB/c mice that were infected with K. pneumoniae. After 30 h of treatment with phage BUCT541 of the multiplicity of infection (MOI) = 10, the K. pneumoniae in the lungs of mice was lower than 10⁴ CFU/mL, compared to the control group 10⁹ CFU/mL. Together, these findings indicate that phage BUCT541 holds great promise as an alternative therapy with excellent stability and a wide lysis range for the treatment of MDR-KP ST23 infection.

Successful treatment of acute respiratory distress syndrome caused by hypervirulent Klebsiella pneumoniae with extracorporeal membrane oxygenation and continuous renal replacement therapy: A case report and literature review

Hypervirulent Klebsiella pneumoniae (hvKP) causes invasive infections and leads to high morbidity and mortality rates. Here, we report the case of a Chinese man with diabetes mellitus who developed acute respiratory distress syndrome and septic shock due to hvKP belonging to the K1 strain. The patient was treated with venovenous extracorporeal membrane oxygenation and continuous renal replacement therapy, in combination with antibiotics and recovered well. Clinicians should be aware of fatal infections caused by hvKP and investigate the best treatment options for patients at various stages of infection.

Characterization of virulence factors and antibacterial activity of curcumin in hypervirulent Klebsiella pneumoniae

Aim: Klebsiella pneumoniae is a threat to human health due to its carbapenem-resistance and hypervirulent phenotype. Curcumin is a well-known antimicrobial agent. Hence, it is important to investigate the antivirulence activity of curcumin against hypervirulent K. pneumoniae isolates. Materials & methods: Carbapenemase presence and prevalence of hypervirulent isolates were determined. Inhibition of biofilm formation and expression of virulence genes were analyzed by colorimetry and real-time PCR tests. Results: Sixteen hypervirulent K. pneumoniae isolates were identified. The optimum activity of curcumin was detected at 1/2 minimum inhibitory concentration. Curcumin possessed appropriate antibiofilm, anti-efflux and anticapsule activities. Conclusion: According to the crucial role of biofilm, capsule and efflux systems in the pathogenesis of hypervirulent K. pneumoniae, curcumin may be used to improve anti-Klebsiella treatment.