Emergence of Hypervirulent ST11-K64 Klebsiella pneumoniae Poses a Serious Clinical Threat in Older Patients

Predicting Antibiotic Tolerance in hvKP and cKP Respiratory Infections Through Biofilm Formation Analysis and Its Resistance Implications

Introduction

Respiratory infections are a major global health concern, with Klebsiella pneumoniae standing out due to its evolving antibiotic resistance. This study compares the resistance profiles of hypervirulent Klebsiella pneumoniae (hvKP) and classical Klebsiella pneumoniae (cKP), aiming to shed light on their clinical implications.

Methods

We analyzed 86 cases, comprising 42 hvKP and 44 cKP strains, using comprehensive antimicrobial susceptibility testing and clinical data evaluation to assess antibiotic tolerance and resistance mechanisms.

Results

Our findings reveal distinct resistance patterns between hvKP and cKP, highlighting the role of chromosomal mutations and plasmid-mediated gene transfer in conferring antibiotic resistance. Notably, hvKP strains exhibited unique resistance trends, including the production of extended-spectrum β-lactamases (ESBLs) and carbapenemases, differing from those of cKP.

Discussion

This research underscores the importance of continuous surveillance and the development of targeted therapies against antibiotic-resistant Klebsiella pneumoniae. It emphasizes the critical need for judicious antibiotic use and novel therapeutic approaches to combat respiratory infections caused by these increasingly resistant pathogens.

Differences in molecular characteristics and expression of virulence genes in carbapenem-resistant and sensitive Klebsiella pneumoniae isolates in Ningbo, China

Background

In recent years, Klebsiella pneumoniae has attracted attention because of its increasing drug resistance. At the same time, the migration and pathogenicity caused by its virulence genes also bring many difficulties to the diagnosis and treatment of clinical infections. However, it is currently unclear whether there are differences in virulence and pathogenicity with changes in drug resistance.

Objective

To understand the differences in molecular characteristics and expression of virulence genes in carbapenem-resistant Klebsiella pneumoniae (CRKP) and carbapenem-sensitive Klebsiella pneumoniae (CSKP).

Methods

Using polymerase chain reaction (PCR), we examined capsule polysaccharide-related genes and virulence genes in 150 clinical isolates of CRKP and 213 isolates of CSKP from the local area in Ningbo, China. Multilocus sequence typing (MLST) was used to analyze the phylogenetic relationships of clinical Klebsiella pneumoniae isolates. Furthermore, real-time quantitative PCR (RT-qPCR) was used to analyze the expression differences of common virulence genes in CSKP and CRKP, and the virulence was further verified by the larval model of Galleria mellonella.

Results

The study found that the detection rates of genes rmpA, iroB, peg-344, magA, aerobactin, alls, kfu, and entB were significantly higher in CSKP compared to CRKP. The capsule gene types K1 and K2 were more common in CSKP, while K5 was more common in CRKP. Hypervirulent Klebsiella pneumoniae (hvKP) was predominantly from CSKP. CRKP strains exhibited noticeable homogeneity, with ST11 being the predominant sequence type among the strains. CSKP strains showed greater diversity in ST types, but ST23 was still the predominant sequence type. Carbapenem-sensitive hypervirulent Klebsiella pneumoniae (CS-hvKP) had higher expression of rmpA and rmpA2 genes compared to carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP). In the wax moth virulence model, the survival rate of CS-hvKP was significantly lower than that of CR-hvKP.

Conclusion

There is a significant difference in the distribution of virulence genes between CSKP and CRKP, with CSKP carrying a significantly greater number of virulence genes. Furthermore, compared to CSKP, CRKP strains exhibit noticeable homogeneity, with ST11 being the predominant sequence type among the strains. Additionally, in terms of virulence gene expression efficiency and virulence, CSKP is significantly higher than CRKP.

The dynamic evolution and IS26-mediated interspecies transfer of a blaNDM-1-bearing fusion plasmid leading to a hypervirulent carbapenem-resistant Klebsiella pneumoniae strain harbouring blaKPC-2 in a single patient

OBJECTIVES

To characterize the evolution and interspecies transfer of plasmids between Klebsiella pneumoniae and Escherichia coli within a single patient.

METHODS

Minimum inhibitory concentrations were measured using broth microdilution assays. Conjugation assays, string tests, and Galleria mellonella infection model experiments were also conducted. Whole-genome sequencing was performed on the Illumina and Nanopore platforms. Antimicrobial resistance determinants, insertion sequences, and virulence factors were identified using ABRicate/ResFinder database, ISFinder, and virulence factor database. Wzi and capsular polysaccharide (KL) were typed using Kleborate and Kaptive. Multi-locus sequence typing (MLST), replicon typing, and single nucleotide polymorphism analyses were conducted using the BacWGSTdb server.

RESULTS

The carbapenem-resistant K. pneumoniae 2111KP was characterized as ST11, wzi64, and KL64, with a positive string test result and a relatively high virulence phenotype. Analysis of the 2111KP genome revealed that blaNDM-1 was located in a 268,400-bp IncFIB/IncHI1B/IncX3 conjugative plasmid (p2111KP-1), regulated by IS26, IS5, and ISKox3. p2111KP-1 was also a rmpA2-associated virulence plasmid with an iutA-iucABCD gene cluster and a IS26-mediated multidrug-resistant fusion plasmid, which contained 8-bp (AGCTGCAC or GGCCTTTG) target site duplications. Segments flanked by IS26 of p2111KP-1 were 99.99% identical to a 49,016-bp E. coli plasmid.

CONCLUSIONS

This study provided direct evidence of plasmid fusion via IS26 between two different bacterial species within one patient and revealed the process by which genetic elements conferring carbapenem resistance and virulence were simultaneously transferred between these species. It highlights the need for strategic antibiotic use and rigorous monitoring to prevent the plasmid-mediated fusion and transmission of drug-resistance/virulence factors.

Expansion of healthcare-associated hypervirulent KPC-2-producing Klebsiella pneumoniae ST11/KL64 beyond hospital settings

The spread of carbapenemase-producing Klebsiella pneumoniae beyond hospital settings is a global critical issue within a public health and One Health perspective. Another worrisome concern is the convergence of virulence and resistance in healthcare-associated lineages of K. pneumoniae leading to unfavorable clinical outcomes. During a surveillance study of WHO critical priority pathogens circulating in an impacted urban river in São Paulo, Brazil, we isolate two hypermucoviscous and multidrug-resistant K. pneumoniae strains (PINH-4250 and PINH-4900) from two different locations near to medical centers. Genomic investigation revealed that both strains belonged to the global high-risk sequence type (ST) ST11, carrying the bla_KPC-2 carbapenemase gene, besides other medically important antimicrobial resistance determinants. A broad virulome was predicted and associated with hypervirulent behavior in the Galleria mellonella infection model. Comparative phylogenomic analysis of PINH-4250 and PINH-4900 along to an international collection of publicly available genomes of K. pneumoniae ST11 revealed that both environmental strains were closely related to hospital-associated K. pneumoniae strains recovered from clinical samples between 2006 and 2018, in São Paulo city. Our findings support that healthcare-associated KPC-2-positive K. pneumoniae of ST11 clone has successfully expanded beyond hospital settings. In summary, aquatic environments can become potential sources of international clones of K. pneumoniae displaying carbapenem resistance and hypervirulent behaviors, which is a critical issue within a One Health perspective.

Virulence factors in carbapenem-resistant hypervirulent Klebsiella pneumoniae

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

Infection with Carbapenem-resistant Hypervirulent Klebsiella Pneumoniae: clinical, virulence and molecular epidemiological characteristics

BACKGROUND

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) is gradually becoming the dominant nosocomial pathogens in the healthcare setting.

METHODS

A retrospective study was conducted on patients with CR-KP from July 2021 to May 2022 in a teaching hospital. We identified bacterial isolates, collected the clinical data, and performed antimicrobial susceptibility testing, hypermucoviscosity string test, antimicrobial and virulence-associated genotype, as well as multi-locus sequence typing. CR-hvKP was defined as the presence of some combination of rmpA and/or rmpA2 with iucA, iroB, or peg-344. SPSS was used for data analysis. Univariate logistic regression analyses were used for risk factor and all statistically significant variables were included in the multivariate model. Statistical significance was taken to be P < 0.05.

RESULTS

A total of 69 non-duplicated CR-KP isolates were collected, 27 of which were CR-hvKP. Out of the 69 CR-KP strains under investigation, they were distributed across 14 distinct sequence types (STs), wherein ST11 exhibited the highest prevalence, constituting 65.2% (45/69) of the overall isolates. The principal carbapenemase genes identified encompassed blakpc-2, blaNDM-1, and blaOXA-48, with blakpc-2 prevailing as the predominant type, accounting for 73.9% (51/69). A total of 69 CR-KP strains showed high resistance to common clinical antibiotics, with the exception of ceftazidime/avibactam. The ST11 (P = 0.040), ST65 (P = 0.030) and blakpc-2 ST11 clones (P = 0.010) were found to be highly related to hvKp. Regarding the host, tracheal intubation (P = 0.008), intracranial infection (P = 0.020) and neutrophil count (P = 0.049) were significantly higher in the patients with CR-hvKP. Multivariate analysis showed tracheal intubation to be an independent risk factor for CR-hvKP infection (P = 0.030, OR = 4.131). According to the clinical data we collected, tracheal intubation was performed mainly in the elderly with severe underlying diseases, which implied that CR-hvKP has become prevalent among elderly patients with comorbidities.

CONCLUSIONS

The prevalence of CR-hvKP may be higher than expected in the healthcare setting. CR-hvKP is gradually becoming the dominant nosocomial pathogen, and its prevalence and treatment will be a major challenge. It is essential to enhance clinical awareness and management of CR-hvKP infection.

Emergence of Carbapenemase-Producing Hypervirulent Klebsiella pneumoniae in Switzerland

Increasing occurrence of multidrug-resistant (MDR) and hypervirulent (hv) Klebsiella pneumoniae (MDR-hvKp) convergent clones is being observed. Those strains have the potential of causing difficult-to-treat infections in healthy adults with an increased capacity for mortality. It is therefore crucial to track their dissemination to prevent their further spread. The aim of our study was to investigate the occurrence of carbapenemase-producing hvKp isolates in Switzerland and to determine their genetic profile. A total of 279 MDR carbapenemase-producing K. pneumoniae from patients hospitalized all over Switzerland was investigated, and a rate of 9.0% K. pneumoniae presenting a virulence genotype was identified. Those isolates produced either KPC, NDM, or OXA-48 and had been either recovered from rectal swabs, urine, and blood. A series of previously reported K. pneumoniae clones such as ST23-K1, ST395-K2, and ST147-K20 or ST147-K64 were identified. All the isolates defined as MDR-hvKp (4.7%) possessed the aerobactin and the yersiniabactin clusters. The ST23-K1s were the only isolates presenting the colibactin cluster and achieved higher virulence scores. This study highlights the occurrence and circulation of worrisome MDR-hvKp and MDR nonhypervirulent K. pneumoniae (MDR-nhv-Kp) isolates in Switzerland. Our findings raise an alert regarding the need for active surveillance networks to track and monitor the spread of such successful hybrid clones representing a public health threat worldwide.

Molecular Profiling of a Multi-Strain Hypervirulent Klebsiella pneumoniae Infection Within a Single Patient

Background

The rising prevalence of infections caused by carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-hvKP) has outpaced our understanding of their evolutionary diversity. By straining the antimicrobial options and constant horizontal gene transfer of various pathogenic elements, CR-hvKP poses a global health threat.

Methods

Six KP isolates (KP1~KP6) from urine, sputum and groin infection secretion of a single patient were characterized phenotypically and genotypically. The antimicrobial susceptibility, carbapenemase production, hypermucoviscosity, serum resistance, virulence factors, MLST and serotypes were profiled. Genomic variations were identified by whole-genome sequencing and the phylogenetic differentiation was analyzed by Enterobacterial repetitive intergenic consensus (ERIC)-PCR.

Results

All KP strains were multi-drug resistant. Four of them (KP1, KP3, KP5 and KP6) belonged to ST11-K64, with high genetic closeness (relatedness coefficient above 0.96), sharing most resistance and virulence genes. Compared with KP1, the later isolates KP3, KP5 and KP6 acquired bla _KPC-1 and lost bla _SHV-182 genes. KP2 and KP4 had the same clonal origin of ST35-K16 (relatedness coefficient 0.98), containing almost identical genes for resistance and virulence. They were non-mucoid and carried bla _NDM-5 gene.

Conclusion

A co-infection with two types of CR-hvKP affiliated with different clades within a single patient amplified the treatment difficulties. In addition to source control and epidemiological surveillance, investigation of the in-host interactions between CR-hvKP variants may provide valuable treatment solutions.

Emergence of a NDM-1-producing ST25 Klebsiella pneumoniae strain causing neonatal sepsis in China

Carbapenem-resistant Klebsiella pneumoniae (CRKP) seriously threaten the efficacy of modern medicine with a high associated mortality rate and unprecedented transmission rate. In this study, we isolated a clinical K. pneumoniae strain DY1928 harboring bla_NDM-1 from a neonate with blood infection. Antimicrobial susceptibility testing indicated that DY1928 was resistant to various antimicrobial agents, including meropenem, imipenem, ceftriaxone, cefotaxime, ceftazidime, cefepime, piperacillin-tazobactam, and amoxicillin-clavulanate. S1 nuclease-pulsed field gel electrophoresis (S1-PFGE), southern blot and conjugation experiment revealed that the bla_NDM-1 gene was located on a conjugative plasmid of IncA/C2 type with a 147.9 kb length. Whole-genome sequencing showed that there was a conservative structure sequence (bla_NDM-1-ble-trpF-dsbD) located downstream of the bla_NDM-1 gene. Multilocus sequence typing (MLST) classified DY1928 as ST25, which was a hypervirulent K. pneumoniae type. Phylogenetic analysis of genomic data from all ST25 K. pneumoniae strains available in the NCBI database suggested that all bla_NDM-1 positive strains were isolated in China and had clinical origins. A mouse bloodstream infection model was constructed to test the virulence of DY1928, and 11 K. pneumoniae strains homologous to DY1928 were isolated from the feces of infected mice. Moreover, we found that DY1928 had a tendency to flow from the blood into the intestine in mice and caused multiple organ damage. To our knowledge, this is the first study to report an infection caused by bla_NDM-1-positive ST25 K. pneumoniae in the neonatal unit. Our findings indicated that stricter surveillance and more effective actions were needed to reduce the risk of disseminating such K. pneumoniae strains in clinical settings, especially in neonatal wards.

Hypervirulent carbapenem-resistant Klebsiella pneumoniae causing highly fatal meningitis in southeastern China

Klebsiella pneumoniae (K. pneumoniae) is one of the most common causes of bacterial meningitis worldwide. The purpose of this study was to investigate the clinical and microbiological characteristics of K. pneumoniae meningitis, as well as the association of antimicrobial resistance, virulence, and patient prognosis. The clinical data of patients with K. pneumoniae meningitis from 2014 to 2020 in a tertiary teaching hospital were retrospectively evaluated. Antimicrobial susceptibility profiles were performed by the agar dilution method and broth microdilution method. The isolates were detected for virulence-related genes, resistance genes, capsular serotypes, and molecular subtypes. A total of 36 individuals with K. pneumoniae meningitis were included in the study, accounting for 11.3% (36/318) of all cases of bacterial meningitis. Of the 36 available isolates, K1, K47, and K64 were tied for the most frequent serotype (7/36, 19.4%). MLST analysis classified the isolates into 14 distinct STs, with ST11 being the most common (14/36, 38.9%). Carbapenem resistance was found in 44.4% (16/36) of the isolates, while hypervirulent K. pneumoniae (HvKP) was found in 66.7% (24/36) of the isolates. The isolates of hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP) were then confirmed to be 36.1% (13/36). Importantly, individuals with meningitis caused by Hv-CRKP had a statistically significant higher mortality than the other patients (92.3%, 12/13 vs. 56.5%, 13/23; P < 0.05). The high percentage and fatality of K. pneumoniae-caused meningitis, particularly in Hv-CRKP strains, should be of significant concern. More effective surveillance and treatment solutions will be required in future to avoid the spread of these life-threatening infections over the world.

Epidemiological characteristics and molecular evolution mechanisms of carbapenem-resistant hypervirulent Klebsiella pneumoniae

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP), a type of Klebsiella pneumoniae (KP) that exhibits hypervirulence and carbapenem resistance phenotypes, can cause severe infections, both hospital- and community-acquired infections. CR-hvKP has brought great challenges to global public health and is associated with significant morbidity and mortality. There are many mechanisms responsible for the evolution of the hypervirulence and carbapenem resistance phenotypes, such as the horizontal transfer of the plasmid carrying the carbapenem resistance gene to hypervirulent Klebsiella pneumoniae (hvKP) or carbapenemase-producing Klebsiella pneumoniae (CRKP) acquiring a hypervirulence plasmid carrying a virulence-encoding gene. Notably, KP can evolve into CR-hvKP by acquiring a hybrid plasmid carrying both the carbapenem resistance and hypervirulence genes. In this review, we summarize the evolutionary mechanisms of resistance and plasmid-borne virulence as well as the prevalence of CR-hvKP.

Genomic Evolution of ST11 Carbapenem-Resistant Klebsiella pneumoniae from 2011 to 2020 Based on Data from the Pathosystems Resource Integration Center

(1) Objective: ST11 carbapenem-resistant Klebsiella pneumoniae (CRKP) is widespread throughout the world, and the mechanisms for the transmission and evolution of major serotypes, ST11-KL47 and ST11-KL64, were analyzed to investigate the global distribution and evolutionary characteristics of ST11 CRKP; (2) Methods: The Pathosystems Resource Integration Center (PATRIC) database was downloaded and all K. pneumoniae from 2011 to 2020 were screened to obtain ST11 CRKP genome assemblies with basic information. The relationship of serotype evolution between KL47 and KL64 was then investigated using statistical and bioinformatic analysis; (3) Results: In total, 386 ST11 CRKP isolates were included for analysis. Blood (31.09%, 120/386), respiratory tract (23.06%, 89/386), and feces (20.21%, 78/386) were the major sources of samples. China was the leading country where ST11 CRKP was isolated. KL47 and KL64 were found to be the most prevalent serotypes. ST11-KL64 CRKP [median 78(P25~P75: 72~79.25)] had remarkably more virulence genes than the KL47 [median 63(P25~P75: 63~69)], and the distinction was statistically significant (p < 0.001). A differential comparison of virulence genes between KL47 and KL64 revealed 35 differential virulence genes, including rmpA/rmpA2, iucABCD, iutA, etc. The comparison of the recombination of serotype-determining regions between the two serotypes revealed that KL64 CRKP carried more nucleotide sequences in the CD1-VR2-CD2 region than KL47 CRKP. More nucleotide sequences added approximately 303 base pairs (bp) with higher GC content (58.14%), which might facilitate the evolution of the serotype toward KL64; (4) Conclusions: KL47 and KL64 have become the predominant serotypes of ST11 CRKP. KL64 CRKP carries more virulence genes than KL47 and has increased by approximately 303 bp through recombinant mutations, thus facilitating the evolution of KL47 to KL64. Stricter infection prevention and control measures should be developed to deal with the epidemic transmission of ST11-KL64 CRKP.

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.