A point mutation in recC associated with subclonal replacement of carbapenem-resistant Klebsiella pneumoniae ST11 in China

Clinical and laboratory insights into the threat of hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKP) typically causes severe invasive infections affecting multiple sites in healthy individuals. In the past, hvKP was characterized by a hypermucoviscosity phenotype, susceptibility to antimicrobial agents, and its tendency to cause invasive infections in healthy individuals within the community. However, there has been an alarming increase in reports of multidrug-resistant hvKP, particularly carbapenem-resistant strains, causing nosocomial infections in critically ill or immunocompromised patients. This presents a significant challenge for clinical treatment. Early identification of hvKP is crucial for timely infection control. Notably, identifying hvKP has become confusing due to its prevalence in nosocomial settings and the limited predictive specificity of the hypermucoviscosity phenotype. Novel virulence predictors for hvKP have been discovered through animal models or machine learning algorithms, while standardization of identification criteria is still necessary. Timely source control and antibiotic therapy have been widely employed for the treatment of hvKP infections. Additionally, phage therapy is a promising alternative approach due to escalating antibiotic resistance. In summary, this narrative review highlights the latest research progress in the development, virulence factors, identification, epidemiology of hvKP, and treatment options available for hvKP infection.

Global evolutionary dynamics of virulence genes in ST11-KL47 carbapenem-resistant Klebsiella pneumoniae

ST11-KL47 is a hypervirulent carbapenem-resistant Klebsiella pneumoniae (CRKP) that is highly prevalent in China and poses a major public health risk. To investigate the evolutionary dynamics of virulence genes in this subclone, we analysed 78 sequenced isolates obtained from a long-term study across 29 centres from 17 cities in China. Virulence genes were located in large hybrid pNDM-Mar-like plasmids (length: ∼266 kilobases) rather than in classical pK2044-like plasmids. These hybrid plasmids, derived from the fusion of pK2044 and pNDM-Mar plasmids mediated by insertion sequence (IS) elements (such as ISKpn28 and IS26), integrated virulence gene fragments into the chromosome. Analysis of 217 sequences containing the special IncFIB (pNDM-Mar) replicon using public databases indicated that these plasmids typically contained T4SS-related and multiple antimicrobial resistance genes, were present in 24 countries, and were found in humans, animals, and the environment. Notably, the chromosomal integration of virulence genes was observed in strains across five countries across two continents. In vivo and in vitro models showed that the large hybrid plasmid increased the host fitness cost while increasing virulence. Conversely, virulence genes transferred to chromosomes resulted in increased fitness and lower virulence. In conclusion, virulence genes in the plasmids of ST11-KL47 CRKP are evolving, driven by adaptive negative selection, to enable vertical chromosomal inheritance along with conferring a survival advantage and low pathogenicity.

The prevalence and mechanisms of heteroresistance to ceftazidime/avibactam in KPC-producing Klebsiella pneumoniae

OBJECTIVES

To investigate the prevalence and mechanisms of ceftazidime/avibactam heteroresistance in KPC-producing Klebsiella pneumoniae (KPC-KP) isolates, as well as the role of heteroresistance in the transition of ceftazidime/avibactam susceptibility to resistance.

METHODS

Clinical KPC-KP isolates were obtained from a tertiary hospital in China from 2016 to 2017 and 2019 to 2020. Antimicrobial susceptibility was determined by the broth microdilution method. Population analysis profiles were used to assess ceftazidime/avibactam heteroresistance. WGS and molecular cloning were conducted to reveal heteroresistance mechanisms and molecular characteristics.

RESULTS

The findings indicated that the transition of ceftazidime/avibactam susceptibility to resistance during the treatment of KPC-KP infection is primarily attributed to the heteroresistance exhibited by KPC-KP isolates towards ceftazidime/avibactam. Among 355 ceftazidime/avibactam-susceptible KPC-KP isolates (indicating a resistance rate of 0%), 41 (11.55%) exhibited ceftazidime/avibactam heteroresistance, with the primary mechanism being the presence of KPC mutant subpopulations. These KPC variants, arising from point mutations, deletions and insertions, significantly increased ceftazidime/avibactam resistance while alongside enhanced carbapenem susceptibility. Notably, 11 new KPC variants were identified. Furthermore, four heteroresistant isolates were caused by mixed infection involving subpopulations carrying NDM-1 or NDM-5. Phylogenetic analysis indicated that the clonal spread of ST11-KL64 KPC-KP may be correlated with the prevalence of heteroresistance.

CONCLUSIONS

Ceftazidime/avibactam heteroresistance, primarily driven by pre-existing KPC variants, underscores the importance of considering heteroresistance in ceftazidime/avibactam therapeutics. Awareness of these dynamics is crucial for the effective and sustainable clinical application of ceftazidime/avibactam.

Tracing the possible evolutionary trends of Morganella morganii: insights from molecular epidemiology and phylogenetic analysis

Morganella morganii, encompassing two subspecies, subsp. morganii and subsp. sibonii, is a common opportunistic pathogen, notable for intrinsic resistance to multiple antimicrobial agents. Despite its clinical significance, research into the potential evolutionary dynamics of M. morganii remains limited. This study involved the analysis of genome sequences from 431 M. morganii isolates, comprising 206 isolates that cause host infections, obtained from this study and 225 from the NCBI genome data sets. A diverse array of antimicrobial resistance genes (ARGs) was identified in M. morganii isolates, including mcr-1, tet(X4), tmexCD-toprJ, and various carbapenemase genes. In addition, a novel blaKPC-2-bearing plasmid with demonstrated conjugative capability was discovered in M. morganii. The majority of virulence-related genes (VRGs), except for the hlyCABD gene cluster, were found in almost all M. morganii. Three novel genospecies of M. morganii were identified, designated as M. chanii, M. variant1, and M. variant2. Compared to M. sibonii, M. chanii genospecies possessed a greater number of flagellar-related genes, typically located within mobile genetic elements (MGEs), suggesting potential for better environmental adaptability. Phylogenetic analysis further disclosed that M. morganii was divided into 12 sequence clusters (SCs). Particularly, SC9 harbored an elevated abundance of ARGs and VRGs, mainly toxin-related genes, and was associated with a higher presence of MGEs compared to non-SC9 strains. The collective findings suggest that M. morganii undergoes evolution driven by the influence of MGEs, thereby significantly enhancing its adaptability to selective pressures of environmental changes and clinical antimicrobial agents.IMPORTANCEThe growing clinical significance of Morganella morganii arises from its abundant virulence factors and antimicrobial resistance genes, resulting in elevated infection rates and increased clinical scrutiny. However, research on the molecular epidemiology and evolutionary trends of M. morganii has been scarce. Our study established a list of virulence-related genes (VRGs) for M. morganii and conducted a large-scale epidemiological investigation into these VRGs. Based on genomic classification, three novel genotypes of M. morganii were identified, representing evolutionary adaptations and responses to environmental challenges. Furthermore, we discovered the emergence of a sequence cluster enriched with antimicrobial resistance genes, VRGs, and mobile genetic elements, attributed to the selective pressure of antimicrobial agents. In addition, we identified a novel conjugative plasmid harboring the blaKPC-2 gene. These findings hold significance in monitoring and comprehending the epidemiology of M. morganii.

Genomic and immunocyte characterisation of bloodstream infection caused by Klebsiella pneumoniae

OBJECTIVES

The aim of this study was to evaluate the characteristics of immunocyte associated with bloodstream infection (BSI) caused by Klebsiella pneumoniae (Kpn).

METHODS

Patients with BSI-Kpn were included from 2015 to 2022 in our hospital. Immunocyte subpopulations of enrolled BSI-Kpn patients were tested on the same day of blood culture using multicolor flow cytometry analysis. Antibiotic susceptibility test was determined by agar dilution or broth dilution method. All included isolates were subjected to whole genome sequencing and comparative genomics analysis. Clinical and genetic data were integrated to investigate the risk factors associated with clinical outcome.

RESULTS

There were 173 patients with non-duplicate BSI-Kpn, including 81 carbapenem-resistant Kpn (CRKP), 30 extended-spectrum β-lactamases producing Kpn (ESBL-Kpn), 62 none CRKP or ESBL-Kpn (S-Kpn). Among 68 ST11-CRKP isolates, ST11-O2v1:KL64 was the most common serotypes cluster (77.9%, 53/68), followed by ST11-OL101: KL47 (13.2%, 9/68). Compared with CSKP group, subpopulations of immunocyte in patients with CRKP were significantly lower (P < 0.01). In patients with ST11-O2v1:KL64 BSI-Kpn, the level of cytotoxic T lymphocytes (CD3 + CD8 +) is the highest, while the B lymphocytes (CD3-CD19 +) was the least. In addition, the level of immunocyte in patients with Kpn co-harbored clpV-ybtQ-qacE were lower than that in patients with Kpn harbored one of clpV, ybtQ or qacE and without these three genes. Furthermore, co-existence of clpV-ybtQ-qacE was independently associated with a higher risk for 30-day mortality.

CONCLUSIONS

The results demonstrate that patients with BSI-CRKP, especially for ST11-O2v1:KL64, exhibit lower leukomonocyte counts. In addition, BSI-Kpn co-harbored clpV-ybtQ-qacE is correlated to higher 30-day mortality.

Adaptive attenuation of virulence in hypervirulent carbapenem-resistant Klebsiella pneumoniae

The emergence of nosocomial infections caused by hypervirulent and carbapenem-resistant K. pneumoniae (hv-CRKP) has become a significant public health challenge. The genetic traits of virulence and resistance plasmids in hv-CRKP have been extensively studied; however, research on the adaptive evolution strategies of clinical strains inside the host was scarce. This study aimed to understand the effects of antibiotic treatment on the phenotype and genotype characteristics of hv-CRKP. We investigated the evolution of hv-CRKP strains isolated from the same patient to elucidate the transition between hospital invasion and colonization. A comparative genomics analysis was performed to identify single nucleotide polymorphisms in the rmpA promoter. Subsequent validation through RNA-seq and gene deletion confirmed that distinct rmpA promoter sequences exert control over the mucoid phenotype. Additionally, biofilm experiments, cell adhesion assays, and animal infection models were conducted to illuminate the influence of rmpA promoter diversity on virulence changes. We demonstrated that the P12T and P11T promoters of rmpA possess strong activity, which leads to the evolution of CRKP into infectious and virulent strains. Meanwhile, the specific sequence of polyT motifs in the rmpA promoter led to a decrease in the lethality of hv-CRKP and enhanced cell adhesion and colonization. To summarize, the rmpA promoter of hv-CRKP is utilized to control capsule production, thereby modifying pathogenicity to better suit the host's ecological environment.IMPORTANCEThe prevalence of hospital-acquired illness caused by hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) is significant, leading to prolonged antibiotic treatment. However, there are few reports on the phenotypic changes of hv-CRKP in patients undergoing antibiotic treatment. We performed a comprehensive examination of the genetic evolutionary traits of hv-CRKP obtained from the same patient and observed variations in the promoter sequences of the virulence factor rmpA. The strong activity of the promoter sequences P11T and P12T enhances the consistent production of capsule polysaccharides, resulting in an invasive strain. Conversely, weak promoter activity of P9T and P10T is advantageous for exposing pili, hence improving bacterial cell attachment ability and facilitating bacterial colonization. This finding also explains the confusion of some clinical strains carrying wild-type rmpA but exhibiting a low mucoid phenotype. This adaptive alteration facilitates the dissemination of K. pneumoniae within the hospital setting.

Virulence gene distribution and molecular epidemiological characteristics of carbapenem-resistant Klebsiella pneumoniae in the ICU

OBJECTIVES

The drug-resistant genes carried by carbapenem-resistant Klebsiella pneumoniae (CRKP) limit clinical treatment options, and its virulence genes severely affect patient prognosis. This study aims to investigate the distribution of virulence genes, capsular serotypes, and molecular epidemiological characteristics of CRKP in ICU, to understand the characteristics of CRKP infections in ICU, and to provide a scientific basis for effective monitoring and control of CRKP infections in ICU.

METHODS

A total of 40 non-duplicate strains of CRKP isolated from the ICU of Guangdong Provincial People's Hospital between January 2021 and December 2022 were collected and analyzed. Whole-genome sequencing was used to analyze the distribution of resistance genes, virulence genes, and capsular serotypes of the strains. The sequences of 7 housekeeping genes of CRKP genome were uploaded to the Klebsiella pneumoniae (KPN)multilocus sequence typing (MLST) database to determine the sequence types (STs) of the strains.

RESULTS

The age of the 40 ICU CRKP-infected patients was (69.03±17.82) years old, with various underlying diseases, and there were 20 patients with improved clinical outcome and 20 patients with death. The isolated strains primarily originated from mid-stream urine and bronchoalveolar lavage fluid. Whole-genome sequencing results revealed that the strains predominantly carried blaKPC-1 (29 strains, 72.5%) and blaNDM-1 (6 strains, 15.0%), with 5 strains carrying both blaKPC-1 and blaNDM-1. Various virulence genes were detected, among which the carriage rates of genes such as entA, entB, entE, entS, fepA, fepC, fepG, yag/ecp, and ompA reached 100%, while the carriage rates of genes such as entD, fimB, iroB, iroD, fes,and pla were low. The CRKP strains isolated from ICU were predominantly ST11 (27 cases, 67.5%), with KL64 being the main capsular serotype (29 cases, 72.5%). A total of 23 ST11-KL64 CRKP strains were detected, accounting for 57.5%.

CONCLUSIONS

The main type of ICU CRKP is ST11-KL64, carrying various virulence genes, primarily those related to iron absorption. Furthermore, blaKPC has shifted from blaKPC-2 to blaKPC-1. Therefore, close monitoring of the molecular epidemiological changes of CRKP is necessary, and strict control measures should be implemented to effectively curb the occurrence of CRKP infections.

Clinical and Molecular Characteristics of Patients with Bloodstream Infections Caused by KPC and NDM Co-Producing Carbapenem-Resistant Klebsiella pneumoniae

Purpose

Klebsiella pneumoniae carbapenemase (KPC) and New Delhi metallo-β-lactamase (NDM) co-producing carbapenem-resistant Klebsiella pneumoniae (KPC-NDM-CRKP) isolates have been increasingly reported worldwide but have not yet been systematically studied. Thus, we have conducted a study to compare the risk factors, molecular characteristics, and mortality involved in clinical bloodstream infections (BSIs) caused by KPC-NDM-CRKP and KPC-CRKP strains.

Methods

A retrospective study was conducted on 231 patients with BSIs caused by CRKP at Jinling Hospital in China from January 2020 to December 2022. Antimicrobial susceptibility testing, carbapenemase genes detection and whole-genome sequencing were performed subsequently.

Results

Overall, 231 patients were included in this study: 25 patients with KPC-NDM-CRKP BSIs and 206 patients with KPC-CRKP BSIs. Multivariate analysis implicated ICU-acquired BSI, surgery within 30 days, and longer stay of hospitalization prior to CRKP isolation as independent risk factors for KPC-NDM-CRKP BSIs. The 30-day mortality rate of the KPC-NDM-CRKP BSIs group was 56% (14/25) compared with 32.5% (67/206) in the KPC-CRKP BSIs control group (P = 0.02). The ICU-acquired BSIs, APACHE II score at BSI onset, and BSIs caused by KPC-NDM-CRKP were independent predictors for 30-day mortality in patients with CRKP bacteremia. The most prevalent ST in KPC-NDM-CRKP isolates was ST11 (23/25, 92%), followed by ST15 (2/25, 8%).

Conclusion

In patients with CRKP BSIs, KPC-NDM-CRKP was associated with an excess of mortality. The likelihood that KPC-NDM-CRKP will become the next "superbug" highlights the significance of epidemiologic surveillance and clinical awareness of this pathogen.

Expansion and transmission dynamics of high risk carbapenem-resistant Klebsiella pneumoniae subclones in China: An epidemiological, spatial, genomic analysis

AIMS

Carbapenem-resistant Klebsiella pneumonia (CRKP) is a global threat that varies by region. The global distribution, evolution, and clinical implications of the ST11 CRKP clone remain obscure.

METHODS

We conducted a multicenter molecular epidemiological survey using isolates obtained from 28 provinces and municipalities across China between 2011 and 2021. We integrated sequences from public databases and performed genetic epidemiology analysis of ST11 CRKP.

RESULTS

Among ST11 CRKP, KL64 serotypes exhibited considerable expansion, increasing from 1.54% to 46.08% between 2011 and 2021. Combining our data with public databases, the phylogenetic and phylogeography analyses indicated that ST11 CRKP appeared in the Americas in 1996 and spread worldwide, with key clones progressing from China's southeastern coast to the inland by 2010. Global phylogenetic analysis showed that ST11 KL64 CRKP has evolved to a virulent, resistant clade with notable regional spread. Single-nucleotide polymorphism (SNP) analysis identified BMPPS (bmr3, mltC, pyrB, ppsC, and sdaC) as a key marker for this clade. The BMPPS SNP clade is associated with high mortality and has strong anti-phagocytic and competitive traits in vitro.

CONCLUSIONS

The high-risk ST11 KL64 CRKP subclone showed strong expansion potential and survival advantages, probably owing to genetic factors.

Chitosan modified magnetic nanocomposite for biofilm destruction and precise photothermal/photodynamic therapy

Getting rid of the biofilms is a major challenge when treating skin and soft tissue infections (SSTI), an inflammatory illness brought on by bacteria. Traditional magnetic materials have a limited dispersibility and a biofilm permeable property, making it challenging to remove biofilms and causing infection to linger. To solve these problems, we developed a kind of magnetic composite nanoplatform coated with indocyanine green carbon dots and modified with chitosan modification (Fe-ICGCDs@CS). Fe-ICGCDs@CS has high dispersibility and improves the conductivity of biofilms under magnetic action. Fe-ICGCDs@CS can adsorb bacteria via the positive charge and achieve precise photothermal sterilization and photodynamic therapy (PDT). Moreover, by catalyzing hydrogen peroxide (2 mM), Fe-ICGCDs@CS can produce oxygen to relieve the anoxic state in the deep layer of biofilms and activate dormant bacteria to make them sensitive to external stimuli. All in all, unlike the common "just kill" sterilization model, Fe-ICGCDs@CS can accurately kill bacteria and be recovered by an external magnetic field at the end of treatment, thus reducing the potential biological toxicity of nanomaterials. Therefore, the proposed Fe-ICGCDs@CS provides a new antibacterial method with low biotoxicity for clinical application in the treatment of biofilm infections.

Increase in antioxidant capacity associated with the successful subclone of hypervirulent carbapenem-resistant Klebsiella pneumoniae ST11-KL64

The acquisition of exogenous mobile genetic material imposes an adaptive burden on bacteria, whereas the adaptational evolution of virulence plasmids upon entry into carbapenem-resistant Klebsiella pneumoniae (CRKP) and its impact remains unclear. To better understand the virulence in CRKP, we characterize virulence plasmids utilizing a large genomic data containing 1219 K. pneumoniae from our long-term surveillance and publicly accessible databases. Phylogenetic evaluation unveils associations between distinct virulence plasmids and serotypes. The sub-lineage ST11-KL64 CRKP acquires a pK2044-like virulence plasmid from ST23-KL1 hypervirulent K. pneumoniae, with a 2698 bp region deletion in all ST11-KL64. The deletion is observed to regulate methionine metabolism, enhance antioxidant capacity, and further improve survival of hypervirulent CRKP in macrophages. The pK2044-like virulence plasmid discards certain sequences to enhance survival of ST11-KL64, thereby conferring an evolutionary advantage. This work contributes to multifaceted understanding of virulence and provides insight into potential causes behind low fitness costs observed in bacteria.

Distinct evolution of ST11 KL64 Klebsiella pneumoniae in Taiwan

Carbapenem-resistant ST11_KL64 Klebsiella pneumoniae emerged as a significant public health concern in Taiwan, peaking between 2013 and 2015, with the majority of isolates exhibiting OXA-48 as the sole carbapenemase. In this study, we employed whole-genome sequencing to investigate the molecular underpinnings of ST11_KL64 isolates collected from 2013 to 2021. Phylogenomic analysis revealed a notable genetic divergence between the ST11_KL64 strains in Taiwan and those in China, suggesting an independent evolutionary trajectory. Our findings indicated that the ST11_KL64_Taiwan lineage originated from the ST11_KL64 lineage in Brazil, with recombination events leading to the integration of ICEKp11 and a 27-kb fragment at the tRNAASN sites, shaping its unique genomic landscape. To further elucidate this unique sublineage, we examined the plasmid contents. In contrast to ST11_KL64_Brazil strains, which predominantly carried blaKPC-2, ST11_KL64_Taiwan strains exhibited the acquisition of an epidemic blaOXA-48-carrying IncL plasmid. Additionally, ST11_KL64_Taiwan strains consistently harbored a multi-drug resistance IncC plasmid, along with a collection of gene clusters that conferred resistance to heavy metals and the phage shock protein system via various Inc-type plasmids. Although few, there were still rare ST11_KL64_Taiwan strains that have evolved into hypervirulent CRKP through the horizontal acquisition of pLVPK variants. Comprehensive characterization of the high-risk ST11_KL64 lineage in Taiwan not only sheds light on its epidemic success but also provides essential data for ongoing surveillance efforts aimed at tracking the spread and evolution of ST11_KL64 across different geographical regions. Understanding the molecular underpinnings of CRKP evolution is crucial for developing effective strategies to combat its emergence and dissemination.