Phenotypic and Genotypic Characterization of Carbapenem-resistant Enterobacteriaceae: Data From a Longitudinal Large-scale CRE Study in China (2012-2016)

Unveiling the Clonal Dynamics and transmission mechanism of Carbapenem-Resistant Klebsiella pneumoniae in the ICU environment

CRKP infections are a significant public health threat due to their high mortality and limited treatment options. This study aimed to investigate CRKP colonization and clonal dissemination mechanism in an ICU. From August 2019 to December 2019, 8668 samples were collected from patients and the ICU environment for CRKP screening. Positive samples underwent antimicrobial susceptibility testing, whole-genome sequencing, and molecular epidemiological analysis. Disinfectant sensitivity and ultraviolet (UV) resistance experiments were conducted to evaluate clonal persistence. The overall CRKP positive rate was 4.85% (420/8668), with higher rates in patients (14.77%, 247/1672) compared to environmental surfaces (2.47%, 173/6996). Intestinal and ventilator-related surfaces were identified as high-risk colonization sites. Molecular analysis revealed six sequence types, with ST11-KL64 (44.05%, 185/420) and ST15-KL112 (24.05%, 101/420) as dominant clones, both exhibiting elevated virulence. Notably, the emerging ST15-KL112 clone demonstrated enhanced resistance to disinfectants including chlorhexidine (MIC 8 mg/L) and benzalkonium chloride (32 mg/L). While most isolates produced KPC-2 (72.86%), OXA-232 prevalence (25.23%) exceeded prior reports. Crucially, ST11 strains survived standard UV disinfection (60-second exposure) at rates 1.3- to 5-fold higher than other clones (p๤0.01). Our findings highlight the critical role of disinfectant resistance in sustaining CRKP transmission. To mitigate outbreaks, we advocate for disinfectant rotation protocols targeting disinfectant-resistant clones and prolonged UV exposure times in ICUs. The persistence of resistant CRKP clones in the ICU environment, particularly their high tolerance to disinfectants, highlights the urgent need for enhanced infection control strategies, including tailored disinfection protocols and surveillance programs.

Spread of the Fosfomycin resistance fosA3 gene via the IS26 mobile element between plasmids and the chromosome of carbapenem-resistant Escherichia coli in China

OBJECTIVE

This study investigated fosA3-positive strains selected from carbapenem-resistant Escherichia coli (CREC) and further characterized them through genomic and phenotypic analyses.

METHODS

fosA3-positive CREC strains were subjected to agar dilution. Whole-genome sequencing (WGS) was used to identify molecular mechanisms of fosfomycin resistance and to investigate plasmid structure characteristics through comparative analysis. Conjugative transfer experiments were used to evaluate plasmid transfer ability, followed by plasmid stability assessment. Growth rate analysis evaluated the fitness costs of transconjugants. Phylogenetic analysis was performed on fosA3-positive CREC strains. Furthermore, analysis of fos genes carrying E. coli sequence types (STs) from the NCBI database explored the evolution and spread of fosfomycin resistance.

RESULTS

Between 2016 and 2023, a total of 11.23% CREC strains (10/89) carrying fosA3 were collected from a hospital for further analysis. These ten fosA3-positive strains were also resistant to fluoroquinolones and ceftazidime-avibactam. The fosA3 gene was located within a similar genetic background (IS26-fosA3-1811bp-IS26) on plasmids or chromosomes. The fosA3-carrying IncFII(pHN7A8)-IncX3 cointegrate plasmid pEC00-2-145k was transferable, with fitness cost of 20% to host. Furthermore, three of ten fosA3-positive CREC strains belonged to ST156. Analysis of fos genes carrying E. coli strains from China in the NCBI database identified ST156 (5.39%, 147/2,725) and ST167 (5.21%, 142/2,725) as predominant STs.

CONCLUSIONS

This study revealed fosA3 in CREC strains was associated with IS26 and spreads fosfomycin resistance through horizontal transfer, occurring both on chromosomes and plasmids. The first fosA3-carrying cointegrate plasmid pHN7A8-IncX3-type in E. coli isolates was reported, highlighting a new route of fosfomycin resistance spread. Additionally, notable diversity of ST among fosA3-carrying E. coli strains highlights complexity of fosfomycin resistance dissemination and the importance of surveillance and control measures.

Accelerated detection of carbapenem resistance in Klebsiella pneumoniae via single-cell Raman spectroscopy

Antibiotic resistance poses a significant global public health challenge, particularly concerning carbapenem-resistant Klebsiella pneumoniae (CRKP). A Raman-based antimicrobial susceptibility testing (R-AST) method was developed, utilizing D₂O-labeled single-cell Raman spectroscopy alongside the Metabolic Inhibition Level (MIL) for rapid CRKP antimicrobial susceptibility testing and carbapenemase enzyme typing. By analyzing 30,000 single-cell Raman spectra from 57 K. pneumoniae strains, the R-AST accurately detected CRKP within two hours. Furthermore, R-AST was able to differentiate between amikacin-sensitive and amikacin-resistant strains within the CRKP category, thereby providing potential treatment options. Notably, both R-AST classifications demonstrated 100% category agreement with the Vitek®-2 Compact system. The R-AST demonstrated greater accuracy in distinguishing carbapenemase types compared to the carbapenemase inhibitor enhancement test in K. pneumoniae, achieving an overall accuracy of 95.74% (95% CI: 85.46-98.77%) in enzyme typing. However, it misclassified 2 out of 21 KPC-producing CRKP strains as KPC and NDM-coproducing CRKP strains. Conversely, the overall accuracy of the carbapenemase inhibitor enhancement test was 93.62% (95% CI: 82.69-97.66%), with 3 out of 9 KPC and NDM-coproducing strains being missed. By delivering reliable results within 2 h, the R-AST provides an efficient, dependable, and broadly applicable approach to rapid antimicrobial susceptibility testing in clinical settings, potentially mitigating antibiotic misuse and the spread of drug-resistant bacteria.

Molecular epidemiology of New Delhi metallo-β-lactamase-producing Escherichia coli in retail market chickens, Shandong, China

Background

The global spread of carbapenem-resistant Escherichia coli is a major public health concern. An investigation of their presence in the human and food chain products would facilitate the elucidation of the route of their food-borne transmission. Thus, the aim of this study was to investigate the prevalence of NDM-positive E. coli isolates in chicken at retail markets in Shandong, China.

Methods

A total of 60 NDM-positive isolates were recovered from 531 E. coli isolates obtained from chickens at the retail market in Shandong. Antimicrobial susceptibility testing and polymerase chain reaction screening were performed to investigate the phenotype and genotype of carbapenemase resistance. Genomic characteristics of the -producing isolates were determined by WGS and bioinformatic analysis.

Results

All of these isolates were multidrug-resistant (MDR), with a majority exhibiting resistance to meropenem, ampicillin, ceftazidime, cefotaxime, florfenicol, sulfamethoxazole/trimethoprim, and tetracycline. Whole genome sequencing (WGS) analysis indicated that these isolates were belonged to 18 distinct sequence types (STs), with the most prevalent STs being ST515 (17/60) and ST69 (11/60). Additionally, WGS analysis revealed that clonal spread of NDM-positive ST69 and ST515 E. coli isolates at markets in different cities in Shandong. Phylogenomic analysis showed that NDM-positive E. coli isolates from chickens were closely related to those of human origin.

Conclusion

This study provides a new insight into the spread of NDM-positive E. coli isolates from retail chicken, and offers essential data for public health management.

Epidemiology and outcomes associated with MBL-producing Enterobacterales: A systematic literature review

The increasing prevalence of infections due to metallo-β-lactamase (MBL)-producing Enterobacterales poses a serious concern given the limited treatment options available. This systematic literature review (SLR) describes the molecular epidemiology, geographical distribution, and clinical outcomes of such infections. Systematic searches of literature published between January 2013 and May 2023 were performed, and 39 studies with an MBL sample size of ≥25 isolates and ≥2 well-defined outcomes were eligible. Most of the studies were from Asia (21/39) followed by Europe (11/39) and evaluated more than two species (24/39). Overall, the percentage of MBL-producing isolates ranged from 6.8%-100.0%. Among 6620 MBL-producers, the majority were from Europe (3837/6620; 58.0%), followed by Asia (2079/6620; 31.4%). New Delhi MBL (NDM)-producers (5668/6620; 85.6%) were the most frequent across all regions, with NDM-1 as the common variant. The majority of IMP-producing isolates (586/592; 99.0%) came from Asia, while the majority of VIM-producing isolates were found in Europe (322/371; 86.8%). Studies focused on MBL-specific outcomes (n = 28) reported reduced susceptibility (<80.0%) to most antimicrobials except for colistin and tigecycline. Six studies reported significantly longer hospital and/or ICU stay due to MBL-Enterobacterales compared to other infection groups. Common mortality measures reported were overall mortality (18.8%-57.0%; 9 studies), in-hospital mortality (11.1%-55.3%; 6 studies), and 30-day mortality (0%-36.4%; 7 studies). Previous antibiotic use (9 studies) and hospital and/or ICU stay (8 studies) were common risk factors for colonization/infection and mortality. Reporting of MBL prevalence across regions will provide a better understanding of the infection burden and prevent further spread.

Genomic characteristics and phylogenetic analyses of colonization and infection with carbapenem-resistant Klebsiella pneumoniae in multicenter intensive care units: a cohort study

Carbapenem-resistant Klebsiella pneumoniae (CRKp) poses a major threat to global public health. This study aimed to investigate the genomic characteristics and phylogenetic relatedness of colonization and infection with CRKp among intensive care unit (ICU) patients. A total of 61 CRKp isolates, including 29 non-ICU-acquired and 32 ICU-acquired strains, were collected by active screening and infection culture from 16 ICUs through a multicenter cohort study. Following whole-genome sequencing (WGS), seven sequence types (STs) were identified, with ST11 (60.7%) being the most dominant, followed by ST15 (27.9%). Most strains (93.4%) carried the blaKPC-2 gene, while 9.8% and 3.3% of strains carried either the blaNDM-1 gene or both genes. A high abundance of virulence genes including iutA (55.7%), rmpA (18.0%), and rmpA2 (52.5%) were identified, with iutA +rmpA2 (37.7%) being the most common combination. The IncHI1B plasmid was identified in all of the 34 strains carrying the detected virulence genes. Furthermore, results from cgMLST analysis revealed 10 clusters with highly homogeneous CRKp strains, from which the potential interregional and intrahospital spread of CRKp were hypothesized. Here, this study reveals the widespread distribution of CRKp as well as locally specific strains in different regions of Anhui Province. The observed high abundance of virulence genes requires additional attention and continued monitoring. Taken together, these findings highlight the need for coordinated efforts between healthcare facilities and networks to aid CRKp control strategies and prevent spread. Moreover, we emphasize the importance of WGS in revealing additional insights, thus improving epidemiological studies and transmission control of CRKp.

IMPORTANCE

Carbapenem-resistant K. pneumoniae (CRKp) has spread rapidly to different parts of the world and poses a serious threat to global health. High genetic diversity in CRKp can introduce complexities in disease treatment and management. Intensive care unit (ICU) patients are more susceptible to acquire CRKp infections. However, most CRKp studies have focused on strains isolated from infections, rather than cases of asymptomatic CRKp colonization. This study analyzed clinical CRKp isolates from ICU patients as well as isolate cases of active colonization screening. Findings reveal the genetic diversity of CRKp in different regions of Anhui Province, emphasizing the necessity for a more comprehensive investigation of the genomic characteristics and phylogenetic relatedness of CRKp in different regions. Data regarding antimicrobial resistance genes, virulence genes, and genetic relatedness will improve the understanding of the potential risk of CRKp to public health and aid guidance for prevention and control of CRKp.

Carbapenem-resistant Klebsiella pneumoniae infections in Chinese children: in vitro activities of ceftazidime-avibactam and aztreonam-avibactam against carbapenemase-producing strains in a two-center study

Objective

This study assessed epidemiology characteristics, carbapenem-resistance genes, and drug resistance to ceftazidime-avibactam (CZA) and aztreonam-avibactam (AZA) in children with carbapenem-resistant Klebsiella Pneumoniae (CRKP) infections.

Methods

A total of 363 non-repetitive CRKP strains were collected from children who underwent two tertiary children's hospital between 1 January 2021 and 30 June 2024 in Chongqing and Kunming in Southwest China. Carbapenem resistance genes and antimicrobial susceptibility were analyzed. Basic clinical characteristics of the patients were obtained from medical records.

Results

blaNDM-5, blaNDM-1, and blaKPC-2 were the predominant carbapenemase genes; their detection rates were 35.8%, 30.3%, and 25.3%, respectively. Patients in the KPC-2-producing Klebsiella pneumoniae (KPC-KP) (median age, 90 days) were older than those producing NDM-1 and NDM-5 Klebsiella pneumoniae (NDM-KP) (median age, 37 days) (P < 0.05). The detection rate of NDM-KP in the neonatal unit was higher compared with KPC-KP (62.5% vs. 9.8%, P < 0.05), while the detection rate of NDM-KP in the intensive care unit (ICU) was decreased compared with KPC-KP (9.6% vs. 40.2%, P < 0.05). NDM-KP had lower resistance rates to aminoglycosides and fluoroquinolones than KPC-KP; the resistance rate of aminoglycosides and fluoroquinolones among NDM-KP and KPC-KP in Chongqing was increased compared with Kunming. The sensitivity rates of KPC-KP to CZA and NDM-KP to AZA were 100%, and the MIC50 of the CRKP to CZA and AZA were 2 μg/mL and 0.125μg/mL, respectively.

Conclusions

The epidemiological characteristics of Chinese children with CRKP infections, including the resistance genes and the antibiotic resistance of CRKP, exhibited significant variation between the two regions.KPC-KP strains had higher antimicrobial resistance in patients and thus should be given more attention in clinics and infection control.

ST11 carbapenem-resistant Klebsiella pneumoniae clone harbouring capsular type KL25 becomes the primarily prevalent capsular serotype in a tertiary teaching hospital in China

BACKGROUND

The spread of carbapenem-resistant Klebsiella pneumoniae (CRKP) that produces K. pneumoniae carbapenemase-2 has garnered significant attention due to its increasing prevalence. In China, the dissemination of K. pneumoniae carbapenemase-2-producing CRKP is predominantly linked to sequence type 11 (ST11), with capsular serotypes KL47 and KL64 being the primary capsular identified.

METHODS

A total of 64 CRKP-ST11 strains were collected from 2020 to 2023 and whole-genome sequencing was performed on all isolated ST11-CRKP strains. Antibiotic susceptibility was tested using the VITEK 2 system. Growth curve tests and in vitro competition experiments were used to assess the growth adaptability of different capsular type isolates. Moreover, the biofilm assessment and phagocytosis assays were performed to evaluate CRKP isolate virulence.

RESULTS

During the observed period, a notable subclonal shift was perceived within the prevailing ST11-CRKP clone, wherein the previously dominant KL64 and KL47 serotypes have been largely supplanted by the KL25 serotype since 2022. The ST11-KL25-CRKP strain significantly outgrew both ST11-KL64-CRKP and ST11-KL47-CRKP. Additionally, ST11-KL25-CRKP displayed a greater enhanced capacity to form biofilms than ST11-KL64-CRKP and ST11-KL47-CRKP. Furthermore, ST11-KL25-CRKP demonstrated enhanced resistance to phagocytosis than both of its counterparts.

CONCLUSIONS

ST11-KL25-CRKP possesses a remarkable level of adaptability and has the potential to regionally replace ST11-KL64-CRKP as the predominant strain in the region. Additionally, this novel and high-risk ST11-KL25-CRKP strain may indicate stronger virulence.

Genomically defined hypervirulent Klebsiella pneumoniae contributed to early-onset increased mortality

The presence of all five of the virulence-associated genes iucA, iroB, peg-344, rmpA, and rmpA2 is presently the most accurate genomic means for predicting hypervirulent Klebsiella pneumoniae (hvKp-p). With this longitudinal cohort study, we firstly provide novel insights into the clinical and genomic characteristics of hvKp-p in high-risk regions. Through propensity score matching, we show that hvKp-p is less likely to acquire antimicrobial resistance but develops more severe disease and result in increased mortality. HvKp-p are predominantly isolated from hospital settings and caused pneumonia in majority of the cases. ST23 and KL1 are the most common types in the hvKp-p cohort. Community-acquired and healthcare-associated infections are also identified as independent risk factors for hvKp-p. This genomic definition, albeit imperfect, offers a practical and efficient alternative to murine models, allowing for early identification and timely intervention in clinical settings.

An Unusual 'Gift' from Humans: Third-Generation Cephalosporin-Resistant Enterobacterales in migratory birds along the East Asian-Australasian Flyway

Migratory birds play a pivotal role in the global dissemination of antimicrobial resistance genes (ARGs), with shorebirds relying on coastal wetlands during their long-distance migrations, environments often contaminated and conducive to ARG transmission. However, systematic investigations into antimicrobial resistance (AMR) in shorebirds remain scarce. During spring and autumn of 2023, we collected 893 throat and cloacal swabs from 480 shorebirds, representing 28 species, at Chongming Dongtan, a critical stopover along the East Asian-Australasian Flyway. Our analysis identified six strains, including four extra-intestinal pathogenic E. coli (ExPEC) and two K. pneumoniae, that exhibited resistance to third-generation cephalosporins, with three ExPEC strains exhibiting significant virulence in Galleria mellonella infection assays. We identified two conjugative plasmids: E042113F_p1, carrying the blaCMY-2 gene in E. coli, and M50_p2, carrying the blaKPC-2 gene in a hypervirulent K. pneumoniae with a virulence plasmid harboring the aerobactin system. Bioinformatic and experimental analyses confirmed that these plasmids could transfer without any fitness cost, remaining stable for at least 30 passages. Surprisingly, genomic tracing revealed that among the plasmids similar to E042113F_p1 (blaCMY-2), the earliest was identified in a Chinese swallow in 2015, with subsequent detections in wild birds from Mongolia (2017), Russia (2018), and Australia (2019). Notably, these E04-CMY-like/M50-KPC-like plasmids predominantly originated from human sources, underscoring the pivotal role of human activity in the cross-species transmission of AMR. This human-mediated transmission of resistance elements into wildlife posed a substantial risk for amplifying and disseminating AMR through long-range migratory bird movements, highlighting the urgent need for international collaboration under a One Health framework. Integrated surveillance, environmental management, and stringent antibiotic stewardship are critical to mitigating the risks posed by migratory birds in amplifying and spreading AMR across ecosystems.

Fecal carriage and molecular characterization of carbapenem-resistant Enterobacteriaceae from hospitalized children in a tertiary hospital of Shandong, China

BACKGROUND

The prevalence of carbapenem-resistant Enterobacteriaceae (CRE) has emerged as a serious public health problem worldwide, and the data on the fecal carriage of CRE strains in hospitalized children remain limited. This study aimed to investigate the molecular characteristics of intestinal colonization of CRE in hospitalized children in Shandong, China.

METHODS

A retrospective study was conducted from August to November 2023. Antimicrobial susceptibility testing was performed by the broth microdilution method. Carbapenemase genes, drug resistance genes, and plasmid replicon types were detected using multiplex real-time PCR and whole-genome sequencing. Multilocus sequence typing (MLST) was used to determine the genetic relationships between strains.

RESULTS

A total of 20 CRE isolates were identified from 432 fecal samples, with a fecal carriage rate of 4.6%. The CRE isolates predominantly consisted of Escherichia coli (E. coli, n = 13) and Klebsiella strains (n = 6). CRE isolates showed a high resistance rate of 90-100% to seven β-lactam antibiotics. Resistance rates for other antibiotics such as trimethoprim-sulfamethoxazole, tetracycline, azithromycin, ciprofloxacin, chloramphenicol, nalidixic acid, and streptomycin were 90, 85, 85, 80, 75, 75, and 75%, respectively. CRE isolates showed low resistance to amikacin (20%), and none of the isolates were resistant to tigecycline. Additionally, the multidrug resistance rate of CRE isolates was 95%. All CRE strains carried sulfonamide antibiotic and β-lactamase resistance genes, of which the most common β-lactamase resistance genes were bla NDM-1 (n = 9), bla NDM-5 (n = 7) and bla OXA-1 (n = 7). Resistance genes to tetracycline and macrolide antibiotics were also widespread among the strains. The study found that IncFIB and IncFII series plasmids were present in 84 and 42% of the CRE strains, respectively. Additionally, Col, IncFIA, IncC, IncHI2, and IncX series plasmids were also detected. MLST analysis revealed diverse sequence types (STs) among CRE isolates, with ST167 being a common ST among E. coli isolates.

CONCLUSION

This study revealed bla NDM E. coli were the dominant isolates in fecal samples of hospitalized children in Shandong Province, with a broad multidrug resistance to antibiotics, emphasizing that infection control measures need to be taken to limit the spread of these strains.

Synergistic combination of ceftazidime and avibactam with Aztreonam against MDR Klebsiella pneumoniae in ICU patients

The proliferation of multidrug-resistant, metallo-beta-lactamase-producing Klebsiella pneumoniae (MBL-producing K. pneumoniae) poses a major threat to public health resulting in increasing treatment costs, prolonged hospitalization, and mortality rate. Treating such bacteria presents substantial hurdles for clinicians. The combination of Aztreonam (ATM) and ceftazidime/avibactam (CAZ/AVI) is likely the most successful approach. The study evaluated the in vitro activity of CAZ/AVI in combination with ATM against MBL-producing K. pneumoniae clinical isolates collected from Suez Canal University Hospital patients. Carbapenem-resistant K. pneumoniae were isolated and identified from different specimens. The presence of metallo-β-lactamases was detected phenotypically by modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM) testing, and genotypically for the three metallo-β-lactamase genes: blaNDM, blaIMP, and blaVIM by conventional PCR method. The synergistic effect of CAZ/AVI with ATM against MBL-producing K. pneumoniae was detected by ceftazidime-avibactam combination disks and E-test for antimicrobial susceptibility testing. Out of the 65 K. pneumoniae isolates recovered, 60% (39/65) were carbapenem-resistant (CRKP). According to the mCIM and eCIM tests, 89.7% (35/39) of CRKP isolates were carbapenemase-positive, and 68.6% (24/35) were metallo-β-lactamase (MBL)-positive. By using the conventional PCR, at least one of the MBL genes was present in each metallo-bata-lactamase-producing isolate: 8.3% carried the blaVIM gene, 66.7% the blaNDM, and 91.7% the blaIMP gene. After doing the disk combination method for ceftazidime-avibactam plus Aztreonam, 62.5% of the isolates shifted from resistance to sensitivity. Also, ceftazidime/avibactam plus Aztreonam resistance was reduced markedly among CRKP using the E-test. The addition of Aztreonam to ceftazidime/avibactam is an effective therapeutic option against MBL-producing K. pneumoniae.Clinical Trials Registry: Pan African Clinical Trials Registry. Trial No.: PACTR202410744344899. Trial URL: https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=32000.

Genomic characteristics of ST6115 carbapenem-resistant Klebsiella pneumoniae coharboring bla NDM-1 and bla IMP-4

Objectives

The aim of this study is to characterize the genomic features of ST6115 carbapenem-resistant Klebsiella pneumoniae (CRKP) co-harboring bla NDM-1 and bla IMP-4.

Methods

The genome sequences of one ST6115 Klebsiella pneumoniae (KP) strain and 12 ST17 KP strain were obtained through whole genome sequencing (WGS). Subsequently, a phylogenetic analysis was employed to ascertain the clonal relationship of these strains. The antimicrobial susceptibility testing (AST) was evaluated through the application of the minimum inhibitory concentration (MIC) methodology by the broth microdilution method. Annotation and analysis of the genome enabled the identification of the plasmid structure and the comparative analysis of the genetic background. Finally, the conjugation transfer experiment was conducted to assess the transferability of the plasmid pHD8428-NDM-IMP.

Results

A comparable phylogenetic analysis revealed that ST6115 HD8428 and the majority of ST17 strains (9/12) were clustered on the same clade, which suggests a close relationship between two ST types. Additionally, HD8428 showed particularly close genetic similarity to HD11490, with a single-nucleotide polymorphism (SNP) difference of only 273. The analysis of the antibiotic resistance genes carried by the 13 strains revealed that all strains carry extended-spectrum β-lactamase (ESBL) genes. AST revealed that HD8428 exhibited resistance to a diverse range of antibiotics. The bla NDM-1 and bla IMP-4 genes were identified as being located on the plasmid pHD8428-NDM-IMP. Further analysis demonstrated that the bla NDM-1 gene was present on ΔTn125, while the bla IMP-4 gene was located on In1377-2. The results of the conjugation experiment indicated that plasmid pHD8428-NDM-IMP may pose a risk for the transmission of antibiotic resistance in healthcare settings.

Conclusion

We report a clinical ST6115 strain HD8428 and identify the coexistence of bla NDM-1 and bla IMP-4 in the IncHI5 type plasmid pHD8428-NDM-IMP. HD8428 was resistant to a wide range of antibiotics and harbored the transmissible plasmid pHD8428-NDM-IMP, which made it a potential threat to public health. Our study indicates that the healthcare system and services should remain vigilant regarding the spread and prevalence of ST6115.

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.

Molecular Epidemiological Characteristics of bla IMP-4-Carrying Klebsiella pneumoniae ST-11 in Hospitalized Patients

Purpose

To investigate the molecular epidemiology and risk factors of carbapenem-resistant Klebsiella pneumoniae (CRKP) infection.

Patients and Methods

Patient's clinical data and CRKP strains were collected from November 2017 to December 2018 at a tertiary hospital in Wuhan, China. The antimicrobial susceptibilities, carbapenem-resistant genes, multi-locus sequence typing (MLST), homologous analysis, and risk factors for CRKP were determined.

Results

A total of 203 CRKP strains were isolated, and 98.5% (200/203) of patients were nosocomially infected. The mortality rate was 17.7% (36/203). All 203 strains were confirmed as carbapenemases -producing strains. The most predominant carbapenemase gene was bla IMP-4 (81.3%, 165/203), followed by bla KPC-2 (25.1%, 51/203) and bla NDM-1 (23.2%, 47/205). Of the 203 strains, 28 (13.8%) had both bla KPC-2 and bla IMP-4 genes, 23 (11.3%) had both bla IMP-4 and bla NDM-1 genes, 20 (9.9%) had bla KPC-2, bla IMP-4 and bla NDM-1 three genes. MLST analysis showed that there were 48 ST typologies (including 7 new STs), of which ST-11 was the most prevalent (59.6%, 121/203). Phylogenetic analysis showed that 203 CRKP isolates came from 7 clusters and exhibited a strong correlation with the isolation source. eBURST analyses indicated that CRKP isolates have undergone different evolutionary processes. Patients with ST-11 CRKP underwent more mechanical ventilation (50% vs 32.9%, P=0.020) and gastric catheterization (15.7% vs 6.1%, P=0.042) within 3 months before sample collection, and also had higher drug-resistance rate than non-ST-11 CRKP. Comparing with CSKP (carbapenem-sensitive Klebsiella pneumoniae), gastrointestinal disease (odds ratio [OR]=6.168, P=0.003), nosocomial infection (OR=5.573, P=0.012), antibiotic exposure (OR=4.131, P=0.004), urinary catheterization (OR=3.960, P=0.031) and venous/arterial catheterization (OR=2.738, P=0.026) within the preceding 3 months were independent risk factors for CRKP infection.

Conclusion

The IMP-4 was the most predominant carbapenemase and bla IMP-4 bearing Klebsiella pneumoniae ST-11 was spreading in the hospital. Nosocomial infections, antibiotic exposure, and urinary and venous/arterial catheterization within 3 months were the risk factors for developing CRKP infection.

Multidrug-resistant ST11-KL64 hypervirulent Klebsiella pneumoniae with multiple bla- genes isolated from children's blood

Introduction

Hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) poses an increasing public health risk due to its high treatment difficulty and associated mortality, especially in bone marrow transplant (BMT) patients. The emergence of strains with multiple resistance mechanisms further complicates the management of these infections.

Methods

We isolated and characterized a novel ST11-KL64 hv-CRKP strain from a pediatric bone marrow transplantation patient. Antimicrobial susceptibility testing was performed to determine resistance patterns. Comprehensive genomic analysis was conducted to identify plasmid types, virulence factors, and antimicrobial resistance genes, as well as potential resistance mechanisms associated with mutations and plasmid-mediated variants.

Results

The isolated hv-CRKP strain exhibited multidrug resistance to carbapenem, tigecycline, and polymyxin. Genomic analysis revealed that the IncHI1B/repB plasmid carried virulence factors (rmpA, ΔrmpA2, iucABCD, iutA), while IncFII/IncR and IncFII plasmids harbored resistance genes [bla C T X - M - 6 5 , bla T E M - 1 B , rmtB, bla S H V - 1 2 , bla K P C - 2 , qnrS1, bla L A P - 2 , sul2, dfrA14, tet(A), tet(R)]. The coexistence of bla C T X - M - 6 5 , bla T E M - 1 B , bla S H V - 1 2 , bla L A P - 2 ,and bla K P C - 2 in one hv-CRKP strain is exceptionally rare. Additionally, the Tet(A)-S251A variant in the conjugative plasmid pTET-4 may confer tigecycline resistance. Mutations in MgrB, PhoPQ, and PmrABCDK were identified as potential contributors to increased polymyxin resistance. Interestingly, plasmid-encoded restriction-modification systems and Retron regions were identified, which could potentially confer phage resistance.

Discussion

The combination of virulence and antimicrobial resistance factors in the ST11-KL64 hv-CRKP strain represents a significant challenge for treating immunocompromised pediatric patients. Particularly concerning is the resistance to polymyxin and tigecycline, which are often last-resort treatments for multidrug-resistant infections. The findings highlight the urgent need for effective surveillance, infection control measures, and novel therapeutic strategies to manage such hypervirulent and multidrug-resistant pathogens.

Analysis of the virulence of a lethal, carbapenem-resistant hypervirulent KPC-33-producing Klebsiella pneumoniae: Emergence of ST11-KL64 hv-CRKP in ICU

OBJECTIVE

Hypervirulent and carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) poses a serious threat to public health. Here, we analyse a case of systemic infection caused by a hv-CRKP, which ultimately led to the patient's death from sepsis. And a total of 30 CRKPs were analyzed to elucidate the molecular epidemiological features of CRKPs in the hospital, and to provide a basis for clinical anti-infective therapy.

METHODS

In this case, a total of 7 K. pneumoniae strains were isolated from the blood, sputum, urine, and feces of the patient. The Vitek-2 compact system was used to identify the strains and perform antimicrobial susceptibility testing. Biofilm formation, siderophore production assays and Galleria mellonella infection model were used to verify the virulence phenotypes of the strains in the case. Whole-genome sequencing was conducted on the four hv-CRKP isolated from different samples in the case and 26 other CRKP collected in our hospital from September to November in 2022, using the Illumina Hiseq 6000 high-throughput sequencing platform to analyse the resistance and virulence genes.

RESULTS

In the case, after 7 days of treatment with ceftazidime-avibactam (CZA), the resistance profile of the strains changed. The strain that was initially sensitive to CZA developed to resistant, resistant to imipenem (IPM) developed to sensitive, and resistant to meropenem (MEM) developed to intermediate. Whole-genome sequencing revealed that the four strains in the case were all ST11-KL64 K. pneumoniae, and the change in resistance phenotype was due to the mutation from blaKPC-2 to blaKPC-33. KPN7 had a total of six plasmids, with siderophore-related genes iucABCD and iutA, and mucoid phenotype-related gene rmpA2 located on plasmid p4-KPN7; resistance genes blaKPC-33, blaTEM-1B, and blaCTX-M-65 located on plasmid p5-KPN7; and virulence genes fim, irp, iutA, and ybt located on the chromosome. Biofilm formation and siderophore production assays confirmed that the seven K. pneumoniae strains isolated in this case had strong biofilm formation and siderophore production capabilities. Galleria mellonella Infection Model showed that KPN4 and KPN7 was phenotypically highly virulent and KPN7 performed lower virulence compared to KPN4. Apart from the 4 hv-CRKP strains, other 26 CRKP strains all carried blaKPC-2, and 69.2% (18/26) were ST-11 and 30.8%(8/26) were ST-15. And 83.3% (15/18) were ST11-KL64 strains, followed by ST11-KL25 strains 11.1%(2/18) and ST11-KL47 strain 5.6%(1/18). All the eight ST-15 strains were KL-19.

CONCLUSION

The ST11-KL64 hv-CRKP clone spread widely in ICU carried numerous resistance and virulence genes, and under antibiotic pressure, they easily underwent mutations resulting in changes in resistance phenotypes, especially in mutations of blaKPC-2 gene in acquiring resistance to CZA. Therefore, clinical attention should be paid to such strains, and the use of antibiotics should be adjusted promptly based on the susceptibility of the strains to antimicrobial agents.

Molecular characterization of ST15 carbapenem-resistant Klebsiella pneumoniae isolated in a single patient

BACKGROUND

The carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious threat to antibiotic applicability and public health. During treatment, K. pneumoniae (KP) frequently exhibits shifts in drug-resistant phenotypes, complicating clinical treatment as it transitions from sensitivity to resistance. In this study, we analysed the clinical and molecular characteristics of drug resistance changes in KP strains isolated from a single patient, and the potential mechanisms underlying these resistance changes.

METHODS

Antimicrobial susceptibility test and string test were conducted to evaluate the resistant and virulent characterization of the strains. Pulsed-field gel electrophoresis (PFGE) was used to investigate the homology relationship between the strains. The whole genome sequencing and phylogenetic analysis of 9 representative isolates was also performed. The transfer ability of the drug-resistant plasmid was studied by plasmid conjugation experiment. The transconjugants were verified by polymerase chain reaction amplification of specific genes, antimicrobial susceptibility test and PFGE.

RESULTS

Our results revealed that 9 KP strains, isolated from the same patient, exhibited 'resistance-sensitivity-resistance-sensitivity' alternately to carbapenems. The differences in DNA fingerprint bands among the nine KP isolates were ≤3, which can be classified as the same PFGE type. Phylogenetic analysis showed that these 9 strains constituted a distinct branch within the phylogenetic tree. All nine KP strains belonged to the ST15-KL19 clone. Six of the strains were classified as CRKP, all of which carried 11 drug resistance genes: oqxB, oqxA, fosA6, aac(3)-lld, blaSHV-28, blaKPC-2, blaOXA-1, mph(A), tet(A), catB3 and aac(6')-lb-cr, mediating drug resistance to quinolones, fosfomycin, aminoglycosides, β-lactam, carbapenems, macrolides and chloramphenicol, belonging to multi-drug resistant bacteria. The carbapenem-resistant plasmid p2-KP3762-1 was found to transfer within species, from CRKP to hypervirulent KPRJF293HA, carbapenem-sensitive KP KP3657 and Escherichia coli C600 at a frequency of (1.19 ± 1.58) ×10-6, (1.09 ± 1.38) ×10-7 and (10.9 ± 9.53) ×10-6 respectively, resulting in the dissemination of carbapenem resistance genes.

CONCLUSIONS

In this study, KP strains isolated from a single patient exhibited an alternating phenotype of resistant-sensitive-resistant-sensitive to carbapenems. The 9 KP isolates share a high degree of genetic similarity. The plasmid p2-KP3762-1, harbouring the carbapenem resistance gene blaKPC-2, may undergo inter-strain and inter-clone transfer via conjugation in the patient during treatment. Furthermore, our findings suggest that the pathogens in this patient are likely to have a common ancestral origin.

Pharmacokinetic/pharma-codynamic study of pralurbactam (FL058) combined with meropenem in a neutropenic murine thigh infection model

Introduction

Pralurbactam (FL058) is a novel β-lactamase inhibitor with good inhibitory activity on class A, C, and D β-lactamases. This study aimed to evaluate the pharmacokinetic/pharmacodynamic (PK/PD) relationship of pralurbactam/meropenem in a neutropenic murine thigh infection model.

Methods

After 2-h infection, neutropenic mice was treated with meropenem every 2 h alone or in combination with pralurbactam at different dosing frequencies for 24 h, and the colony count in the thighs was determined before and after treatment. The maximum effect model was fit to the PK/PD relationship to determine the PK/PD index and targets for pralurbactam in combination with meropenem resulting in a static effect and 1-log10 kill.

Results

The plasma drug concentration-time data demonstrated that the PK profiles of pralurbactam were consistent with a one-compartment model. Pralurbactam demonstrated a linear PK profile in mice plasma. The percent time of free drug above 1 mg/L (%fT > 1 mg/L) was the PK/PD index that best described the bacterial killing effect of pralurbactam/meropenem over 24 h. When the PK/PD index %fT > 1 mg/L reached 38.4% and 63.6%, pralurbactam/meropenem combination would achieve bacteriostatic effect and 1-log10 reduction against Klebsiella pneumoniae in thigh bioburden, respectively.

Conclusion

These PK/PD data derived from mouse thigh infection models will be used to inform the optimal dosing regimen of pralurbactam/meropenem combination in clinical trials.

A novel small RNA PhaS contributes to polymyxin B-heteroresistance in carbapenem-resistant Klebsiella pneumoniae

In recent years, polymyxin has been used as a last-resort therapy for carbapenem-resistant bacterial infections. The emergence of heteroresistance (HR) to polymyxin hampers the efficacy of polymyxin treatment by amplifying resistant subpopulation. However, the mechanisms behind polymyxin HR remain unclear. Small noncoding RNAs (sRNAs) play an important role in regulating drug resistance. The purpose of this study was to investigate the effects and mechanisms of sRNA on polymyxin B (PB)-HR in carbapenem-resistant Klebsiella pneumoniae. In this study, a novel sRNA PhaS was identified by transcriptome sequencing. PhaS expression was elevated in the PB heteroresistant subpopulation. Overexpression and deletion of PhaS were constructed in three carbapenem-resistant K. pneumoniae strains. Population analysis profiling, growth curve, and time-killing curve analysis showed that PhaS enhanced PB-HR. In addition, we verified that PhaS directly targeted phoP through the green fluorescent protein reporter system. PhaS promoted the expression of phoP, thereby encouraging the expression of downstream genes pmrD and arnT. This upregulation of arnT promoted the 4-amino-4-deoxyL-arabinosaccharide (L-Ara4N) modification of lipid A in PhaS overexpressing strains, thus enhancing PB-HR. Further, within the promoter region of PhaS, specific PhoP recognition sites were identified. ONPG assays and RT-qPCR analysis confirmed that PhaS expression was positively modulated by PhoP and thus up-regulated by PB stimulation. To sum up, a novel sRNA enhancing PB-HR was identified and a positive feedback regulatory pathway of sRNA-PhoP/Q was demonstrated in the study. This helps to provide a more comprehensive and clear understanding of the underlying mechanisms behind polymyxin HR in carbapenem-resistant K. pneumoniae.

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.

Characterization of novel phage pK3-24 targeting multidrug-resistant Klebsiella pneumoniae and its therapeutic efficacy in Galleria mellonella larvae

Klebsiella pneumoniae is a common, conditionally pathogenic bacterium that often has a multidrug-resistant phenotype, leading to failure of antibiotic therapies. It can therefore induce serious diseases, including community-acquired pneumonia and bloodstream infections. As an emerging alternative to antibiotics, phages are considered key to solving the problem of drug-resistant bacterial infections. Here, we report a novel phage, pK3-24, that mainly targets ST447 K. pneumoniae. Phage pK3-24 is a T7-like short-tailed phage with a fast adsorption capacity that forms translucent plaques with halos on bacterial lawns. The optimal multiplicity of infection (MOI) is 0.01, and the average burst size is 50 PFU/mL. Phage pK3-24 shows environmental stability, surviving at below 50 °C and at pH values of 6-10. It has a double-stranded DNA genome of 40,327 bp and carries no antibiotic-resistance, virulence, or lysogeny genes. Phylogenetic analysis assigned phage pK3-24 to the genus Przondovirus as a new species. Phage pK3-24 inhibited the production of biofilm. Moreover, treatment with pK3-24 at doses with an MOI > 1 effectively reduced the mortality of Galleria mellonella larvae infected with ST447 K. pneumoniae.

In vitro mimicry of in vivo KPC mutations by ceftazidime-avibactam: phenotypes, mechanisms, genetic structure and kinetics of enzymatic hydrolysis

Ceftazidime-avibactam (CZA) is employed for the treatment of infections caused by Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-KP). Resistance to CZA is frequently linked to point mutations in the blaKPC. We conducted in vitro simulations of in vivo blaKPC mutations using CZA. Four pre-therapy KPC-KP isolates (K1, K2, K3, and K4) were evaluated, all initially exhibited susceptibility to CZA and produced KPC-2. The crucial distinction was that following CZA treatment, the blaKPC-2 mutated in K1, K2, and K3, rendering them resistant to CZA, while K4 achieved microbiological clearance, and blaKPC-2 remained unaltered. The induction assay identified various blaKPC-2 variants, including blaKPC-25, blaKPC-127, blaKPC-100, blaKPC-128, blaKPC-137, blaKPC-138, blaKPC-144 and blaKPC-180. Our findings suggest that the resistance of KPC-KP to CZA primarily results from the emergence of KPC variants, complemented by increased blaKPC expression. A close correlation exists between avibactam concentration and the rate of increased CZA minimum Inhibitory concentration, as well as blaKPC mutation. Inadequate avibactam concentration is more likely to induce resistance in strains against CZA, there is also a higher likelihood of mutation in the blaKPC-2 and the optimal avibactam ratio remains to be determined. Simultaneously, we selected a blaKPC-33-producing K. pneumoniae strain (mutated from blaKPC-2) and induced it with imipenem and meropenem, respectively. The blaKPC-2 was detected during the process, indicating that the mutation is reversible. Clinical use of carbapenems to treat KPC variant strains increases the risk of infection, as the gene can mutate back to blaKPC-2, rendering the strain even more cross-resistant to carbapenems and CZA.

Overexpression of blaSHV-12 caused by tandem amplification contributed to ceftazidime/avibactam resistance in hypervirulent and carbapenem-resistant Klebsiella pneumoniae

We identified a novel ceftazidime/avibactam (CAZ/AVI) resistance mechanism in endemic sequence type 11 hypervirulent and carbapenem-resistant Klebsiella pneumoniae isolated from a patient who had not been exposed CAZ/AVI. Overexpression of blaSHV-12 caused by tandem gene amplification contributed to CAZ/AVI resistance instead of the carriage of blaKPC-2. Enhanced genomic surveillance is essential to identify emerging variants.

Ceftazidime-avibactam treatment dilemma of blaKPC-2-containing Klebsiella pneumoniae due to the development of co-existence of mixed strains carrying blaKPC-2 or blaKPC-33 in lung transplant recipients

BACKGROUND

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a significant threat to immunocompromised populations, including lung transplant recipients. This study investigates mixed CRKP strains carrying either blaKPC-2 or blaKPC-33 following ceftazidime-avibactam (CAZ/AVI) exposure, particularly in the context of lung transplantation. Mixed CRKP strains with shifting resistance phenotypes were frequently identified in patients exposed to CAZ/AVI. We aimed to elucidate the transitional state of blaKPC variants by selecting CAZ/AVI-sensitive and -resistant CRKP strains from a lung transplantation patient.

METHODS

The blaKPC-variant-carrying CRKP strains were collected from lung transplant recipients exposed to CAZ/AVI in less than two years. Antibiotic susceptibility testing (AST) was conducted using microbroth dilution, and whole-genome sequencing (WGS) was used to identify genotypes and resistance mechanisms. Limiting dilution, drop-plate, and in vitro induction experiments determined blaKPC-variant changes during CAZ/AVI administration. qPCR primers/probes were designed to identify blaKPC-2 mutations.

RESULTS

Among 104 lung transplant recipients infected by blaKPC-harboring CRKP strains and receiving CAZ/AVI, 10 (9.6%) experienced changing resistance phenotypes. The limiting dilution method found that Patient 10's CRKP strains carried either blaKPC-2 or blaKPC-33. The drop-plate experiment showed differing growth patterns on CAZ/AVI mediums. The in vitro induction experiment demonstrated shifting from blaKPC-2 to blaKPC-33.

CONCLUSIONS

The study identified a "transitional state" of the mixed CRKP strains carrying either blaKPC-2 or blaKPC-33 in CAZ/AVI-exposed patients. Molecular diagnostics are crucial for identifying mixed strains and the transitional state of blaKPC variants, guiding treatment decisions in this complex landscape.

Characterization of a Novel Sequence Type (ST) 6758 Klebsiella Pneumoniae and the Role of IncX3 Plasmid in the Transmission of bla NDM

Purpose

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged as a significant public health threat, particularly as a superbug responsible for nosocomial infections. In this study, we report a novel sequence type 6758 of K. pneumoniae harboring the bla NDM-1 gene.

Material and Methods

Antimicrobial susceptibility testing was conducted according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). The complete genome sequence of the strain was determined using the Illumina NovaSeq 6000 platform and long-read MinION sequencer. Genomic features and resistance mechanisms of the strain were further comprehensively analysed using various bioinformatics approaches.

Results

Antimicrobial susceptibility testing revealed that this strain exhibited resistance to multiple antimicrobials, including ceftazidime, ceftriaxone, cefazolin, cefepime, imipenem, meropenem, ampicillin/sulbactam, and sulfamethoxazole/trimethoprim. The genome analysis identified sixteen resistance genes. The bla NDM-1 carbapenemase gene is located on a 47,823 bp IncX3-type plasmid (pNDM-CRKP331). A total of 41 K. pneumoniae strains carrying similar IncX3-type plasmids were retrieved from the NCBI database, representing 20 sequence types (STs) across 11 countries. The most common resistance gene carried by these IncX3-type plasmids is bla NDM, and all these plasmids contain only the bla NDM gene. The bla NDM-carrying IncX3-type plasmids are widely prevalent in K. pneumoniae in China, spanning 15 STs.

Conclusion

In summary, our study reports the first genome sequence of an ST 6758 K. pneumoniae strain containing the class B β-lactamase bla NDM-1 isolated from a clinical sample. Given the global emergence of bla NDM, measures should be taken to prevent the spread of these bla NDM-carrying IncX3-type plasmids. Our findings contribute to the understanding of the transmission mechanisms of bla NDM in K. pneumoniae.

An increased prevalence of carbapenem-resistant hypervirulent Klebsiella pneumoniae associated with the COVID-19 pandemic

BACKGROUND

Klebsiella pneumoniae (Kp) is a common community-acquired and nosocomial pathogen. Carbapenem-resistant and hypervirulent (CR-hvKp) variants can emerge rapidly within healthcare facilities and impacted by other infectious agents such as COVID-19 virus.

METHODS

To understand the impact of COVID-19 virus on the prevalence of CR-hvKp, we accessed Kp genomes with corresponding metadata from GenBank. Sequence types (STs), antimicrobial resistance genes, and virulence genes, and those scores and CR-hvKp were identified. We analyzed population diversity and phylogenetic characteristics of five most common STs, measured the prevalence of CR-hvKp, identified CR-hvKp subtypes, and determined associations between carbapenem resistance gene subtypes with STs and plasmid types. These variables were compared pre- and during the COVID-19 pandemic.

FINDINGS

The proportion of CR-hvKp isolates increased within multiple STs in different continents during the COVID-19 pandemic and persistent CR-hvKp subtypes were found in common STs. blaKPC was dominant in CG258, blaKPC-2 was detected in 97 % of the ST11 CR-hvKp, blaNDM subtypes were prominent in ST147 (87.4 %) and ST307 (70.8 %); blaOXA-48 and its subtypes were prevalent in ST15 (80.5 %). The possession of carbapenemase genes was different among subclades from different origins in different periods of time within each ST. IncFIB/IncHI1B hybrid plasmids contained virulence genes and carbapenemase genes and were predominant in ST147 (67.37 %) and ST307 (56.25 %).

INTERPRETATION

The prevalence of CR-hvKp increased during the COVID-19 pandemic, which was evident by an increase in local endemic clones. This process was facilitated by the convergence of plasmids containing carbapenemase genes and virulence genes. These findings have implications for the appropriate use of antimicrobials and infection prevention and control during outbreaks of respiratory viruses and pandemic management.

High prevalence of carbapenem-resistant Enterobacter cloacae complex in a tertiary hospital over a decade

The aim of this study was to explore the mechanisms and molecular epidemiology of carbapenem resistance in the carbapenem-resistant Enterobacter cloacae complex (CRECC) over a decade in a tertiary hospital in Zhejiang, China. From January 2011 to December 2021, we collected a total of 931 Enterobacter cloacae complex (ECC) isolates from a tertiary hospital in Zhejiang, China. Antimicrobial susceptibility tests were performed. Whole-genome sequencing was used to analyze the molecular characteristics of the CRECC isolates. For carbapenem-resistant strains, efflux inhibitor assay and quantitative real-time PCR (qRT-PCR) were performed to evaluate the function of efflux pumps. A total of 82 CRECC isolates were detected, and the rate of resistance for carbapenems was 8.8%, increasing from 5.5% in 2011 to 18.3% in 2019, with an overall increasing trend, with Enterobacter hormaechei subsp. hoffmannii being the predominant species. Among the CRECC, 24 (24/931) isolates were found to produce carbapenemases, including NDM-1, NDM-5, IMP-4, and KPC-2. Among all carbapenemases, NDM-1 was the most prevalent, accounting for 62.5% (15/24) of carbapenemases, followed by NDM-5 (5/24). Genes encoding extended-spectrum beta-lactamases (47/82) and AmpC (76/82) were also identified, with blaSHV-12 and blaACT being the predominant ones, respectively. Multilocus sequence typing revealed 28 different sequence types, among which ST78 was the predominant, followed by ST93 and ST177. IncFIB was the most common type of plasmid replicon. Efflux inhibitor assay and qRT-PCR indicated that the overexpression of efflux pumps was involved in carbapenem resistance mechanisms. Additionally, disrupted outer membrane proteins also contribute to carbapenem resistance. The detection rate of CRECC was rising in the tertiary hospital. BlaNDM-1 and blaNDM-5 were the main carbapenem resistance genes. Our study revealed the presence of carbapenem-resistant ECC strains, emphasizing the need for effective infection prevention approaches to reduce the prevalence of CRECC.

IMPORTANCE

The emergence and spread of the carbapenem-resistant Enterobacter cloacae complex (CRECC) have become a significant public health problem. CRECC strains frequently harbor multiple drug resistance genes and can be epidemic within healthcare facilities. The study explored the characteristics and prevalence of CRECC strains in the same hospital over a decade, which provides a theoretical basis for epidemiologic surveillance and clinical treatment.

Disruption of mgrB gene by ISkpn14 sourced from a blaKPC-2 carrying plasmid mediating polymyxin resistance against carbapenem-resistant Klebsiella pneumoniae during treatment: study on the underlying mechanisms

BACKGROUND

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections poses global challenges, with limited options available for targeted therapy. Polymyxin was been regarded as one of the most important last-resort antimicrobial agents. Many factors could accelerate the resistance evolution of polymyxin. Insertion sequence (IS) inserted into mgrB is the main polymyxin resistance mechanism in K. pneumoniae. In this study, two CRKPs (KP31157 and KP31311) were isolated from the urine of a patient, shifting from susceptible to resistant as the mgrB inserted by ISkpn14. We intended to explore the origin of the IS and underlying mechanisms resulting in polymyxin resistance.

METHODS

The within-host evolution relationship and molecular features of both CRKPs were determined by pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS). pKP31311_KPC-2 plasmid genome structures contained in the above two CRKPs were aligned with the homologic plasmids, retrieved from the NCBI genome database via comparative genomic analysis. The plasmids encoding ISkpn14 elements flanked by direct repeat (DR) or not were analyzed. The mRNA expression, plasmid curing and in vitro antibiotics inducing experiment were employed to understand the potential mechanism of polymyxin resistance.

RESULTS

Both strains, sharing homology, exhibited polymyxin resistance due to the insertion of ISkpn14 into the mgrB gene, influenced by minocycline exposure. Minocycline and tigecycline could accelerate polymyxin resistance (P < 0.05), validated by an in vitro induction experiment. The ISkpn14 without DR flanked expressed about 4 times higher than that with DR. The frequency of the mgrB insertion induced by polymyxin was significantly reduced (0 strain detected) after the blaKPC-2-carrying plasmid was eliminated.

CONCLUSIONS

This study provides direct experimental evidence that the ISkpn14 element causing mgrB inactivation and polymyxin resistance in K. pneumoniae originates from blaKPC-2-carrying plasmids. Minocycline exposure will accelerate the evolution of polymyxin resistance. Understanding the dynamics of IS transposition and its association with antibiotic exposure is crucial for developing effective strategies to reduce the emergence of polymyxin resistance in CRKP.

Virulence plasmid with IroBCDN deletion promoted cross-regional transmission of ST11-KL64 carbapenem-resistant hypervirulent Klebsiella pneumoniae in central China

BACKGROUND

Carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-hvKP) caused infections of high mortality and brought a serious impact on public health. This study aims to evaluate the epidemiology, resistance and virulence characteristics of CR-hvKP and to identify potential drivers of cross-regional transmission in different regions of China, in order to provide a basis for developing targeted prevention measures.

METHODS

Clinical K. pneumoniae strains were collected from Jiujiang and Nanchang in Jiangxi province between November 2021 to June 2022. Clinical data of patients (age, sex, source of infection, and diagnosis) were also gathered. We characterized these strains for their genetic relatedness using PFGE, antimicrobial and virulence plasmid structures using whole-genome sequencing, and toxicity using Galleria mellonella infection model.

RESULTS

Among 609 strains, 45 (7.4%) CR-hvKP were identified, while the strains. isolated from Nanchang and Jiujiang accounted for 10.05% (36/358) and 3.59% (9/251). We observed that ST11-KL64 CR-hvKP had an overwhelming epidemic dominance in these two regions. Significant genetic diversity was identified among all ST11-KL64 CR-hvKP cross-regional transmission between Nanchang and Jiujiang and this diversity served as the primary driver of the dissemination of clonal groups. Virulence genes profile revealed that ST11-KL64 CR-hvKP might harbour incomplete pLVPK-like plasmids and primarily evolved from CRKP by acquiring the hypervirulence plasmid. We found the predominance of truncated-IncFIB/IncHI1B type virulence plasmids with a 25 kb fragment deletion that encoded iroBCDN clusters.

CONCLUSION

ST11-KL64 is the most cross-regional prevalent type CR-hvKPs in Jiangxi province, which mainly evolved from CRKPs by acquiring a truncated-IncHI1B/IncFIB virulence plasmid with the deletion of iroBCDN. Stricter surveillance and control measures are urgently needed to prevent the epidemic transmission of ST11-KL64 CR-hvKP.

Decoding the origins, spread, and global risks of mcr-9 gene

BACKGROUND

The global spread of the plasmid-mediated mcr (mobilized colistin resistance) gene family presents a significant threat to the efficacy of colistin, a last-line defense against numerous Gram-negative pathogens. The mcr-9 is the second most prevalent variant after mcr-1.

METHODS

A dataset of 698 mcr-9-positive isolates from 44 countries is compiled. The historical trajectory of the mcr-9 gene is reconstructed using Bayesian analysis. The effective reproduction number is used innovatively to study the transmission dynamics of this mobile-drug-resistant gene.

FINDINGS

Our investigation traces the origins of mcr-9 back to the 1960s, revealing a subsequent expansion from Western Europe to the America and East Asia in the late 20th century. Currently, its transmissibility remains high in Western Europe. Intriguingly, mcr-9 likely emerged from human-associated Salmonella and exhibits a unique propensity for transmission within the Enterobacter. Our research provides a new perspective that this host preference may be driven by codon usage biases in plasmids. Specifically, mcr-9-carrying plasmids prefer the nucleotide C over T compared to mcr-1-carrying plasmids among synonymous codons. The same bias is seen in Enterobacter compared to Escherichia (respectively as their most dominant genus). Furthermore, we uncovered fascinating patterns of coexistence between different mcr-9 subtypes and other resistance genes. Characterized by its low colistin resistance, mcr-9 has used this seemingly benign feature to silently circumnavigate the globe, evading conventional detection methods. However, colistin-resistant Enterobacter strains with high mcr-9 expression have emerged clinically, implying a strong risk of mcr-9 evolving into a global "true-resistance-gene".

INTERPRETATION

This study explores the mcr-9 gene, emphasizing its origin, adaptability, and dissemination potential. Given the high mcr-9 expression colistin-resistant strains was observed in clinically the prevalence of mcr-9 poses a significant challenge to drug resistance prevention and control within the One Health framework.

FUNDING

This work was partially supported by the National Natural Science Foundation of China (Grant No. 32141001 and 81991533).

Monitoring of Klebsiella pneumoniae Infection and Drug Resistance in 17 Pediatric Intensive Care Units in China from 2016 to 2022

Objective

To investigate the characteristics and drug resistance patterns of Klebsiella pneumoniae (K. pneumoniae) infection in pediatric intensive care unit (PICU).

Methods

K. pneumoniae strains from 17 domestic PICUs were analyzed for overall condition and drug resistance using WHO-NET software.

Results

From 2016 to 2022, there was a linear increase in the detection rate of K. pneumoniae (P<0.05), with a total of 2591 (9.7%) strains detected. The primary sites of K. pneumoniae detection were the respiratory tract (71.1%), blood (8.6%), and urinary tract (7.1%). K. pneumoniae's resistance to penicillin drugs exceeded 90%, and are over 50% to cephalosporins. Resistance to cefoperazone-sulbactam decreased from 51.7% to 25.7%, and ranged from 9.1% to 20.8% for ceftolozane-tazobactam. Carbapenem-resistant K. pneumoniae strains constituted 32.3%. Resistance to imipenem and meropenem have decreased to 33.8% and 40.2%, while increased to 35.2% for ertapenem. Levofloxacin and amikacin resistance rates have decreased to 25.7% and 9.1%, but remain high at 63.8% for moxifloxacin and 44.6% for ciprofloxacin. K. pneumoniae demonstrated the lowest resistance rates to polymyxin B (0.9%), tigecycline (2.2%), and polymyxin E (3.1%). No strain of K. pneumoniae was resistant to both polymyxin B and meropenem. However, some strains showed co-resistance to meropenem with other antibiotics, including tigecycline (2%), imipenem (16%), amikacin (27%), colistin (37%), and levofloxacin (41%).

Conclusion

The rates of isolation and drug resistance of K. pneumoniae in PICU have significantly increased over 7 years. Careful antibiotic use, infection control strategies, and appropriate antibiotic combinations are crucial in addressing this problem.

The correlation between intestinal colonization and infection of carbapenem-resistant Klebsiella pneumoniae: A systematic review

As a widely spread Gram-negative bacteria, Klebsiella pneumoniae (KP) mainly causes acquired infections in hospitals, such as lung infections, urinary tract infections, and bloodstream infections. In recent years, the number of multidrug-resistant KP strains has increased dramatically, posing a great threat to human health. Carbapenem-resistant KP (CRKP) can be colonized in human body, especially in gastrointestinal tract, and some colonized patients can be infected during hospitalization, among which invasive operation, underlying disease, admission to intensive care unit, antibiotic use, severity of the primary disease, advanced age, operation, coma, and renal failure are common risk factors for secondary infection. Active screening and preventive measures can effectively prevent the occurrence of CRKP infection. Based on the epidemiological status, this study aims to discuss the correlation between colonization and secondary infection induced by CRKP and risk factors for their happening and provide some reference for nosocomial infection prevention and control.

Predictors of Mortality, Drug Resistance, and Determinants among Carbapenem-Resistant Enterobacteriales Infections in Chinese Elderly Patients

Elderly patients with carbapenem-resistant Enterobacteriales (CRE) infections represent considerable mortality rates. But data on the risk factors for the death of elderly patients following such infection remain limited. We aimed to assess the clinical outcomes, identify mortality-associated risk factors, and determine the antibiotic resistance and resistance genes of isolates for these patients. Hospitalized patients aged ≥65 years with CRE infection from January 2020 to December 2020 were retrospectively reviewed. Isolates identification and molecular characterization of CRE were carried out. Logistic regression analysis was applied to assess the potential factors associated with mortality. Of the 123 elderly patients with CRE infection included in our study, the all-cause mortality rate was 39.8% (49/123). The most prevalent pathogen was carbapenem-resistant Klebsiella pneumoniae (CRKP, 116 of 123). The overall rates of multidrug-resistant (MDR) and extensively drug-resistant (XDR) were 100.0% and 66.7%. All CRE isolates exclusively harbored a singular variant of carbapenemase gene, such as bla KPC-2, bla IMP-4, bla NDM-5, or bla OXA-48, while 98.4% of isolates harbored more than one β-lactamase gene, of which 106 (86.2%) isolates harbored bla CTX-M, 121 (98.4%) isolates harbored bla TEM, and 116 (94.3%) isolates harbored bla SHV. Multivariable logistic regression analysis revealed that mechanical ventilation (adjusted odds ratio (AOR) = 33.607, 95% confidence interval (CI): 4.176-270.463, P < 0.001), use of tigecycline during hospitalization (AOR = 5.868, 95% CI: 1.318-26.130, P = 0.020), and APACHE II score (AOR = 1.305, 95% CI: 1.161-1.468, P < 0.001) were independent factors associated with increasing the mortality of patients with CRE infection, while admission to intensive care unit (ICU) during hospitalization (AOR = 0.046, 95% CI: 0.004-0.496, P = 0.011) was a protective factor. CRE-infected elderly patients with mechanical ventilation, use of tigecycline during hospitalization, and high APACHE II score were related to poor outcomes. The isolates carried various antibiotic genes and presented high antibiotic resistance. These findings provide crucial guidance for clinicians to devise appropriate strategies for treatment.

Relationship between virulence and carbapenem resistance phenotype of Klebsiella pneumoniae from blood infection: identification of a carbapenem-resistant and hypervirulent strain

OBJECTIVES

To investigate the relationship between the virulence and the carbapenem resistance phenotype of Klebsiella pneumoniae from blood infection, and to identify carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-HVKP)strains.

METHODS

A total of 192 Klebsiella pneumoniae strains were isolated from blood culture of patients with bloodstream infections from 2016 to 2019, of which 96 isolates were carbapenem-resistant Klebsiella pneumoniae (CRKP) and 96 were carbapenem-sensitive Klebsiella pneumoniae (CSKP). The drug susceptibility was detected by VITEK-2 automatic microbial analyzer; carbapenemase genes, virulence genes and capsule typing were detected by polymerase chain reaction; the high viscosity phenotype of strains was detected by string test, and the genome characteristics of CR-HVKP were detected by whole genome sequencing. Serum killing and biofilm formation test were used to further verify the virulence of CR-HVKP.

RESULTS

There were significant differences in drug resistance to common antibiotics, except for minocycline between CSKP and CRKP isolates (all P<0.05). 92 out of 96 CRKP isolates carried carbapenemase genes, mainly blaKPC-2. The string tests were positive in 4 isolates of CRKP and 36 isolates of CSKP (P<0.05). The detection rates of virulence genes Kfu, aerobictin, iutA, ybtS, rmpA, magA, allS, and capsule antigen K1 and K2 in CSKP group were significantly higher than those in CRKP group (all P<0.05). One HVKP strain was detected in the CRKP group (CR-HVKP) and 36 HVKP was detected in the CSKP group (P<0.05). The CR-HVKP strain belonged to the MLST412, serotype K57, expressed iutA, entB, mrkD, fimH, and rmpA virulence genes, and showed strong biofilm formation and significantly increased serum resistance. Whole genome sequencing results showed that this CR-HVKP isolate carried blaSHV-145, blaTEM-1, blaCTX-M-3, fosA6, oqxA5, oqxB26, and aac(3)-IId resistance genes, accompanied by abnormalities in outer membrane protein K (OmpK) 35 and OmpK36.

CONCLUSIONS

The drug resistance of CRKP is significantly higher than that of CSKP, while CRKP carrying fewer virulence genes in both number and types compared to CSKP. A new MLST type of carbapenem-resistant and hypervirulent Klebsiella pneumoniae strain has been detected, which requires clinical awareness and epidemiological monitoring.

PathoTracker: an online analytical metagenomic platform for Klebsiella pneumoniae feature identification and outbreak alerting

Clinical metagenomics (CMg) Nanopore sequencing can facilitate infectious disease diagnosis. In China, sub-lineages ST11-KL64 and ST11-KL47 Carbapenem-resistant Klebsiella pneumoniae (CRKP) are widely prevalent. We propose PathoTracker, a specially compiled database and arranged method for strain feature identification in CMg samples and CRKP traceability. A database targeting high-prevalence horizontal gene transfer in CRKP strains and a ST11-only database for distinguishing two sub-lineages in China were created. To make the database user-friendly, facilitate immediate downstream strain feature identification from raw Nanopore metagenomic data, and avoid the need for phylogenetic analysis from scratch, we developed data analysis methods. The methods included pre-performed phylogenetic analysis, gene-isolate-cluster index and multilevel pan-genome database and reduced storage space by 10-fold and random-access memory by 52-fold compared with normal methods. PathoTracker can provide accurate and fast strain-level analysis for CMg data after 1 h Nanopore sequencing, allowing early warning of outbreaks. A user-friendly page ( http://PathoTracker.pku.edu.cn/ ) was developed to facilitate online analysis, including strain-level feature, species identifications and phylogenetic analyses. PathoTracker proposed in this study will aid in the downstream analysis of CMg.

Retrospective analysis of molecular characteristics, risk factors, and outcomes in carbapenem-resistant Klebsiella pneumoniae bloodstream infections

BACKGROUND

Klebsiella pneumoniae (KP) is the second most prevalent Gram-negative bacterium causing bloodstream infections (BSIs). In recent years, the management of BSIs caused by KP has become increasingly complex due to the emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP). Although numerous studies have explored the risk factors for the development of CRKP-BSIs, the mortality of patients with KP-BSIs, and the molecular epidemiological characteristics of CRKP, the variability in data across different populations, countries, and hospitals has led to inconsistent conclusions. In this single-center retrospective observational study, we utilized logistic regression analyses to identify independent risk factors for CRKP-BSIs and factors associated with mortality in KP-BSI patients. Furthermore, a risk factor-based prediction model was developed. CRKP isolates underwent whole-genome sequencing (WGS), followed by an evaluation of microbiological characteristics, including antimicrobial resistance and virulence genes, as well as epidemiological characteristics and phylogenetic analysis.

RESULTS

Our study included a total of 134 patients with KP-BSIs, comprising 50 individuals infected with CRKP and 84 with carbapenem-susceptible Klebsiella pneumoniae (CSKP). The independent risk factors for CRKP-BSIs were identified as gastric catheterization (OR = 9.143; CI = 1.357-61.618; P = 0.023), prior ICU hospitalization (OR = 4.642; CI = 1.312-16.422; P = 0.017), and detection of CRKP in non-blood sites (OR = 8.112; CI = 2.130-30.894; P = 0.002). Multivariate analysis revealed that microbiologic eradication after 6 days (OR = 3.569; CI = 1.119-11.387; P = 0.032), high Pitt bacteremia score (OR = 1.609; CI = 1.226-2.111; P = 0.001), and inappropriate empirical treatment after BSIs (OR = 6.756; CI = 1.922-23.753; P = 0.003) were independent risk factors for the 28-day mortality in KP-BSIs. The prediction model confirmed that microbiologic eradication after 6.5 days and a Pitt bacteremia score of 4.5 or higher were significant predictors of the 28-day mortality. Bioinformatics analysis identified ST11 as the predominant CRKP sequence type, with blaKPC-2 as the most prevalent gene variant. CRKP stains carried multiple plasmid-mediated resistance genes along with some virulence genes. Phylogenetic analysis indicated the presence of nosocomial transmission of ST11 CRKP within the ICU.

CONCLUSIONS

The analysis of risk factors for developing CRKP-BSIs and the association between KP-BSIs and 28-day mortality, along with the development of a risk factor-based prediction model and the characterization of CRKP strains, enhances clinicians' understanding of the pathogens responsible for BSIs. This understanding may help in the timely administration of antibiotic therapy for patients with suspected KP-BSIs, potentially improving outcomes.

Double blaKPC-2 copies quadrupled minimum inhibitory concentration of ceftazidime-avibactam in hospital-derived Klebsiella pneumoniae

To illustrate the genomic and drug resistance traits of the Klebsiella pneumoniae Kpn_XM9, which harbors a transposon (Tn) As1 and was barely susceptible to ceftazidime-avibactam (CZA). Whole-genome sequencing, gene deletion, antimicrobial susceptibility, and conjugation tests were carried out to illustrate the traits of Kpn_XM9. As confirmed by whole-genome sequencing, the Kpn_XM9 harbored a 5,523,536 bp chromosome and five plasmids with lengths being 128,129, 196,512, 84,812, 43,695, and 5,596 bp, respectively. Plasmid p1_Kpn_XM9 (128,219 bp) contained four resistance genes, blaCTX-M-65, blaTEM-1B, rmtB, and two copies of blaKPC-2. Genes blaKPC-2 were bracketed by ISKpn17 and ISKpn16 within a new composite Tn3-like TnAs1. The two tandem repeats, positioned opposite each other, were spaced 93,447 bp apart in p1_Kpn_XM9. Kpn_XM9 belonged to K64 and sequence type (ST) 11. The Kpn_XM9 was resistant to amikacin, aztreonam, ticarcillin/clavulanic acid, piperacillin/tazobactam, ceftazidime, cefepime, imipenem, meropenem, tobramycin, ciprofloxacin, levofloxacin, doxycycline, minocycline, tigecycline, colistin, and trimethoprim/sulfamethoxazole; it was barely susceptible to CZA with a minimum inhibitory concentration of 8/4 µg/mL, which declined to 2/4 µg/mL after a 18,555 bp nucleotide was knocked out and one copy of blaKPC-2 was sustained on p1_Kpn_XM9. Kpn_XM9 had virulence genes encoding Types 1 and 3 fimbriae, four siderophores, and capsular polysaccharide anchoring protein but no genes upregulating capsular polysaccharide synthesis. The Kpn_XM9 presented a classical phenotype with extreme drug resistance. The emergence of double copies of blaKPC-2 in a single plasmid from the predominant ST11 K. pneumoniae represents a new therapeutic challenge.IMPORTANCEWith the wide use of ceftazidime-avibactam against carbapenem-resistant organisms, its resistance is increasingly documented; among the corresponding resistance mechanisms, mutations of blaKPC-2 or blaKPC-3 into other subtypes are dominant to date. However, more copies of blaKPC-2 may also greatly increase the minimum inhibitory concentration of ceftazidime-avibactam, which could be conferred by transposon As1 and insertion sequence 26 and should be of concern.

Modification of carbapenemase inhibition test and comparison of its performance with NG-Test CARBA 5 for detection of carbapenemase-producing Enterobacterales

AIMS

Adequately and accurately identifying carbapenemase-producing Enterobacterales (CPE) is vital for selecting appropriate antimicrobial therapy and implementing effective infection control measures. This study aims to optimize the phenotypic detection method of carbapenemase for routine diagnostics in clinical microbiology laboratories.

METHODS AND RESULTS

Carbapenemase genes in 2665 non-duplicate CRE clinical strains collected from various regions of China were confirmed through whole-genome sequencing (WGS). The carbapenemase inhibition test (CIT) was conducted and interpreted using different methods and breakpoints, then compared with the NG-Test CARBA 5 for carbapenemase detection. The diagnostic performance of the CIT method was optimal when the carbapenemase types were determined by comparing the inhibition zone diameters of the imipenem disc with 3-aminophenylboronic acid (APB) plus ethylenediaminetetraacetic acid (EDTA) to those of the imipenem disc with either APB or EDTA alone, with a breakpoint of 4 mm. The overall sensitivities of the current CIT, the modified CIT, and NG-Test CARBA 5 were 91.4%, 94.9%, and 99.9%, respectively. For detecting isolates co-producing Klebsiella pneumoniae carbapenemase (KPC) and metallo-β-lactamases (MBLs), the modified CIT method had higher sensitivity than the current method (70.0% vs. 53.3%), though this difference was not statistically significant (P = 0.063). The NG-Test CARBA 5 showed excellent performance for multi-carbapenemases diagnosis, with sensitivity and specificity of 97.1% and 100%, respectively.

CONCLUSIONS

Optimizing and standardizing the CIT method for clinical use is necessary. It has certain advantages in diagnosing multi-carbapenemase and rare carbapenemase production. However, for identifying common carbapenemase types, the NG-Test CARBA 5 demonstrated superior performance.

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.

Large-scale comparative analysis reveals phylogenomic preference of blaNDM-1 and blaKPC-2 transmission among Klebsiella pneumoniae

blaNDM-1 and blaKPC-2 are responsible for the global increase in carbapenem-resistant Klebsiella pneumoniae, posing a great challenge to public health. However, the impact of phylogenetic factors on the dissemination of blaNDM-1 and blaKPC-2 is not yet fully understood. This study established a global dataset of 4051 blaNDM-1+ and 10,223 blaKPC-2+ K. pneumoniae genomes, and compared their transmission modes on a global scale. The results showed that blaNDM-1+ K. pneumoniae genomes exhibited a broader geographical distribution and higher sequence type (ST) richness than blaKPC-2+ genomes, indicating higher transmissibility of the blaNDM-1 gene. Furthermore, blaNDM-1+ genomes displayed significant differences in ST lineage, antibiotic resistance gene composition, virulence gene composition and genetic environments compared with blaKPC-2+ genomes, suggesting distinct dissemination mechanisms. blaNDM-1+ genomes were predominantly associated with ST147 and ST16, whereas blaKPC-2+ genomes were mainly found in ST11 and ST258. Significantly different accessory genes were identified between blaNDM-1+ and blaKPC-2+ genomes. The preference for blaKPC-2 distribution across certain countries, ST lineages and genetic environments underscores vertical spread as the primary mechanism driving the expansion of blaKPC-2. In contrast, blaNDM-1+ genomes did not display such a strong preference, confirming that the dissemination of blaNDM-1 mainly depends on horizontal gene transfer. Overall, this study demonstrates different phylogenetic drivers for the dissemination of blaNDM-1 and blaKPC-2, providing new insights into their global transmission dynamics.

Co-existence of two plasmids harboring transferable resistance-nodulation-division pump gene cluster, tmexCD1-toprJ1, and colistin resistance gene mcr-8 in Klebsiella pneumoniae

BACKGROUND

The emergence of plasmid-mediated mobile colistin resistance (mcr) gene poses a great challenge to the clinical application of polymyxins. To date, mcr-1 to mcr-10 have been found in animals, humans, and the environment. Among them, mcr-8 was first identified in Klebsiella pneumoniae (K. pneumoniae) of swine origin, and then mcr-8.1 to mcr-8.5 were successively identified. Notably, K. pneumoniae is the major host of the mcr-8 gene in both animals and humans. This study aims to explore the characteristics of K. pneumoniae strains carrying the mcr-8 gene and tmexCD1-toprJ1 gene cluster and investigate the correlation between these two antibiotic resistance genes.

METHODS

The isolates from the poultry farms and the surrounding villages were identified by mass spectrometer, and the strains positive for mcr-1 to mcr-10 were screened by polymerase chain reaction (PCR). The size of the plasmid and the antimicrobial resistance genes carried were confirmed by S1-nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern hybridization, and the transferability of the plasmid was verified by conjugation experiments. Antimicrobial susceptibility testing (AST) and whole genome sequencing (WGS) were used to characterize the strains.

RESULTS

Two K. pneumoniae isolates (KP26 and KP29) displaying polymyxin resistance were identified as mcr-8 gene carriers. Besides that, tigecycline-resistant gene cluster tmexCD1-toprJ1 was also found on the other plasmid which conferred strain resistance to tigecycline. Through epidemiological analysis, we found that the mcr-8 gene has dispersed globally, circulating in the human, animals, and the environment. Furthermore, our analysis suggests that the coexistence of mcr-8 and tmexCD1-toprJ1 on a single plasmid might evolved through plasmid recombination.

CONCLUSIONS

Although the mcr-8 and tmexCD1-toprJ1 gene clusters in the two strains of K. pneumoniae in this study were on two different plasmids, they still pose a potential threat to public health, requiring close monitoring and further study.

Comparison of three colloidal gold immunoassays and GeneXpert Carba-R for the detection of Klebsiella pneumoniae blaKPC-2 variants

The increasing use of ceftazidime-avibactam has led to the emergence of a wide range of ceftazidime-avibactam-resistant blaKPC-2 variants. Particularly, the conventional carbapenemase phenotypic assay exhibited a high false-negative rate for KPC-2 variants. In this study, three colloidal gold immunoassays, including the Gold Mountainriver CGI test, Dynamiker CGI test and NG-Test CARBA5, and GeneXpert Carba-R, were used to detect the presence of KPC-2 carbapenemase and its various variants in 42 Klebsiella pneumoniae strains. These strains covered blaKPC-2 (13/42) and 16 other blaKPC-2 variants including blaKPC-12 (1/42), blaKPC-23 (1/42), blaKPC-25 (1/42), blaKPC-33 (6/42), blaKPC-35 (1/42), blaKPC-44 (1/42), blaKPC-71 (1/42), blaKPC-76 (8/42), blaKPC-78 (1/42), blaKPC-79 (1/42), blaKPC-100 (1/42), blaKPC-127 (1/42), blaKPC-128 (1/42), blaKPC-144 (1/42), blaKPC-157 (2/42), and blaKPC-180 (1/42). For KPC-2 strains, all four assays showed 100% negative percentage agreement (NPA) and 100% positive percentage agreement (PPA) with sequencing results. For all 16 KPC-2 variants, GeneXpert Carba-R showed 100% NPA and 100% PPA, and the three colloidal gold immunoassays showed 100% NPA, while the PPAs of the Gold Mountainriver CGI test, Dynamiker CGI test, and NG-Test CARBA5 were 87.5%, 87.5%, and 68.8%, respectively. We also found a correlation between the mutation site in the amino acid of the variants and false-negative results by colloidal gold immunoassays. In conclusion, the GeneXpert Carba-R has been proven to be a reliable method in detecting KPC-2 and its variants, and the colloidal gold immunoassay tests offer a practical and cost-effective approach for their detection. For the sample with a negative result by a colloidal gold immunoassay test but not matching the drug-resistant phenotype, it is recommended to retest using another type of kit or the GeneXpert Carba-R assay, which can significantly improve the accuracy of detection.

Clinical risk factors and outcomes of carbapenem-resistant Escherichia coli nosocomial infections in a Chinese teaching hospital: a retrospective study from 2013 to 2020

The emergence of carbapenem-resistant Escherichia coli strains poses a considerable challenge to global public health, and little is known about carbapenemase-producing E. coli strains in Tianjin, China. This study aimed to investigate the risk factors for infections with carbapenem-resistant E. coli (CREC) strains. This retrospective case-control study was conducted at a tertiary teaching hospital. A total of 134 CREC clinical isolates were collected from the General Hospital of Tianjin Medical University between 2013 and 2020. The control group was selected at a ratio of 1:1 from patients with nosocomial carbapenem-susceptible E. coli infection. Risk factors for nosocomial CREC infection and clinical outcomes were analyzed using univariate and multivariate analyses. Multivariate analysis revealed that cephalosporin exposure (odd ratio OR = 2.01), carbapenem exposure (OR = 1.96), glucocorticoid exposure (OR = 32.45), and surgical history (OR = 3.26) were independent risk factors for CREC infection. The in-hospital mortality rate in the CREC group was 29.1%, and age >65 years (OR = 3.19), carbapenem exposure (OR = 3.54), and central venous catheter insertion (OR = 4.19) were independent risk factors for in-hospital mortality in patients with CREC infections. Several factors were identified in the development of nosocomial CREC infections. The CREC isolates were resistant to most antibiotics. Reducing CREC mortality requires a comprehensive consideration of appropriate antibiotic use, underlying diseases, and invasive procedures.IMPORTANCEEscherichia coli is an opportunistic pathogen that causes severe hospital-acquired infections. The spread of carbapenem-resistant E. coli is a global threat to public health, and only a few antibiotics are effective against these infections. Consequently, these infections are usually associated with poor prognosis and high mortality. Therefore, understanding the risk factors associated with the causes and outcomes of these infections is crucial to reduce their incidence and initiate appropriate therapies. In our study, several factors were found to be involved in nosocomial carbapenem-resistant E. coli (CREC) infections, and CREC isolates were resistant to most antibiotics. Reducing CREC mortality needs a comprehensive consideration of whether antibiotics are used appropriately, underlying diseases, and invasive interventions. These findings provide valuable evidence for the development of anti-infective therapy, infection prevention, and control of CREC-positive infections.

Emergence of a clinical Klebsiella pneumoniae harboring an acrAB-tolC in chromosome and carrying the two repetitive tandem core structures for bla KPC-2 and bla CTX-M-65 in a plasmid

Objective

The emergence of clinical Klebsiella pneumoniae strains harboring acrAB-tolC genes in the chromosome, along with the presence of two repetitive tandem core structures for bla KPC-2 and bla CTX-M-65 genes on a plasmid, has presented a significant clinical challenge.

Methods

In order to study the detailed genetic features of K. pneumoniae strain SC35, both the bacterial chromosome and plasmids were sequenced using Illumina and nanopore platforms. Furthermore, bioinformatics methods were employed to analyze the mobile genetic elements associated with antibiotic resistance genes.

Results

K. pneumoniae strain SC35 was found to possess a class A beta-lactamase and demonstrated resistance to all tested antibiotics. This resistance was attributed to the presence of efflux pump genes, specifically acrAB-tolC, on the SC35 chromosome. Additionally, the SC35 plasmid p1 carried the two repetitive tandem core structures for bla KPC-2 and bla CTX-M-65, as well as bla TEM-1 with rmtB, which shared overlapping structures with mobile genetic elements as In413, Tn3, and TnAs3. Through plasmid transfer assays, it was determined that the SC35 plasmid p1 could be successfully transferred with an average conjugation frequency of 6.85 × 10-4.

Conclusion

The structure of the SC35 plasmid p1 appears to have evolved in correlation with other plasmids such as pKPC2_130119, pDD01754-2, and F4_plasmid pA. The infectious strain SC35 exhibits no susceptibility to tested antibioticst, thus effective measures should be taken to prevent the spread and epidemic of this strain.

Genetic background of aminoglycoside-modifying enzymes in various genetic lineages of clinical aminoglycosides-resistant E. coli and K. pneumoniae isolates in Tunisia

AIMS

This study was conducted to evaluate the in vitro activity of clinically relevant aminoglycosides and to determine the prevalence of genes encoding aminoglycoside modifying enzymes (AMEs) and 16S ribosomal RNA (rRNA) methyltransferases among aminoglycoside-resistant E. coli (n = 61) and K. pneumoniae (n = 44) clinical isolates. Associated resistances to beta-lactams and their bla genes as well as the genetic relatedness of isolates were also investigated.

MATERIALS AND METHODS

A total of 105 aminoglycoside-resistant E. coli (n = 61) and K. pneumoniae (n = 44) isolates recovered between March and May 2017 from 100 patients hospitalized in different wards of Charles Nicolle Hospital of Tunis, Tunisia, were studied. Minimal inhibitory concentrations of aminoglycoside compounds were determined by broth microdilution method. Aminoglycosides resistance encoding genes [aph(3´)-Ia, aph(3') IIa, aph(3´)-VIa, ant(2″)-Ia, aac(3)-IIa, aac(3)-IVa, aac(6')-Ib, rmtA, rmtB, rmtC, armA, and npmA] and bla genes were investigated by PCR and sequencing. Genetic relatedness was examined by multilocus sequence typing (MLST) for representative isolates.

RESULTS

High rates of aminoglycoside resistance were found: gentamicin (85.7%), tobramycin (87.6%), kanamycin (78.0%), netilmincin (74.3%), and amikcin (18.0%). Most common AME gene was aac(3)-IIa (42%), followed by aac(6')-Ib (36.2%) and aph(3')-VIa (32.4%). The majority of isolates were resistant to beta-lactams and blaCTX-M-15 was the most common ESBL. The blaNDM-1 and blaOXA-48 were also produced by 1 and 23 isolates, respectively. Novel sequence types have been reported among our isolates and high-risk clonal lineages have been detected, such as E. coli ST43 (ST131 in Achtman MLST scheme) and K. pneumoniae (ST11/ST13).

CONCLUSIONS

The high prevalence of aminoglycoside resistance rates and the diversity of corresponding genes, with diverse β-lactamase enzymes among genetically heterogeneous clinical isolates present a matter of concern.

Mortality associated with carbapenem resistance in Klebsiella pneumoniae bloodstream infection: A propensity score-matched study

OBJECTIVE

Klebsiella pneumoniae are common pathogens causing bloodstream infection (BSI) that increasingly express carbapenem resistance worldwide. To date, no study has precisely investigated the impact of carbapenem resistance in K. pneumoniae (CRKP) BSI on mortality.

METHODS

This retrospective study included 87 patients with CRKP BSI and 321 patients with carbapenem-susceptible K. pneumoniae (CSKP) BSI from 2015 to 2020. Propensity score analyses with stabilized inverse probability of treatment weighting (IPTW-S) was applied to balance covariates. The hazard ratio for 30-day mortality associated with carbapenem resistance was estimated using Cox regression and Kaplan-Meier curves.

RESULTS

The 30-day crude mortality rates were 43.7% in patients with CRKP BSI and 17.8% in patients with CSKP BSI (P < .001). Age ≥55 years, underlying hematological malignancies and hemodialysis were independently associated with mortality in CRKP BSI. A skin or soft-tissue infection source, urinary catheter, and underlying chronic obstructive pulmonary disease were predictors of mortality in CSKP BSI. The group characteristics were well balanced after IPTW-S. The adjusted hazard ratio for 30-day mortality for CRKP BSI was 1.607 (interquartile range, 0.814-3.171).

CONCLUSIONS

Carbapenem resistance was not associated with a significant increase in 30-day mortality in KP BSI; patient and disease factors were primary determinants of outcomes.

Distribution and molecular characterization of carbapenemase-producing gram-negative bacteria in Henan, China

This study aimed to investigate the epidemiological characteristics and trends over time of carbapenemase-producing (e.g., KPC, NDM, VIM, IMP, and OXA-48) Gram-negative bacteria (CPGNB). Non-duplicated multi-drug resistant Gram-negative bacteria (MDRGNB) were collected from the First Affiliated Hospital of Zhengzhou University from April 2019 to February 2023. Species identification of each isolate was performed using the Vitek2 system and confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry according to the manufacturer's instructions. PCR detected carbapenem resistance genes in the strains, strains carrying carbapenem resistance genes were categorized as CPGNB strains after validation by carbapenem inactivation assay. A total of 5705 non-repetitive MDRGNB isolates belonging to 78 different species were collected during the study period, of which 1918 CPGNB were validated, with the respiratory tract being the primary source of specimens. Epidemiologic statistics showed a significant predominance of ICU-sourced strains compared to other departments. Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa were the significant CPGNB in Henan, and KPC and NDM were the predominant carbapenemases. Carbapenem-resistant infections in Henan Province showed an overall increasing trend, and the carriage of carbapenemase genes by CPGNB has become increasingly prevalent and complicated. The growing prevalence of CPGNB in the post-pandemic era poses a significant challenge to public safety.

Characteristic of KPC-12, a KPC Variant Conferring Resistance to Ceftazidime-Avibactam in the Carbapenem-Resistant Klebsiella pneumoniae ST11-KL47 Clone Background

Background

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are a great threat to public health worldwide. Ceftazidime-avibactam (CZA) is an effective β-lactam/β-lactamase inhibitors against CRKP. However, reports of resistance to CZA, mainly caused by Klebsiella pneumoniae carbapenemase (KPC) variants, have increased in recent years. In this study, we aimed to describe the resistance characteristics of KPC-12, a novel KPC variant identified from a CZA resistant K. pneumoniae.

Methods

The K. pneumoniae YFKP-97 collected from a patient with respiratory tract infection was performed whole-genome sequencing (WGS) on the Illumina NovaSeq 6000 platform. Genomic characteristics were analyzed using bioinformatics methods. Antimicrobial susceptibility testing was conducted by the broth microdilution method. Induction of resistant strain was carried out in vitro as previously described. The G. mellonella killing assay was used to evaluate the pathogenicity of strains, and the conjugation experiment was performed to evaluate plasmid transfer ability.

Results

Strain YFKP-97 was a multidrug-resistant clinical ST11-KL47 K. pneumoniae confers high-level resistance to CZA (16/4 μg/mL). WGS revealed that a KPC variant, KPC-12, was carried by the IncFII (pHN7A8) plasmids (pYFKP-97_a and pYFKP-97_b) and showed significantly decreased activity against carbapenems. In addition, there was a dose-dependent effect of bla KPC-12 on its activity against ceftazidime. In vitro inducible resistance assay results demonstrated that the KPC-12 variant was more likely to confer resistance to CZA than the KPC-2 and KPC-3 variants.

Discussion

Our study revealed that patients who was not treated with CZA are also possible to be infected with CZA-resistant strains harbored a novel KPC variant. Given that the transformant carrying bla KPC-12 was more likely to exhibit a CZA-resistance phenotype. Therefore, it is important to accurately identify the KPC variants as early as possible.

Molecular epidemiology and risk factors for carbapenem-resistant Enterobacteriaceae infections during 2020-2021 in Northwest China

OBJECTIVES

Severe infection caused by Carbapenem-resistant Enterobacteriaceae (CRE) is a challenge for clinical anti-infective therapy, and clinical intervention to improve control of CRE is of great significance. The study aims to determine the molecular epidemiology and risk factors of CRE infections to provide evidence for effective control of nosocomial infection in patients with CRE.

METHODS

A total of 192 non-repetitive CRE strains were collected from January 2020 to December 2021 in Northwest China. To explore the risk factors of CRE infection by univariate and Logistic regression analysis, 1:1 case-control study was used to select Carbapenem sensitive Enterobacteriaceae (CSE) infection patients at the same period as the control group.

RESULTS

Among the 192 CRE strains, the most common isolates included Klebsiella pneumoniae (Kpn) and Enterobacter cloacae (Ecl). The CRE strain showed the lowest rate of resistance to amikacin at 58.3. 185 CRE strains carried carbapenemase resistance genes of concern in this study. KPC-2 (n=94) was the most common carbapenemase, followed by NDM-1 (n=69), NDM-5 (n=22) and IMP-4 (n=5). OXA-48 and VIM were not detected. And KPC-2 was the most common in all strains. Logistic regression analysis implicated days of invasive ventilator-assisted ventilation (OR=1.452; 95 % CI 1.250～1.686), antibiotic combination therapy (OR=2.149; 95 % CI 1.128～4.094), hypoalbuminemia (OR=6.137; 95 % CI 3.161～11.913), history of immunosuppressant use (OR=25.815; 95 % CI 6.821～97.706) and days of hospitalization (OR=1.020; 95 % CI 1.006～1.035) as independent risk factors associated with CRE infection. Age (OR=0.963; 95% CI 0.943～0.984) and history of hormone use (OR=0.119; 95 % CI 0.028～0.504) were protective factors for CRE infection (P < 0.05).

CONCLUSIONS

The resistance of commonly used antibiotics in clinical is severe, and CRE strains mainly carry KPC-2 and NDM-1. Multiple risk factors for CRE infection and their control can effectively prevent the spread of CRE.