Phylogeny and expression patterns of ERF genes that are potential reproductive inducers in hybrid larch.

BACKGROUND: Larch is an important component of northern forests and a major cultivated tree species in restoration of forest cover using improved seed material. In recent years, the continuous low seed production has severely affected the production of improved variety seedlings and natural regeneration. However, research on the reproductive growth of gymnosperms is extremely scarce. RESULTS: In this study, based on differential transcriptome analysis of two asexual reproductive phases, namely high-yield and low-yield, we further screened 5 ERF family genes that may affect the reproductive development of larch. We analyzed their genetic relationships and predicted their physicochemical properties. The expression patterns of these genes were analyzed in different tissues, developmental stages, hormone treatments, and environmental conditions in hybrid larch. CONCLUSION: The results showed that all 5 genes were induced by low temperature and ABA, and their expression patterns in different tissues suggested a suppressive role in the development of female cones in larch. Among them, LkoERF3-like1 and LkoERF071 may be involved in the flowering age pathway. This study enriches the scarce research on reproductive development in gymnosperms and provides a theoretical basis and research direction for regulating the reproductive development of larch in seed orchards.

Effects of congruent emotional contexts during encoding on recognition: An ERPs study.

Past research showed that emotional contexts can impair recognition memory for the target item. Given that item-context congruity may enhance recognition memory, the present study aims to examine the effect of the congruent emotional encoding contexts on recognition memory. Participants studied congruent word-picture pairs (e.g., the word "cow" - a picture describing a cow) and incongruent word-picture pairs (e.g., the word "cow" - a picture describing a goat) and, subsequently, were asked to report the nature of the picture (emotional or neutral). Behavioral results revealed that emotional contexts impaired source but not item recognition, with congruent word-context mitigating this impairment and enhancing item recognition. Neural results from ERPs and theta oscillations found the recollection process, as shown by the LPC old/new effect and theta oscillations, for both item and source recognition across emotional contexts, irrespective of congruity. Meanwhile, the familiarity process as indexed by the FN400 old/new effect was found only for item recognition in congruent emotional contexts. These findings suggest that the congruent relationship of item-context could mitigate the emotion-induced source memory impairment and enhance item memory, with neural results elucidating the memory processes involved in retrieval of emotional information. Specifically, while emotion-related information generally elicits the recollection-based memory process, only congruent emotional information elicits the familiarity-based process.

Deciphering mechanisms of bla NDM gene transmission between human and animals: a genomics study of bacterial isolates from various sources in China, 2015 to 2017.

BackgroundIn China, the bla NDM gene has been recovered from human bacterial isolates since 2011. After 2014, detections of this gene in animal and food bacterial isolates have increasingly been reported.AimWe aimed to understand how bla NDM-bearing bacteria could spread between humans, animals, and animal-derived food.MethodsA total of 288 non-duplicate Escherichia coli strains, including 130 bla NDM-carrying and 158 bla NDM-negative strains were collected from clinical (humans), food-producing animals (pigs) and food (retail pork) sources between 2015 and 2017. The strains were whole genome sequenced. Core-genome-multilocus-sequence-typing was conducted. To investigate if sequence types (STs) found in human, animal or food samples could have a prior origin in a clinical, animal or food-borne animal reservoir, discriminant analysis of principal components (DAPC) was used. Plasmids bearing bla NDM were characterised.ResultsThe 130 bla NDM-carrying E. coli strains comprised a total of 60 STs, with ST167 (10/51), ST77 (6/33) and ST48 (6/46) being most prevalent in clinical, animal and food sources, respectively. Some ST10 and ST167 strains were respectively found among all three sources sampled, suggesting they might enable transfer of bla NDM between sources. DAPC analysis indicated possible transmissions of ST167 from humans to animals and ST10 from animals to human. In 114 of 130 bla NDM-carrying isolates, bla NDM was located on an IncX3 plasmid.ConclusionThis study in a Chinese context suggests that cross-species transmission of certain STs of E. coli harbouring bla NDM on mobile elements, may facilitate the spread of carbapenem-resistant Enterobacteriaceae. Stringent monitoring of bla NDM-bearing E. coli in ecosystems is important.

Prognostic evaluation of serum osteopontin in patients with anti-MDA5 antibody-positive dermatomyositis associated interstitial lung disease.

BACKGROUND: The anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibody was significantly associated with dermatomyositis associated with interstitial lung disease (DM-ILD) and poor survival in patients. However, there was no convenient and accurate biomarker can predict the poor prognosis of anti-MDA5 positive DM-ILD. This study aimed to evaluate the clinical significance of osteopontin (OPN) in anti-MDA5 positive DM-ILD patients. METHODS: The subjects were 43 patients diagnosed DM-ILD with anti-MDA5 antibody. The clinical data were obtained through a review of patient medical records. The serum samples were collected at the time of initial admission and detected for OPN concentrations and ferritin. In addition, immunohistochemistry analysis for OPN was performed on the lung sections of two patients with DM-ILD and six patients with early-stage lung cancer as normal control. RESULTS: The median value of serum OPN in patients with anti-MDA5 positive DM-ILD was 1755.65 pg/ml. Immunohistochemical findings for OPN suggested that the expression of OPN in alveolar epithelial cells and macrophages of anti-MDA5-positive ILD patients was more obvious. Significant correlations between serum OPN and ferritin levels were observed (r = 0.317, P = 0.038). Although OPN and ferritin were both associated with mortality in Univariate Cox hazards analysis, OPN was an independent predictor of the prognosis of DM-ILD rather than ferritin in Multivariate Cox hazards analysis. CONCLUSION: OPN can be expressed in lung tissues but also can exist as a secreted form in serum, and serum OPN may be a more valuable prognostic biomarker in DM-ILD patients with anti-MDA5 antibody than the serum ferritin.

An IncR Plasmid Harbored by a Hypervirulent Carbapenem-Resistant Klebsiella pneumoniae Strain Possesses Five Tandem Repeats of the blaKPC-2::NTEKPC-Id Fragment.

Completed sequences of three plasmids from a carbapenem-resistant hypervirulent Klebsiella pneumoniae isolate, SH9, were obtained. In addition to the pLVPK-like virulence-conferring plasmid (pVir-CR-HvKP_SH9), the two multidrug-resistant plasmids (pKPC-CR-HvKP4_SH9 and pCTX-M-CR-HvKP4_SH9) were predicted to originate from a single pKPC-CR-HvKP4-like multireplicon plasmid through homologous recombination. Interestingly, the blaKPC-2 gene was detectable in five tandem repeats exhibiting the format of an NTEKPC-Id-like transposon (IS26-ΔTn3-ISKpn8-blaKPC-2-ΔISKpn6-korC-orf-IS26). The data suggest an important role of DNA recombination in mediating active plasmid evolution.

Occurrence and distribution of polybrominated diphenyl ethers in soils from an e-waste recycling area in northern China.

Polybrominated diphenyl ethers (PBDEs) are widespread persistent organic pollutants (POPs) because of their extensive use in diverse electronic products, which have posed great threats to human health and ecosystem. In this study, a total of 54 soil samples were collected from an e-waste recycling area in Tianjin, northern China for analyzing the occurrence and distribution of 14 PBDE congeners. The concentrations of BDE 209, ∑13PBDEs and ∑14PBDEs in the soils from Ziya e-waste recycling area were 2.9-2666 ng/g dw (dry weight) (average 90 ng/g dw), 3.0-41 ng/g dw (average 13 ng/g dw) and 5.9-2699 ng/g dw (average 103 ng/g dw), respectively. The ∑14PBDEs concentration showed a dramatic decrease from the central area to the surrounding area. Generally, PBDEs in the northern part showed higher levels than the southern part of the e-waste recycling area due to the wind direction in Tianjin. Deep soil was less polluted by PBDEs, which largely comes from the deposition, migration and infiltration of PBDEs in the surface soils. Overall, PBDEs level in the studied area was much lower than some typical e-waste recycling areas in south China, such as Guiyu and Qingyuan, but significantly higher than the non-e-waste recycling areas. BDE 209, BDE 138 and BDE 28 were the three dominant PBDE congeners in the soil. Principal component analysis (PCA) indicated that the commercial penta-BDEs and deca-BDE could be considered as the main sources of PBDEs pollution in this region. Redundancy analysis (RDA) suggested that the local PBDEs sources rather than soil properties influenced the PBDEs distribution in Ziya e-waste recycling area. This study systematically revealed the occurrence and distribution of PBDEs in soils from the biggest established circular economy park in northern China.

Identification and Characterization of Conjugative Plasmids That Encode Ciprofloxacin Resistance in Salmonella.

This study aimed to characterize novel conjugative plasmids that encode transferable ciprofloxacin resistance in Salmonella In this study, 157 nonduplicated Salmonella isolates were recovered from food products, of which 55 were found to be resistant to ciprofloxacin. Interestingly, 37 of the 55 CiprSalmonella isolates (67%) did not harbor any mutations in the quinolone resistance-determining regions (QRDR). Six Salmonella isolates were shown to carry two novel types of conjugative plasmids that could transfer the ciprofloxacin resistance phenotype to Escherichia coli J53 (azithromycin resistant [Azir]). The first type of conjugative plasmid belonged to the ∼110-kb IncFIB-type conjugative plasmids carrying qnrB-bearing and aac(6')-Ib-cr-bearing mobile elements. Transfer of the plasmid between E. coli and Salmonella could confer a ciprofloxacin MIC of 1 to 2 µg/ml. The second type of conjugative plasmid belonged to ∼240-kb IncH1/IncF plasmids carrying a single PMQR gene, qnrS Importantly, this type of conjugative ciprofloxacin resistance plasmid could be detected in clinical Salmonella isolates. The dissemination of these conjugative plasmids that confer ciprofloxacin resistance poses serious challenges to public health and Salmonella infection control.

Recombination of plasmids in a carbapenem-resistant NDM-5-producing clinical Escherichia coli isolate.

Objectives: To investigate the genetic features of five plasmids recovered from an NDM-5-producing clinical Escherichia coli strain, BJ114, and to characterize the plasmid recombination event that occurred during the conjugation process. Methods: The genetic profiles of the five plasmids were determined by PCR, conjugation, S1-PFGE, Southern hybridization and WGS analysis. Plasmid sequences were analysed with various bioinformatic tools. Results: Complete sequences of five plasmids were obtained. Two small plasmids, pBJ114-141 and pBJ114-46, were speculated to have recombined into a large fusion plasmid, pBJ114T-190. When conjugated to other E. coli strains, some of the fusion plasmids were able to be resolved into the original two single plasmids. A non-conjugative plasmid, pBJ114-96, exhibited a high degree of sequence identity with the phage P7-like plasmid as well as an mcr-1-bearing plasmid. Another plasmid, pBJ114-78, was found to contain multidrug resistance genes and various mobile elements. Conclusions: The fusion plasmid recoverable from the transconjugant was found to be generated as a result of a recombination event that occurred upon interaction between a blaNDM-5-carrying plasmid and another plasmid present in the parental strain. Such recombination events presumably play a potential role in the dissemination of the blaNDM genes among different plasmids and pathogenic bacterial strains.

IncFII Conjugative Plasmid-Mediated Transmission of blaNDM-1 Elements among Animal-Borne Escherichia coli Strains.

This study aims to investigate the prevalence and transmission dynamics of the blaNDM-1 gene in animal Escherichia coli strains. Two IncFII blaNDM-1-encoding plasmids with only minor structural variation in the MDR region, pHNEC46-NDM and pHNEC55-NDM, were found to be responsible for the transmission of blaNDM-1 in these strains. The blaNDM-1 gene can be incorporated into plasmids and stably inherited in animal-borne E. coli strains that can be maintained in animal gut microflora even without carbapenem selection pressure.

Molecular Characterization of Escherichia coli Isolates Carrying mcr-1, fosA3, and Extended-Spectrum-ß-Lactamase Genes from Food Samples in China.

This study surveyed the prevalence of mcr-1 in extended-spectrum-ß-lactamase (ESBL)-producing Escherichia coli strains of food origin in China and identified strains that carried mcr-1, fosA3, and ESBL genes, which were carried in various plasmids. The mcr-1 and ESBL genes could be cotransferred by one or more types of plasmids. The presence of these multidrug-resistant E. coli strains in food products might pose a huge threat to public health.

Complete genetic analysis of plasmids carrying mcr-1 and other resistance genes in an Escherichia coli isolate of animal origin.

Objectives: To investigate the genetic features of three plasmids recovered from an MCR-1 and ESBL-producing Escherichia coli strain, HYEC7, and characterize the transmission mechanism of mcr-1 . Methods: The genetic profiles of three plasmids were determined by PCR, S1-PFGE, Southern hybridization and WGS analysis. The ability of the mcr-1 -bearing plasmid to undergo conjugation was also assessed. The mcr-1 -bearing transposon Tn 6330 was characterized by PCR and DNA sequencing. Results: Complete sequences of three plasmids were obtained. A non-conjugative phage P7-like plasmid, pHYEC7- mcr1 , was found to harbour the mcr-1 -bearing transposon Tn 6330 , which could be excised from the plasmid by generating a circular intermediate harbouring mcr-1 and the IS Apl1 element. The insertion of the circular intermediate into another plasmid, pHYEC7-IncHI2, could form pHNSHP45-2, the original IncHI2-type mcr-1 -carrying plasmid that was reported. The third plasmid, pHYEC7-110, harboured two replicons, IncX1 and IncFIB, and comprised multiple antimicrobial resistance mobile elements, some of which were shared by pHYEC7-IncHI2. Conclusions: The Tn 6330 element located in the phage-like plasmid pHYEC7- mcr1 could be excised from the plasmid and formed a circular intermediate that could be integrated into plasmids containing the IS Apl1 element. This phenomenon indicated that Tn 6330 is a key element responsible for widespread dissemination of mcr-1 among various types of plasmids and bacterial chromosomes. The dissemination rate of such an element may be further enhanced upon translocation into phage-like vectors, which may also be transmitted via transduction events.

Genetic characterization of mcr-1-bearing plasmids to depict molecular mechanisms underlying dissemination of the colistin resistance determinant.

OBJECTIVES: To analyse and compare mcr-1-bearing plasmids from animal Escherichia coli isolates, and to investigate potential mechanisms underlying dissemination of mcr-1. METHODS: Ninety-seven ESBL-producing E. coli strains isolated from pig farms in China were screened for the mcr-1 gene. Fifteen mcr-1-positive strains were subjected to molecular characterization and bioinformatic analysis of the mcr-1-bearing plasmids that they harboured. RESULTS: Three major types of mcr-1-bearing plasmids were recovered: IncX4 (∼33 kb), IncI2 (∼60 kb) and IncHI2 (∼216-280 kb), among which the IncX4 and IncI2 plasmids were found to harbour the mcr-1 gene only, whereas multiple resistance elements including blaCTX-M, blaCMY, blaTEM, fosA, qnrS, floR and oqxAB were detected, in various combinations, alongside mcr-1 in the IncHI2 plasmids. The profiles of mcr-1-bearing plasmids in the test strains were highly variable, with coexistence of two mcr-1-bearing plasmids being common. However, the MIC of colistin was not affected by the number of mcr-1-carrying plasmids harboured. Comparative analysis of the plasmids showed that they contained an mcr-1 gene cassette with varied structures (mcr-1-orf, ISApl1-mcr-1-orf and Tn6330), with the IncHI2 type being the most active in acquiring foreign resistance genes. A novel transposon, Tn6330, with the structure ISApl1-mcr-1-orf-ISApl1 was found to be the key element mediating translocation of mcr-1 into various plasmid backbones through formation of a circular intermediate. CONCLUSIONS: The mcr-1 gene can be disseminated via multiple mobile elements including Tn6330, its circular intermediate and plasmids harbouring such elements. It is often co-transmitted with other resistance determinants through IncHI2 plasmids. The functional mechanism of Tn6330, a typical composite transposon harbouring mcr-1, should be further investigated.

Widespread distribution of mcr-1-bearing bacteria in the ecosystem, 2015 to 2016.

The recently discovered colistin resistance-encoding element, mcr-1, adds to the list of mobile resistance genes whose products rapidly erode the antimicrobial efficacy of not only the commonly used antibiotics, but also the last line agents of carbapenems and colistin. The relative prevalence of mcr-1-bearing strains in various ecological niches including 1,371 food samples, 480 animal faecal samples, 150 human faecal samples and 34 water samples was surveyed using a novel in-house method. Bacteria bearing mcr-1 were commonly detected in water (71% of samples), animal faeces (51%), food products (36%), and exhibited stable carriage in 28% of human subjects surveyed. Such strains, which exhibited variable antibiotic susceptibility profiles, belonged to various Enterobacteriaceae species, with Escherichia coli being the most dominant in each specimen type. The mcr-1 gene was detectable in the chromosome as well as plasmids of various sizes. Among these, two conjugative plasmids of sizes ca 33 and ca 60 kb were found to be the key vectors that mediated mcr-1 transmission in organisms residing in various ecological niches. The high mcr-1 carriage rate in humans found in this study highlights the importance of continued vigilance, careful antibiotic stewardship, and the development of new antimicrobials.

Solvent and α-secondary kinetic isotope effects on ß-glucosidase.

ß-Glucosidase from sweet almond is a retaining, family 1, glycohydrolase. It is known that glycosylation of the enzyme by aryl glucosides occurs with little, if any, acid catalysis. For this reaction both the solvent and α-secondary kinetic isotope effects are 1.0. However, for the deglucosylation reaction (e.g., kcat for 2,4-dinitrophenyl-ß-D-glucopyranoside) there is a small solvent deuterium isotope effect of 1.50 (±0.06) and an α-secondary kinetic isotope effect of 1.12 (±0.03). For aryl glucosides, kcat/KM is very sensitive to the pKa of the phenol leaving group [ßlg≈-1; Dale et al., Biochemistry25 (1986) 2522-2529]. With alkyl glucosides the ßlg is smaller (between -0.2 and -0.3) but still negative. This, coupled with the small solvent isotope effect on the pH-independent second-order rate constant for the glucosylation of the enzyme with 2,2,2-trifluoroethyl-ß-glucoside [D2O(kcat/KM)=1.23 (±0.04)] suggests that there is more glycone-aglycone bond fission than aglycone oxygen protonation in the transition state for alkyl glycoside hydrolysis. The kinetics constants for the partitioning (between water and various alcohols) of the glucosyl-enzyme intermediate, coupled with the rate constants for the forward (hydrolysis) reaction provide an estimate of the stability of the glucosyl-enzyme intermediate. This is a relatively stable species with an energy about 2 to 4 kcal/mol higher than that of the ES complex. This article is part of a Special Issue entitled: Enzyme Transition States from Theory and Experiment.

Molecular Characterization of Escherichia coli Strains Isolated from Retail Meat That Harbor blaCTX-M and fosA3 Genes.

A total of 55 cefotaxime-resistantEscherichia coliisolates were obtained from retail meat products purchased in Shenzhen, China, during the period November 2012 to May 2013. Thirty-seven of these 55 isolates were found to harbor ablaCTX-Mgene, with theblaCTX-M-1group being the most common type.blaCMY-2was detected in 16 isolates, alone or in combination with other extended-spectrum ß-lactamase (ESBL) determinants. Importantly, thefosA3gene, which encodes fosfomycin resistance, was detected in 12 isolates, with several being found to reside in the conjugative plasmid that harbored theblaCTX-Mgene. The insertion sequence IS26was observed upstream of some of theblaCTX-M-55andfosA3genes. Conjugation experiments showed thatblaCTX-Mgenes from 15 isolates were transferrable, with Inc I1 and Inc FII being the most prevalent replicons. High clonal diversity was observed among theblaCTX-Mproducers, suggesting that horizontal transfer of theblaCTX-Mgenes amongE. colistrains in retail meats is a common event and that such strains may constitute an important reservoir ofblaCTX-Mgenes, which may be readily disseminated to other potential human pathogens.

Widespread Dissemination of Carbapenem-Resistant Escherichia coli Sequence Type 167 Strains Harboring blaNDM-5 in Clinical Settings in China.

This study reports the increasing prevalence of clinical Escherichia coli of sequence type 167 (ST167) carrying both blaNDM-1 and blaNDM-5 on the conjugative IncX3 plasmid in various parts of China. Close surveillance is needed to monitor the future dissemination of ST167 strains that harbor blaNDM-5 or other blaNDM-like genes.

Vegetation resilience assessment and its climatic driving factors: Evidence from surface coal mines in northern China.

Vegetation resilience is a key concept for understanding ecosystem responses to disturbances and is essential for maintaining ecosystem sustainability. However, assessing vegetation resilience remains challenging, especially for areas with significant disturbances and ecological restoration, such as surface coal mine ecosystems. Vegetation resilience assessment requires a combination of disturbance magnitude, recovery magnitude, and recovery time. In this study, we propose a vegetation resilience assessment method by integrating disturbance magnitude, recovery magnitude and recovery time. Forty-six surface coal mines in northern China were analysed as the study areas. A geographical detector model was used to explore the influence of climatic factors on vegetation resilience. The results indicated that the vegetation resilience curves included three shapes, inverted U-shaped, S-shaped, and monotonically decreasing, and the different disturbance-recovery relationships of the curves indicated that natural and social factors jointly changed the ecological restoration process. The vegetation resilience of the 46 surface coal mines varies widely, ranging from 0.87 to 7.22, showing a spatial decreasing trend from east to west. The explanatory power of different climatic factors on vegetation resilience by indirectly affecting hydrothermal conditions varies, with the effect of atmospheric pressure being the most significant and the superposition of the two climatic factors enhancing the effect on vegetation resilience. This study enriches the understanding of vegetation resilience assessment and provides important information to guide the differentiation of ecological restoration and resource development of surface coal mines in different regions.

Kechuanning Gel Plaster Exerts Anti-inflammatory and Immunomodulatory Effects on Ovalbumin-induced Asthma Model Rats via ERK Pathway.

BACKGROUND: We aimed to evaluate the therapeutic effects of Kechuanning gel plaster on ovalbumin (OVA)-induced rat model of asthma. METHODS: Rats were injected with OVA to induce asthma, and Kechuanning gel plaster was administered after the OVA challenge. The immune cell counts in the bronchial alveolar lavage fluid (BALF) were calculated after Kechuanning gel plaster administration. The levels of immune factors in BALF and serum OVA-specific IgE levels were analyzed. Western blot analysis and immunohistochemistry were carried out to analyze the following proteins: C-FOS, C-JUN, RAS p21 protein activator 1 (RASA1), matrix metalloproteinase 9 (MMP9), RAF1, p-MEK1, tissue inhibitor of metalloproteinase-1 (TIMP1), and p-extracellular signal-regulated kinase 1 (ERK1). RESULTS: Administration of Kechuanning gel plaster led to decreased immune cell counts, inflammatory cytokines (interleukin (IL)-1ß, IL13, and IL17), and OVA-specific IgE expression. Compared to the normal group, the C-FOS, C-JUN, RASA1, MMP9, RAF1, MEK1, TIMP1, and p- ERK1 expressions in the model group were significantly increased, whereas Kechuanning gel plaster administration decreased C-JUN, MMP9, TIMP1, RAF1, MEK1, p-ERK1, C-FOS, and RASA1 protein levels. CONCLUSION: Kechuanning gel plaster exerted its therapeutic effects on OVA-induced asthma model rats through the ERK signaling pathway. Kechuanning gel plaster could be considered as a potential alternative therapeutic agent for the management of asthma.

Clinical use of tigecycline may contribute to the widespread dissemination of carbapenem-resistant hypervirulent Klebsiella pneumoniae strains.

The emergence of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) poses grave threats to human health. These strains increased dramatically in clinical settings in China in the past few years but not in other parts of the world. Four isogenic K. pneumoniae strains, including classical K. pneumoniae, carbapenem-resistant K. pneumoniae (CRKP), hypervirulent K. pneumoniae (hvKP) and CR-hvKP, were created and subjected to phenotypic characterization, competition assays, mouse sepsis model and rat colonization tests to investigate the mechanisms underlying the widespread nature of CR-hvKP in China. Acquisition of virulence plasmid led to reduced fitness and abolishment of colonization in the gastrointestinal tract, which may explain why hvKP is not clinically prevalent after its emergence for a long time. However, tigecycline treatment facilitated the colonization of hvKP and CR-hvKP and reduced the population of Lactobacillus spp. in animal gut microbiome. Feeding with Lactobacillus spp. could significantly reduce the colonization of hvKP and CR-hvKP in the animal gastrointestinal tract. Our data implied that the clinical use of tigecycline to treat carbapenem-resistant K. pneumoniae infections facilitated the high spread of CR-hvKP in clinical settings in China and demonstrated that Lactobacillus spp. was a potential candidate for anticolonization strategy against CR-hvKP.

Enhancing resistance, but not virulence attributed to the high mortality caused by carbapenem-resistant Klebsiella pneumoniae.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged as a global threat due to its high mortality in clinical patients. However, the specific mechanisms underlying this increased mortality remain unclear. The objective of this study is to investigate how the development of a resistance phenotype contributes to the significantly higher mortality associated with this pathogen. To achieve this, a collection of isogeneic strains was generated. The clinical carbapenem-susceptible K. pneumoniae (CSKP) strain HKU3 served as the control isolate, while HKU3-KPC was created through conjugation with a blaKPC-2-bearing plasmid and served as clinical CRKP strain. Using a sepsis model, it was demonstrated that both HKU3 and HKU3-KPC exhibited similar levels of virulence. Flow cytometry, RNA-seq, and ELISA analysis were employed to assess immune cell response, M1 macrophage polarization, and cytokine storm induction, revealing that both strains elicited comparable types and levels of these immune responses. Subsequently, meropenem was utilized to treat K. pneumoniae infection, and it was found that meropenem effectively reduced bacterial load, inhibited M1 macrophage polarization, and suppressed serum cytokine production during HKU3 (CSKP) infection. However, these effects were not observed in the case of HKU3-KPC (CRKP) infection. These findings provide evidence that the high mortality associated with CRKP is attributed to its enhanced survival within the host during antibiotic treatment, resulting in a cytokine storm and subsequent host death. The development of an effective therapy for CRKP infections could significantly reduce the mortality caused by this pathogen.