Objective:To report the nationwide surveillance results of pathogenic profiles and antimicrobial resistance patterns of Gram-positive bloodstream infections in China in 2023.Methods:The clinical isolates of Gram-posttive bacteria from blood cultures were collected in member hospitals of National Bloodstream Infection Bacterial Resistant Investigation Collaborative System（BRICS）during January to December 2023. Antimicrobial susceptibility testing was performed using the dilution method recommended by the Clinical and Laboratory Standards Institute（CLSI）. Statistical analyses were conducted using WHONET 5.6 and SPSS 25.0 software.Results:A total of 4 385 Gram-positive bacterial isolates were obtained from 60 participating center. The top five pathogens were Staphylococcus aureus（ n=1 544，35.2%），coagulase-negative Staphylococci（ n=1 441，32.9%）， Enterococcus faecium（ n=574，13.1%）， Enterococcus faecalis（ n=385，8.8%），and α-hemolytic Streptococci（ n=187，4.3%）. The prevalence of methicillin-resistant Staphylococcus aureus（MRSA）and methicillin-resistant coagulase-negative Staphylococci（MRCNS）was 26.2%（405/1 544）and 69.8%（1 006/1 441），respectively. Notably，all Staphylococci remained susceptible to glycopeptide or daptomycin. Staphylococcus aureus demonstrated excellent susceptibility（>97.0%）to cephalobiol，rifampicin，trimethoprim-sulfamethoxazole，linezolid，minocycline，tigecycline，and eravacycline. No Enterococcus exhibiting resistance to linezolid were detected. Glycopeptide resistance was uncommon but more frequent in Enterococcus faecium（resistance to vancomycin and teicoplanin：both 1.7%）compared to Enterococcus faecalis（both 0.3%）. The detection rates of MRSA and MRCNS exhibited significant regional variations across the country（ χ2=17.674 and 148.650，respectively，both P<0.001）. No vancomycin-resistant Enterococci were detected in central China. Institutional comparison demonstrated higher prevalence of MRSA（ χ2=14.111， P<0.001）and MRCNS（ χ2=4.828， P=0.028）in provincial hospitals than that in municipal hospitals. Socioeconomic analysis identified elevated detection rates of both MRSA（ χ2=18.986， P<0.001）and MRCNS（ χ2=4.477， P=0.034）in less developed regions（per capita GDP

Objective:To report the results of bacterial resistant investigation collaborative system（BRICS）on the distribution and antimicrobial resistance profile of clinical Gram-negative bacteria isolates from bloodstream infections in China in 2023，and provide reference for clinical tretment of bloodstream infections and prevention and control of bacterial resistance.Methods:The clinical isolates of Gram-negative bacteria from blood cultures in member hospitals of BRICS were collected during January 2023 to December 2023. Antibiotic susceptibility tests were conducted by agar dilution or broth dilution methods recommended by Clinical and Laboratory Standards Institute（CLSI）. WHONET 5.6 and SPSS 25.0 were used to analyze the data.Results:During the study period，11 492 strains of Gram-negative bacteria were collected from 60 hospitals，of which 10 098（87.9%）were Enterobacterales and 1 394（12.1%）were non-fermentative bacteria. The top 5 bacterial species were Escherichia coli（50.0%）， Klebsiella pneumoniae（26.1%）， Pseudomonas aeruginosa（5.1%）， Acinetobacter baumannii complex（5.0%）and Enterobacter cloacae complex（4.1%）. The ESBL-producing rates in Escherichia coli， Klebsiella pneumoniae and Proteus mirablilis were 46.8%（2 685/5 741），18.3%（549/2 999）and 44.0%（77/175），respectively. The prevalence of carbapenem-resistant Escherichia coli（CREC）and carbapenem-resistant Klebsiella pneumoniae（CRKP）were 1.3%（76/5 741）and 15.0%（450/2 999）；32.9%（25/76）and 78.0%（351/450）of CREC and CRKP were sensitive to ceftazidime/avibactam combination，respectively. 94.7%（72/76）and 90.2%（406/450）of CREC and CRKP were sensitive to aztreonam/avibactam combination. Furthermore，57.9%（44/76）and 79.1%（356/450）were sensitive to imipenem/relebactam combination. The prevalence of carbapenem-resistant Acinetobacter baumannii（CRAB）complex was 64.6%（370/573），while more than 80.0% of CRAB complex was sensitive to tigecycline，eravacycline and polymyxin B. The prevalence of carbapenem-resistant Pseudomonas aeruginosa（CRPA）was 17.0%（99/581）. There were differences in the composition ratio of Gram-negative bacteria in bloodstream infections and the prevalence of important Gram-negative bacteria resistance among different regions in China，with statistically significant differences in the prevalence of CREC，CRKP，CRPA and CRAB complex（ χ2=10.6，28.6，10.8 and 19.3， P<0.05）. The prevalence of ESBL-producing Escherichia coli， CREC，CRAB complex and CRKP were higher in provincial hospitals than those in municipal hospitals（ χ2=12.5，9.8，12.7 and 57.8，all P<0.01）. Conclusions:Gram-negative bacteria are the main pathogens causing bloodstream infections in China，and Escherichia coli is ranked in the top，while the trend of Klebsiella pneumoniae increases continuously with time. CRKP infection shows a slow upward trend，CREC infecton maintains a low prevalence level，and CRAB complex infection continues to exhibit a high prevalence rate. The composition and resistance patterns of pathogens causing bloodstream infections vary to some extent across different regions and levels of hospitals in China.

Aim To explore the effect of hydroxysafflor yellow A(HSYA)on lipocalin 2(LCN2)-induced fer-roptosis in HT22 cells and the related mechanism.Methods Thirty male Sprague-Dawley(SD)rats were used to establish the middle cerebral artery occlu-sion/reperfusion(MCAO/R)model by the suture method.The rats were randomly divided into the Sham group,the MCAO/R group,and the MCAO/R+HSYA group.The infarct area was measured by TTC staining,and the degree of neurological deficit was evaluated by the Z-Longa scoring method.The expressions of LCN2 and 24P3R in brain tissues were detected by Western blot.LCN2 protein was added to HT-22 cells,and the cells were divided into the normal group,the LCN2 group,and the LCN2+HSYA group.The optimal con-centration of LCN2-induced neuronal ferroptosis was screened by LDH assay and Western blot,and the ex-pression levels of ferritin,FPN1,GPX4,SLC7A11,COX2,and 24P3R were detected.LCN2 was knocked down by siRNA transfection,and the expressions of GPX4 and ferritin were detected.The contents of glu-tathione(GSH),malondialdehyde(MDA),GPX4,and Fe2+were determined by colorimetry,and the expres-sion of GPX4 was detected by immunofluorescence.The binding force between HSYA and LCN2 was ana-lyzed by molecular docking technology.Results Ani-mal experiments showed that HSYA could reduce the cerebral infarction area and decrease the neurological function score of MCAO/R rats.Compared with the sham group,the levels of LCN2 and 24P3R increased in the MCAO/R group,while HSYA inhibited their ex-pressions.Cell experiments showed that the optimal concentration of LCN2 to induce ferroptosis in HT22 cells was 2 μmol·L-1.After knocking down LCN2 by siRNA transfection,compared with the LCN2 group,the expression levels of GPX4 and ferritin in the siLCN2 group increased significantly.Compared with the nor-mal group,the expressions of SLC7A11,GPX4,FPN1,ferritin,and GSH in the LCN2 group decreased signifi-cantly,while the concentration of Fe2+,and the expres-sions of MDA,COX2,and 24P3R increased.HSYA could increase the expressions of SLC7A11,GPX4,FPN1,ferritin,and GSH,reduce the contents of Fe2+and MDA,and inhibit the expressions of COX2 and 24P3R.Molecular docking showed that the binding en-ergy between HSYA and LCN2 was-8.0 kJ·mol-1.Conclusion HSYA can inhibit LCN2-induced ferrop-tosis in HT22 cells through the SLC7A11/GPX4 signa-ling pathway.

Objective:To investigate the functional characteristics of the prefrontal cortex in patients with schizophrenia (SCZ) during resting state and analyze its association with clinical symptoms.Methods:Twenty-eight hospitalized patients with SCZ (SCZ group) were selected from November 2023 to May 2024, and 28 healthy controls (HC group) were recruited concurrently. By using functional near-infrared spectroscopy (fNIRS) technology, data on the concentration changes of oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) in the prefrontal cortex during resting state were collected from all subjects to measure cortical hemodynamic activity. Regional activation values and functional connectivity (FC) values among brain areas were analyzed. Clinical symptoms in patients were assessed using the positive and negative syndrome scale (PANSS).SPSS 25.0 software was employed for statistical analysis. Between-group comparisons were performed using independent samples t-tests or Mann-Whitney U tests. Spearman correlation analysis and general linear regression models were applied to examine relationships between prefrontal cortical functional characteristics and clinical symptoms. Results:The levels of HbO in the right inferior frontal gyrus and left frontal pole area were significantly higher in the SCZ group (1.5 (1.0, 3.0)μmol/L, 1.0 (1.0, 2.8)μmol/L) than those in the HC group (-0.01 (-0.05, 0.02)μmol/L, -0.02 (-0.07, 0.03)μmol/L) ( Z=-6.46, -6.50, both P<0.01). The levels of HbR in the bilateral dorsolateral prefrontal cortex were significantly higher in the SCZ group (0.02 (-0.01, 0.07)μmol/L, 0.01 (-0.01, 0.03)μmol/L) than those in the HC group (-0.01 (-0.03, 0.01)μmol/L, -0.01 (-0.02, 0.01)μmol/L) ( Z=-2.46, -1.98, both P<0.05).The SCZ group showed significantly higher HbO-based FC values in the frontal pole-temporal pole (0.49±0.21) and temporal pole-dorsolateral prefrontal cortex (0.36±0.25) compared to the HC group (0.33±0.18, 0.15±0.19) ( t=3.02, 3.44, both P<0.01). Conversely, the SCZ group exhibited significantly lower HbR-based FC in the frontal pole-inferior frontal gyrus (0.15±0.13) and inferior frontal gyrus-temporal pole (0.27±0.37) compared to the HC group (0.33±0.26, 0.77±0.48) ( t=-3.17, -4.23, both P<0.01). Correlation analysis revealed that in the SCZ group, the level of HbO in the right inferior frontal gyrus was positively correlated with negative symptoms, positive symptoms, excitement/hostility, and PANSS total score ( r=0.45-0.64, all P<0.05), and the level of HbO in the left frontal pole area was positively correlated with excitement/hostility and PANSS total score ( r=0.57, 0.50, both P<0.01), while the FC value between the frontal pole and temporal pole areas showed a negative correlation with excitement/hostility ( r=-0.39, P<0.05). Regression analysis demonstrated that, the HbO concentration in the right inferior frontal gyrus significantly positively predicted PANSS total score, positive symptoms, and negative symptoms ( β=0.70, 0.64, 0.55, all P<0.01).The HbO concentration in the left frontal pole area significantly positively predicted excitement/hostility ( β=0.77, P<0.01).The frontal pole-temporal pole HbO-based FC significantly negatively predicted excitement/hostility scores ( β=-0.42, P<0.01). Conclusion:Patients with SCZ exhibit hyperactivation of localized prefrontal cortex brain regions and dysfunction of functional connectivity during resting state, which are significantly associated with core clinical symptoms including positive, negative, and excitement/hostility symptoms.

Objective:To investigate the characteristics of resting-state mirror homotopic connectivity and the gray matter volume of brain in patients with neuropsychiatric systemic lupus erythematosus (NPSLE).Methods:From June 2020 to March 2023, a total of 35 NPSLE patients (NPSLE group) and 30 non-NPSLE patients (non-NPSLE group) were selected from Taizhou People's Hospital Affiliated to Nanjing Medical University, another 31 healthy volunteers were recruited as the healthy controls(HC group). All participants underwent resting-state functional magnetic resonance imaging (rs-fMRI) and mini-mental state examination (MMSE) assessments. The patients in NPSLE and non-NPSLE groups were additionally assessed using the fatigue scale for motor and cognitive functions (FSMC) and the hospital anxiety and depression scale (HADS).The DPABI V7.0 toolkit based on the MATLAB platform was used to preprocess the rs-fMRI data and calculate the voxel-mirrored homotopic connectivity(VMHC) indexes, and the differences in VMHC between groups were evaluated by covariance analysis in SPM12.0 software, and the VMHC values of brain regions with significant differences were extracted for further comparison between the two groups.Partial correlation analysis was performed to investigate the association between VMHC values and clinical parameters in NPSLE patients.The brain regions with significant differences between NPSLE patients and non-NPSLE patients were used as region of interest (ROI), and gray matter volumes within these ROIs were then calculated by VBM8 toolbox.Results:(1)There were statistically significant differences in the VMHC values of bilateral precentral gyrus, bilateral dorsolateral superior frontal gyrus, bilateral medial and paracingulate gyrus, bilateral parahippocampal gyrus, bilateral middle occipital gyrus, bilateral postcentral gyrus, and bilateral superior temporal gyrus among the 3 groups( F=11.246-14.102, all P<0.05). The NPSLE group exhibited significantly lower VMHC values in these regions compared to both the non-NPSLE group and HC group (all P<0.05), but there were no significant differences in these regions between the non-NPSLE group and HC group (all P>0.05).(2) The gray matter volumes of bilateral dorsolateral superior frontal gyrus(right: (0.57±0.11)mm 3, (0.65±0.08)mm 3, t=-3.409, P=0.001; left: (0.53±0.10)mm 3, (0.60±0.07)mm 3, t=-3.082, P=0.003), bilateral precentral gyrus(right: (0.32±0.06)mm 3, (0.35±0.04)mm 3, t=-2.044, P=0.045; left: (0.39±0.06)mm 3, (0.42±0.04)mm 3, t=-2.505, P=0.015), right medial and paracingulate gyrus((0.66±0.08)mm 3, (0.70±0.07)mm 3, t=-2.491, P=0.015) and left superior temporal gyrus((0.57±0.09)mm 3, (0.61±0.06)mm 3, t=- 2.344, P=0.022) in the NPSLE group were smaller than those of non-NPSLE group.(3)Correlation analysis showed that the VMHC value of dorsolateral superior frontal gyrus was positively correlated with IgA level in NPSLE patients ( r=0.353, P=0.047). Conclusion:Patients with NPSLE generally have decreased mirror homotopy functional connectivity in the cerebral hemispheres, accompanied by a decrease in gray matter volume in some brain regions, which can provide a certain neuroimaging basis for the pathogenesis of brain injury.

Aim To explore the effect of hydroxysafflor yellow A(HSYA)on lipocalin 2(LCN2)-induced fer-roptosis in HT22 cells and the related mechanism.Methods Thirty male Sprague-Dawley(SD)rats were used to establish the middle cerebral artery occlu-sion/reperfusion(MCAO/R)model by the suture method.The rats were randomly divided into the Sham group,the MCAO/R group,and the MCAO/R+HSYA group.The infarct area was measured by TTC staining,and the degree of neurological deficit was evaluated by the Z-Longa scoring method.The expressions of LCN2 and 24P3R in brain tissues were detected by Western blot.LCN2 protein was added to HT-22 cells,and the cells were divided into the normal group,the LCN2 group,and the LCN2+HSYA group.The optimal con-centration of LCN2-induced neuronal ferroptosis was screened by LDH assay and Western blot,and the ex-pression levels of ferritin,FPN1,GPX4,SLC7A11,COX2,and 24P3R were detected.LCN2 was knocked down by siRNA transfection,and the expressions of GPX4 and ferritin were detected.The contents of glu-tathione(GSH),malondialdehyde(MDA),GPX4,and Fe2+were determined by colorimetry,and the expres-sion of GPX4 was detected by immunofluorescence.The binding force between HSYA and LCN2 was ana-lyzed by molecular docking technology.Results Ani-mal experiments showed that HSYA could reduce the cerebral infarction area and decrease the neurological function score of MCAO/R rats.Compared with the sham group,the levels of LCN2 and 24P3R increased in the MCAO/R group,while HSYA inhibited their ex-pressions.Cell experiments showed that the optimal concentration of LCN2 to induce ferroptosis in HT22 cells was 2 μmol·L-1.After knocking down LCN2 by siRNA transfection,compared with the LCN2 group,the expression levels of GPX4 and ferritin in the siLCN2 group increased significantly.Compared with the nor-mal group,the expressions of SLC7A11,GPX4,FPN1,ferritin,and GSH in the LCN2 group decreased signifi-cantly,while the concentration of Fe2+,and the expres-sions of MDA,COX2,and 24P3R increased.HSYA could increase the expressions of SLC7A11,GPX4,FPN1,ferritin,and GSH,reduce the contents of Fe2+and MDA,and inhibit the expressions of COX2 and 24P3R.Molecular docking showed that the binding en-ergy between HSYA and LCN2 was-8.0 kJ·mol-1.Conclusion HSYA can inhibit LCN2-induced ferrop-tosis in HT22 cells through the SLC7A11/GPX4 signa-ling pathway.

Objective:To investigate the functional characteristics of the prefrontal cortex in patients with schizophrenia (SCZ) during resting state and analyze its association with clinical symptoms.Methods:Twenty-eight hospitalized patients with SCZ (SCZ group) were selected from November 2023 to May 2024, and 28 healthy controls (HC group) were recruited concurrently. By using functional near-infrared spectroscopy (fNIRS) technology, data on the concentration changes of oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) in the prefrontal cortex during resting state were collected from all subjects to measure cortical hemodynamic activity. Regional activation values and functional connectivity (FC) values among brain areas were analyzed. Clinical symptoms in patients were assessed using the positive and negative syndrome scale (PANSS).SPSS 25.0 software was employed for statistical analysis. Between-group comparisons were performed using independent samples t-tests or Mann-Whitney U tests. Spearman correlation analysis and general linear regression models were applied to examine relationships between prefrontal cortical functional characteristics and clinical symptoms. Results:The levels of HbO in the right inferior frontal gyrus and left frontal pole area were significantly higher in the SCZ group (1.5 (1.0, 3.0)μmol/L, 1.0 (1.0, 2.8)μmol/L) than those in the HC group (-0.01 (-0.05, 0.02)μmol/L, -0.02 (-0.07, 0.03)μmol/L) ( Z=-6.46, -6.50, both P<0.01). The levels of HbR in the bilateral dorsolateral prefrontal cortex were significantly higher in the SCZ group (0.02 (-0.01, 0.07)μmol/L, 0.01 (-0.01, 0.03)μmol/L) than those in the HC group (-0.01 (-0.03, 0.01)μmol/L, -0.01 (-0.02, 0.01)μmol/L) ( Z=-2.46, -1.98, both P<0.05).The SCZ group showed significantly higher HbO-based FC values in the frontal pole-temporal pole (0.49±0.21) and temporal pole-dorsolateral prefrontal cortex (0.36±0.25) compared to the HC group (0.33±0.18, 0.15±0.19) ( t=3.02, 3.44, both P<0.01). Conversely, the SCZ group exhibited significantly lower HbR-based FC in the frontal pole-inferior frontal gyrus (0.15±0.13) and inferior frontal gyrus-temporal pole (0.27±0.37) compared to the HC group (0.33±0.26, 0.77±0.48) ( t=-3.17, -4.23, both P<0.01). Correlation analysis revealed that in the SCZ group, the level of HbO in the right inferior frontal gyrus was positively correlated with negative symptoms, positive symptoms, excitement/hostility, and PANSS total score ( r=0.45-0.64, all P<0.05), and the level of HbO in the left frontal pole area was positively correlated with excitement/hostility and PANSS total score ( r=0.57, 0.50, both P<0.01), while the FC value between the frontal pole and temporal pole areas showed a negative correlation with excitement/hostility ( r=-0.39, P<0.05). Regression analysis demonstrated that, the HbO concentration in the right inferior frontal gyrus significantly positively predicted PANSS total score, positive symptoms, and negative symptoms ( β=0.70, 0.64, 0.55, all P<0.01).The HbO concentration in the left frontal pole area significantly positively predicted excitement/hostility ( β=0.77, P<0.01).The frontal pole-temporal pole HbO-based FC significantly negatively predicted excitement/hostility scores ( β=-0.42, P<0.01). Conclusion:Patients with SCZ exhibit hyperactivation of localized prefrontal cortex brain regions and dysfunction of functional connectivity during resting state, which are significantly associated with core clinical symptoms including positive, negative, and excitement/hostility symptoms.

Objective:To investigate the characteristics of resting-state mirror homotopic connectivity and the gray matter volume of brain in patients with neuropsychiatric systemic lupus erythematosus (NPSLE).Methods:From June 2020 to March 2023, a total of 35 NPSLE patients (NPSLE group) and 30 non-NPSLE patients (non-NPSLE group) were selected from Taizhou People's Hospital Affiliated to Nanjing Medical University, another 31 healthy volunteers were recruited as the healthy controls(HC group). All participants underwent resting-state functional magnetic resonance imaging (rs-fMRI) and mini-mental state examination (MMSE) assessments. The patients in NPSLE and non-NPSLE groups were additionally assessed using the fatigue scale for motor and cognitive functions (FSMC) and the hospital anxiety and depression scale (HADS).The DPABI V7.0 toolkit based on the MATLAB platform was used to preprocess the rs-fMRI data and calculate the voxel-mirrored homotopic connectivity(VMHC) indexes, and the differences in VMHC between groups were evaluated by covariance analysis in SPM12.0 software, and the VMHC values of brain regions with significant differences were extracted for further comparison between the two groups.Partial correlation analysis was performed to investigate the association between VMHC values and clinical parameters in NPSLE patients.The brain regions with significant differences between NPSLE patients and non-NPSLE patients were used as region of interest (ROI), and gray matter volumes within these ROIs were then calculated by VBM8 toolbox.Results:(1)There were statistically significant differences in the VMHC values of bilateral precentral gyrus, bilateral dorsolateral superior frontal gyrus, bilateral medial and paracingulate gyrus, bilateral parahippocampal gyrus, bilateral middle occipital gyrus, bilateral postcentral gyrus, and bilateral superior temporal gyrus among the 3 groups( F=11.246-14.102, all P<0.05). The NPSLE group exhibited significantly lower VMHC values in these regions compared to both the non-NPSLE group and HC group (all P<0.05), but there were no significant differences in these regions between the non-NPSLE group and HC group (all P>0.05).(2) The gray matter volumes of bilateral dorsolateral superior frontal gyrus(right: (0.57±0.11)mm 3, (0.65±0.08)mm 3, t=-3.409, P=0.001; left: (0.53±0.10)mm 3, (0.60±0.07)mm 3, t=-3.082, P=0.003), bilateral precentral gyrus(right: (0.32±0.06)mm 3, (0.35±0.04)mm 3, t=-2.044, P=0.045; left: (0.39±0.06)mm 3, (0.42±0.04)mm 3, t=-2.505, P=0.015), right medial and paracingulate gyrus((0.66±0.08)mm 3, (0.70±0.07)mm 3, t=-2.491, P=0.015) and left superior temporal gyrus((0.57±0.09)mm 3, (0.61±0.06)mm 3, t=- 2.344, P=0.022) in the NPSLE group were smaller than those of non-NPSLE group.(3)Correlation analysis showed that the VMHC value of dorsolateral superior frontal gyrus was positively correlated with IgA level in NPSLE patients ( r=0.353, P=0.047). Conclusion:Patients with NPSLE generally have decreased mirror homotopy functional connectivity in the cerebral hemispheres, accompanied by a decrease in gray matter volume in some brain regions, which can provide a certain neuroimaging basis for the pathogenesis of brain injury.

Objective:To report the nationwide surveillance results of pathogenic profiles and antimicrobial resistance patterns of Gram-positive bloodstream infections in China in 2023.Methods:The clinical isolates of Gram-posttive bacteria from blood cultures were collected in member hospitals of National Bloodstream Infection Bacterial Resistant Investigation Collaborative System（BRICS）during January to December 2023. Antimicrobial susceptibility testing was performed using the dilution method recommended by the Clinical and Laboratory Standards Institute（CLSI）. Statistical analyses were conducted using WHONET 5.6 and SPSS 25.0 software.Results:A total of 4 385 Gram-positive bacterial isolates were obtained from 60 participating center. The top five pathogens were Staphylococcus aureus（ n=1 544，35.2%），coagulase-negative Staphylococci（ n=1 441，32.9%）， Enterococcus faecium（ n=574，13.1%）， Enterococcus faecalis（ n=385，8.8%），and α-hemolytic Streptococci（ n=187，4.3%）. The prevalence of methicillin-resistant Staphylococcus aureus（MRSA）and methicillin-resistant coagulase-negative Staphylococci（MRCNS）was 26.2%（405/1 544）and 69.8%（1 006/1 441），respectively. Notably，all Staphylococci remained susceptible to glycopeptide or daptomycin. Staphylococcus aureus demonstrated excellent susceptibility（>97.0%）to cephalobiol，rifampicin，trimethoprim-sulfamethoxazole，linezolid，minocycline，tigecycline，and eravacycline. No Enterococcus exhibiting resistance to linezolid were detected. Glycopeptide resistance was uncommon but more frequent in Enterococcus faecium（resistance to vancomycin and teicoplanin：both 1.7%）compared to Enterococcus faecalis（both 0.3%）. The detection rates of MRSA and MRCNS exhibited significant regional variations across the country（ χ2=17.674 and 148.650，respectively，both P<0.001）. No vancomycin-resistant Enterococci were detected in central China. Institutional comparison demonstrated higher prevalence of MRSA（ χ2=14.111， P<0.001）and MRCNS（ χ2=4.828， P=0.028）in provincial hospitals than that in municipal hospitals. Socioeconomic analysis identified elevated detection rates of both MRSA（ χ2=18.986， P<0.001）and MRCNS（ χ2=4.477， P=0.034）in less developed regions（per capita GDP

Objective:To report the results of bacterial resistant investigation collaborative system（BRICS）on the distribution and antimicrobial resistance profile of clinical Gram-negative bacteria isolates from bloodstream infections in China in 2023，and provide reference for clinical tretment of bloodstream infections and prevention and control of bacterial resistance.Methods:The clinical isolates of Gram-negative bacteria from blood cultures in member hospitals of BRICS were collected during January 2023 to December 2023. Antibiotic susceptibility tests were conducted by agar dilution or broth dilution methods recommended by Clinical and Laboratory Standards Institute（CLSI）. WHONET 5.6 and SPSS 25.0 were used to analyze the data.Results:During the study period，11 492 strains of Gram-negative bacteria were collected from 60 hospitals，of which 10 098（87.9%）were Enterobacterales and 1 394（12.1%）were non-fermentative bacteria. The top 5 bacterial species were Escherichia coli（50.0%）， Klebsiella pneumoniae（26.1%）， Pseudomonas aeruginosa（5.1%）， Acinetobacter baumannii complex（5.0%）and Enterobacter cloacae complex（4.1%）. The ESBL-producing rates in Escherichia coli， Klebsiella pneumoniae and Proteus mirablilis were 46.8%（2 685/5 741），18.3%（549/2 999）and 44.0%（77/175），respectively. The prevalence of carbapenem-resistant Escherichia coli（CREC）and carbapenem-resistant Klebsiella pneumoniae（CRKP）were 1.3%（76/5 741）and 15.0%（450/2 999）；32.9%（25/76）and 78.0%（351/450）of CREC and CRKP were sensitive to ceftazidime/avibactam combination，respectively. 94.7%（72/76）and 90.2%（406/450）of CREC and CRKP were sensitive to aztreonam/avibactam combination. Furthermore，57.9%（44/76）and 79.1%（356/450）were sensitive to imipenem/relebactam combination. The prevalence of carbapenem-resistant Acinetobacter baumannii（CRAB）complex was 64.6%（370/573），while more than 80.0% of CRAB complex was sensitive to tigecycline，eravacycline and polymyxin B. The prevalence of carbapenem-resistant Pseudomonas aeruginosa（CRPA）was 17.0%（99/581）. There were differences in the composition ratio of Gram-negative bacteria in bloodstream infections and the prevalence of important Gram-negative bacteria resistance among different regions in China，with statistically significant differences in the prevalence of CREC，CRKP，CRPA and CRAB complex（ χ2=10.6，28.6，10.8 and 19.3， P<0.05）. The prevalence of ESBL-producing Escherichia coli， CREC，CRAB complex and CRKP were higher in provincial hospitals than those in municipal hospitals（ χ2=12.5，9.8，12.7 and 57.8，all P<0.01）. Conclusions:Gram-negative bacteria are the main pathogens causing bloodstream infections in China，and Escherichia coli is ranked in the top，while the trend of Klebsiella pneumoniae increases continuously with time. CRKP infection shows a slow upward trend，CREC infecton maintains a low prevalence level，and CRAB complex infection continues to exhibit a high prevalence rate. The composition and resistance patterns of pathogens causing bloodstream infections vary to some extent across different regions and levels of hospitals in China.