AIM:To explore the influence of exogenous hydrogen sulfide ( H2 S) on coagulation and fibrinoly-sis in ferric chloride ( FeCl3 )-induced mouse carotid artery thrombosis .METHODS: The mice were divided into sham control group, model group, different concentrations (12.5, 25 and 50μmol/kg) of sodium hydrosulfide (NaHS, H2S do-nor) groups and 30 mg/kg clopidogrel ( positive control ) group.Intraperitoneal injection of NaHS at different concentra-tions and oral administration of clopidogrel bisulfate were performed for 3 d prior to FeCl 3-induced carotid artery thrombo-sis.The frozen sections of the carotid artery were collected to perform HE staining , and the thrombus pattern and the chan-ges of vascular pathology were observed .The thrombus was weighed to calculate thrombosis inhibitory rate .Prothrombin time ( PT) , activated partial thromboplastin time ( APTT) , fibrinogen ( FIB) and fibrinogen degradation product ( FDP) in the mice were also measured by a coagulometer .The plasma levels of thromboxane B 2 ( TXB2 ) , 6-keto-prostaglandin F 1α(6-keto-PGF1α) and plasminogen activator inhibitor (PAI) were detected by ELISA.RESULTS: Compared with model group, NaHS dose-dependently inhibited the formation of carotid artery thrombus .NaHS treatment reduced the contents of TXB2 and PAI, and recovered 6-keto-PGF1αcontent in thrombosis model group .In NaHS treatment groups , 6-keto-PGF1α/TXB2 and thrombus weight was negatively correlated .NaHS treatment prolonged PT and APTT , reduced the content of FIB, but increased the level of FDP in thrombosis model group .CONCLUSION:Hydrogen sulfide prevents FeCl 3-induced carotid artery thrombosis by inhibiting coagulation and activating fibrinolysis .

Objective To investigate the dynamic characteristic changes of gastrointestinal mucosa and its relationship with disease progression in rats with acute cerebral infarction. Methods Fifty-six male Wistar rats were selected as the study subjects, and they were divided into three groups: normal control, sham operation and cerebral infarction model groups by random number table method. The middle cerebral artery occlusion (MCAO) model was prepared by the modified Longa thread embolic method. The levels of gastrin (GAS) were monitored in each group after modeling for 24 hours, 4 days and 7 days; after the rats were killed, the sections of gastric antrum and small intestine were taken and stained with hematoxylin-eosin (HE) staining method, the histopathological changes of gastric and small intestinal mucosa were observed under light microscope, in the mean time the gastric and small intestinal mucosal pathological scores were also performed, and the differences of pathological scores among the three groups were compared. Results There were no statistical significant differences in GAS, gastrointestinal mucosa and small intestinal mucosal pathological scores between the normal control group and sham operation group at each time point (all P > 0.05); the GAS level in cerebral infarction model group was decreased gradually with time prolongation, reaching the lowest level 7 days after modeling, but the GAS level in cerebral infarction model group was significantly higher than that in normal group and shamoperation group (ng/L: 205.02±7.68 vs. 130.51±8.03, 145.29±7.68, both P < 0.05). The pathological scores of gastrointestinal mucosa and small intestinal mucosa in the cerebral infarction model group were increased first and then decreased with time prolongation, peaked on 4th day and decreased significantly on 7th day, the pathological scores of gastrointestinal mucosa and small intestinal mucosa in the cerebral infarction model group at each time point were significantly higher than those in the normal control group and sham-operated group (gastric mucosal pathological score: 82.50±2.95 vs. 21.38±1.57, 36.10±3.41; small intestinal mucosal pathological score: 62.00±2.78 vs. 18.25±1.39, 25.55±1.75, all P < 0.05). Under light microscopy, the normal control group showed complete normal morphological appearance, normal structure, orderly arrangement of villi and no infiltration of inflammatory cells; in shamoperation group, inflammatory cells infiltrated the lamina propria at each time point, and there were villi slightly uneven, enlarged stroma, congestion, edema occasionally seen and no obvious ulcer; in cerebral infarction model group, the various layers of gastrointestinal mucosal were not very clear, the glands were arranged irregularly and the capillaries dilated, and in part of tissues, congestion, hemorrhage, edema and inflammatory cell infiltration were seen obviously. Conclusion The injury of gastrointestinal mucosa in acute stage of cerebral infarction should be related to the stress stimulation and disease progress of cerebral infarction itself, not due to the abnormal secretion of GAS.

Objective: To evaluate the clinical effect of clear aligners in the anterior region in non-extraction cases by establishing a three-dimensional model of crown-root fusion to guide clinical application. Methods: Eleven patients visiting the orthodontic department of Xuzhou Stomatological Hospital from December 2020 to December 2021 were collected, and the orthodontic plan was designed using Maestro 3D Dental Studio scheduling software to obtain the expected three-dimensional model of the patient's orthodontic treatment result. CBCT, intraoral scan, and 3D reconstruction software were used to create a postoperative model of the patient. The crown and root data were aligned in Geomagic Studio 2014, and differences in torque and axial inclination between the actual model after treatment and the predicted model of the anterior teeth before treatment were compared in 3-matic. Results: The actual torque angles of the anterior teeth were all smaller than the predicted angles before treatment, with the highest realization rate of 77.55% for lateral incisors and the lowest of 60.70% for central incisors; the actual axial inclination angles of the anterior teeth were also smaller than the predicted angles before treatment, with the highest realization rate of 81.49% for central incisors and the lowest of 74.95% for cuspids. Conclusion A digital model of crown-root integration based on a combination of 3D reconstruction and intraoral scanning techniques is advantageous in assessing the efficacy of clear aligners. In non-extraction cases with clear aligner, the efficiency of movement is higher for small areas of the anterior region.

Objective To compare the efficacy, safety, and survivability of TCbHP versus AC-THP in the neoadjuvant therapy of HER2-positive breast cancer in real-world. Methods Clinical data of patients with HER2 positive breast cancer, who have received TCbHP or AC-THP as neoadjuvant therapy and completed surgery in 11 third-class hospitals in various cities of Hebei Province, were retrospectively collected.The total pathological complete remission (tpCR) rate, the incidence of grade 3 or higher adverse reactions and the completion rate of the given approaches were compared. Results A total of 110 cases were collected, including 78 cases in the TCbHP group and 32 cases in the AC-THP group.The tpCR rate of the TCbHP group was higher than that of the AC-THP group, but the difference was not statistically significant (64.10% vs. 56.25%, P=0.441).No significant difference was found in the breast pathologic complete response (bpCR) and axillary pathologic complete response (apCR) rates between the TCbHP group and the AC-THP group (70.51% vs. 56.25%, P=0.150;78.21% vs. 84.38%, P=0.462).Exploratory analysis revealed that the tpCR rate of the TCbHP group was significantly higher than that of the AC-THP group in patients with HR-positive breast cancer (51.11% vs. 22.22%, P=0.036).As for the patients with HR-negative breast cancer, the tpCR rate of the AC-THP group tended to be higher than that of the TCbHP group (100% vs. 81.82%, P=0.088).The incidence of grade 3 or higher adverse reactions in the TCbHP group was slightly higher than that in the AC-THP group (12.82% vs. 9.38%, P=0.753).No deaths occurred in the whole group.Moreover, no significant difference was observed in the completion rate of the given approaches between the TCbHP group and the AC-THP group (92.31% vs. 90.63%, P=0.718). Conclusion In real-world clinical practice, the neoadjuvant therapy of TCbHP and AC-THP are effective, safe, and well tolerated among patients with HER2-positive breast cancer.The tpCR rate between the two approaches was not significantly different.The AC-THP regimen could also be considered as one of the optimal regimens for HER2-positive breast cancer in neoadjuvant therapy.

Objective:To investigate the bacterial isolate distribution and differences of antimicrobial resistance among community-acquired infection，healthcare-associated infection and hospital-acquired infection.Methods:Bacterial isolates from clinical specimens were collected in Xi'an No.1 Hospital between January 2019 and December 2023 and categorized into community-acquired infection（CAI），healthcare-associated infection（HCAI）and hospital-acquired infection（HAI）. The bacterial distribution and antimicrobial resistance differences among the three groups were compared. Data were analyzed with SPSS 22.0 statistical software.Results:A total of 9 762 bacterial strains were collected：2 258 strains（23.1%）in CAI group，763 strains（7.8%）in HCAI group and 6 741 strains（69.1%）in HAI group. In HCAI group，the detection rate of Escherichia coli was lower than that in CAI group，and higher than that in HAI group（ χ2=106.335 and 69.603，both P<0.001）. The detection rates of Pseudomonas aeruginosa and Acinetobacter baumannii in HCAI group were higher than those in CAI group（ χ2=35.749 and 65.098，both P<0.001），and lower than those in HAI group（ χ2=26.350 and 115.885，both P<0.001）. The detection rate of Staphylococcus aureus in HCAI group was higher than that in CAI and HAI groups（ χ2=5.745 and 13.992，both P<0.05）. In HCAI group，the detection rate of methicillin-resistant Staphylococcus aureus（MRSA）was lower than that in HAI group（ χ2=69.005， P<0.001）；and MRSA in HCAI demonstrated higher resistance to levofloxacin and moxifloxacin than that in CAI group（ χ2=13.634 and 13.083，both P<0.001），and lower than that in HAI group（ χ2=17.927 and 21.937，both P<0.001）. The resistance rates of Escherichia coli to piperacillin/tazobactam，ceftriaxone，ceftazidime，cefoperazone/sulbactam，ciprofloxacin and levofloxacin in HCAI group were higher than those in CAI group，and the resistance rates to cefoperazone/sulbactam，meropenem，imipenem and amikacin in HCAI group were lower than those in HAI group（all P<0.05）. For Klebsiella pneumoniae，the resistance rate in HCAI group was higher than that in CAI group and lower than that in HAI group to all antibacterial agents，except for nitrofurantoin（all P<0.01）. For Pseudomonas aeruginosa，the resistance rate in HCAI group was higher than that in CAI group（ χ2=14.107，14.819，16.822 and 15.998，all P<0.001）and lower than that in HAI group（ χ2=7.821，4.671，18.070 and 17.552，all P<0.05）to piperacillin/tazobactam，cefoperazone/sulbactam，meropenem and imipenem. Acinetobacter baumannii in HCAI group demonstrated lower resistance to piperacillin/tazobactam，meropenem，imipenem，ciprofloxacin and levofloxacin than that in HAI group（ χ2=32.263，31.526，42.417，25.277 and 6.798，all P<0.01）. Conclusion:The bacterial distribution and antimicrobial resistance in HCAI group are different from CAI and HAI groups. It is recommended to carry out precise antibiotic resistance surveillance in different categories of infections for rational antibiotic use.

Objective:Gastric cancer in adolescents is rare, with only a few cases reported in the literature. The purpose of this study is to investigate the clinicopathological features and prognostic factors of gastric cancer in adolescents aged 10-24 years.Methods:A case-controlled study was performed. The clinicopathological data of gastric cancer patients aged 10-24 years who were treated at the First Medical Center of Chinese PLA General Hospital from February 2000 to February 2017 were retrospectively collected and compared with those patients over 40 years old at the same period, which were randomly selected in a ratio of 1:2. All the patients were followed up until June 2019 and Cox proportional hazard model was used to analyze prognostic factors in the adolescent patients.Results:A total of 63 adolescent gastric cancer patients (0.4% of all 14 794 gastric cancer patients) were enrolled, including 31 males (49.2%) and 32 females (50.8%), with a mean body mass index of (19.5±4.3) kg/m 2. Before diagnosis, Only 35 cases (55.6%) had warning symptoms such as weight loss, ascites, obstruction, hematemesis, black stool, etc.; 5 cases (7.9%) had a family history of gastrointestinal tumor. The median duration of symptoms before diagnosis was 3 months. At diagnosis, 58 cases (92.1%) were poorly differentiated, 57 cases (90.5%) were T3-4 stage, 19 cases (30.2%) were signet ring cell cancer or mucous adenocarcinoma, 57 cases (90.5%) had lymph node metastasis, and 36 cases (57.1%) had distant metastasis. Twenty-nine patients (46.0%) underwent radical surgery, 12 patients underwent palliative surgery, 5 patients underwent exploratory laparotomy, 17 patients were unable to operate due to late stage. Of 56 cases (88.9%) with TNM stage Ⅲ-Ⅳ, 51 patients (81.0%) received chemotherapy. Of the 126 patients over 40 years old, 98 cases (77.8%) were male and 28 cases (22.2%) were female, and the mean body mass index was (23.8±3.2) kg/m 2. There were 60 cases (47.6%) with low differentiation, 90 cases (71.4%) with T3-4, 16 cases (12.7%) with signet ring cell cancer and mucous cell cancer, 79 cases (62.7%) with lymph node metastasis, and 12 cases (9.5%) with distant metastasis. A total of 115 cases (91.3%) underwent radical surgery. Of 74 cases (58.7%) with TNM stage Ⅲ-Ⅳ, 67 cases received (53.2%) chemotherapy. The 63 adolescent gastric cancer patients had lower body mass index, and higher proportion in female, poorly differentiation, signet ring cell cancer and mucous cell cancer, T3-4 stage, lymph node metastasis, distant metastasis, TNM stage Ⅲ-Ⅳ and receiving chemotherapy compared with 126 gastric cancer patients over 40 years old (all P<0.05). Among the 63 adolescent gastric cancer patients, 52 cases (82.5%) were followed up with median follow-up time of 72.1 (36.1, 100.8) months, and the median survival time was 10.4 months (95% CI: 6.5-15.1). The 1-year, 3-year and 5-year survival rates were 44.2%, 25.0% and 18.0%, respectively. Univariate analysis showed that the depth of tumor invasion (HR=7.15, 95% CI:1.71-29.89, P=0.007), lymph node metastasis (HR=6.00, 95% CI:1.42 - 25.42, P=0.015), distant metastasis (HR=7.25, 95% CI: 3.25 - 16.18, P<0.001), TNM stage (HR=5.49, 95% CI: 1.67-18.12, P=0.005) and tumor resection (HR=0.18, 95% CI: 0.09-0.37, P<0.001) were the risk factors affecting the prognosis of adolescent gastric cancer patients. Multivariate survival analysis showed that distant metastasis was an independent factor for gastric cancer survival in adolescents (HR=3.67, 95% CI: 1.32-10.19, P=0.012). Conclusions:Gastric cancer in adolescents is insidious and progresses rapidly. Most of them are in the advanced stage at diagnosis and have low rate of radical excision.

Objective:Gastric cancer in adolescents is rare, with only a few cases reported in the literature. The purpose of this study is to investigate the clinicopathological features and prognostic factors of gastric cancer in adolescents aged 10-24 years.Methods:A case-controlled study was performed. The clinicopathological data of gastric cancer patients aged 10-24 years who were treated at the First Medical Center of Chinese PLA General Hospital from February 2000 to February 2017 were retrospectively collected and compared with those patients over 40 years old at the same period, which were randomly selected in a ratio of 1:2. All the patients were followed up until June 2019 and Cox proportional hazard model was used to analyze prognostic factors in the adolescent patients.Results:A total of 63 adolescent gastric cancer patients (0.4% of all 14 794 gastric cancer patients) were enrolled, including 31 males (49.2%) and 32 females (50.8%), with a mean body mass index of (19.5±4.3) kg/m 2. Before diagnosis, Only 35 cases (55.6%) had warning symptoms such as weight loss, ascites, obstruction, hematemesis, black stool, etc.; 5 cases (7.9%) had a family history of gastrointestinal tumor. The median duration of symptoms before diagnosis was 3 months. At diagnosis, 58 cases (92.1%) were poorly differentiated, 57 cases (90.5%) were T3-4 stage, 19 cases (30.2%) were signet ring cell cancer or mucous adenocarcinoma, 57 cases (90.5%) had lymph node metastasis, and 36 cases (57.1%) had distant metastasis. Twenty-nine patients (46.0%) underwent radical surgery, 12 patients underwent palliative surgery, 5 patients underwent exploratory laparotomy, 17 patients were unable to operate due to late stage. Of 56 cases (88.9%) with TNM stage Ⅲ-Ⅳ, 51 patients (81.0%) received chemotherapy. Of the 126 patients over 40 years old, 98 cases (77.8%) were male and 28 cases (22.2%) were female, and the mean body mass index was (23.8±3.2) kg/m 2. There were 60 cases (47.6%) with low differentiation, 90 cases (71.4%) with T3-4, 16 cases (12.7%) with signet ring cell cancer and mucous cell cancer, 79 cases (62.7%) with lymph node metastasis, and 12 cases (9.5%) with distant metastasis. A total of 115 cases (91.3%) underwent radical surgery. Of 74 cases (58.7%) with TNM stage Ⅲ-Ⅳ, 67 cases received (53.2%) chemotherapy. The 63 adolescent gastric cancer patients had lower body mass index, and higher proportion in female, poorly differentiation, signet ring cell cancer and mucous cell cancer, T3-4 stage, lymph node metastasis, distant metastasis, TNM stage Ⅲ-Ⅳ and receiving chemotherapy compared with 126 gastric cancer patients over 40 years old (all P<0.05). Among the 63 adolescent gastric cancer patients, 52 cases (82.5%) were followed up with median follow-up time of 72.1 (36.1, 100.8) months, and the median survival time was 10.4 months (95% CI: 6.5-15.1). The 1-year, 3-year and 5-year survival rates were 44.2%, 25.0% and 18.0%, respectively. Univariate analysis showed that the depth of tumor invasion (HR=7.15, 95% CI:1.71-29.89, P=0.007), lymph node metastasis (HR=6.00, 95% CI:1.42 - 25.42, P=0.015), distant metastasis (HR=7.25, 95% CI: 3.25 - 16.18, P<0.001), TNM stage (HR=5.49, 95% CI: 1.67-18.12, P=0.005) and tumor resection (HR=0.18, 95% CI: 0.09-0.37, P<0.001) were the risk factors affecting the prognosis of adolescent gastric cancer patients. Multivariate survival analysis showed that distant metastasis was an independent factor for gastric cancer survival in adolescents (HR=3.67, 95% CI: 1.32-10.19, P=0.012). Conclusions:Gastric cancer in adolescents is insidious and progresses rapidly. Most of them are in the advanced stage at diagnosis and have low rate of radical excision.

ObjectiveBased on ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry（UPLC-Q-TOF-MS）， network pharmacology and pharmacodynamics， to investigate the pharmacodynamic material basis and mechanism of Hei Xiaoyaosan in improving learning and memory ability of insomnia rats. MethodUPLC-Q-TOF-MS was used to characterize the chemical constituents of Hei Xiaoyaosan. Network pharmacology was applied to construct the network of active ingredients-intersecting targets-pathways， and molecular docking was performed on key ingredients and core targets. Sixty 8-week-old male SD rats were selected and randomly divided into blank group， model group， Hei Xiaoyaosan low， medium， and high dose groups（3.82， 7.65， 15.30 g·kg^-1）， and zolpidem tartrate group（0.5 mg·kg^-1）， with 10 rats in each group. Except for the blank group， the insomnia model was induced by intraperitoneal injection of p-chlorophenylalanine（PCPA） for 4 consecutive days. Rats in each dosing group were administered the corresponding dose by gavage， once a day for 14 consecutive days. Morris water maze test was utilized to assess the learning and memory ability of rats， transmission electron microscopy was employed to examine the ultrastructure of hippocampal synapses， enzyme-linked immunosorbent assay（ELISA） was conducted to analyze the levels of 5-hydroxytryptamine（5-HT）， interleukin-6（IL-6）， and tumor necrosis factor-α（TNF-α） in hippocampal tissues， and Western blot was performed to detect the expression levels of tumor suppressor protein p53（TP53）， rat sarcoma virus（RAS）， epidermal growth factor receptor（EGFR）， cyclic adenosine monophosphate（cAMP）-response element binding protein（CREB） binding protein（CREBBP）， glycogen synthase kinase-3β（GSK-3β）， protein kinase B1（Akt1）， nitric oxide synthase 1（NOS1）， phosphorylated（p）-Akt1， and p-GSK-3β in hippocampal tissues. Additionally， real-time fluorescence quantitative polymerase chain reaction（Real-time PCR） was used to assess the mRNA expression levels of TP53， RAS， EGFR， CREBBP， GSK-3β， Akt1 and NOS1. ResultA total of 176 components were identified in Hei Xiaoyaosan， mainly flavonoids， triterpene saponins， phenylpropanoids and other compounds. Network pharmacological analysis revealed that TP53， V-Ha-Ras Harvey Rat sarcoma viral oncogene homolog（HRAS）， neuroblastoma sarcoma viral oncogene homolog（NRAS）， EGFR， CREBBP， GSK-3β， Akt1 and NOS1 were the key targets of Hei Xiaoyaosan in treating insomnia. The core targets were predominantly associated with cAMP， RAS， Ras-associated protein 1（Rap1）， advanced glycation end products（AGE）/receptor for AGE（RAGE）， and EGFR signaling pathways， and the key active ingredients of Hei Xiaoyaosan in treating insomnia were 8-shogaol， ligustilide F， 6-gingerol， levistilide A and senkyunolide E. Animal experiment results demonstrated that Hei Xiaoyaosan medium and high dose groups significantly increased body weight， shortened sleep latency and prolonged sleep duration in insomnia rats（P<0.01）， significantly decreased escape latency and increased platform crossing frequency（P<0.01）， and improved the pathological changes of hippocampal synaptic ultrastructure. Meanwhile， the two groups could significantly elevate 5-HT level， Akt1 mRNA expression， Akt1 and p-Akt1 protein expression（P<0.01）， reduce inflammatory factor levels（P<0.01）， and down-regulate protein expression levels of TP53， RAS， NOS1， EGFR， CREBBP， GSK-3β and p-GSK-3β（P<0.01）， as well as mRNA expression levels of TP53， RAS， NOS1， EGFR， CREBBP and GSK-3β in hippocampal tissues（P<0.01）. ConclusionThis study determined that the five key active ingredients（8-shogaol， ligustilide F， 6-gingerol， levistilide A and senkyunolide E） in Hei Xiaoyaosan may improve the learning and memory ability of insomnia rats by regulating signaling pathways such as cAMP， RAS， and EGFR， providing an important reference for its mechanism research and clinical application.

Objective:To investigate the bacterial composition and antimicrobial resistance profile of clinical isolates from bloodstream infections in China.Methods:The clinical bacterial strains isolated from blood culture were collected during January 2020 to December 2020 in member hospitals of Blood Bacterial Resistant Investigation Collaborative System (BRICS). Antibiotic susceptibility tests were conducted by agar dilution or broth dilution methods recommended by Clinical Laboratory Standards Institute(CLSI, USA). WHONET 5.6 was used to analyze data.Results:During the study period, 10 043 bacterial strains were collected from 54 hospitals, of which 2 664 (26.5%) were Gram-positive bacteria and 7 379 (73.5%) were Gram-negative bacteria. The top 10 bacterial species were Escherichia coli (38.6%), Klebsiella pneumoniae (18.4%), Staphylococcus aureus (9.9%), coagulase-negative Staphylococci (7.5%), Pseudomonas aeruginosa (3.9%), Enterococcus faecium (3.3%), Enterobacter cloacae (2.8%), Enterococcus faecalis (2.6%), Acinetobacter baumannii (2.4%) and Klebsiella spp (1.8%). The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus aureus were 27.6% and 74.4%, respectively. No glycopeptide- and daptomycin-resistant Staphylococci were detected. More than 95% of Staphylococcus aureus were sensitive to rifampicin and SMZco. No vancomycin-resistant Enterococci strains were detected. Extended spectrum β-lactamase (ESBL) producing Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis were 48.4%, 23.6% and 36.1%, respectively. The prevalence rates of carbapenem-resistance in Escherichia coli and Klebsiella pneumoniae were 2.3% and 16.1%, respectively; 9.6% of carbapenem-resistant Klebsiella pneumoniae strains were resistant to ceftazidime/avibactam combination. The prevalence rate of carbapenem-resistance in Acinetobacter baumannii was 60.0%, while polymyxin and tigecycline showed good activity against Acinetobacter baumannii. The prevalence rate of carbapenem-resistance of Pseudomonas aeruginosa was 23.2%. Conclusions:The surveillance results in 2020 showed that the main pathogens of bloodstream infection in China were gram-negative bacteria, while Escherichia coli was the most common pathogen, and ESBL-producing strains declined while carbapenem-resistant Klebsiella pneumoniae kept on high level. The proportion and the prevalence of carbapenem-resistant Pseudomonas aeruginosa were on the rise slowly. On the other side, the MRSA incidence got lower in China, while the overall prevalence of vancomycin-resistant Enterococci was low.

Objective:To report the results of national surveillance on the distribution and antimicrobial resistance profile of clinical bacterial isolates from bloodstream infections in China in 2021.Methods:The clinical bacterial strains isolated from blood culture from member hospitals of Blood Bacterial Resistant Investigation Collaborative System (BRICS) were collected during January 2021 to December 2021. Antibiotic susceptibility tests were conducted by agar dilution or broth dilution methods recommended by Clinical Laboratory Standards Institute (CLSI). WHONET 5.6 was used to analyze data.Results:During the study period, 11 013 bacterial strains were collected from 51 hospitals, of which 2 782 (25.3%) were Gram-positive bacteria and 8 231 (74.7%) were Gram-negative bacteria. The top 10 bacterial species were Escherichia coli (37.6%), Klebsiella pneumoniae (18.9%), Staphylococcus aureus (9.8%), coagulase-negative Staphylococci (6.3%), Pseudomonas aeruginosa (3.6%), Enterococcus faecium (3.6%), Acinetobacter baumannii (2.8%), Enterococcus faecalis (2.7%), Enterobacter cloacae (2.5%) and Klebsiella spp (2.1%). The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus aureus were 25.3% and 76.8%, respectively. No glycopeptide- and daptomycin-resistant Staphylococci was detected; more than 95.0% of Staphylococcus aureus were sensitive to ceftobiprole. No vancomycin-resistant Enterococci strains were detected. The rates of extended spectrum B-lactamase (ESBL)-producing isolated in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis were 49.6%, 25.5% and 39.0%, respectively. The prevalence rates of carbapenem-resistance in Escherichia coli and Klebsiella pneumoniae were 2.2% and 15.8%, respectively; 7.9% of carbapenem-resistant Klebsiella pneumoniae was resistant to ceftazidime/avibactam combination. Ceftobiprole demonstrated excellent activity against non-ESBL-producing Escherichia coli and Klebsiella pneumoniae. Aztreonam/avibactam was highly active against carbapenem-resistant Escherichia coli and Klebsiella pneumoniae. The prevalence rate of carbapenem-resistance in Acinetobacter baumannii was 60.0%, while polymyxin and tigecycline showed good activity against Acinetobacter baumannii (5.5% and 4.5%). The prevalence of carbapenem-resistance in Pseudomonas aeruginosa was 18.9%. Conclusions:The BRICS surveillance results in 2021 shows that the main pathogens of blood stream infection in China are gram-negative bacteria, in which Escherichia coli is the most common. The MRSA incidence shows a further decreasing trend in China and the overall prevalence of vancomycin-resistant Enterococci is low. The prevalence of Carbapenem-resistant Klebsiella pneumoniae is still on a high level, but the trend is downwards.