Objective To compare the success rate, time of tumor formation and number of tumors in three methods of tumor transplantation, in order to seek an ideal animal model for molecular imaging study. Methods Forty-eight BALB/C-nu/nu nude mice were randomly divided into three groups (each n=16). Tumor tissue mass of 2 mm3 was injected into subcutaneous of nude mice in experiment group. Tumor tissue mass of 1 mm3 was applied in control group 1. Tumor cells suspension liquid was injected into subcutaneous of nude mice in control group 2. The tumor formation rate, the time of tumor formation and the number of tumors were observed. MRI scanning were performed 3-6 weeks after implantation. Results The rate of tumor formation of three groups was 93.75%, 75.00% and 43.75%, respectively. The time of tumor formation was (21.7±2.4), (29.8±2.9) and (34.6±3.9) days, respectively. The rate of solitary nodule implanted tumor was 93.33% in experiment group, higher than that in control group 1 (75.00%) and control group 2 (14.29%). The tumors were hypointense on T1WI and hyperintense on T2WI. Conclusion Transplantation 2 mm3 tumor tissue mass is effective to set up the subcutaneous implanted tumor models with a high success rate of tumor formation, a short time of tumor formation and high rate of solitary tumors, being suitable for the study of molecular imaging. The models can undertake conventional T1WI, T2WI and T2-mapping imaging, and the imaging qualities are good.

Objective:To analyze the bacteria spectrum and antimicrobial resistance profile of bacterial meningitis among children in Baoji.Methods:Based on the acute meningeal and encephalitis syndrome surveillance project, cerebrospinal fluid samples were collected from 774 cases of bacterial meningitis in Baoji Municipal Maternal and Health Hospital from January 2016 to December 2023. Bacterial culture and drug sensitivity test were carried out.Results:A total of 105 positive strains were isolated with the detection rate of 13.57% (105/774). Among them, gram-positive strains accounted for 80.00% (84/105), mainly including Staphylococcus epidermidis, Staphylococcus hominis, and Streptococcus pneumoniae. Gram-negative bacteria accounted for 20.00% (21/105), and the predominant strain was Escherichia coli. Pathogenic bacteria were detected in every month of the year, with two peaks in March and September (26.67%, 28/105). The youngest was infected 20 min after birth, and the oldest was nine years old. There were statistical differences in the detection rates among different age groups (χ 2=35.91, P<0.05). The positive rate in the toddler group was lower than that in the infant group, the pre-school age group and the school age group, respectively (χ 2=15.01, 7.09, and 10.08; all P<0.05). There was no statistical difference between the toddler group and the neonate group (χ 2=1.60, P>0.05). The strains detected in the neonate group accounted for 44.76% (47/105), mainly including Escherichia coli and Staphylococcus epidermidis; the strains in the infant group accounted for 26.67% (28/105), mainly including Streptococcus pneumoniae; the strains in the toddler group accounted for 3.81% (4/105), mainly including Staphylococcus epidermidis; the strains in the pre-school age accounted for 11.43% (12/105), mainly including Staphylococcus epidermidis; the strains in the school age group accounted for 13.33% (14/105), mainly including Streptococcus pneumoniae. The results of drug sensitivity test showed that the resistance rates of Staphylococcus epidermidis to ampicillin/sulbactam, clindamycin, and levofloxacin were 47.06% (8/17), 41.18% (7/17), and 23.53% (4/17), respectively. Staphylococcus epidermidis strains were sensitive to vancomycin and linezolid. All of the Streptococcus pneumoniae strains were resistant to erythromycin and clindamycin, but sensitive to vancomycin and linezolid. The resistance rate of Streptococcus pneumoniae to penicillin was 69.23% (9/13). The resistance rates of Escherichia coli to ampicillin, levofloxacin, ceftriaxone, and cefotaxime were 66.67% (8/12), 41.67% (5/12), 33.33% (4/12), and 41.67% (5/12), respectively, but they were sensitive to ampicillin/sulbactam, cefoperazone/sulbactam, amikacin, and meropenem. Streptococcus agalactis strains were sensitive to penicillin, linezolid, and vancomycin, but resistant to erythromycin, clindamycin, ampicillin, and levofloxacin. Conclusions:The main pathogens causing bacterial meningitis in Baoji city are Staphylococcus epidermidis, Streptococcus pneumoniae, and Escherichia coli. The distribution of bacteria is varied in different age groups. The diagnosis and treatment of bacterial meningitis should be made based on the bacterial spectrum characteristics and the results of antimicrobial resistance profile.

In recent years, the burden of chronic and non-communicable diseases has become more serious in China, and the area specific heterogeneities are obvious. Southwestern China is a vast area with many ethnic groups and distinctive characteristics. While the local health resources are relatively limited, and the prevention and control of high-risk chronic diseases is challenging. In order to comprehensively analyze the disease distribution and potential exposure risk in populations in different ethnic groups in southwestern China, a natural population cohort study in southwestern China (multi-ethnic cohort study) was launched in 2017 with the support of the "Precision Medicine Research" Key Project, National Key Research and Development Program of China. At present, this cohort consists of 119 556 participants aged 30-79 years (18-79 years in Tibet Autonomous Region) and pregnant women in five provinces (municipality), i.e. Sichuan, Yunnan, Guizhou, Tibet, and Chongqing. A large-scale, multi-ethnic, high-quality natural population cohort with biobank has been established. The study has made some significant progress in the evaluation of the health impact of environmental and lifestyle factors in southwestern China and developed an innovative model for large cohort establishment in less developed areas. The results of this study can provide a reference for the establishment and research of large natural population cohorts in complex geographical scenarios, and serve as high-quality basic resources for China's precision medicine research and disease prevention and control decisions in areas with multi-ethnic groups.