Selection markers are essential tools in gene editing, the utility of such systems is inherently constrained by species-specific limitations, governed by divergent host genetic backgrounds and metabolic compatibility. To address this limitation, we leveraged the CRISPR/Cas9 system to develop a universal counter-selection tool. We designed and introduced an sgRNA expression cassettes as counter-selection markers, which directs the Cas9 protein to target and cleave genomic DNA, allowing for the selection of the strains where the sgRNA expression cassette has been replaced. Optimized to target multiple copy sites with sgRNA, this system significantly enhances cell lethality, boosting counter-selection efficiency to over 85.00%. This counter-selection tool is not limited to single strains and is suitable for various scenarios, including multi-copy plasmid assembly and plasmid editing, demonstrating broad application potential.
CRISPR-Cas Systems/genetics* ; Gene Editing/methods* ; RNA, Guide, CRISPR-Cas Systems/genetics* ; Plasmids/genetics*

Objective:To investigate the iodine nutrition status of children aged 8 - 10 and pregnant women in Xining City, Qinghai Province.Methods:From 2019 to 2021, a stratified cluster sampling method was used to divide 7 counties (districts) under the jurisdiction of Xining City, Qinghai Province into 5 sampling areas according to east, west, south, north, and center each year. One township (town, street) was selected from each area. Forty non boarding students aged 8 to 10 from each primary school (half male and half female, age balanced) and 20 pregnant women from each township (town, street) location were selected to collect edible salt samples at home and a random urine sample to measure salt iodine and urinary iodine level. B-ultrasound was used to measure thyroid volume in children and the goiter rate was calculated.Results:A total of 6 534 samples of household edible salt were collected from children and pregnant women, with an average salt iodine concentration of 25.58 mg/kg. The coverage rate of iodized salt was 97.50% (6 371/6 534), and the qualified iodized salt consumption rate was 89.46% (5 845/6 534). A total of 4 362 urine samples were collected from children, with a median urinary iodine level of 183.10 μg/L. The difference between different years was statistically significant ( H = 20.27, P < 0.001). A total of 2 169 urine samples were collected from pregnant women, with a median urinary iodine level of 168.90 μg/L. The difference between different years was statistically significant ( H = 107.09, P < 0.001). A total of 3 336 cases of thyroid gland examination were conducted in children, including 33 cases of thyroid enlargement, with a goiter rate of 0.99%. There was a statistically significant difference between different years (χ 2 = 15.00, P < 0.001). Conclusion:From 2019 to 2021, children aged 8 to 10 and pregnant women in Xining City are at an appropriate level of iodine, and the achievements in prevention and treatment of iodine deficiency disorders still need to be continuously consolidated.

Objective:To investigate the iodine nutrition status of children aged 8 - 10 and pregnant women in Xining City, Qinghai Province.Methods:From 2019 to 2021, a stratified cluster sampling method was used to divide 7 counties (districts) under the jurisdiction of Xining City, Qinghai Province into 5 sampling areas according to east, west, south, north, and center each year. One township (town, street) was selected from each area. Forty non boarding students aged 8 to 10 from each primary school (half male and half female, age balanced) and 20 pregnant women from each township (town, street) location were selected to collect edible salt samples at home and a random urine sample to measure salt iodine and urinary iodine level. B-ultrasound was used to measure thyroid volume in children and the goiter rate was calculated.Results:A total of 6 534 samples of household edible salt were collected from children and pregnant women, with an average salt iodine concentration of 25.58 mg/kg. The coverage rate of iodized salt was 97.50% (6 371/6 534), and the qualified iodized salt consumption rate was 89.46% (5 845/6 534). A total of 4 362 urine samples were collected from children, with a median urinary iodine level of 183.10 μg/L. The difference between different years was statistically significant ( H = 20.27, P < 0.001). A total of 2 169 urine samples were collected from pregnant women, with a median urinary iodine level of 168.90 μg/L. The difference between different years was statistically significant ( H = 107.09, P < 0.001). A total of 3 336 cases of thyroid gland examination were conducted in children, including 33 cases of thyroid enlargement, with a goiter rate of 0.99%. There was a statistically significant difference between different years (χ 2 = 15.00, P < 0.001). Conclusion:From 2019 to 2021, children aged 8 to 10 and pregnant women in Xining City are at an appropriate level of iodine, and the achievements in prevention and treatment of iodine deficiency disorders still need to be continuously consolidated.

To understand the pathogenicity,virulence genes,drug resistance genes,and drug resistance of Staphylococcus aureus isolated from yaks in some areas of Lhasa and Nagqu City,55 yak nasal swab samples were analyzed for S.aureus in this study.The cocci were isolated and identified,and the carriage of virulence genes and drug resistance genes,as well as the pathogenicity and drug sensitivity of the isolated S.aureus strains,were detected with PCR,artificially infected mice,and the K-B drug susceptibility disk method.Seven strains of S.aureus were isolated from the 55 yak nasal swab samples,with an iso-lation rate of 12.73％.The isolated strains were all pathogenic to mice,with a fatality rate exceeding 60％.These seven strains of S.aureus carried three drug resistance genes(tetM,tet,and mecA)and six virulence genes(seb,sec,clfA,hla,hlb,and nuc).The detection rate of the three drug resistance genes was 100％,whereas the detection rate of the six virulence genes in the isolates ranged from 83.33％to 100％.The resistance rates of the isolated strains to penicillin,ampicillin,and cotrimox-azole reached 85.71％-100％,whereas the resistance rates to tetracycline and ceftazidime were both 28.57％.Thus,yaks in Lhasa and Nagqu cities were found to be infected by S.aureus strains carrying various drug-resistance genes and virulence genes.These strains were highly pathogenic and showed sensi-tivity to most antibacterial drugs.These findings may serve as a reference for treating S.aureus infection in yaks in the cities of Lhasa and Nagqu.

AIM: To investigate the effects of hypobaric hypoxia in plateau on tear indexes and related anatomical structures in rabbits.METHODS: A total of 18 healthy New Zealand rabbits were selected and randomly divided into plateau group and control group, with 9 rabbits(18 eyes)in each group. The plateau group was housed in the Simulated Climate Cabin for Special Environment of Northwest of China, simulating hypobaric hypoxia at an altitude of 6 000 m. The control group was housed in a clean animal room with atmospheric pressure and oxygen. Changes in the tear meniscus height and non-invasive tear break-up time were detected by using RHCT-1 corneal topographer dry eye comprehensive analysis system, changes in tear secretion was measured by Schirmer Ⅰ test, before intervention and on the 3, 7 d, 2 and 4 wk. Meanwhile, the changes in tear composition before and after intervention in the plateau environment were analyzed using Raman Spectroscopy. The histopathological changes of the lower lid conjunctiva, cornea, lacrimal gland, and Hardarian gland were observed by hematoxylin-eosin(HE)staining after 4 wk of intervention, and the expression of mucin 5AC(MUC5AC)in conjunctiva was detected by immunohistochemistry.RESULTS: Compared with the control group, Schirmer Ⅰ test, tear meniscus height, first and average non-invasive tear break-up time in the plateau group decreased significantly since 3 d, and the difference was significant with the extension of observation time(P<0.05). The above indexes increased from 2 wk. After 4 wk of intervention, the protein and lipid content of the tear composition of rabbits in the plateau group increased, and the nucleic acid content decreased compared with the pre-intervention period. Compared with the control group, rabbits in the plateau group showed thickening of corneal stromal edema, an increase in the number of conjunctival cup cells, increase in the level of expression of MUC5AC, an increase in the level of expression of MUC5AC, an atrophy and flattening of cytoplasm in lacrimal epithelial cells, an enlargement of glandular lumen, and no obvious destructive changes in the Hardarian glands.CONCLUSION: Acute plateau environment can destroy the homeostasis of rabbit ocular surface, so that the tear secretion and the tear film stability decreases, but within a certain period of time, rabbits undergo compensation with the habituation to the hypobaric hypoxia environment, which can increase the tear secretion to a certain extent and restore the tear film stability.

The examinations of tear quality and volume are important indicators for the diagnosis of dry eye disease. Tests commonly used in clinical practice to diagnose dry eye disease include testing of tear volume and tear film stability to assess the severity of the condition, and analyzing and labeling of tear components under laboratory conditions to diagnose clinical staging and also to guide clinical supplementation of relevant components to target treatment. Accurate assessment of tear production and compositional changes enables clinicians to effectively monitor the severity of dry eye disease and evaluate the effectiveness of therapeutic measures. With the development of optical imaging technology and artificial intelligence in recent years, the combination of clinical tear indicators and examination techniques has enabled the application of new testing methods that provide more convenient, rapid and accurate testing, greatly improving the diagnosis and treatment of dry eye disease in the clinic.

Objective:To explore the impact of problem-inquiry teaching based on the concept of science-technology-engineering-arts-mathematics (STEAM) on the critical thinking and practical abilities of clinical interns in neurology.Methods:The 194 clinical interns majoring in clinical medicine and enrolled in 2020 were selected as subjects. The 98 interns from classes 1-4 were included in the traditional group with traditional teaching, and the 96 clinical interns from classes 5-8 were included in the teaching reform group with problem-inquiry teaching based on the STEAM concept. After the internship, the assessment scores (basic theoretical knowledge, professional theoretical knowledge, classroom performance), critical thinking, practical ability, and teaching satisfaction were compared between the two groups of interns.Results:The assessment scores of the teaching reform group [(40.97±3.26) for basic theoretical knowledge, (42.12±2.95) for professional theoretical knowledge, and (38.47±2.78) for classroom performance] were significantly higher than those of the traditional group [(38.14±3.07), (40.33±2.83), and (35.89±2.71)] (all P<0.05). After the internship, the California Critical Thinking Disposition Inventory-Chinese Version scores of both groups of clinical interns increased, and the score was higher in the teaching reform group than in the traditional group. The Leicester Assessment Package score (82.49±6.71), case writing score (85.63±5.34), and teaching satisfaction (91.67%) of the teaching reform group were significantly higher than those of the traditional group [(77.35±6.23), (82.57±5.12), and 79.59%] (all P<0.05). Conclusions:Problem-inquiry teaching based on the STEAM concept can improve the theoretical knowledge level of clinical interns in neurology, promote their active speaking, enhance their critical thinking and practical abilities, and increase teaching satisfaction.

Objective:To explore the impact of problem-inquiry teaching based on the concept of science-technology-engineering-arts-mathematics (STEAM) on the critical thinking and practical abilities of clinical interns in neurology.Methods:The 194 clinical interns majoring in clinical medicine and enrolled in 2020 were selected as subjects. The 98 interns from classes 1-4 were included in the traditional group with traditional teaching, and the 96 clinical interns from classes 5-8 were included in the teaching reform group with problem-inquiry teaching based on the STEAM concept. After the internship, the assessment scores (basic theoretical knowledge, professional theoretical knowledge, classroom performance), critical thinking, practical ability, and teaching satisfaction were compared between the two groups of interns.Results:The assessment scores of the teaching reform group [(40.97±3.26) for basic theoretical knowledge, (42.12±2.95) for professional theoretical knowledge, and (38.47±2.78) for classroom performance] were significantly higher than those of the traditional group [(38.14±3.07), (40.33±2.83), and (35.89±2.71)] (all P<0.05). After the internship, the California Critical Thinking Disposition Inventory-Chinese Version scores of both groups of clinical interns increased, and the score was higher in the teaching reform group than in the traditional group. The Leicester Assessment Package score (82.49±6.71), case writing score (85.63±5.34), and teaching satisfaction (91.67%) of the teaching reform group were significantly higher than those of the traditional group [(77.35±6.23), (82.57±5.12), and 79.59%] (all P<0.05). Conclusions:Problem-inquiry teaching based on the STEAM concept can improve the theoretical knowledge level of clinical interns in neurology, promote their active speaking, enhance their critical thinking and practical abilities, and increase teaching satisfaction.

Objective:To analyze the external quality control assessment results of urinary iodine, salt iodine and water iodine in iodine deficiency disorders laboratories in Qinghai Province, to evaluate the testing capacity of provincial, municipal and county-level laboratories and the operation of external quality control network, so as to provide quality assurance for consolidating and eliminating iodine deficiency disorders.Methods:In 2021, 1 provincial, 8 municipal, and 43 county-level laboratories in Qinghai Province had participated in the assessment of urinary iodine and salt iodine, while 1 provincial and 8 municipal-level laboratories had participated in the assessment of water iodine. The assessment results were evaluated using the method of reference value ± uncertainty of external quality control samples.Results:All laboratories that participated in the assessment had provided feedback. One provincial-level laboratory passed the assessment of urinary iodine, salt iodine, and water iodine. Among 8 municipal-level laboratories, 2 laboratories failed the urinary iodine assessment, with a pass rate of 6/8; the assessment of salt iodine and water iodine in 8 laboratories were all qualified. Among 43 county-level laboratories, 7 laboratories failed the urinary iodine assessment, with a pass rate of 83.7% (36/43); the assessment of salt iodine in 43 laboratories were all qualified.Conclusions:The external quality control network of iodine deficiency disorders laboratories in Qinghai Province has fully covered all municipal and county-level laboratories. The testing capability of provincial-level laboratory is stable and maintains a high level; the testing quality of some municipal and county-level laboratories is still unstable and needs to be further strengthened.

Objective:To verify the revised method of cerium sulfate catalytic spectrophotometry for iodide index of "Standard Examination Methods for Drinking Water-Nonmetal Parameters" (GB/T 5750.5-2006).Methods:From July to September 2019, the Laboratory of Department for Endemic Disease Prevention and Control of Qinghai Institute for Disease Prevention and Control verified the revised method (determination of iodide in drinking water by cerium sulfate catalytic spectrophotometry) of cerium sulfate catalytic spectrophotometry (hereinafter referred to as original method) in "Standard Examination Methods for Drinking Water-Nonmetal Parameters" (GB/T 5750.5-2006). The revised method was verified according to the requirements of "Standard Examination Methods for Drinking Water-Water Analysis Quality Control" (GB/T 5750.3-2006), including standard curve, detection limit, precision, accuracy and actual sample determination.Results:The linear range of the revised method was 0 - 20.0 μg/L, the correlation coefficient was - 0.999 4 - 0.999 8, and the detection limit was 0.231 μg/L. The relative standard deviation ( RSD) of low, medium and high iodine water samples of 6 times detection ranged from 1.4% to 9.6%, and the recoveries of low and medium water samples ranged from 89.0% to 108.0%. The detection results of national first-class reference materials for iodine composition analysis in water were within the range of standard value ± uncertainty. There was no significant difference in the test of results of 12 tap water samples between the revised method and the original standard method ( t = - 0.075, P > 0.05). Conclusion:The revised method has a good linear relationship of standard curve, high precision and accuracy, and good reproducibility, is simple and easy to operate, and is suitable for promotion and application.