RESUMEN
Objective@#To analyze the level and trend of microbial contamination in food in rural compulsory education schools in Baiyin City, so as to provide a reference for playing an early warning role in eliminating potential food safety hazards as soon as possible.@*Methods@#According to the "National Food Contaminants and Harmful Factors Risk Monitoring Workbook", etc., 8 pathogenic bacteria such as Salmonella, Listeria monocytogenes, Staphylococcus aureus, total bacterial count, and 2 hygienic indicator bacteria of coliform were tested.@*Results@#A total of 908 food samples were collected from 2013 to 2021, 47 were positive and the overall positive rate was 5.18%. The positive rate of samples collected in different years showed a downward trend year by year. The detected pathogenic bacteria ranked from high to low as follows: Escherichia coli (1.87%), Bacillus cereus (0.99%), Staphylococcus aureus (0.44%), mold (0.33%), Listeria monocytogenes (0.22%). Hygiene indicator bacteria total number of bacteria exceeded the standard rate was higher (2.09%). Among all kinds of food, milk and dairy products, frozen food, cold food, barbecue, rice and flour products had higher positive rates. According to quarterly statistics, the positive rate in the first and second quarters was relatively high.@*Conclusion@#There are different degrees of microbial contamination risks in the food of rural compulsory education schools. All relevant departments should pay attention to the current situation of school food hygiene and safety in poverty stricken areas, and strengthen rural compulsory education school food, especially for milk and dairy products, frozen food, cold food, Supervision of key foods such as barbecue, rice and flour products, and efforts to improve their safety standards, do a good job in school food hygiene and safety, and ensure the healthy growth of young people.
RESUMEN
Immortalized human precartilaginous stem cells (IPSCs) were established to provide stable cell resource for the study of the molecular mechanism of gene targeting on the differentiation of PSCs.Plasmid pCMVSV40T/PUR containing simian virus 40 large T antigen gene (SV40Tag) was transfected into human PSCs by using lipofectin transfection.Colonies were isolated by puromycin selection and expanded by multiple passages,lmmunohistochemistry,RT-PCR and Southern blotting were used to identify the transfected cells and to detect the expression and integration of SV40Tag in expanded cell lines.The positive colonies were isolated and subcultured,designated immortalized precartilaginous stem cells (IPSCs),which were confirmed as fibroblast growth factor receptor-3 (FGFR-3) positive cells by immunohistochemistry and RT-PCR.SV40Tag cDNA was found in cultured IPSCs of passage 8 by Southern blotting,and the expressions of SV40Tag mRNA and protein were confirmed by RT-PCR.These findings suggested that IPSCs strain with SV40Tag was constructed successfully.