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Mao Y.,Jilin Institute for Food Control
Yejin Fenxi/Metallurgical Analysis | Year: 2016

Proficiency testing is an action to evaluate the ability of participants according to the pre-specified criterions based on the inter-laboratory comparison. Quartile and iteration are two robust statistical analysis methods dealing with the data of proficiency testing, which can be used to calculate the target standard deviation and evaluate whether the laboratory data are qualified. The calculation results of two robust statistical methods were compared by analyzing the multi-data sources of proficiency testing. The analysis results showed that the inter-laboratory detection ability exhibited significant difference and the data of proficiency testing distributed dispersedly when the ratio of normalization interquartile range of laboratory data to the reproducibility standard deviation (H value) based on empirical model was larger than 2 or the robust coefficient of variation (CV) was larger than 0.05. At this time, the number of iterative calculation was more than 1 and the ratio of normalization interquartile range to robust standard deviation was larger than 1. In other words, the quartile method broadened the evaluation standard of proficiency testing. © 2016, CISRI Boyuan Publishing Co., Ltd. All right reserved. Source


Han L.-H.,Jilin Institute for Food Control | Wang X.,Jilin Institute for Food Control | Li J.-T.,Jilin Institute for Food Control
Chinese Journal of Biologicals | Year: 2015

Objective To develop, verify and preliminarily apply a multiplex PCR (mPCR) method for rapid detection of salmonella, shigella and Staphylococcus aureus in health foods. Methods PCR amplification was performed by the optimized system under the optimized reaction condition, using the primers designed according to the invA gene of salmonella, ipaH gene of shigella and nuc gene of Staphylococcus aureus in Gen Bank, and the amplified products were identified by 3% agarose gel electrophoresis. The developed mPCR method was verified for specificity, sensitivity and reproducibility. Salmonella, shigella and Staphylococcus aureus were mixed in an equal quantity, diluted 10-fold serially, added into 10 batches of pathogen-free protein powder and 10 batches of pathogen-free homogenates of dietic tea and detected by the developed mPCR, of which the results were compared with those of routine biochemical test in GB. Results The reaction system of mPCR was optimized as follows: 10 x PCR buffer 2.0 μ1, dNTPs 2.5 μl, Taq DNA enzyme 0.6 μ1, upstream and downstream primers, 1.5 μ1 for each, magnesium ion 1.0 μ1, added with ddH2O to a volume of 25 μ1. Of the 10 bacterial strains, salmonella, 2 shigella strains and S. aureus were identified as positive, while the others as negative. The homologies of invA, ipaH and nuc genes were 99%, 99% and 100% to those in GenBank, respectively. Specific target bands were amplified from salmonella, shigella and S. aureus each at a concentration of 101 ∼ 105 CFU/ml. Specific reaction bands were observed in amplified products of mixed bacterial liquid at five concentrations. The specific gene fragments of salmonella, shigella and S. cmreus were amplified by the developed mPCR from 10 batches of bacterial protein powder and 10 batches of dietic tea, both added with bacteria, with a detection limit of 102 CFU/ml, which was consistent with the result of routine biochemical test in GB. Conclusion The developed mPCK method for salmonella, shigella and S. aureus in health foods showed high specificity, sensitivity and reproducibility, which met the practical needs for rapid and accurate detection of various pathogenic microorganisms. Source


Han L.-H.,Jilin Institute for Food Control | Dong S.-C.,Jilin Institute for Food Control | Wang J.-F.,Jilin Institute for Food Control | Li J.-T.,Jilin Institute for Food Control
Chinese Journal of Biologicals | Year: 2015

Objective: To develop and verify a PCR-ELISA method for salmonella. Methods: Primers and probes were designed according to the invA gene of salmonella, based on which PCK, nucleic acid hybridization and ELISA were performed, and the condition for degeneration reaction, concentration of probe, time and temperature for hybridization and time for coloration were optimized, the cut-off value for judgments of negative and positive results were determined, and the sensitivity, specificity and reproducibility were verified. The salmonella in 22 batches of pills of traditional Chinese herbs and 27 hatches of milk, infected artificially, were determined by the developed PCR-ELISA method, and the results were compared with those by PCR and by GR4789. Results: The optimal sodium hydroxide concentration for degeneration of nucleic acids, Digoxin-labeled probe, time and temperature for hybridization and time for coloration were 150 mmol/L, 50 pmol/ml, 50 °C, 60 min and 50 min respectively. The cut-off value for judgment of negative and positive results was 0. 265. The detection limit of the developed method was 0. 5 pg/μ1, indicating a high sensitivity. The salmonella fragment was amplified specifically, indicating high specificity of the method. Both the CVs of results of intra- and inter-assays were less than 10%, indicating high reproducibility of the developed method. The positive rate of salmonella in 22 batches of pills of traditional Chinese herbs and 27 batches of milk determined by PCR-ELISA was significantly higher than that by PCR and basically consistent with that by GIH789. Conclusion: The optimized PCR-ELISA method showed high specificity, sensitivity and reproducibility, which might be used for rapid detection of salmonella in foods and drugs. Source

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