Research On Rapid Detection Method Of Staphylococcus Aureus In Food

With the improvement of living standards and frequently occurrence offood safety incidengts, People pay more and more attention to food safety.Staphylococcus aureus is one of pathogens which could cause food spoilage.As widely exists in nature, Staphylococcus aureus have great possibility ofcontaminating food. Staphylococcus aureus will reproduce and secrete toxicsubstance under favorable conditions which could easily cause bacterial foodpoisoning. However, as main detection method of Staphylococcus aureus, theflat detection method has much shortcoming such as Time-consuming andlaborious in operation, the existing detection methods for Staphylococcusaureus can’t meet the needs of the real-time detection. In order to address thisproblem, this paper study a rapid detection method of Staphylococcus aureuswhich is based on selective cultivate and computer vision technology, Theresearch process and the conclusions are as follows.The thesis does research on ingredient of Staphylococcus aureusselection culture medium. According to experiment, we selected suitableinhibitors and enhancers and get formula Staphylococcus aureus selectionculture medium. The formula is as follows: Tryptone17.0g/L, the plant peptone3.0g/L, sodium chloride68g/L, dipotassium hydrogen phosphate2.5g/L,glucose2.5g/L, sodium pyruvate5g/L, glycine9g/L, potassium tellurite60mg/L,phenethyl alcohol3.8ml/L. The preparation of the medium are as follows: Allthe ingredients are dissolved in the water except potassium tellurite, thenadjust the pH to7.4±0.1. The medium was sterilized under high pressure, thencooled to room temperature,6ml sterile1%potassium tellurite is added to thecoolant and mixed. The performance of the medium is detected, The growth ofbacteria is inhibit except Staphylococcus aureus in the Staphylococcus aureusselection culture medium.With Staphylococcus aureus reducing potassium tellurite, black material isproduce. Staphylococcus aureus which are cultivated in the Staphylococcusaureus selection culture medium has the best coloring effect in4h. The digitalimage of Staphylococcus aureus are collected in4h and analyzed. Medianfiltering method is used to eliminate image noise. The Staphylococcus aureuscells are separated from background by the global threshold segmentation method. At last, the Staphylococcus aureus characteristics including area,roundness, rectangularity, eccentricity are calculate. Staphylococcus aureusrecognition model is established by the BP neural network, and it canaccurately distinguish between the Staphylococcus aureus cells and otherbacterias.Accuracy of rapid detection method to Staphylococcus aureu is analysedby compared with the traditional plate count method. The range of detectingStaphylococcus aureu in food is from10cfu/ml(g) to107cfu/ml(g). Thestandard curve is established between the rapid detection methods andtraditional Baird-Parker plate count method. The results showed a highcorrelation (R2>0.99) between two detection methods. And there are nosignificant differences between two detection methods by significance test.