Study On Rapid Detection Of Viable Salmonella And Staphylococcus Aureus In Dairy Products And Design Of Food Microbiology Laboratory

Dairy products are various foods made by industrial processing with raw goat milk or cow milk as raw materials.Because of their unique flavor and rich nutrition,they play an important role in people's diet.But dairy products are also very susceptible to microbial contamination.Foodborne pathogens such as viable Salmonella is the main causes of human food poisoning caused by contaminated dairy products.Once people consumes milk products containing such viable bacteria,it is very likely to cause extremely serious harm to health.For such viable bacteria,traditional detection methods have the disadvantages of complicated operation,high cost,and time-consuming.Therefore,it is very important to establish a fast and effective detection method for detecting viable foodborne pathogens in dairy products.In this study,PMAxx was used to pre-treat the samples to eliminate the interference of dead bacteria on the detection of viable bacteria.At the same time,we combined PMAxx with recombinase aided amplification(RAA)technology(PMAxx-RAA)to achieve rapid and sensitive detection of viable Salmonella and Staphylococcus aureus in milk.In order to further achieve the rapid detection of actual samples,some improvements on the basis of the traditional microbiology laboratory have been developed with additional detection systems such as RAA rapid detection method,which can provide infrastructures for rapid screening experiments or confirmation experiments.The contents of each chapterin this article are as follows:In chapter 1,the detection methods and research progress of foodborne pathogens in dairy products are reviewed.In chapter 2,PMAxx-RAA based method was developed to detect Salmonella in milk.The results showed that four target Salmonella strains had their corresponding fluorescence amplification curves while other 24 non-target strains showed no fluorescent amplification curves,indicating good specificity of this method.The effects of PMAxx have been verified and the results showed that the PMAxx could permeate the dead cells and inhibit its DNA from RAA detection;the proposed method developed in this study showed that the limit of detection(LOD)in pure culture medium was 2.8×10~3CFU/m L;the LOD in spiked milk was 1.8×10~3CFU/m L and the detection time was 40 min;the developed PMAxx-RAA method achieved the rapid detection of viable Salmonella in milk samples.In chapter 3,PMAxx-RAA method was developed to detect viable Staphylococcus aureus in milk.The results indicated that the designed primers based on nuc gene showed good specificity in RAA detection.Under the optimized PMAxx concentration(20?M),the LOD of this method in pure culture was 7.4×10~4CFU/m L,and in spiked milk were 5.4×10~2CFU/m L or 5.4×10~1CFU/m L after 3 h and 6 h enrichment,respectively.In addition,the detection time was 20 min.The PMAxx-RAA method developed in this study provided a new strategy for viable Staphylococcus aureus detetion in milk.In chapter 4,we completed a design scheme for food microbiology laboratory.The food microbiology laboratory designed in this chapter integrates a variety of detection systems such as traditional culture method and RAA rapid detection method,establishing a hardware basis for rapid screening experiments or confirmation experiments,which can effectively shorten the detection time and improve the detection efficiency.This design focuses on the layout,division and function,structure and decoration,basic configuration of laboratory equipment,etc.of the food microbiology laboratory,and finally can achieve a series of operations such as sample processing,microbial culture,separation and identification,and molecular biology detection.This designed scheme provides a good foundation and guarantee for microbiological testing.