| Staphylococcus aureus (SA) is an important pathogen causing a variety of diseases inmankind and animal. It is widely distributed in nature such as the air, water, soil, and feces ofhuman and animal. Staphylococcus aureus also is the main reason for causing food poisoningin human. There were reported that Staphylococcus aureus have been found in any types offood, especially in animal derived food. It is an important way for ensuring food safety byrapidly detect staphylococcus aureus in animal derived food. The conventional detectionmethods of Staphylococcus aureus includ isolation and identification of bacteria (coagulasetest, nuclease resistant test, mannitol fermentation experiments, latex agglutinationexperiment), immunological methods (enzyme-linked immunosorbent assay, counter immunoelectrophoresis) and other molecular biologic methods. Currently, the molecular biologicmethod has been widely used in detection of staphylococcus aureus in food, due to theconvenient operation, specific, and low requirement for samples. The microbial contaminationin raw milk mainly become from diseased cow with mastitis, the process of milking and etc.The raw milk is raw material for milk products, and the raw milk were sold as food with anybeing treated. It is a serious threat to consumers if the raw milk is contamined bystaphylococcus aureus.Staphylococcus aureus will adsorb on the gastrointestinal mucosa of human or animal,and secret many kinds of enterotoxin (SE) to trigger diseases or food poisoning. Theenterotoxin A (SEA) is a main causal agent of food poisoning with the strongest virulence,heat-stable nuclease (NUC) is the specific enzyme and a identifiable sign of staphylococcusaureus, beta lactamase (BLAZ) is enzyme for hydrolyzing β-lactam antibiotics and is themost common mechanism of bacterial resistance to antibiotics, bring the difficulties forbacterial disease clinical medication.In this study, a multiplex PCR based on three virulent genes (SEA,NUC,BLAZ) ofstaphylococcus aureus was developed and were used for detecting the staphylococcus aureus in raw milk of Yangling county. The104milk samples were collected in13sites for raw milkselling.The results as follows:(1) A multiple PCR detection method for3Saphylococcus aureus virulence genes wassucessfully established. It had a good specificity and the susceptibility for virlent genes ofSEA, NUC and BLAZ were56cfu/mL,56cfu/mL and5.6×102cfu/mL,respectively. In rawmilk,5.6×102cfu/mL was for limit detection of Saphylococcus aureus.(2)104milk samples were collected from13different fresh raw milk point-of-sales. theseparate relevance ratio of virlent genes of NUC, SEA, and BLAZ were were11.5%0%and8.7%, repectively. The relevance ratio of both virlent genes NUC and BLAZ was8.7%.(3) The higher relevance ratio of Saphylococcus aureus was detected from raw milk inpoint-of-sales⑨, it was about87.5%（7/8）and about25.0%（2/8）in the samples frompoint-of-sales⑤and,12.5%（1/8）in the point-of-sales⑥. The results suggested that ithad a less possibility of Saphylococcus aureus cotamination in raw milk of Yangling, but notall livestock farm, some should be brought to the forefront.In summary, a multiple PCR detection method for3Saphylococcus aureus virulencegenes was established sucessfully in this study and the investigation of Staphylococcus aureuscontamination in the raw milk at Yangling was abtained. This study provides first-handinformation for the dairy safety management. |
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