| In recent years, food safety has drawn a lot of departments’ and consumer’ concerns, andmicrobial contamination is the key point of food safety. Milk and dairy products arenutrient-rich, drawing a lot of favour, meanwhile those are culture for microbes. Oncecontaminated, microbes can multiply rapidly under certain conditions, causing the corruptionof milk and milk prducts, it may even cause food poisoning and the spread of other disease.According the investigation, a large amount of cases caused by milk safety is due to thecontamination of foodborne pathogens in the milk, and Staphylococcus aureus, Escherichiacoli, and Clostridium difficile become the primary microbes causing disease. Escherichia colidistributes widely, and could be detected in the human beings and animals. In most occasions,it could not lead to disease, except some special serotypes of Escherichia coli may become isthreat to the human and animals. For the present, the research of the milk safety is focus onthe analysis and control of the hazard, and the quality of raw milk. However, the milkproducts could be contaminated in a series of processes such as raw materials, dairyproductions, transportation and storage. All of the processing equipment and material couldincrease the amount of the microbes in the milk products. At the same time, the procedure ofsterilization, concentration, spray drying, and packaging may have an influence on theproducts. Therefore,through research possible contamination sources of microbial species inthe dairy industry, which can help companies to develop appropriate policies and takecorresponding measures to control the quality and safety of milk and its products.E.coli is notstrictly required for its growth environment,and could easily lead to contamination in foodproduction, may exist in all aspects of production.It is also regarded as the indication of fecalcontamination of food bacteria, commonly used as the standard of food, water or sanitaryquality of drug testing.So this study choose Escherichia coli as investigation object in thedairy enterprise production，for it’s contamination in the enterprise need a depth study.A total of534samples were collected from three diary processing plants locatedsurround Xi’an and Yangling. Via the isolation and identification of Escherichia coli in thesamples, the present study has a research on the distribution of Escherichia coli in differentsamples. Then the serotypes, virulence genes, antimicrobial resistance were tested. Finally, the present study clustered the isolates by PFGE and provided some evidence on thecontamination, characteristic, and source of Escherichia coli. The results of this research areas follows:1A tatal number of32positive samples were isolated, from which,53positive strainswere got, the contamination rate was5.99%.The rates of the isolation in B and C plant are10.71%and5.61%, while there is no strain isolate from A plant. The highest rate ofcontamination in different sampling sites was raw milk, followed by the packing plant vents,water pipes in the factory, packaging department station and the soil beside workshop.2All strains have serotypes and virulence gene (aggR, elt, eae, ipaH, stx, est) detection.We found that none of them carried virulence genes, and the dominant serotypes were O125:H5, O1: H2and O125: H18except undetermined serotypes.3The results of drug sensitivity tests showed that all the E.coli detected were sensitiveto Gatifloxacin Kanamycin Amikacin and Amoxicillin/Clavulanic acid, the resistance rates ofthe strains to Trimethoprim/Sulfamethoxazole are highest, the resistance to other seven kindsof antimicrobials has certain degree, the resistance rates are not high.4Through sorting E.coli from different sources with PFGE method, we found somescattered genotypes homology analysis of a total of13gene clusters with85%similarity, thetwo main gene clusters contain14and5strains respectively. |
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