| Staphylococcus aureus,which is widely distributed in nature,is a kind of zoonotic pathogen,which is easy to cause dairy cow mastitis and then pollute dairy products.It is also a common foodborne pathogen that can cause food poisoning incidents through the intestinal toxin it carries,which is life-threatening when severe.Biofilms are a form of self-protection for bacteria that not only survive in harsh environments for long periods of time,but also resist the host’s immune response and routine killing effects.With the increase in people’s demand for nutrition,the safety hazards brought about by the contamination of dairy products are worth pondering.Due to the relatively blank pollution survey of raw milk and commercially available raw milk in Urumqi,this study studied the prevalence of Staphylococcus aureus in raw milk in Urumqi,the carrying of classic enterotoxins between strains and the relevant characteristics of biofilm formation,in order to provide a reference for the prevention and control of Staphylococcus aureus in raw bovine milk in Urumqi.The results of this study are as follows:1.A total of 1 037 milk samples were collected from Urumqi,isolated and purified by selective medium,identified by PCR method combined with identification medium,and a total of 86 strains of Staphylococcus aureus were isolated by comparing the 16 S r RNA sequence on the NCBI,with a separation rate of 8.29%.The homology and genetic evolution analysis of Staphylococcus aureus isolated from 13 strains of raw milk from different sources were carried out,and the homology of the strains was between93.7% and 99.7%,and the genetic differences were between 0.3 and 6.6,and the results showed that the homology between the strains of different sources was high and the genetic differences were small.One methicillin-resistant Staphylococcus aureus was detected in 86 isolates.2.34 strains(39.53%)of the 86 strains of bacteria did not carry any classical enterotoxin genes by PCR,52 strains(60.47%)carried classic enterotoxin genes,and one strain carried multiple classical enterotoxin genes.Among them,there are 21 strains(24.42%)carrying sea,23 strains(26.74%)carrying seb,8 strains(9.3%)carrying sec,and 18 strains(20.93%)carrying sed,all of which do not carry the see gene.There are 37 strains that carry one type of enterotoxin,12 strains of two types of enterotoxin,and 3strains of three types of enterotoxin.Methicillin-resistant Staphylococcus aureus carries only the sea gene.3.The film-forming capacity was detected by the 96-well plate method,and 9 relevant film-forming genes were detected by the PCR method,and 70 of the 86 strains had strong film-forming capacity,8strains had medium film-forming capacity,4 strains had weak film-forming capacity,and 4 strains did not have film-forming capacity.Strains carrying the fnb A gene accounted for 12.79%,strains carrying the fnb B gene accounted for 23.26%,strains carrying the clf A gene accounted for 56.98%,clf B gene carried 89.53%,strains carrying the cna gene accounted for 9.3%,sar A gene carried 65.12%,strains carrying the ccp gene accounted for 45.35%,strains carrying the lux S gene accounted for 62.79%,and the ica A gene was not detected.Methicillin-resistant Staphylococcus aureus is a strong membrane-forming capacity strain that carries two membrane-forming genes,clf B and sar A.The above results show that there is a certain degree of Staphylococcus aureus contamination in raw cow milk in Urumqi area,and through genetic evolution and homology analysis,it indicates that the strain may have exogenous secondary pollution in the transportation and sales links,and there is also a possibility of horizontal transmission;The carrying rate of classical enterotoxin in the isolate strain is high,and the seb and sea types are the mainstay,which increases the risk of food poisoning;the biofilm forming ability in the isolate strain is strong,and there are widespread cases of carrying a variety of membrane-forming genes,and the results show that the formation of the Staphylococcus aureus biofilm is linked to the adhesion factor and regulatory genes,which is the result of the joint regulation of multiple genes,which brings certain challenges to the prevention and control of Staphylococcus aureus pollution. |
