| Salmonella,Staphylococcus aureus,Pathogenic Escherichia coli O157:H7 and Listeria monocytogenes are important foodborne pathogens that threaten food safety at present.China has the largest pork market in the world and is the largest producer and consumer of pork.The slaughtering chain of live pigs is the last link for the pork to enter the market,so it is very important to strengthen the detection of these food-borne pathogens in the slaughtering chain.In this paper,the epidemic situation of food-borne pathogens in pigs before slaughter and after slaughter in slaughterhouse was detected and investigated.The drug-resistant phenotype and drug-resistant gene analysis of the isolated Salmonella strains were carried out,and the virulence gene carrying situation was investigated.From June 2019 to August 2020,pig body samples,such as anus swab,nose swab,electroanal swab,electroanal swab,nose swab,nose swab,depilated body surface swab,split body surface swab and cooling body surface swab,were collected from large-scale slaughterhouses in different regions of Henan and Shaanxi provinces.A total of 6 batches(1,953 samples)were collected,and the nasal swabs were only used for the separation of Staphylococcus aureus.The collected samples were routine isolated and identified for Salmonella,Staphylococcus aure us,pathogenic Escherichia coli O157:H7 and Listeria monocytogenes according to national standard GB4789-2016.Secondly,according to the American Association for Clinical and Laboratory Standards Antibacterial Sensitivity Test Standard,the microbroth dilution method was used to detect the resistance of Salmonella isolates.Finally,according to the designed primers of 9 pairs of drug resistance genes and 9 pairs of virulence genes of Salmonella,the carrying conditions of drug resistance genes and virulence genes of Salmonella isolates were detected.A total of 276 strains of Salmonella were isolated from slaughterhouse samples in different areas of Henan and Shaanxi provinces,with a positive rate of 21.9%(276/1263).A total of 184 strains of Staphylococcus aureus were isolated,with a positive rate of 12.3%(184/1493).Two other foodborne pathogens,Pathogenic Escherichia coli O157:H7 and Listeria monocytogenes were not detected.From the perspective of pig slaughterhouses,Salmonella detection rate of Shaanxi slaughterouses was generally higher than Henan slaughterhouses.The highest detection rate was Xianyang A slaughterhouse(47.7%),while the lowest was Luohe A slaughterhouse(13.9%).In the slaughtering process,the detection rate of Salmonella in the slaughtering process and the hemp electrolysis process(37.4%and 26.5%,respectively,with an average detection rate of 32.0%)was significantly higher than that in the body swabs(20.5%for hair removal,17.1%for splitting,14.5%for cooling,with an average of 17.4%).In the environmental samples,The positive rate of the lower white dirty ground was the highest(15.0%)and the lowest(5.0%)in the cooling room.The overall isolation rate of S.aureus was slightly lower than that of Salmonella(21.9%for Salmonella and 12.3%for S.aureus),and there was little difference between pig slaughterhouses.Among them,Luohe B slaughterhouse and Xinzheng slaughterhouse had higher detection rates(19.1%and 13.7%,respectively),while Luoyang slaughterhouse and Luohe A slaughterhouse had lower detection rates(9.3%and 6.3%,respectively).From the slaughtering stage,the isolation rates of S.aureus were 26.5%,17.0%and 22.6%in nose swabs of pigs before slaughter,anastomosis and head amputation,respectively,which were significantly higher than those in body swabs(5.3%for depilation,5.7%for splitting and 3.7%for cooling,with an average of 4.9%).In the environmental samples,the detection rates were high(16.7%and 20.0%,respectively),but only in the tool handle and under the white dirt floor.The above results indicate that:1)Salmonella and Staphylococcus aureus contamination is common in the slaughtering process of pigs,and secondary contamination also exists in the slaughterhouse environment to varying degrees;2)Among different slaughterhouses,the detection rates of Salmonella and Staphylococcus aureus increased and decreased with the seasonal changes;3)The detection rate of food-borne pathogens decreased gradually with the progress of different slaughtering links,which was related to the effective sanitary management measures taken by the slaughterhouse.The antimicrobial susceptibility of 276 Salmonella isolates was tested by microdilution method.The results showed that all Salmonella isolates from slaughterhouse showed resistance to one or more antimicrobial agents(100%).Among the 12 drugs tested,Salmonella had the most common resistance to flfenicol(FLR),and the resistance rate was as high as 93.8%.The drug resistance rate to tetracycline(TET)was also high,90.2%.The drug resistance rates were 71.7%,71.0%,68.5%,67.8%,65.6%and 64.1%,respectively,for kanamycin(KAN),enrofloxacin(ENR),gentamicin(GEN),quindox(OQX),streptomycin(STR)and colistin(CL).The drug resistance rates to ceftazidime(CAZ),cefquinoxime(CEQ)and ciprofloxacin(CIP)were 44.2%,40.9%and 23.9%,respectively.Most of the strains were sensitive to amikacin,and the drug resistance rate was only 1.5%.At the same time,Salmonella showed severe multidrug resistance,up to 96.7%(267/276),in which up to 81.9%of the strains could tolerate more than 5 antibiotics at the same time.Only 2 strains(0.7%)were least resistant to 1 antibiotic.From the perspective of bacterial resistance spectrum,276 Salmonella isolates produced 93 kinds of drug-resistant spectrum advantages of drugresistant spectrum have GEN/ENR has/STR/TET OQX KAN/FLR(6.9%),GEN/ENR has/CL/CIP/STR/TET/OQX/KAN/FLR/CAZ(6.5%),GEN/ENR has yet/TET OQX KAN/CEQ/FLR(6.2%),GEN/ENR has/CL/STR/TET OQX/KAN/FLR/CAZ(5.1%),GEN/ENR has/CL/CIP/Yet STR/TET OQX KAN/CEQ/FLR CAZ(5.1%).PCR results for drug resistance genes of Salmonella showed that the drug resistance gene of 276 Salmonella isolates was more serious.Among the five drug resistance genes,sulfonamide sull-? gene carried the highest rate(93.5%).blaTEM-1(92.8%),aadA1(91.3%),tetracycline(90.6%)and quinolone parC(83.0%)were the next most common types,and blaSHV(14.1%)was the lowest.For Salmonella virulence genes of PCR detection results show that the sseL,mogA,bcfA detection rate is highest,at 100.0%;Second is invA,mgtC,fimA,hisJ,araB,detection rate of 99.6%,99.3%,98.9%,96.0%,93.5%,the lowest for the fliC,at 80.1%.Can be found in the slaughterhouse batches,8 virulence gene has two batches,with 100%for A and B in Shaanxi province,Luohe and only fliC virulence genes carry rate is less than 100%,but the Shaanxi B the fliC the carrying rate of nearly 100%(97.8%);Carry six virulence genes of 100%for Xinzheng and Luohe B,xinzheng except flimA and fliC virulence genes,Luohe B is in addition to the araB and fliC virulence genes;Carry five virulence genes of 100%for Shaanxi A,in addition to the araB,fimA and fliC virulence genes;Carry four virulence genes of 100%for Luoyang,only sseL,mogA,bcfA and araB.The results of this study showed that Salmonella and Staphylococcus aureus were seriously polluted in pigs to be slaughtered in large-scale slaughterhouses in different areas of Henan and Shaanxi provinces,and Pathogenic Escherichia coli O157:H7 and Listeria monocytogenes were not detected in the other two foodborne pathogens.There are different degrees of pollution in the slaughtering process of live pigs,among which the pollution is more serious in the slaughtering process,hemp power process and head breaking process.The overall drug resistance of Salmonella isolates was serious,with widespread resistance to flfenicol(FLR)and tetracycline(TET),and multiple drug resistance existed widely.The drug resistance and virulence genes of Salmonella isolates are more serious,and it is common to carry multiple drug resistance and virulence genes simultaneously. |
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