| Streptococcus suis is a common important pathogens of pigs.It not only infects animals,but also infects humans,which is caused huge losses to the pig industry.Therefore,infection with S.suis is not only a problem in the aquaculture industry,but also a public health problem.According to the epidemic characteristics,the proportion of healthy pigs carrying S.suis is far higher than that of infected pigs,so it is more harmful to the people directly or indirectly exposed to pigs.Therefore,the investigation of the epidemiology of S.suis in healthy pigs has more important reference significance.Through the investigation of the epidemic situation of S.suis in a healthy pig farm in a slaughterhouse in a certain city of Jiangsu Province,we can understand the local epidemic characteristics,and provide a basis for local prevention and control strategies and reveal the Pathogenicity of S.suis.1.Epidemiological survey of S.suis in a slaughterhouse in a city of Jiangsu Province.A total of 120 pig tonsils were collected from a slaughterhouse in a city of Jiangsu Province from October to December 2018 to identify and isolate S.suis,and to detect serotype characteristics and virulence factors.The purpose is to understand the local epidemic situation and provide a basis for local prevention and control strategies.the housekeeping gene gdh encoding glutamate dehydrogenase and DNA repair protein recN were used as S.suis-specific genens.PCR result showed that:65%(78/120)of tonsil were positive for both gdh and recN,A total of 285 single colonies were isolated from the identified tonsil,and the isolated single colonies were identified by serotype.A total of 18 serotypes were identified in 235 strains,of which the highest separation rate was type3(16.5%,47/285).The remaining serotypes were:type31(15.4%,44/285),Type 2(13.7%,39/285).Type 16(8.1%,23/285),Type 9(6.8%,19/285),Type 4(6.0%,17/285),and Type12(5.6%,16/285),type14(3.2%,9/285),type7(2.1%,6/285),type 33(1.4%,4/285),type 5(1.1%,3/285),Type 25(1.1%,3/285),Type 11(0.4%,1/285),Type 15(0.4%,1/285),Type 23(0.4%,1/285),Type 24(0.4%,1/285),type 28(0.4%,1/285).Type 4 0.4%(1/285),Type 28 0.4%(1/285),unknown serotype 50.55 strains of tonsil were selected to detect sbp2’,mrp,epf,sly four virulence factors.The results showed that only 6 strains were detected virulence factors,and one strain of type 1 were detected sly virulence factor,and the other were detected sbp2’,mrp,epf;one of the two strains detected sbp2’,mrp,epf,sly.the other were detected sly virulence factors;type 3 and type 4 were detected Only sly virulence factors,and other strains that did not detect virulence factors were attenuated strains.2.S.suis type 2 resistant phenotype and drug resistance genotype detectionA total of 62 strains including 56 strains of S.suis selected from the laboratory strain library and 6 strains isolated from a slaughterhouse were selected to take drug sensitivity test.The selected eight kinds of drug sensitive piece of paper were cefotaxime,erythromycin,tetracycline,chloramphenicol,ofloxacin,clindamycin,gentamicin,vancomycin.The results of drug susceptibility test showed that these 62 strains of S.suis have different degrees of resistance to the common 8 drugs.mainly resistant to tetracycline,clindamycinand erythromycin,and the highest proportion of tetracycline-resistant bacteria,reaching 96.8%.(60/62);followed by clindamycin and erythromycin,which were 38.7%(24/62)and 30.6%(19/62)respectively.Sensitivity to chloramphenicol,ofloxacin,vancomycin,gentamicin and cefotaxime was 93.5%(58/62),93.5%(58/62),95.2%(59/62),90.3%(56/62),90.3%(56/62).The multi-drug resistance rate the stock strains in this laboratory is lower,and the multi-drug resistance types of the 6 isolates in a slaughterhouse are up to 8 species,accounting forl.6%.The most resistant species among the 62 strains is one(tetracycline),accounting for 48.4%,and the resistance types are 2 and 3,accounting for 12.9%and 29.0%respectively.ZY05719 and 05ZYH33 were found to have aminoglycosamine and tetracycline resistance genes in the phenotypes and genotypes of seven strains of P1/7,ZY05719,SC19,SC070731,05ZYH33,T15 and LSM102,but the phenotype was only for tetracycline Resistance;SC 19 has aminoglycoside and tetracycline resistance genes,but the phenotype is only resistant to tetracycline and clindamycin;The biggest difference in performance is T15,which does not have any drug resistance genes,but it is resistant to ceftiofur,erythromycin,tetracycline,chloramphenicol,and gentamicin.The above conclusions found that there is a certain genotype of resistance,but the phenotype does not necessarily have the same,and vice versa.3.The exploration on the selective mechanism of Streptococcus SuisS.suis is an important pathogen commonly found in pigs,so how to quickly identify and isolate S.suis is of great significance.In this experiment,three antibiotics were used,namely Naphthyridinic acid,polymyxin B,tetracycline,the minimum concentration of S.suis growth was determined by MIC test,and the PCR products of specific segments such as 16S rRNA were performed by the second generation sequencing platform.High-throughput sequencing to analyze the proportion of each microbial community in the sample.The purpose is to prove whether the screening concentration of these three antibiotics can inhibit the growth of other bacteria,and make S.suis become the dominant flora.The results showed that after repeated screening,the final concentrations of nalidixic acid,polymyxin B and tetracycline were 20 mg/L,24 mg/L and 8 mg/L respectively.The community structure of the 16S rRNA sequencing results at the genus level showed that the main dominant bacteria in the four samples were Escherichia and Shigella.And P1 and X1 include the Actinomycetes in addition to the two genera.The relative test results of the four samples were consistent.The proportion of Streptococcus in P3 was the highest in the four samples,but the proportion of Streptococcus in the medium supplemented with antibiotics was lower than that in the normal medium.The test results did not reach the expected results. |
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