Epidemiological Survey Of Streptococcus Suis Serotype 2,7,9 In Parts Of Guangxi In 2017

Streptocccus suis(SS)is an important animal pathogen that naturally lives in the pig’s upper respiratory tract,genitalia and digestive tract.Some of these variants can evolve to highly contagious zoonotic pathogens that can cause meningitis,sepsis,and arthritis,and can severely cause toxic shock syndrome.Streptococcus suis can not only bring huge economic losses to the breeding industry,but also seriously threaten public health and safety.Therefore,making epidemiological investigation of Streptococcus suis in Guangxi have a greatsignificance for the prevention and control of Streptococcus suis diseaseIn this study,527 samples of pig tissues and nasal swabs were collected from 6 cities and counties in Guangxi.SS from the samples was selected by the selection medium.205 SS strains(38.9%)were isolated.Among them,the highest rate of SS strains in Daxin.County and Napo County,which were 65.0%(65/100)and 66.3%(71/107)respectively,while the SS strains carrier rate of Vietnamese smuggled pigs captured in Jingxi City reached 30.0%(45/150).At the same time,the isolated SS was identified by serotyping primer.The results showed that 24 strains(11.7%)are SS2,2 strains are SS7(1.0%)and 15 strains(7.3%)are SS9 were identify in 205 strains of SS.By Analyzing the SS with different epidemic serotypes in different regions revealed that serotypes 2 is prevalent in Daxin County,Napo County and Dongxing City,while erotype 9 is prevalent in Jingxi samples which from Viet Nam.The difference between the pathogenicity of Streptococcus suis is closely related to the distribution of the virulence factors of this strain,and 205 strains of the major virulence genes of Streptococcus suis were detected.The results showed that 111 strains(54.2%)of SS had virulence gene SLY;53 SS strains(25.9%)had virulence gene MRP;68 strains(33.2%)SS has virulence gene EF;172 SS strains(83.9%)have virulence gene ORF2.The four virulence gene carrying rates of Streptococcus suis were ORF2>SLY>EF>MRP in descending order;the regions with high virulence gene carrying rates are Napo County and Daxin County.Count the virulence gene of the same serotype showed that SS2 mainly carry the MRP and EF virulence genes;SS7 mainly carry the EF virulence genes;SS9 mainly carry ORF2 and SLY virulence genes.Seven SS strains were screened by zebrafish model with high pathogenicity.In order to better prevent and control pig streptococcosis,the resistance of isolated SS2,SS7,and SS9 strains was measured,and the immune effect of SS2 vaccine was evaluated.The paper disc diffusion method was used to determine the resistance of 41 SS strains to 35 clinically common antibiotics.The results showed that the JX87 strain of Vietnam smuggling pigs in Jingxi City is only sensitive to one antibiotic;while JX83 strain is sensitive to three antibiotic The 41 strains had strong resistance to tetracycline,polymyxin B,and aztreonam and other antibiotics;this shows that Guangxi SS has a strong resistance.Three pig farms were randomly selected,and two pig farms were given two swine streptococcal vaccine immunizations respectively.The control farms were not immunized with the vaccines.Nasal swabs and sera were collected before and 1st and 2nd immunization of the piglets,30 days and 60 days after the immunization.The samples were subjected to SS isolate identification and detection of Streptococcus suis serotype 2 antibodies.The results showed that piglets immunized with SS2 vaccine produced higher levels of antibodies,and piglets were not carried SS2.Piglets not immunized with SS2 vaccine can produce antibodies,but the antibody level is low.Piglets were carried SS2,indicating that the immunity of SS2 vaccine is better.