Isolation,Identification And Analysis Of Some Biological Traits Of Streptococcus Suis In Sichuan Area

Streptococcus suis,a common bacterial contagious disease on pig farms,can cause swine meningitis,septicemia,endocarditis,arthritis and pneumonia,which result in severe economic loss in the global swine sector.And it is also a crucial pathogenic bacterium that can infect both people and animals.This study detected and analyzed the drug resistance,virulence genotype distribution and serotype of Streptococcus suis that isolated and obtained from the Sichuan area,so as to provide technical reference for the prevention and treatment of Streptococcus suis in Sichuan area.Between 2017 and 2019,we collected diseased pigs that are suspected to infect Streptococcus suis from various-scale pig farms in Sichuan Province.we totally got 62 strains of Streptococcus suis through isolation and culture of bacterial,specific PCR identify and testing and contrasting sequence.And in the lungs,the isolation rate is the highest.Most Streptococcus suis shows mixed infections with other pathogens.We identified Streptococcus suis type 1,2,7 and 9 of 62 isolated strains by the method of PCR genotyping.Among them,there are 4 strains of type 1(6.45%),10 strains of type 2(16.13%),17 strains of type 7(27.42%),6 strains of type 9(9.68%),and 25 strains of unknown serotype(40.32%).The results illustrate that multiple serotype infections of Streptococcus suis exist in Sichuan area,among which type 7 and type 2 of Streptococcus suis are the major and widespread serotypes.According to the five major virulence genes of Streptococcus suis(mrp?orf2?gdh?sly?epf),we designed and synthesized the corresponding primer sequences to detect 62 strains of Streptococcus suis.The results are gdh(62/100%),mrp(45/72.58%),sly(4/6.45%),orf2(29/46.77%),epf(20/32.26%).62 isolated strains of Streptococcus suis can be divided into 12 genotypes,and the strain with virulence genotype of gdh+mrp+erf+sly+orf2+shows the strongest virulence in the pathogenicity test in mice.We selected 17 antibacterial drugs that commonly used in the clinic,and we used K-B paper agar diffusion method to carry out the drug susceptibility test on 62 strains of Streptococcus suis.The results show that the multiple drug resistance of streptococcus suis isolated from Sichuan is severe,and the number of isolated strains with multiple drug resistance capacity is 59(95.16%).The drug resistance to tetracycline,erythromycin and clindamycin is the most severe,accounting for 72.58%,82.26% and 83.87% respectively.However,the susceptibility to ?-lactams and quinolone antibiotics is better.The results of resistance genes for tetracyclines and macrolides are tet M(40/64.51%),tet O(49/79.03%),mef A(3/4.84%),erm B(53/85.48%),which are consistent with the results of drug susceptibility test.In accordance with the results,we recommend that ?-lactams and quinolone antibiotics can be preferred to use in clinical treatment.