| Streptococcus suis(S.suis) is a common bacterial infectious diseases,which is distributed worldwide, causing huge economic losses to the global pig industry. It mainly causes pigs meningitis, arthritis, septicemia, endocarditis, encephalitis, abortions, polyserositis, and bronchopneumonia.There are 35 serotypes,serotype 1 to 34 and serotype 1/2.The main pathogenic serotypes are 1,2,7 and 9,particularly serotype 2,and serotype 3 with pneumonia.In order to know the infection,epidemic serotype,drug resistance and pathogenicity of S.suis in Sichuan,the following research was done in this study.1、Infection survey of S.suis 2 in SichuanIn order to know the infection of S.suis 2 in Sichuan,526 pig serum which were from Chengdu, Ya’an, Ziyang etc (32 counties) 43 farm of Sichuan in the two past years was detected by ELISA.33 farms are Suis 2 positive farms and the positive rate of farms was 78.57%.212 serum samples tested are positive for S.suis 2,and the average positive rate of pig serum was 40.30%.The results showed that infection of S.suis 2 in Sichuan was serious.The positive rate of sow was highest,followed by nursery and finishing pigs, 65.77%,39.88%,29.15% respectively.2、Serotype survey of S.suis in SichuanS.suis was isolated and identified from diseased pigs that were from Chengdu, Ya’an, Guang’an etc (18 counties),and there were 34 S.suis isolates.S.suis 1、2、7、9 and 3 were identified by PCR.There were 16 S.suis 2 (47.1%),9 S.suis 7 (26.5%),1 S.suis 9,4 S.suis 3 (11.8%),and 4 isolates were unknown (11.8%).It showed that there were infected with multiple serotypes of S.suis in Sichuan,and serotype 2 was the predominant serotype, followed by serotype 7 and 3.3、The main virulence gene research of S.suis and pathogenicity experiments of representative strains of S.suis 2 in SichuanThree major virulence genes mrp,epf and sly were detected by PCR.As a result,9 mrp+(26.5%),14 epf+(41.2%),26 sly+(76.5%).There were three virulence phenotypes in 34 S.suis isolates,9 mrp+epf+sly+(56.3%),5 mrp-epf+sly+(31.3%),2 mrp-epf-sly-(12.5%),and mrp+epf+sly+was dominant genotype.The purified PCR amplification products of cps 2J、 mrp、epf and sly gene from 16 S.suis 2 were sequenced and analysised.And the result showed that the homology of the four virulence gene nucleotide sequence between 16 S. suis 2 and the Suis reference strains of domestic and foreign were 98.5%～100%、 99.6%-100%、99.4%-100%、98.2%-100% respectively,indicating that the virulence genes of S.suis 2 in Sichuan is relatively stable.Pathogenicity tests in mice was done with 3 S.suis 2 isolates.The result showed that virulence genotype mrp+epf+sly+was most virulent strains,followed by mrp-epf+sly+, mrp-epf-sly-was weakest.4、Drug resistance research of S.suis in Sichuan18 kinds of commonly used antibiotics were used to detect the drug sensitivity of 34 S.suis isolates. S.suis in Sichuan resistant to multiple antibiotics, drug resistance Multiple drug resistance spectrum(More than 70% of isolates resistant) is Gentamicin-kanamycin-amikacin-tetracycline-doxycycline-erythromycin-azithromycin-lin comycin-sulfamethoxazole. More than 90% of the isolates were sensitive to Amoxicillin,Ampicillin,Cephalosporin V,Ceftriaxone,so these antibiotics can be used for treating when Streptococcus suis occur. |
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