Isolation And Identification Of Streptococcus From Swine In Henan Province And Preparation Of The Inactive Vaccine

In order to investigate the prevalence and serogroup distribution of Streptococcus from swine in Henan province, 113 strains of Streptococcus were isolated from clinical diseased pigs from 16 regions of Henan province, and then the strains were identified by cultivation, biochemical event, and serological agglutination. The results showed that they had many characteristics of Streptococcus, such as morphology, Gram staining, culture and haemolysis characters, and etc, except for chemical event: fermenting glucose, lactose, Trehalose; not fermenting dahlin and not starch-splitting, and not growing in broth at at PH9.6; Fermentation of mannitol, glucitol, Salicin and csculin differs from strains. Latex agglutination test showed that 3 strains belonged to Lancefield group C Streptococcus, account for 2.8%, Lancefield group D Streptococcus was 19 strains, account for 17.8%, no group A, B, F, G existed, others was unkown groups of Streptococcus. Among the 113 strains, 16 strains was Streptococcus suis based on the species-specific PCR assay detecting the gdh gene coding for glutamate dehydrogenase.Drugresistant test indicated that the Streptococcus strains isolated were high sensitive to Ceftriaxone, Penicillin, Ampicillin, Vancomycin and novobiocin; moderate sensitive to Amikacin, Ofloxacin and Ciprofloxacin; resistant to Erythromycin, Tetracycline, Clindamycin and Lincomycin. And the drugresistance ranges was rather vast, taking on multidrug resistant, among these, 6 strains was triplication, tetramerous and deca-plex drugresistance strains, account for 5.6% (6/108); and there were 16 strains resistant to five or nine kinds of drugs, account for 14.8%(16/108); and strains of resistance to six kinds of drugs was 17, account for 15.7%(17/108); and resistance to seven or eight kinds of drugs was 18 strains, account for 16.7%(18/108); and there were 3 strains resistant to eleven drugs, account for 2.7%(3/108); and until now, no strains were found sensititive to the detected drugs.By Plate—agglutination assay using Streptococcus suis type 2(SS2) bacterial antigen, 1609 serum samples collected from 17 regions of 87 pig farms in Henan province in order to better investigate the seroepidemiology of SS2 in Henan, the results showed that the average antibody positive rate of SS2 in blood of healthy pigs ranged from 83.33% to 100%, and the positive pig farms was 83, account for 95.40% of that detected, among these, the individual positive rate of pigs ranged from 2.5% to 100%, and pig farms of positive rates above 50% were 68%, account for 81.93%, and the average positive of total samples detected was 50.96%.Based on the research above, four strains of high pathogenicity and high immunogenicity were screened out for using as vaccine strains by determining its minimum lethal dose(MLD) to mouse, which contains each strain of group C Streptococcus, group D Streptococcus, Streptococcus suis type 2, and also Enterococcus faecalis, these strains were prepared for vaccine supplemented with the adjuvant of aluminium hydroxide. The challenge test using mouse showed that the prepared inactived vaccine of quadravalence had a high immunoprotection rate of 100%.