Isolation, Identification and Pathogenicity Analysis of Streptococcus suis Type 2  

作　　者：Zicheng MA Yan LI Jinyuan GU Tao PENG Zhaohu LIU Hongyu WANG Fanliang MENG Fangkun WANG Sidang LIU 

机构地区：[1]College of Animal Science and Technology,Shandong Agricultural University,Taian 271018,China [2]Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control and Prevention,Shandong Agricultural University,Taian 271018,China [3]Shandong Provincial Engineering Technology Research Center of Animal Disease Control and Prevention,Taian 271018,China

出　　处：《Agricultural Biotechnology》2019年第4期64-68,共5页农业生物技术（英文版）

基　　金：Supported by National Key Basic Research Program of China(973 Program)(2017YFD0500605)

摘　　要：[Objectives]This study aimed to investigate the pathogenicity,growth characteristics and drug resistance of Streptococcus suis type 2.[Methods]Bacterial isolation and identification,biochemical experiments,determination of growth curve and correlation curve between OD 600 values and viable counts,drug susceptibility tests,pathogenicity analysis,and histopathological observations were carried out.[Results]The Streptococcus strain isolated from infected pigs was identified as Streptococcus suis type 2,which was named TA01 strain.TA01 strain reached the growth peak at 6-8 h post-incubation,and viable counts gradually declined after 8 h of incubation.The correlation equation between OD 600 values and viable counts is y=24.659 x-1.076 1,R^2=0.996 7.TA01 strain was sensitive to penicillin,erythromycin,florfenicol and oxacillin,and resistant to ciprofloxacin,polymyxin B and clindamycin.According to the results of pathogenicity analysis,all the mice in 3.6×10^9 cfu/mouse group died within 48,and these dead mice exhibited acute pyaemia septica.Based on the Reed-Muench formula,it was calculated that LD 50 of TA01 strain was 1.137×10^8 cfu/mouse.Pathological examination showed obvious blue-stained bacteria clusters,accompanied by neutrophil infiltration.[Conclusions]TA01 strain was a virulent strain of Streptococcus suis type 2.Compared with Streptococcus strains which were isolated and reported in China,TA01 strain exhibited strong virulence and rapid proliferation.[Objectives] This study aimed to investigate the pathogenicity, growth characteristics and drug resistance of Streptococcus suis type 2. [Methods] Bacterial isolation and identification, biochemical experiments, determination of growth curve and correlation curve between OD600 values and viable counts, drug susceptibility tests, pathogenicity analysis, and histopathological observations were carried out. [Results] The Streptococcus strain isolated from infected pigs was identified as Streptococcus suis type 2, which was named TA01 strain. TA01 strain reached the growth peak at 6-8 h post-incubation, and viable counts gradually declined after 8 h of incubation. The correlation equation between OD600 values and viable counts is y=24.659x-1.076 1, R2=0.996 7. TA01 strain was sensitive to penicillin, erythromycin, florfenicol and oxacillin, and resistant to ciprofloxacin, polymyxin B and clindamycin. According to the results of pathogenicity analysis, all the mice in 3.6×109 cfu/mouse group died within 48, and these dead mice exhibited acute pyaemia septica. Based on the Reed-Muench formula, it was calculated that LD50 of TA01 strain was 1.137×108 cfu/mouse. Pathological examination showed obvious blue-stained bacteria clusters, accompanied by neutrophil infiltration. [Conclusions] TA01 strain was a virulent strain of Streptococcus suis type 2. Compared with Streptococcus strains which were isolated and reported in China, TA01 strain exhibited strong virulence and rapid proliferation.

关 键 词：STREPTOCOCCUS SUIS TYPE 2 ISOLATION and IDENTIFICATION Growth curve Drug sensitivity test PATHOGENICITY LD 50 determination 

分 类 号：S85[农业科学—兽医学]