江苏省中部地区猪链球菌主要致病血清型分子流行病学调查

Study on molecular epidemiology of major pathogenic Streptococcus suis serotypes in middle part of Jiangsu province

目的了解江苏省中部地区正常猪群猪链球菌及主要致病血清型分布。方法采集江苏省中部地区正常屠宰猪样本303份，用聚合酶链反应（PCR）法进行猪链球菌及主要致病血清型的检测，并对3株分离的猪链球菌菌株进行系统的生物学和分子遗传学鉴定。结果303份猪标本中，2005年正常猪群中猪链球菌的携带率达88．0％，其中1（或14）型、2（或1／2）型、7型和9型携带率分别为9．6％、8．5％、11．3％、29．5％；2006年正常猪群中猪链球菌的携带率为82．5％，1（或14）型、2（或1／2）型、7型和9型携带率分别为17．6％、2．4％、25．8％、20．0％；3株分离菌株均为2型，2a毒力因子表现型为cps2^＋／gdh^＋／mrp^-／epf^-／sly^-／fops^＋／orf2^＋／89k^-，2f、14e毒力因子表现型均为cps2^＋／gdh^＋／mrp^-／epf／sly^-／fbps^-／orf2^-／89k；3株分离菌株对阿莫西林、氨苄西林、青霉素等高度敏感，但对阿米卡星和四环素有显著的耐药性；对BALB／c小鼠和家兔无明显致病性。结论江苏省中部地区正常猪群中猪链球菌携带率处于较高水平，多种血清型同时存在，毒力因子表型与流行毒力株有显著差异。

Objective To determine the prevalence of Streptococcus suis and major pathogenic serotypes in middle part of Jiangsu province. Methods Tonsillar specimens from 303 slaughtered pigs aged 6 to 8 months were investigated for the presence of Streptococcus suis and major pathogenic serotypes by polymerase chain reaction （PCR） method. Bacteriological examination compared with molecular genetics identification for three Streptococcus suis isolates were also done. Results The overall carrier rate of Streptococcus suis was up to 88.0%, with the percentages of serotype 1 （14）, 2 （1/2）, 7 and 9 were 9.6 %, 8.5 % , 11.3 % and 29.5 % respectively in 2005. While in 2006, the prevalence of Streptococcus suis was 82.5% ,with capsular types 1 （14）,2（1/2）,7 and 9 were accounted for 17.6% ,2.4% ,25.8% and 20.0 % of all the specimens. All the three isolates belonged to Streptococcus suis serotype 2,named 2a,2f and 14e, which exhibiting the virulent phenotype cps2^＋ /gdh ^＋ /rnrp /epf /sly /flops^＋/off2^＋ /89k , cps2^＋/gdh^＋/mrp /epf^-/sly /flops^-/orf2^-/89k and cps2^＋/gdh^＋/mrp^-/epf/sly^-/fbps^-/orf2^-/89krespectively. These isolates were all susceptible to amoxicillin, ampicillin, penicillin and resistant to amikacin and tetraycline. Clinical signs were not noted in BALB/c mice and rabbit. Conclusion Prevalence of the Streptococcus suis among the healthy herds in the areas was very high, with various capsule types of Streptococcus suis involved in the same herds,and the virulent phenotype of these 3 isolates were very different from those prevalent Streptococcus suis serotype 2 virulent isolates frequently discovered from the epidemic areas.