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目的从基因水平上探究猪链球菌菌株血清不可分型的原因及cps基因簇序列变异规律。方法根据Gen Bank登记号下载并提取41株猪链球菌血清未分型菌株的cps基因簇序列,根据wzy序列确定菌株的cps型别,并与相应血清型标准菌株的cps基因簇进行序列比对研究。结果 41株血清未分型猪链球菌中,共有37株菌的cps型别属于已知血清型。其中18株与其对应的血清型标准菌株的cps基因簇相比出现部分cps基因的插入、缺失、倒转、替换和移码突变等变异;另有19株与其对应的血清型标准菌株的cps基因簇序列相同或相似,除携带血清24型cps基因簇的菌株LSS23、LSS31、LSS37与血清24型标准菌株88-5299A的cps基因簇同源性为96%外,其余16株与其各自的标准菌株的cps基因簇同源性均超过99%。此外,有4株血清未分型菌株属于已知的新cps型别。结论由于猪链球菌cps基因簇序列变异频繁,导致荚膜多糖抗原型别呈多样化趋势,传统的血清凝集方法无法有效应对,亟需引入更灵敏的分子血清分型技术开展监测。
OBJECTIVE: To investigate the reason of the undifferentiation of Streptococcus suis strains and the variation of cps gene cluster sequence at the genetic level. Methods According to the Gen Bank accession number, 41 strains of S.pneumoniae serotypes were cloned and sequenced. The cps type of the isolates was determined according to the wzy sequence. The sequences were aligned with those of the corresponding serotypes the study. Results Among 41 strains of Streptococcus suis serotypes, 37 strains of cps belonged to known serotypes. Among them, 18 cps genes were inserted, deleted, inverted, replaced and frameshift mutation compared with the cps gene cluster of the corresponding serotype standard strains. In addition, 19 cps gene clusters of the corresponding serotype standard strains The sequences were the same or similar except that the cps gene cluster of strains LSS23, LSS31, LSS37 carrying serotype 24 cps gene cluster and serotype 24 strain 88-5299A had 96% homology with the cps gene of the other strains cps gene cluster homology over 99%. In addition, 4 strains of undifferentiated serotypes belong to the known new cps type. Conclusion Due to the frequent variation of cps gene cluster of Streptococcus suis, the antigenic types of capsular polysaccharide are diversified. Traditional methods of serum agglutination can not effectively deal with these problems. It is urgent to introduce a more sensitive molecular serotyping technique for monitoring.