马源马链球菌兽疫亚种3株新疆分离株基因型的鉴定及MLST分析

Identification and MLST analysis of three novel genotypes of Streptococcus equi subsp. zooepidemicus Xinjiang strains

摘要:

[背景] 马链球菌兽疫亚种（Streptococcus equi subsp. zooepidemicus，SeZ）是引起马腺疫的主要病原，还可引起猪链球菌病，加强该菌的地方株分子流行病学监测对有效防控相关疫病十分必要。[目的] 对新疆地区2个马场SeZ分离株进行鉴定和药敏特性分析，并分析3株新疆分离株的分子流行与菌株的遗传进化特征。[方法] 对分离纯化的3株病原菌（ZHZ113、ZHZ211和ZHZ523）进行染色观察、生化及药敏特性检测，对16S rRNA和SeM基因进行遗传进化分析，以链球菌7个管家基因arcC、nrdE、proS、spi、tdk、tpi和yqiL为目的基因对3株分离菌进行多位点序列分型（Multilocus Sequence Typing，MLST）研究。[结果] 3株SeZ的药敏结果显示这3株分离菌对不同抗生素的耐药程度不同，但均对头孢西丁、庆大霉素、链霉素、红霉素、左氧氟沙星、环丙沙星、土霉素等11种药物敏感。16S rRNA基因序列分析显示这3株分离菌均属于Ⅱ群（兽疫链球菌）。3株菌的MLST分型结果分别为ST39、ST419、ST421型，其中ST419和ST421型为SeZ目前尚未见报道的新ST型。SeM基因分析结果显示马源SeZ在不同国家、不同动物和不同时间段上的流行分布存在差异和动态变化的特点。[结论] 3株SeZ分离菌分别与美国犬源及马源菌株亲缘关系较近，反映部分SeZ株在新疆地区的基因型分布及分子流行特点。

Abstract:

[Background] Streptococcus equi subsp. zooepidemicus (SeZ) not only causes swine Streptococcus disease, but also is an important pathogen that causes strangles. Strangle poses a serious threat to the development of horse and donkey industry in China and it is of great significance to strengthen the molecular epidemiological monitoring of the local SeZ isolates for effective prevention and control of strangle. [Objective] To identify the bacteria and detect drug susceptibility, samples were collected from horse farms in Xinjiang. Molecular epidemic and genetic evolution characteristics of the three endemic isolates were also analyzed. [Methods] Isolation and identification, physiological and biochemical test, drug sensitivity test of 3 isolates (ZHZ113, ZHZ211 and ZHZ523), genetic evolution analysis of 16S rRNA and SeM genes were performed. Seven housekeeping genes (arcC, nrdE, proS, spi, tdk, tpi, yqiL) of 3 isolates were amplified and analyzed through multilocus sequence typing (MLST). [Results] Drug sensitivity results showed that all the three isolates were sensitive to 11 drugs like ceftiofuroxime, cefoxitin, gentamicin, streptomycin, erythromycin, doxycycline, levofloxacin, ciprofloxacin, rifampicin, clindamycin and oxytetracycline. The 16S rRNA gene sequence analysis showed that these three isolates belonged to group II (Streptococcus zooepidemicus). The MLST results showed that 3 sequence types ST39, ST419 and ST421 were found and ST419 and ST421 were identified as novel ST genotypes, which have not been reported. From the analysis of SeM gene sequence and the phylogenetic tree we found that there are variations and dynamic changes in the strangles epidemic distribution from the point of view of different countries, different animals and different time. [Conclusion] This study showed that the 3 isolates were closely related to American canine and horse strains and the results provide valuable information to understand the genotype distribution and molecular epidemic characteristics of SeZ in Xinjiang.