苏尼特左旗自毙鼠琥珀葡萄球菌分离株检测研究

  目的   拟通过实验室检测，探究2019年内蒙古自治区锡林郭勒盟苏尼特左旗长爪沙鼠成批死亡的原因。  方法   将所有自毙鼠解剖后，取其脏器接种到赫氏培养基和半胱氨酸心琼脂血培养基上。 对于分离菌株先排除鼠疫菌后，再接种到含有抗生素的半胱氨酸心琼脂血培养基上，同时进行土拉弗朗西斯菌（土拉菌）特异抗原乳胶凝集检测。 其次，对于所有分离菌株提取核酸后，采用16S rRNA基因通用引物进行扩增、测序和同源性比对，并与网上已公布的琥珀葡萄球菌16S rRNA基因序列进行系统进化分析。 另外，用琥珀葡萄球菌悬液感染实验小鼠，在14 d内观察实验小鼠的精神和身体状况。  结果   分离的所有菌株在土拉菌选择性培养基上均不生长，土拉菌特异抗原乳胶凝集检测均为阴性，由此可以排除土拉菌。 经过16S rRNA基因测序和比对，所有分离菌株鉴定为4株琥珀葡萄球菌、1株罗伊乳杆菌、1株阴道乳杆菌和1株粪肠球菌。 系统进化分析显示，本研究获得的3株琥珀葡萄球菌，与9株来自世界其他国家的琥珀葡萄球菌聚在主要谱系分支上。 另外1株琥珀葡萄球菌和来自新疆的琥珀葡萄球菌聚在一个分支上。 实验小鼠感染模型得出，琥珀葡萄球菌的最小致死量为5×108 CFU/mL，亚致死量为108 CFU/mL。   结论   首次发现苏尼特左旗自毙长爪沙鼠体内含有琥珀葡萄球菌，推测琥珀葡萄球菌感染可能是当地长爪沙鼠成批死亡的原因。

Detection of Staphylococcus succinus strains isolated from mice of natural death from Sonid Left Banner

  Objective  To explore the cause of the mass death of Meriones unguiculatus from Sunite Left Banner in 2019 through the laboratory testing.   Methods  After all mice of natural death were dissected, their organs were inoculated on Hirsch medium and cysteine heart agar media enriched with blood（CHAB）. Being considered not to be Yersinia pestis, the isolate was inoculated on CHAB supplemented with antibiotics, and tested by Francisella tularensis-specific antigen latex agglutination. Secondly, for all isolates DNA was extracted, and then amplified using universal primers of 16S rRNA gene. The PCR products amplified with target fragment were sequenced, and then their nucleotide sequences obtained were aligned and performed phylogenetic analysis with published 16S rRNA gene sequences of Staphylococcus succinus online. In addition, the experimental mice were infected with the S. succinus suspension, and their mental and physical conditions were observed within 14 days.   Results  All isolated strains did not grow on the selective medium for F. tularensis and were negative for F. tularensis-specific antigens in latex agglutination, so they were not F. tularensis. After sequencing and alignment of 16S rRNA gene, all isolates were identified as 4 strains of S. succinus, 1 strain of Lactobacillus reuteri, L. vaginalis and Enterococcus faecalis. The phylogenetic analysis indicated that 3 strains of S. succinus obtained in this study were clustered with 9 from the rest of the world on the clade of the major lineage. The rest strain of S. succinus was assigned to a clade with that from Xinjiang. Through the experimental mouse infected model it was found that the minimum lethal dose of S. succinus is 5×108 CFU/mL, and the sublethal dose is 108 CFU/mL.   Conclusion  For the first time, the strains of S. succinus were isolated from mice of natural death from Sonid Left Banner in Inner Mongolia Autonomous Region. It is speculated that infection of S. succinis may be the cause of mass death of local Meriones Unguiculatus.