我国北方部分地区土拉弗菌感染宿主动物的分子流行病学研究

Molecular epidemiological investigation on Francisella tularensis infection hosts in northern China

目的:了解我国北方部分地区宿主动物感染土拉弗菌状况和基因型别。方法:鼠夹诱捕鼠,从鼠脾组织提取DNA,应用巢式PCR检测土拉弗菌,计算并比较各地区及各鼠种阳性率。阳性标本用型特异性引物及短串联重复序列(SSTR9、SSTR16)引物扩增两区域并测序,用C lustalX(5.0)和DNA C lub软件对序列进行比较分析。结果:共捕获鼠421只,分属14种鼠种,其中7个鼠种20份标本PCR检测阳性,总阳性率为4.75%。吉林、新疆、黑龙江、内蒙古和浙江的阳性率分别为11.65%,10.00%,6.54%,1.76%和0%。地区间阳性率差异显著(χ2=20.90,P=0.0003);不同鼠种间阳性率未见差异(χ2=11.82,P=0.066)。对20份扩增阳性标本进行型特异性扩增及SSTR9、SSTR16序列测定并对比分析,结果显示均为土拉弗菌B亚型,但型内差别较大,标本及菌株相互比较均显示基因多态性程度高且地区间有交叉。结论:我国北方部分地区可能依然存在B亚型土拉弗菌型感染(宿主动物)情况,且其基因型内差异较大。

Objective： To investigate Francisella tularensis （F. tularensis） infection of rodents captured in northern China and to identify genotype of F. tularensis. Methods： DNA was isolated from spleens of captured rodents and examined by nested PCR. Twenty positive samples were further amplified with the target of short-sequence tandem repeat region （SSTR） sequenced and analysed by ClustalX （5.0） and DNAClub software. Results： A total of 424 rodents belonging to 14 species were captured. Seven out of the 14 rodent species were positive for F. tularensis and the overall prevalence of F. tularensis was 4.75%, with a wide geographic variation ranging from 11.65% （ Jilin province in northern China） to 0% （Zhejiang Province in southern China）. The geographical difference in infection rate was statistically significant,but there was no significant difference in infection rate among the 7 positive rodent species. Nucleotide sequences analysis showed that the detected strains of F. tularensis all belonged to F. tularensis type B, but the genotype was quite different. Comparison of samples and strains showed high degree of gene polymorphism and geographic overlap was observed among different regions. Conclusion： Infection of F. tularensis in host animals in northern China still exists and the genotype of which has several variants.