佛山市南海区鼠类自然感染恙虫病东方体基因型分析

Genotype analysis of Orientia tsutsugamushi naturally infected rodents in Nanhai District of Foshan

目的 调查佛山市南海区鼠类自然感染恙虫病东方体(Orientia tsutsugamushi, Ot)的情况,了解当地Ot基因型的分布及特点,为防控恙虫病提供科学依据。方法 2017年7月利用鼠夹和鼠笼,在佛山市南海区恙虫病高发镇街采集鼠类动物样本,应用巢式聚合酶链反应(nested polymearse chain reaction, nPCR)扩增技术检测Ot 56kDa型特异性抗原(type-specific antigen, TSA)基因核酸片段,通过核酸序列比对确定Ot基因分型。用MEGA 10.0.5、DNAStar 7.1、MegAlign等生物信息学软件进行同源性与遗传进化分析。结果 共捕获鼠类200只,褐家鼠检出56kDa TSA基因片段6份,黄胸鼠检出1份,阳性率为3.5%(7/200)。南海序列(L65、L68、L118、L119、L122、L150和L153)在核苷酸水平与Kawasaki、Gilliam、TA763、Kato、Kuroki、Karp基因型相似性为71.8%~100.0%,氨基酸水平相似性为54.9%~100.0%。同源性和系统进化分析表明,南海序列与Ot中的Karp型具有较高的同源性和较近的亲缘关系,与其他型同源性较低,亲缘关系较远。L65、L119、L150和L153与台湾TW45R株、云南TN16-28株的核苷酸同源性为100.0%。结论 佛山市南海区存在鼠类Ot自然感染,褐家鼠为其主要宿主,当地恙虫病病原体属于Karp型。

Objective eTo investigate the natural infection of Orientia tsutsgamushi(Ot)isolated from rodents in Nanhai district of Foshan,and to understand the distribution and characteristics of local Ot genotypes,so as to provide a scientific basis for the prevention and control of scrub typhus.Methods In July 2017,rodent traps and cages were used to collect rodent samples in a town street with a high incidence of scrub typhus in Nanhai District of Foshan.Nested polymerase chain reaction(nPCR)amplification was used to detect the 56kDa type-specific antigen(TSA)gene nucleic acid fragments of Ot and the Ot genotype was determined by nucleic acid sequence alignment.Homology and genetic evolution analysis were performed using such bioinformatics softwares as MEGA 10.0.5,DNAStrar 7.1 and MegAlign.ResultsA total of 200 rodents were captured.Six specimens of Rattus norvegicus and one specimen of Rattus flavipectus were confirmed positive for Ot 56kDa TSA gene,with a positive rate of 3.5%(7/200).The 56kDa TSA gene of Nanhai sequences(L65,L68,L118,L119,L122,L150 and L153)showed similarities of 71.8%-100.0%at the nucleotide level and 54.9%-100.0%at the amino acid level with the Kawasaki,Gilliam,TA763,Kato,Kuroki,and Karp genotypes.The homology and phylogenetic analyses showed that Nanhai sequences shared high homology and close ties of consanguinity with the Karp strains of Ot,but had relatively low homology and large ties of consanguinity with other strains.The nucleotide sequence of L65,L119,L15 and L153 shared 100.0%of homology with TW45R strain found in Taiwan and TN16-28 strain found in Yunnan.Conclusion Natural infection of Ot infection is presented in rodents from Nanhai District of Foshan and Rattus norvegicus is the main host.Pathogen of scrub typhus in Nanhai District belongs to Karp type.