2017-2019年济宁市健康人群脑膜炎奈瑟菌流行病学和基因组学分析

Epidemiologic and genomic analysis of Neisseria meningitidis isolated from a healthy population in Jining City during 2017-2019

目的了解济宁市健康人群脑膜炎奈瑟菌流行情况及其基因组特征。方法采集2017-2019年流行前期、流行期、流行后期不同年龄组健康人群的咽拭子标本,进行菌株分离培养、生化试验、血清凝集试验,分离到的菌株进行基因测序,利用PubMLST数据库进行多位点序列分型(MLST)、核心基因组多位点序列分型(cgMLST)、疫苗抗原分析,利用IQ-TREE和Splits Tree构建系统发育树。结果2017-2019年共检测1086份健康人群咽拭子标本,分离出21株脑膜炎奈瑟菌,健康人群平均带菌率为1.93%。其中流行前期带菌率为0.93%,流行期带菌率为2.30%,流行后期带菌率为1.83%。17~19岁人群带菌率较高,3~5岁儿童及≥20岁成人中未检出阳性菌株。检出的21株菌株中,B群15株,C群1株,不可分群5株。通过基因组分析,主要的ST型为ST-12301和ST-14655,ST-17464、ST-17465、ST-17466、ST-17467和ST-17468为本研究新发现的ST型。进行基因测序的19株菌株中,有8株属于4821克隆群,其余菌株不属于确定的克隆群,有3株血清型为不可分群的菌株但其基因型为B型。结论济宁市2017-2019年健康人群中脑膜炎奈瑟菌血清群以B群为主。本研究新发现5种MLST序列型,提示近几年菌株基因组存在微进化。MLST序列型的变迁有可能导致流行模式发生改变,有必要开展持续监测。17~20岁人群带菌率高,应密切关注菌株在人群中的扩散传播,以防引起流脑病例。

Throat swabs from healthy people of different ages in the pre-epidemic,epidemic and post-epidemic periods from 2017 to 2019 were collected.Throat swabs were immediately inoculated on bi-antibiotic chocolate agar plates.After cultivation and isolation,biochemical tests and serocoagulation experiments were performed,and the isolated strains were sequenced.The PubMLST database was used for multilocus sequence typing(MLST),core genome multilocus sequence typing(cgMLST)and vaccine antigen analysis.IQ-TREE and Splits Tree were used to construct phylogenetic trees and diagrams.A total of 1086 throat swab specimens from healthy people between 2017 and 2019 were analyzed,and 21 strains of Neisseria meningitidis were isolated.The average carriage rate in healthy people was 1.98%.The carriage rate was only 0.93%during the pre-epidemic period,but was 2.30%and 1.83%during the epidemic and post-epidemic periods,respectively.The carriage rate was quite high in the 17-19 years old age group.No strains were isolated in children 3-5 years old and adults≥20 years old.Among the 21 strains,15 strains were in serogroup B,one strain was in serogroup C,and five strains could not be grouped.Genomic analysis indicated that the main ST types were ST-12301 and ST-14655.ST-17464,ST-17465,ST-17466,ST-17467 and ST-17468 were newly discovered ST types in this study.A total of 42.1%(8/19)of the sequenced strains belonged to the 4821 clone complex,and the remaining strains did not belong to the discovered clone complex.Three strains could not be grouped by serocoagulation but were predicted by genomic analysis.The Neisseria meningitidis serogroup was mainly Group B in the healthy population from 2017 to 2019 in Jining City.In this study,five new MLST sequence types were found,suggesting genome microevolution in recent years.Changes in MLST sequence patterns may lead to changes in epidemic patterns,and it is necessary to carry out continuous surveillance.The spread of the strain in the population between 17 and 20 years old was high,and close attention should be paid to the spread of the strain in the population to prevent meningitis cases.