致败血症、脑膜炎合并肺炎的14型猪链球菌病原学和分子特征分析

Etiology and molecular analysis of Streptococcus suis type 14 causing sepsis,meningitis and pneumonia

目的通过对患者血液标本中分离出的病原菌进行鉴定和分析,了解14型猪链球菌的病原学和分子特征。方法采用质谱分析和血清凝集试验进行菌种鉴定;采用微量肉汤稀释法分析临床分离菌株的耐药性。采用聚合酶链反应(PCR)检测临床分离菌株的7种主要毒力基因;用二代测序获得基因组信息,并进行平均核苷酸一致性(ANI)、ST分型、耐药基因分析。结果该临床分离菌株与14型猪链球菌诊断血清发生凝集反应,与2型猪链球菌诊断血清不发生凝集反应。PCR检测结果示16S rRNA阳性、cps 2J阴性、cps 14J阳性。分离菌株除对红霉素、阿奇霉素、四环素和克林霉素耐药外,对包括万古霉素在内的其他9种抗菌药物均敏感。除gapdh毒力基因阴性外,该菌株6个主要毒力基因mrp、fbps、sly、orf 2、ef和gdh均为阳性;测序结果示该菌株为ST 1型,系统发育树分析结果示该菌株与前期深圳市和广西壮族自治区分离株具有密切的亲缘关系。结论分离的病原菌为高毒力株14型猪链球菌ST 1型,可导致患者同时并发败血症、脑膜炎和肺炎,目前尚未见相关报道。疫源地应加强疫情预防和监控,避免病例再次出现。

Objective To identify and analyze the pathogenic bacteria isolated from blood samples of patients,and to understand the etiology and molecular characteristics of Streptococcus suis type 14.Methods Mass spectrometry analysis and serum agglutination test were used for identification.The drug resistance was analyzed by microbroth dilution method,and polymerase chain reaction(PCR)was used to determine 7 main virulence genes.Genomic information was obtained by next generation sequencing,and average nucleotide identity(ANI),ST typing and drug resistance gene analysis were performed.Results The isolates showed agglutination reaction with Streptococcus suis type 14,but no agglutination reaction with Streptococcus suis type 2.PCR showed positive 16S rRNA,negative cps 2J and positive cps 14J.The isolate were sensitive to all 9 antibiotics,including vancomycin,except for erythromycin,azithromycin,tetracycline and clindamycin,which were resistant.Except for gapdh virulence gene negative,the 6 main virulence genes,mrp,fbps,sly,orf 2,ef and gdh,were all positive.The sequencing results showed ST 1 type,and phylogenetic tree analysis showed that this isolate had a relationship with previous isolates from Shenzhen City and Guangxi Zhuang Autonomous Region.Conclusions The isolated pathogen is highly virulent isolate Streptococcus suis type 14 ST 1,which can cause complications such as sepsis,meningitis and pneumonia in patients.Currently,there are no relevant reports.Epidemic prevention and monitoring should be strengthened in epidemic areas to avoid the recurrence of cases.