天津市一起停乳链球菌似马亚种感染引起的聚集性发热事件的调查分析

目的 调查一起疑似停乳链球菌似马亚种（Streptococcus dysgalactiae subsp. Equisimilis, SDSE）引起的发聚集性发热事件,为今后处理类似事件积累经验。方法 2020年5月22日天津市某公司内出现不明原因聚集性发热病例,采集24例患者咽拭子标本,采用荧光定量PCR技术、微流体芯片技术、基因测序技术、细菌培养、药敏试验等方法进行病毒、细菌等相关病原体检测。现场采集90份环境样本进行细菌检测。结果 24份咽拭子标本中,9份标本检出溶β-溶血性链球菌,经VITEK2生化鉴定系统及质谱鉴定仪确认为停乳链球菌似马亚种。药敏试验结果显示对万古霉素、氨苄西林、氯霉素、左氧氟沙星、头孢唑林、头孢曲松、青霉素100%敏感,对庆大霉素、红霉素、阿奇霉素、克林霉素、克拉霉素100%耐药,对复方新诺明中度耐药（耐药率为55.6%）,对四环素的耐药率为77.8%,基因组测序结果显示66 666个reads为停乳链球菌似马亚种的基因片段,覆盖基因组长度为2 179 445 bp,覆盖度达到60%。环境样本各项细菌检测指标均合格,未检出β-溶血性链球菌和嗜肺军团菌。结论 这是一起疑似由停乳链球菌似马亚种引起的聚集性发热事件,在天津地区尚属首次。SDSE引起的暴发感染在国内非常罕见,迅速对病原体进行分离鉴定是确定疫情爆发原因的关键。

Investigation and analysis of a cluster fever event caused by Streptococcus dysgalactiae subspequisimilis infection in Tianjin

Objective To investigate a cluster fever event caused by Streptococcus dysgalactiae subsp. equisimilis, and help to better manage the future outbreaks. Methods On 22 May 2020, the a cluster fever cases of unknown origin occurred a company in Tianjin. 24 throat swab specimens were collected from these patients, and fluorescent quantitative PCR technology, microfluidic chip technology, gene sequencing technology, bacterial culture, drug sensitivity test and other methods are used to detect the related pathogens. 90 environmental samples were collected for bacterial detection. Results Among the 24 throat swab specimens, strains of Streptococcus hemolyticus were isolated from the 9 specimens and identified by VITEK2 biochemical identification system and MALDI-TOF MS as Streptococcus dysgalactiae subsp. equisimilis. The antimicrobial susceptibility test suggested that these strains were 100% sensitive to vancomycin, ampicillin, ampicillin, chloramphenicol, levofloxacin, cefazolin, ceftriaxone, penicillin and 100% resistance to gentamicin, erythromycin, azithromycin, clindamycin, clarithromycin. The moderate resistance rate to trimethoprim/sulfamethoxazole was 55.6%. The drug resistance rate to tetracycline was 77.8%. Genome sequencing showed that 66 666 reads were gene fragments of Streptococcus dysgalactiae subsp. equisimilis, covering 2 179 445 bp genome length with the coverage of 60%. All bacterial test indexes of environmental samples were up to standard. β-Streptococcus haemolyticus and Legionella pneumophila were not detected. Conclusion It is the first time that an outbreak of a cluster fever event caused by Streptococcus dysgalactiae subsp. Equisimilis was found in Tianjin. Streptococcus dysgalactiae subsp. equisimilis outbreaks are rare in China, therefore, rapid isolation and identification of pathogens is the key to determine the cause of the outbreak.