Data_Sheet_1_Serotype Distribution, Antimicrobial Susceptibility, Multilocus Sequencing Type and Virulence of Invasive Streptococcus pneumoniae in China: A Six-Year Multicenter Study.docx

Background:Streptococcus pneumoniae is an important human pathogen that can cause severe invasive pneumococcal diseases (IPDs). The aim of this multicenter study was to investigate the serotype and sequence type (ST) distribution, antimicrobial susceptibility, and virulence of S. pneumoniae strains causing IPD in China.
Methods: A total of 300 invasive S. pneumoniae isolates were included in this study. The serotype, ST, and antimicrobial susceptibility of the strains, were determined by the Quellung reaction, multi-locus sequence typing (MLST) and broth microdilution method, respectively. The virulence level of the strains in the most prevalent serotypes was evaluated by a mouse sepsis model, and the expression level of well-known virulence genes was measured by RT-PCR.
Results: The most common serotypes in this study were 23F, 19A, 19F, 3, and 14. The serotype coverages of PCV7, PCV10, PCV13, and PPV23 vaccines on the strain collection were 42.3, 45.3, 73.3 and 79.3%, respectively. The most common STs were ST320, ST81, ST271, ST876, and ST3173. All strains were susceptible to ertapenem, levofloxacin, moxifloxacin, linezolid, and vancomycin, but a very high proportion (>95%) was resistant to macrolides and clindamycin. Based on the oral, meningitis and non-meningitis breakpoints, penicillin non-susceptible Streptococcus pneumoniae (PNSP) accounted for 67.7, 67.7 and 4.3% of the isolates, respectively. Serotype 3 strains were characterized by high virulence levels and low antimicrobial-resistance rates, while strains of serotypes 23F, 19F, 19A, and 14, exhibited low virulence and high resistance rates to antibiotics. Capsular polysaccharide and non-capsular virulence factors were collectively responsible for the virulence diversity of S. pneumoniae strains.
Conclusion: Our study provides a comprehensive insight into the epidemiology and virulence diversity of S. pneumoniae strains causing IPD in China.

背景：肺炎链球菌（Streptococcus pneumoniae）是一类重要的人类病原菌，可引发严重的侵袭性肺炎链球菌疾病（invasive pneumococcal diseases, IPDs）。本项多中心研究旨在调查中国境内引发侵袭性肺炎链球菌疾病的肺炎链球菌菌株的血清型（serotype）、序列型（sequence type, ST）分布、抗菌药物敏感性及毒力特征。
方法：本研究共纳入300株侵袭性肺炎链球菌分离株。分别通过奎伦反应（Quellung reaction）、多位点序列分型（multi-locus sequence typing, MLST）与微量肉汤稀释法（broth microdilution method），测定菌株的血清型、序列型与抗菌药物敏感性。针对流行度最高的血清型菌株，采用小鼠败血症模型（mouse sepsis model）评估其毒力水平，并通过逆转录聚合酶链式反应（reverse transcription polymerase chain reaction, RT-PCR）检测已知毒力基因的表达水平。
结果：本研究中最常见的血清型依次为23F、19A、19F、3与14。本次菌株集合的PCV7、PCV10、PCV13及PPV23疫苗血清型覆盖率分别为42.3%、45.3%、73.3%与79.3%。最常见的序列型为ST320、ST81、ST271、ST876与ST3173。所有菌株均对厄他培南（ertapenem）、左氧氟沙星（levofloxacin）、莫西沙星（moxifloxacin）、利奈唑胺（linezolid）及万古霉素（vancomycin）敏感，但极高比例（>95%）的菌株对大环内酯类（macrolides）与克林霉素（clindamycin）耐药。根据口服剂型、脑膜炎及非脑膜炎折点判定标准，青霉素不敏感肺炎链球菌（penicillin non-susceptible Streptococcus pneumoniae, PNSP）分别占分离株总数的67.7%、67.7%与4.3%。血清型3菌株表现为高毒力水平与低抗菌药物耐药率，而23F、19F、19A及14型菌株则呈现低毒力与高抗生素耐药性。荚膜多糖与非荚膜毒力因子共同介导了肺炎链球菌菌株的毒力多样性。
结论：本研究全面阐明了中国境内引发侵袭性肺炎链球菌疾病的肺炎链球菌菌株的流行病学特征与毒力多样性。