台灣懷孕婦女乙型鏈球菌帶菌之分子流行病學分析

Molecular Epidemiologic Analysis of Group B Streptococcus from Pregnant Women in Taiwan

研究目的：乙型鏈球菌（Group B Streptococcus或Streptococcus agalactiae；簡稱GBS），為25%婦女泌尿和生殖系統之常見菌，可透過生產垂直傳染於新生兒進而引發新生兒肺炎、敗血症和腦膜炎。為了瞭解台灣懷孕婦女本土的流行病資料，本研究分析來自彰濱秀傳醫院從懷孕婦女常規篩檢所分離乙型鏈球菌菌株，進行多種分子基因分析，探討台灣懷孕婦女乙型鏈球菌型分型分佈。
檢體來源與方法：本研究檢體來源是利用彰濱秀傳醫院在2017所凍存的218個乙型鏈球菌菌株。進行臨床8種抗生素抗藥性分析及利用多套式聚合酶連鎖反應（Multiplex polymerase chain reaction）進行莢膜多醣體血清型分型、hvgA基因分析、多點位基因序列分型。
實驗結果：在這218株乙型鏈球菌中，莢膜多醣體型別分佈前三名依序是Type III（25.2%），Type VI（22.5%），Type V（14.7%）。我們更進一步挑選105株進行多點位基因序列分型(MLST)分析，前三名主要序列型（ST）依序為ST1 / Serotype VI（20%），其次為ST12 / Serotype Ib（8.6%），及ST17 /Serotype III（7.6%）。在抗藥性部分，所有菌株對penicillin仍維持100%敏感性，但在Erythromycin（41.3%）和Clindamycin（39.4%）為高度抗藥性。除此之外，本實驗也針對ST17菌株檢測是否攜帶hvgA基因，結果顯示所有ST17菌株（100%）均帶有此毒性基因。
結論：本研究顯示台灣懷孕婦女乙型鏈球菌帶菌率為22%，以serotype III及VI為最主要的兩個型別，ST17雖然比例不高，但均攜帶高致病毒力hvgA基因。目前治療懷孕婦女乙型鏈球菌感染或預防性用藥仍建議以penicillin為首選用藥。

Background: Group B Streptococcus or Streptococcus agalactiae (GBS) is a common pathogen associated with urogenital system infection in 25% of women. Neonatal GBS disease generally manifests as pneumonia, sepsis, and meningitis during delivery. To investigate the molecular epidemiological distribution of GBS in locally pregnant women, GBS strains were obtained from routinely screened-pregnant women at Chang Bing Show Chwan Memorial Hospital (CBSCMH) for further genetic based-molecular analysis.
Materials and methods: We investigated GBS collected in 2017 at Chang Bing Show Chwan Memorial Hospital by analyzing antibiotic resistance, capsular polysaccharide serotyping, carriage of hvgA gene, and multi-locus gene sequence typing (MLST).
Results: In total, 218 out of 957 vaginal swabs were GBS positive (22%), and the leading three serotypes were type III (25.2%), type VI (22.5%), and type V (14.7%). Then, 105 selected strains were further investigated by MLST analysis. The top three main sequence types (ST) were ST1 / Serotype VI (20%), followed by ST12 / Serotype Ib (8.6%), and ST17 / Serotype III (7.6%). Regarding antimicrobial resistance, all strains remained 100% sensitive to penicillin, but highly resistant to erythromycin (41.3%) and clindamycin (39.4%). In addition, all 8 GBS strains with ST17 type carried the hvgA virulence gene (100%).
Conclusion: This study shows that the positivity rate of GBS among pregnant women in Taiwan was 22%, and serotypes III and VI were the leading two serotypes. Although the proportion of ST17 was not high, but they all contained the virulent hvgA gene. At present, penicillin is still recommended as the first choice for the treatment or prevention of beta-streptococcal infection in pregnant women.