Journal of Capital Medical University ›› 2023, Vol. 44 ›› Issue (2): 311-315.doi: 10.3969/j.issn.1006-7795.2023.02.019

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Serum and multilocus sequence typing  of group B streptococcus colonized in  women at 35-37 weeks of pregnancy and their relationship

Liu Jing1, Dong Yuan1*, Ji Tongzhen2   

  1. 1. Laboratory Department of Tsinghua University Hospital, Beijing 100084, China;       2. Department  of Laboratory, Beijing Obstetrics and Gynecology Hospital,Capital Medical University, Beijing 100026, China
  • Received:2022-07-26 Online:2023-04-21 Published:2023-04-18
  • Supported by:
    This study was supported by Young and Middle-aged Discipline Backbone Training Project of Beijing Obstetrics and Gynecology Hospital,Capital Medical University(fcyy201505)

Abstract: Objective  To discuss the serotyping, multilocus sequence typing (MLST) of group B streptococcus (GBS) colonized in reproductive tract of women at 35-37 weeks gestation in an Obstetrics and Gynecology Hospital of Beijing, and to provide reference for clinical prevention and treatment of GBS infection and research and development of vaccines. Methods  Women at 35-37 weeks of gestation were routinely sampled with vaginal and rectal swabs. GBS strains were cultured, identified and isolated. Capsular polysaccharide serotyping and MLST typing were performed by multiplex polymerase chain reaction (PCR) and first generation sequencing, respectively, and the correlation between the two types was analyzed by statistical method. Results  GBS strains were colonized in 147 pregnant women, of which 7 serotypes were found. The first three strains were 38.7% (57/147) of type Ⅲ, 35.3% (52/147) of type Ia, 19.0% (28/147) of type Ib, and 1.4% (2/147) of non-typable (NT) strains. Twenty-two genotypes were found in MLST genotypes. The popular genotypes were ST19 30.6% (45/147), ST10 17.0% (25/147), ST12 12.2% (18/147), ST1 10.2% (15/147) and 3 new genotypes 2.0% (3/147). The correlation between the main serotypes of GBS (Ia, Ib, Ⅲ) and the main types of MLST (ST19, ST10, ST12, ST1) was statistically significant (χ2 =75.29,P< 0.05).The Pearson contingency coefficient was calculated further, C=0.6. Conclusion  In this study, the three most common serotypes (Ⅲ,Ia and Ib) covered 93.2% of GBS colonized in pregnant women (137/147), and GBS capsular polysaccharide protein conjugate vaccines contained the above three serotypes, suggesting that the application of this vaccine may reduce GBS infection in perinatal women in this area. ST19/Ⅲ, ST10/Ia and ST12/Ia types are the main sequence types/serotypes that colonize pregnant women, which provide reference for developing targeted GBS vaccines.In addition, the discovery of new sequences in multilocus sequence typing supplements the MLST database of group B streptococcus.

Key words: This study was supported by group B streptococcus (GBS), pregnant women, serotyping, multilocus sequence typingB

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