Poster Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

Asymptomatic throat and vaginal carriage and household transmission of beta-haemolytic streptococci during pregnancy: a prospective cohort study (#34)

Natalie Tomnikov 1 2 , Kaarin Mäkikallio 3 4 , Jaana Vuopio 1 5 , Päivi Polo-Kantola 3 4 , Kaisu Rantakokko-Jalava 6 , Kaisa Holmberg 3 , Anna Martsinkevichyute 3 , Kirsi Gröndahl-Yli-Hannuksela 1 3
  1. Institute of Biomedicine, Unversity of Turku, Turku, Finland
  2. Turku Doctoral Programme of Molecular Medicine, Unversity of Turku, Turku, Finland
  3. Department of Obstetrics and Gynaecology, Turku University Hospital, Turku, Finland
  4. Obstetrics and Gynaecology, Unversity of Turku, Turku, Finland
  5. Finnish Institute for Health and Welfare, Helsinki, Finland
  6. Clinical microbiology, Turku University Hospital, Turku, Finland

Introduction

Beta-haemolytic streptococci (BHS) cause significant disease burden, but asymptomatic colonization occurs too. Streptococcus pyogenes (GAS) carriage is reported especially in children but is much less studied in adults. S. agalactiae (GBS) colonization of reproductive tract (RT) of pregnant women is well-known.

Methods

A prospective cohort study was carried in 2022-2023, Turku, Finland, to investigate asymptomatic throat and vaginal carriage of BHS, with special focus on GAS and GBS. Household transmission of throat carriage was investigated from partners. Pregnant women and their partners were recruited during the ultrasound scan check-up at mid-pregnancy. Various samples including throat swabs, were then collected from both. At the onset of delivery, a 2nd throat swab and a recto-vaginal GBS screening swab were collected from women. All swabs were cultured for the identification of BHS. A background questionnaire was filled and clinical data (infections, medications during delivery and puerperium time and hospitalizations after hospital discharge) was collected from the patient records of participating women.

Results

Altogether 1075 subjects, 548 pregnant women and 527 partners, were enrolled during the 17 months recruitment. Overall, throat carriage was low for GAS (0,3 %), GBS (0,4 %) and S.dysgalactiae (0,5 %). In women, GBS throat carriage increased from 0,5 % to 1,8 % from mid-pregnancy to delivery. GBS RT carriage was common (15,3 %). Low S.dysgalactiae RT carriage was found as well (0,8 %). 

Conclusion

GAS carriage during pregnancy is very rare whereas GBS was found both from throat and RT samples. Further investigation of clinical data is ongoing.