Serotypes, Clonality, and Virulence Gene Distribution in Streptococcus agalactiae Isolates recovered in Russian Federation in 2021–2024

Background. Streptococcus agalactiae (Group B Streptococcus, GBS) remains a leading cause of severe perinatal infections. The key features of S. agalactiae population in Russia remain underexplored, necessitating comprehensive molecular surveillance.

Aim. This study aimed to perform a comprehensive analysis of the serotype distribution, clonality, and prevalence of genetic virulence determinants in S. agalactiae isolates recovered in Russia in 2021–2024.

Materials and Methods. We analysed 72 non-invasive S. agalactiae isolates. The isolates were collected in Northwestern Federal District between 2021 and 2024 from patients (30 males and 42 females, aged 18–55 years). We recovered the isolates from vaginal, cervical, and urethral swabs, urine, prostate secretion, and semen. We performed initial species identification by standard bacteriological methods, latex agglutination and PCR. The isolates were whole-genome sequenced. We used bioinformatic analysis to derive serotypes, multi-locus sequence types (ST), clonal complexes (CC) and virulence genes from genome data.

Results and Discussion. Our data revealed that serotypes V (34.7 %), Ia (22.2%), and III (22.2 %) were predominant, collectively accounting for 79.1 % of the isolates. The isolates exhibited high genetic diversity, comprising 22 sequence types (STs) grouped into 7 clonal complexes (CCs). The dominant CCs were CC1 (29.2 %), CC23 (23.6 %), CC19 (19.4 %), and CC17 (12.5 %). The most prevalent pilus genotype was PI-1+PI-2a1 (36%). The genes encoding surface protein Srr1 and Alp-like proteins were detected in 80.6% and 58% of isolates, respectively. The isolated of hypervirulent CC17 complex carried hvgA, srr2, and rib genes.

Conclusion. We found that the S. agalactiae isolates exhibited high genetic diversity, with predominant serotypes V, Ia, and III and clonal complexes CC1, CC23, CC19, and CC17. Our analysis revealed a prevalence (12.5%) of the hypervirulent CC17 clone, confirming the circulation of high-risk strains associated with neonatal invasive disease. Our results indicate that a hexavalent conjugate vaccine would likely cover a majority of the circulating strains. We identified specific virulence gene profiles and their association with certain clonal complexes. Our results suggest that the revealed virulence factors are promising targets for serotype-independent vaccine development.

1. Coggins SA, Puopolo KM. Neonatal Group B Streptococcus Disease. Pediatr Rev. 2024;45(2):63–73. doi:10.1542/pir.2023-006154

2. Gonçalves BP, Procter SR, Paul P, et al. Group B streptococcus infection during pregnancy and infancy: estimates of regional and global burden. Lancet Glob Health. 2022;10(6):e807–e819. doi:10.1016/S2214-109X(22)00093-6

3. Stephens K, Charnock-Jones DS, Smith GCS. Group B Streptococcus and the risk of perinatal morbidity and mortality following term labor. Am J Obstet Gynecol. 2023;228(5S):S1305–S1312. doi:10.1016/j.ajog.2022.07.051

4. Paul P, Gonçalves BP, Le Doare K, Lawn JE. 20 million pregnant women with group B streptococcus carriage: consequences, challenges, and opportunities for prevention. Curr Opin Pediatr. 2023;35(2):223–230. doi:10.1097/MOP.0000000000001223

5. Russell NJ, Seale AC, O’Driscoll M, et al. Maternal Colonization With Group B Streptococcus and Serotype Distribution Worldwide: Systematic Review and Meta-analyses. Clin Infect Dis. 2017;65(suppl_2):S100–S111. doi:10.1093/cid/cix658

6. Sadova NV, Zaplatnikov AL, Shipulina ОY, Shargorodskaya AV, Podkopaev VN, Skachkova ТS, Smirnova VS. Streptococcus agalactiae carriage rate among women of childbearing age and its role in the development of congenital infections: preliminary results of a pilot study. Meditsinskiy sovet = Medical Council. 2016;(16):164–166. (In Russ.) https: doi.org/10.21518/2079-701X-2016-16-164-166

7. Vasilyeva VA, Shipitsyna EV, Shalepo KV, Savicheva AM. Molecular epidemiology of infections caused by group B Streptococcus in pregnant women and newborns, and development of preventive vaccines. Journal of Obstetrics and Women’s Diseases. 2018;67(5):62–73. (In Russ.) doi: 10.17816/JOWD67562-73

8. Chuchukina OA, Slavnov NN, Shuraeva SA, Bochkov IA. Rasprostranenie streptokokkov serogruppy V sredi ambulatornykh patsientov v Moskve. Epidemiologiya i infektsionnye bolezni. aktual’nye voprosy. 2016;(4):23–26. (In Russ).

9. Zamarina TV, Alekseeva VV, Merkulova SV, et al. Otsenka spektra chuvstvitel’nosti k antibakterial’nym preparatam izolyatov Streptococcus agalactiae, vydelennykh u zhenshchin reproduktivnogo vozrasta na territorii Volgogradskoi oblasti. Klinicheskaya Mikrobiologiya i Antimikrobnaya Khimioterapiya. 2024;26(Suppl 1):28–29. (In Russ). EDN: XXNKCT.

10. Pena JMS, Lannes-Costa PS, Nagao PE. Vaccines for Streptococcus agalactiae: current status and future perspectives. Front Immunol. 2024;15:1430. doi:10.3389/fimmu.2024.1430901

11. Absalon J, Segall N, Block SL, et al. Safety and immunogenicity of a novel hexavalent group B streptococcus conjugate vaccine in healthy, non-pregnant adults: a phase 1/2, randomised, placebo-controlled, observer-blinded, dose-escalation trial. Lancet Infect Dis. 2021;21(2):263–274. doi:10.1016/S1473-3099(20)30478-3

12. Shipitsyna E, Shalepo K, Zatsiorskaya S, et al. Significant shifts in the distribution of vaccine capsular polysaccharide types and rates of antimicrobial resistance of perinatal group B streptococci within the last decade in St. Petersburg, Russia. Eur J Clin Microbiol Infect Dis. 2020;39(8):1487–1493. doi:10.1007/s10096-020-03864-1

13. Ksenia A. Kolousova, Elena V. Shipitsyna, Kira V. Shalepo, Alevtina M. Savicheva. Virulence and pathogenicity factors of S. agalactiae strains isolated from pregnant women and newborns. Journal of obstetrics and women’s diseases, 2021, 70(5): 15–22 DOI:10.17816/JOWD75671

14. Shalepo KS, Khusnutdinova TA, Budilovskaya OV, Krysanova AA, Sapozhnikov KV, Savicheva AM, Kogan IY. Molecular genetic determinants of virulence of Streptococcus agalactiae isolated from pregnant women and newborns in St. Petersburg and the Leningrad region in 2010–2023. Journal of microbiology, epidemiology and immunobiology. 2024;101(2):217–226. doi: 10.36233/0372-9311-501

15. McGee L, Chochua S, Li Z, et al. Multistate, Population-Based Distributions of Candidate Vaccine Targets, Clonal Complexes, and Resistance Features of Invasive Group B Streptococci Within the United States, 2015-2017. Clin Infect Dis. 2021;72(6):1004–1013. doi:10.1093/cid/ciaa151

16. Khan UB, Jauneikaite E, Andrews R, Chalker VJ, Spiller OB. Identifying large-scale recombination and capsular switching events in Streptococcus agalactiae strains causing disease in adults in the UK between 2014 and 2015. Microb Genom. 2022;8(3):000783. doi:10.1099/mgen.0.000783

17. Kuleshevich EV, Ilyasov YY, Linnik DS, Malchenkova AA, Arzhanova ON, Briko NI, Glushkova EV, Priputnevich TV, Suvorov AN. Russian strains of group B streptococci are different in the content and organization of the PAI-A and PAI-A1 pathogenicity islands. Journal of obstetrics and women’s diseases. 2021;70(4):65–72. doi: 10.17816/JOWD61875

18. Lin SM, Jang AY, Zhi Y, et al. Vaccination With a Latch Peptide Provides Serotype-Independent Protection Against Group B Streptococcus Infection in Mice. J Infect Dis. 2017;217(1):93–102. doi:10.1093/infdis/jix565

19. Santillan DA, Rai KK, Santillan MK, Krishnamachari Y, Salem AK, Hunter SK. Efficacy of polymeric encapsulated C5a peptidase-based group B streptococcus vaccines in a murine model. Am J Obstet Gynecol. 2011;205(3):249.e1–249.e2498. doi:10.1016/j.ajog.2011.06.024

20. de Zoysa A, Edwards K, Gharbia S, Underwood A, Charlett A, Efstratiou A. Non-culture detection of Streptococcus agalactiae (Lancefield group B Streptococcus) in clinical samples by real-time PCR. J Med Microbiol. 2012;61(Pt 8):1086–1090. doi:10.1099/jmm.0.042879-0

21. Prjibelski A, Antipov D, Meleshko D, Lapidus A, Korobeynikov A. Using SPAdes De Novo Assembler. Curr Protoc Bioinformatics. 2020;70(1):e102. doi:10.1002/cpbi.102

22. Gurevich A, Saveliev V, Vyahhi N, Tesler G. QUAST: quality assessment tool for genome assemblies. Bioinformatics. 2013;29(8):1072–1075. doi:10.1093/bioinformatics/btt086

23. Dyster V, Hung H. GBS-Typer-sanger-nf [Internet]. Available at: https: github.com/sanger-bentley-group/GBS-Typer-sanger-nf. Accessed: 8 September 2025.

24. Jolley KA, Bray JE, Maiden MCJ. Open-access bacterial population genomics: BIGSdb software, the PubMLST.org website and their applications. Wellcome Open Res. 2018;3:124. doi:10.12688/wellcomeopenres.14826.1

25. Mangiola S, Papenfuss A. tidyHeatmap: an R package for modular heatmap production based on tidy principles. J Open Source Softw. 2020;5(52):2472. https: doi.org/10.21105/joss.02472

26. Shabayek S, Vogel V, Jamrozy D, Bentley SD, Spellerberg B. Molecular Epidemiology of Group B Streptococcus Colonization in Egyptian Women. Microorganisms. 2022;11(1):38. doi:10.3390/microorganisms11010038

27. Campisi E, Rinaudo CD, Donati C, et al. Serotype IV Streptococcus agalactiae ST-452 has arisen from large genomic recombination events between CC23 and the hypervirulent CC17 lineages. Sci Rep. 2016;6:29799. doi:10.1038/srep29799

28. Tavares T, Pinho L, Bonifácio Andrade E. Group B Streptococcal Neonatal Meningitis. Clin Microbiol Rev. 2022;35(2):e0007921. doi:10.1128/cmr.00079-21

29. Choi JH, Kim TH, Kim ET, Kim YR, Lee H. Molecular epidemiology and virulence factors of group B Streptococcus in South Korea according to the invasiveness. BMC Infect Dis. 2024;24(1):740. doi:10.1186/s12879-024-09625-1

30. Pinto TCA, Oliveira LMA, da Costa NS, et al. Group B Streptococcus awareness month: vaccine and challenges underway. Int J Infect Dis. 2021;110:279–280. doi:10.1016/j.ijid.2021.07.056

31. Inventprise Inc. Phase I/II Study to a Assess the GBS-06 Vaccine Manufactured by Inventprise, Inc., in Healthy, Non-Pregnant, Adult Women of Childbearing Age. [Internet]. National Library of Medicine; 2025. Available at: https: clinicaltrials.gov/study/NCT06611371. Accessed: 8 September 2025.

32. Gori A, Harrison OB, Mlia E, et al. Pan-GWAS of Streptococcus agalactiae Highlights Lineage-Specific Genes Associated with Virulence and Niche Adaptation. mBio. 2020;11(3):e00728–20. doi:10.1128/mBio.00728-20

33. Maeda T, Takayama Y, Fujita T, et al. Comparison between Invasive and Non-Invasive Streptococcus agalactiae Isolates from Human Adults, Based on Virulence Gene Profiles, Capsular Genotypes, Sequence Types, and Antimicrobial Resistance Patterns. Jpn J Infect Dis. 2021;74(4):316–324. doi:10.7883/yoken.JJID.2020.761