Characterization of Group B Streptococcus strains isolated from neonatal invasive diseases in Belgium, 2018.

Introduction
Despite advances in preventive strategies, Group B Streptococcal(GBS) disease is still a leading cause of severe neonatal infections. The Belgian National Reference Centre (NRC) routinely performs surveillances of GBS invasive strains isolated in Belgium.
Methods
All GBS strains isolated from neonatal invasive diseases sent on a voluntary-base to the NRC during the year 2018 were characterized: capsular polysaccharide (CPS)-typing by agglutination and/or PCR, pili-typing with PCR, antimicrobial susceptibility testing, and detection of resistance genes with PCR.
Results
A total of 58 GBS strains isolated from neonatal invasive diseases were available: 33 and 27 from Early-Onset (EOD) and Late-Onset Diseases (LOD). The ratio EOD/LOD is of 1.22. Overall, CPS-type III was predominant (46.9% in EOD and 91.3% in LOD cases) followed by Ia, V, Ib, IV, IX and II in EOD (21.9%, 9.4%, 6.2%, 3.1%, 3.1%, 0.1%). All strains were susceptible to penicillin. Rate of resistance to macrolides and lincosamides was 28%. The main resistant gene detected among these resistant isolates was the ErmB gene (81,3%). About pili-typing, all strains harboured one of the PI-2 variants alone or in combination: the predominant type was PI1, PI2a (39.2%) followed by PI1, PI2b (29.4%), PI2a (21.6%) and PI2b (9.8%). Bacteriemia was the predominant manifestation with meningitis in 12% of EOD and 40% of LOD cases.
Conclusion
The burden of neonatal GBS diseases remains important and prevention strategies need to be improved. CPS-type and pili-type distributions, and resistance rate to macrolides/lincosamides are quite similar to European/North American observations done during the last decade.