Background: Group B Streptococcus (GBS) is the worldwide leading cause of neonatal invasive infections (NII). Recurrent infections are reported but poorly studied.
Methods: A retrospective analysis of GBS NII referred to the French National Reference Centre of Streptococci between 2007 and 2020 was carried out. Clinical information was abstracted from hospitalization reports. Capsular genotyping antibiotic susceptibility testing according to EUCAST recommendations were performed for all isolates. Minimum inhibitory and bactericidal concentrations (MICs and MBCs) of beta-lactam antibiotics were determined for each isolate responsible for recurrent infections, together with Illumina whole genome sequencing (WGS).
Results: A total of 1,325 cases of GBS NII were reported, of which 33 were recurrent infections (2.5%). Median time between recurrence and primary episode was 26 days (range 14 – 66). Eleven out of 17 documented cases of R-NII (65%) occurred in preterm infants. A 100% agreement for the capsular type and CC between isolates responsible for the two episodes was observed. Two capsular types, Ia (4/33, 12%) and III (29/33, 88%), and three CC, CC17 (27/33, 81.8%), CC19 (4/33, 12.1%) and CC23 (2/33, 6.1%), were identified. WGS confirmed the clonal relationship between strains responsible for primary and recurrent infections. All isolates were susceptible to beta-lactams. Two unrelated CC17 isolates (5%) were identified as tolerant (MBC/MIC ≥ 32) to penicillin G or amoxicillin.
Conclusions: Recurrent GBS NII are caused by the same isolate than the primary infection, most often of the hypervirulent CC17 clone, suggesting persistent neonatal colonization or source of contamination.