Early-Onset Group B Streptococcal Infection in Bichorionic/Biamniotic Twins Case Study: Is It Time for Changes in Laboratory Diagnosis and Prevention?

Early-onset infection caused by Streptococcus agalactiae (Group B Streptococcus, GBS) may occur during gestation or delivery and can lead to severe neonatal sepsis, meningitis, or pneumonia. Discordant GBS infections in twin gestations are rare. We report a fatal case of early-onset GBS infection in dichorionic–diamniotic twins conceived via IVF and delivered by caesarean section at 32 weeks’ gestation due to discordant fetal growth and abnormal Doppler indices in Twin A (Umbilical Artery PI = 1.4; Middle Cerebral Artery PI = 1.5). Twin A had Apgar scores of 3, 5, and 5 and rapidly developed tachycardia, respiratory distress, and systemic infection, while Twin B, with Apgar scores of 7, 8, and 9, remained clinically stable. Both infants were admitted to the NICU and underwent routine blood, urine, and cerebrospinal fluid testing. Despite the prompt initiation of parenteral ceftriaxone and respiratory support, Twin A deteriorated rapidly and died within 28 h. GBS was isolated from Twin A’s blood culture, and maternal placental tissue and high vaginal samples collected before antibiotic administration also grew GBS, with all isolates demonstrating identical antimicrobial resistance profiles. Molecular analysis revealed matching rib1 and alp2/3 gene patterns in isolates from the mother and Twin A. Maternal anovaginal immunochromatography at delivery was positive, whereas screening cultures obtained at 29 weeks’ gestation were negative. This case highlights the limitations of culture-based GBS screening in high-risk pregnancies and preterm deliveries and underscores the potential value of molecular assays and point-of-care testing to improve detection of S. agalactiae throughout pregnancy and the peripartum period. Emerging preventive strategies, including modulation of the genital microbiome and maternal vaccination aligned with WHO recommendations, may further reduce the burden of neonatal GBS disease.