Vertical transmission of Group B Streptococcus in a public referral hospital

Background Group B Streptococcus (GBS), a beta-hemolytic Streptococcus , is an important cause of neonatal and maternal morbidity and mortality in Brazil and worldwide. This study aims to evaluate vertical transmission of GBS isolated from parturients and their newborns in a municipal referral hospital in Goiânia, Goiás, Brazil. Methods In this cross-sectional study (August–October 2024), 206 parturients and their newborns were included. Vaginal and anorectal swabs were collected from mothers and nasal and auricular swabs from newborns. Samples underwent microbiological culture and real-time polymerase chain reaction (qPCR), with antimicrobial susceptibility testing performed according to standardized protocols. Results Among the 206 parturients, 26.7% were colonized with GBS, with vertical transmission observed in 64.1% of cases and an overall neonatal prevalence of 16.4%. GBS isolates showed high resistance to tetracycline (57.9%–70.9%), erythromycin (31.6%–54.6%), and clindamycin (42.1%–83.6%), particularly in vaginal and anal samples. Conversely, β-lactams (penicillin, ampicillin, ceftriaxone, and cefazolin) maintained high efficacy (≥ 86%), confirming their role as first-line agents for intrapartum prophylaxis. Resistance to macrolides and lincosamides restricts their use in penicillin-allergic pregnant women. Conclusion The high prevalence of maternal colonization and substantial vertical transmission highlight the urgent need to implement routine screening and intrapartum prophylaxis during prenatal care. Although culture remains the gold-standard for GBS detection, qPCR demonstrated higher sensitivity and may be a useful tool for early diagnosis of maternal colonization, especially in the absence of prenatal follow-up.