Maternal Vaginal Pathogenic Bacterial Colonization and Early-Onset Neonatal Sepsis in Mwanza City, Tanzania: A Prospective Cohort Study
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Background
Early-onset neonatal sepsis (EONS) remains a major cause of neonatal morbidity and mortality in low- and middle-income countries. Maternal vaginal pathogenic bacterial colonization and HIV infection may increase the risk of EONS through vertical transmission and immune dysregulation, but prospective evidence from sub-Saharan Africa is limited. This study assessed the association between maternal HIV status, vaginal pathogenic bacterial colonization, and EONS among women delivering at five selected health facilities in Mwanza City, Tanzania.
Methods
A prospective comparative cohort study was conducted between August 2023 and February 2025 among 580 pregnant women delivering at five selected health facilities in Mwanza City. A maternal lower vaginal swab was collected before delivery for bacterial culture and antimicrobial susceptibility testing. Neonates were followed for seven days after birth to identify EONS using standardized clinical and laboratory criteria, with culture confirmation where applicable. Kaplan–Meier survival analysis and Cox proportional hazards regression were used to estimate incidence rates and identify independent predictors of neonatal sepsis.
Results
Overall, 89 neonates developed EONS, yielding a cumulative incidence of 15.3% and an incidence rate of 2.42 per 100 person-days (95% CI: 1.97–2.98). Twenty-four (27.0%) cases were culture-confirmed, while 65 (73.0%) were clinically diagnosed. Neonates born to colonized mothers had substantially higher sepsis incidence than those born to non-colonized mothers (3.41 vs. 0.34 per 100 person-days). After adjustment, maternal vaginal bacterial colonization was the strongest predictor of neonatal sepsis (adjusted hazard ratio [aHR] 9.52, 95% CI: 3.47–26.09; p<0.001). Maternal HIV infection independently increased the hazard of neonatal sepsis by 76% (aHR 1.76, 95% CI: 1.14–2.73; p=0.011), while maternal malaria doubled the risk (aHR 2.74, 95% CI: 1.43–5.22; p=0.002). Escherichia coli ( E. coli ) accounted for 58.3% of culture-confirmed neonatal infections, followed by both Klebsiella pneumoniae and Staphylococcus aureus (20.8% each).
Conclusion
Maternal vaginal pathogenic bacterial colonization was strongly associated with early-onset neonatal sepsis. Maternal HIV infection and malaria were also independently associated with increased sepsis. The findings support strengthening maternal infection prevention, neonatal surveillance, and microbiological diagnostic capacity, while prospective intervention studies are needed to determine whether targeted screening and prevention of maternal bacterial colonization can reduce neonatal sepsis.
