Maternal–Neonatal Bacterial Concordance and Antimicrobial Susceptibility at Regional Referral Hospital, Northern Tanzania: A Cross-Sectional Study

Abstract Background Maternal microorganisms may contribute to the bacterial communities acquired by newborns around birth, but the extent of maternal–neonatal bacterial concordance and antimicrobial resistance at delivery remains insufficiently characterized in northern Tanzania. Methods We conducted an analytical cross-sectional hospital-based study among 314 mother–neonate pairs at Mawenzi Regional Referral Hospital in Moshi, Tanzania. Maternal vaginal and neonatal rectal swabs were collected immediately after delivery and processed by culture and standard bacterial identification methods. Antimicrobial susceptibility was assessed by Kirby–Bauer disc diffusion and interpreted using Clinical and Laboratory Standards Institute (CLSI) 2023 guidance. Descriptive statistics and reported tests of association were performed using SPSS version27. Results A total of 374 bacterial isolates were recovered, comprising 205 (54.8%) maternal and 169 (45.2%) neonatal isolates. Escherichia coli was the most frequent organism (128/374, 34.2%), followed by Staphylococcus aureus (78/374, 20.9%), Klebsiella pneumoniae (67/374, 17.9%), Pseudomonas spp. (60/374, 16.0%), and Proteus spp. (41/374, 11.0%). There was a strong maternal–neonatal relationship, with a statistically significant organism-specific vertical association demonstrated for Staphylococcus aureus (χ² = 6.34, p = 0.012) and Escherichia coli (χ² = 7.21, p = 0.007). Among the Staphylococcus aureus isolates, high resistance was observed against tetracycline (58%) and amoxicillin (72%). Among the Gram-negative Enterobacteriaceae, high resistance rates were observed for ampicillin and co-trimoxazole, whereas amikacin (90.4% overall susceptibility) and piperacillin-tazobactam (93.9% overall susceptibility) retained excellent clinical efficacy. Pseudomonas spp. isolates demonstrated an 81% susceptibility rate to ceftazidime. Multivariable regression confirmed that caesarean delivery (AOR 1.95, 95% CI 1.30–2.95, p = 0.002) and maternal antibiotic use (AOR 1.62, 95% CI 1.05–2.50, p = 0.031) were key drivers of colonization by hospital-associated organisms. Conclusion Maternal vaginal and neonatal rectal bacterial profiles show substantial phenotypic concordance at delivery, pointing toward significant maternal-to-neonatal microbial transfer. The presence of high baseline resistance to traditional first-line penicillin/amoxicillin, ampicillin, and co-trimoxazole underscores the urgency of strengthening local microbiological surveillance, establishing formal antimicrobial stewardship programs, and optimizing infection prevention measures within regional delivery suites.