Prevalence and predictors of residual antibiotics in children’s blood in community settings in Tanzania

Objective Children account for a significant proportion of antibiotic consumption in low- and middle-income countries, with overuse occurring in formal and informal health sectors. This study assessed the prevalence and predictors of residual antibiotics in the blood of children in Mbeya and Morogoro regions of Tanzania. Methods The cross-sectional community-based survey used two-stage cluster sampling to include children aged under 15 years. For each child, information on recent illness, healthcare-seeking behavior, and use of antibiotics, as well as a dried blood spot sample, were collected. The samples underwent tandem mass spectrometry analysis to quantify the concentrations of 15 common antibiotics. Associations between survey variables and presence of residual antibiotics were assessed using mixed-effects logistic regression. Results In total, 1742 children were surveyed, and 1699 analyzed. The overall prevalence of residual antibiotics in the blood samples was 17.4% (296/1699), the highest among children under the age of five years. The most frequently detected antibiotics were trimethoprim (144/1699; 8.5%), sulfamethoxazole (102/1699; 6.0%), metronidazole (61/1699; 3.6%) and amoxicillin (43/1699; 2.5%). The strongest predictors of residual antibiotics in the blood were observed presence of antibiotics at home (aOR=2.9; 95% CI: 2.0–4.1) and reported consumption of antibiotics in the last two weeks (aOR=2.5; 95% CI: 1.6–3.9). However, half (145/296) of the children who had residual antibiotics in their blood, some with multiple antibiotics, had no reported history of illness or antibiotic consumption in the last two weeks, and antibiotics were not found at home. Discussion This study demonstrated a high prevalence of antibiotic exposure among children in Tanzanian communities, albeit likely underestimated, especially for compounds with short half-lives. A significant proportion of antibiotic exposure was unexplained and may have been due to unreported self-medication or environmental pathways. Incorporating biomonitoring into surveillance strategies can help better understand exposure patterns and design antibiotic stewardship interventions.