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

Introduction Children account for a significant proportion of antibiotic consumption in low- and middle-income countries, with the overuse of antibiotics occurring in both formal and informal health sectors. This study assessed the prevalence and predictors of residual antibiotics in children’s blood in Mbeya and Morogoro regions of Tanzania. Methods The cross-sectional community-based survey used two-stage cluster sampling to include 1,699 children under 15 years of age. For each child, information on recent illness, healthcare-seeking behavior, and the use of antibiotics, as well as a dried blood spot (DBS) 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 The overall prevalence of residual antibiotics in the blood samples was 17.4% (95% CI: 15.6– 19.2), with the highest prevalence among under-five children. The most frequently detected antibiotics were trimethoprim (8.5%), sulfamethoxazole (6.0%), metronidazole (3.6%) and amoxicillin (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 of the children who had residual antibiotics in their blood had no reported history of illness or taking antibiotics in the last two weeks, and antibiotics were not found in the home. Conclusion The study demonstrated high prevalence of antibiotic exposure among children in Tanzanian communities, albeit likely still underestimated, especially for compounds with short half-lives. A significant proportion of antibiotic exposure was unexplained and may be due to unreported self-medication or environmental pathways. Incorporating biomonitoring into surveillance strategies can help to better understand exposure patterns and design antibiotic stewardship interventions. What is already known about this topic? What are the new findings? Recommendations for policy ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The study was funded by the Swiss National Science Foundation (grant #179273). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ifakara Health Institute (IHI/IRB/No: 20-2020), National Institute for Medical Research (NIMR/HQ/R.8a/Vol. IX/3463) and the Ethikkommission Nordwest- und Zentralschweiz (AO_2020-00050). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors