Population-Based Prevalence of Antibiotic Residuals in Low, Moderate and High Malaria Endemicity Areas in Tanzania

Background: Inappropriate antibiotic use drives antimicrobial resistance and remains a global concern. Evidence suggests antibiotic use may be higher among malaria-negative patients compared to malaria-positive ones, but uncertainty persists, particularly in regions with varying malaria prevalence. This study measured antibiotic residuals in three Tanzanian regions with varying malaria epidemiology and analyzed factors influencing their presence. Methods: A cross-sectional household survey was conducted in 2015, covering a population of 6000 individuals across three regions of Tanzania. Dried blood spot samples from a subset of participants were analyzed using broad-range tandem mass spectrometry to detect residual antibiotics. Risk factors associated with antibiotic presence, including household healthcare-seeking behaviors, malaria testing, and other relevant variables, were evaluated. Results: The overall prevalence of residual antibiotics in the study population was 14.4% (438/3036; 95% CI: 11.4–15.8%). Stratified by malaria transmission intensity, antibiotic prevalence was 17.2% (95% CI: 12.9–17.2%) in Mwanza (low), 14.6% (95% CI: 10.6–15.0%) in Mbeya (moderate), and 11.2% (95% CI: 7.9–11.6%) in Mtwara (high). Trimethoprim was the most frequently detected antibiotic (6.1%), followed by sulfamethoxazole (4.4%) and penicillin V (0.001%). Conclusions: Residual antibiotic prevalence did not directly correlate with malaria endemicity but was influenced by healthcare practices, including co-prescription of antibiotics and antimalarials. The higher antibiotic use in malaria-negative cases highlights the need for improved diagnostics to reduce unnecessary use and mitigate antimicrobial resistance in malaria-endemic areas.