Abstract / Summary
Abstract Background Antibiotic residues are commonly reported in food, water, and soil. Despite concerns that chronic, low-dose exposures could perturb the human gut microbiome and select for antimicrobial resistance, it remains unclear how prevalent these exposures are in the general population. The goal of this scoping review was to compile and summarize existing evidence for the detection of antibiotic residues in human samples (e.g., blood, breast milk, urine, stool) from individuals without known, recent antibiotic use. Methods We systematically searched PubMed, Embase, and Scopus (1990 through October 2025) for studies reporting antibiotic detection in humans with no recent antibiotic use, hereafter termed “inadvertent antibiotic exposure” (IAE). All methods for ascertaining recent antibiotic use (e.g. medical record review, self-report) were eligible. No minimum antibiotic abstention period was required for inclusion. Any age, sex, country, or human specimen type was eligible. Literature reviews, case-series, and case control study designs were excluded. Abstract screening, full-text screening, and data extraction were performed in duplicate. Results Thirty-two studies including 11,499 participants from 10 predominantly low- and middle-income countries met inclusion criteria. Most assessed antibiotic activity in urine (n = 24), though stool, breast milk, blood, and fat were also analyzed (< 5 studies each). The average minimum antibiotic abstention time was 3.1 months. At the person level, half of tested participants (standard deviation (SD): 30%) were positive for at least one antibiotic residue or metabolite. Norfloxacin, ofloxacin, and ciprofloxacin were each identified in one fifth of participants. Reported maximum urinary concentrations of ciprofloxacin were comparable to therapeutic levels. We noted substantial gaps that limit the generalizability of current evidence, including no published studies from Europe and North America, reliance on self-report for ascertaining recent antibiotic exposure, and heterogeneity in analytical methods and outcome reporting. Discussion Overall, this review finds evidence of a broad range of antibiotic residues - including agents classified as critically important for human health - in up to 50% of individuals with no recent, self-reported antibiotic exposure. Our results indicate that IAE is common in many low and middle-income countries, although it remains poorly characterized in other settings. Our findings underscore the relevance of investigating the sources and consequences of IAE, including its potential effects on the microbiome and global antimicrobial resistance.