Inorganic arsenic promotes bacterial tolerance to antibiotics in community-derived Escherichia coli isolates

The rise of antibiotic resistance cannot be explained solely by antibiotic misuse; inadvertent exposure to naturally occurring antimicrobials such as heavy metals and metalloids may also contribute. Arsenic, a toxic metalloid with antimicrobial properties, has been linked to increased antibiotic resistance. Building on our previous findings of a positive correlation between arsenic exposure and the prevalence of antibiotic-resistant bacterial colonization among the rural population in Bangladesh, this study investigated the direct effect of arsenic exposure on antibiotic resistance and plasmid transfer in 30 Escherichia coli isolates from arsenic-contaminated areas. Most isolates were arsenic-resistant and carried chromosomal arsenic resistance genes. Exposure to sub-inhibitory concentrations of arsenic increased bacterial tolerance to antibiotics, altered plasmid transfer frequency, and upregulated genes involved in arsenic resistance, antibiotic resistance, conjugation, and efflux systems. Collectively, these findings demonstrate that inorganic arsenic can promote the persistence and spread of antibiotic resistance in natural environments, highlighting the need to consider environmental contaminants in antibiotic resistance mitigation strategies.