Environmental risk assessment as a tool to identify potential hotspots of bacteria resistance worldwide

Pharmaceutical usage has led to the widespread detection of these compounds in aquatic ecosystems worldwide, raising concerns about the selective pressure they can exert on microbial communities. To aid in tackling this global emergency, we undertook an initial step in identifying potential hotspots of bacterial resistance arising from the occurrence of antibiotics in the environment. This was conducted by performing a risk assessment based on the measured environmental concentrations of selected antibiotics, acquired from an international pharmaceutical database, and the respective no-effect concentrations for bacterial resistance of such antibiotics. We identified untreated industrial and hospital sewage as the aquatic matrices of most concern. Regarding treated effluent from wastewater treatment plants, the antibiotic ciprofloxacin and Tunisia exhibit a high-risk quotient. For surface water matrices (rivers and streams), both ciprofloxacin and amoxicillin warrant attention and the countries with the highest risk medians were India, South Africa, and the United States of America. Our study provides an initial basis for highlighting the antibiotics, countries, and aquatic matrices that warrant more attention regarding bacterial resistance. This approach can be applied at national or regional scales for more detailed environmental evaluation and decision-making. Nonetheless, we encourage further investigations to confirm the occurrence of antibiotic-resistant bacteria and antibiotic-resistance genes in the potential hotspots identified in this study.