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From bacteria to fish: ecotoxicological insights into sulfamethoxazole and trimethoprim
Bárbara S Diogo1,2,3, Sara Rodrigues2,3, Oksana Golovko4
1ICBAS, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal.
Abstract:
Sulfamethoxazole (SMX) and trimethoprim (TRIM) are two of the most used antibiotics in the last 50 years, to prevent and treat bacterial infections; however, the available literature about toxicity to non-target organisms is quite discrepant and incomplete. This study aims to assess the SMX and TRIM ecotoxicological effects in standard species: Aliivibrio fischeri (bioluminescence inhibition), Escherichia coli ATCC 25922 (growth inhibition), Lemna minor (growth inhibition and biochemical biomarkers), Daphnia magna (immobilization/mortality, life history traits, and biochemical biomarkers), and Danio rerio (survival, hatching, abnormalities, and biochemical biomarkers). The species tested showed different acute sensitivities to SMX (A. fischeri < D. magna < E. coli < L. minor) and TRIM (L. minor < A. fischeri < D. magna < E. coli). Overall, TRIM reveals less toxicity than SMX, except for E. coli (Ecotoxicological approach based on Antimicrobial Susceptibility Testing - EcoAST procedure). Both antibiotics affect individually (e.g., growth and survival) and sub-individually (e.g., antioxidant defenses) L. minor, D. magna, and D. rerio. This study allowed us to generate relevant data and fill gaps in the literature regarding the effects of SMX and TRIM in aquatic organisms. The here-obtained results can be used to (i) complete and re-evaluate the Safety Data Sheet to improve the assessment of environmental safety and management of national and international entities; (ii) clarify the environmental risks of these antibiotics in aquatic ecosystems reinforcing the inclusion in the 4th Watch List of priority substances to be monitored in whole inland waters by the Water Framework Directive; and (iii) combat the development of antimicrobial resistance, as well as supporting the definition of environmental measurements in the context of European One Health Action Plan. However, it is essential to continue studying these antibiotics to better understand their toxicity at ecologically relevant concentrations and their long-term effects under different climatic change scenarios.
Insights
This study assessed the ecotoxicological effects of sulfamethoxazole (SMX) and trimethoprim (TRIM) on aquatic organisms. TRIM generally showed lower toxicity than SMX, with both impacting non-target species at individual and sub-individual levels.
Area of Science:
- Environmental Science
- Ecotoxicology
- Microbiology
Background:
- Sulfamethoxazole (SMX) and trimethoprim (TRIM) are widely used antibiotics with incomplete ecotoxicological data.
- Understanding their impact on non-target organisms is crucial for environmental safety.
Purpose of the Study:
- To evaluate the ecotoxicological effects of SMX and TRIM on standard aquatic species.
- To fill existing literature gaps regarding the environmental risks of these antibiotics.
Main Methods:
- Tested SMX and TRIM toxicity on Aliivibrio fischeri, Escherichia coli, Lemna minor, Daphnia magna, and Danio rerio.
- Assessed various endpoints including bioluminescence inhibition, growth inhibition, mortality, life history traits, and biochemical biomarkers.
- Employed the Ecotoxicological approach based on Antimicrobial Susceptibility Testing (EcoAST) procedure.
Main Results:
- Species exhibited differential sensitivity to SMX and TRIM.
- TRIM was generally less toxic than SMX, except for E. coli.
- Both antibiotics caused individual and sub-individual effects in L. minor, D. magna, and D. rerio.
Conclusions:
- Generated critical data on SMX and TRIM ecotoxicity in aquatic organisms.
- Results can inform Safety Data Sheets, environmental risk assessments, and regulatory actions (e.g., Water Framework Directive Watch List).
- Findings support antimicrobial resistance combat and One Health initiatives, highlighting the need for further research on long-term and climate change effects.
