Abstract
Background
The misuse of antimicrobial agents in healthcare and animal husbandry has resulted in their release into the environment through wastewater. This, in turn, has led to the emergence and spread of resistant bacteria. Antimicrobials in wastewater not only promote resistance in microbial communities but also interfere with the biodegradation of organic matter.
Objective
The study aimed to detect and evaluate the risk of antimicrobial resistance promotion in the Little Akaki River wastewater by analyzing selected antimicrobial concentration levels.
Methods
In a longitudinal study at Little Akaki River, wastewater samples collected in March-December 2019, June 2020, and August 2022 were analyzed using solid phase extraction with Hydrophilic-Lipophilic Balance (HLB) cartridge to extract antimicrobials. A 10µL extracted sample was injected into Ultra High-Performance Liquid Chromatography (UHPLC) system with binary gradient elution, equipped with a Mass spectrometer operating in ESI + mode.
Results
Ciprofloxacin concentrations ranged from 5.62–9.34µg/L. In the dry season, Cefotaxime concentrations ranged from 1.89–54.86 µg/L, while in the wet season, they ranged from 32.76–64.79 µg/L. Sulfamethoxazole concentrations varied from 29.11-186.25 µg/L in the dry season and from 123.29-248.77 µg/L in the wet season.
Conclusion
Our study identified a potential for widespread antimicrobials resistance emergence in the Little Akaki River. Measured environmental levels of ciprofloxacin, cefotaxime, and sulfamethoxazole exceeded predicted no-effect concentrations (PNEC) for resistance promotion Risk Quotient (RQ) > 2 in both dry and wet seasons. However, erythromycin levels remained safe, below respective PNEC. These findings suggest a high risk of resistance development to these specific antimicrobials in the study site aquatic bacteria, with sulfamethoxazole posing the greatest threat due to its consistently high levels.