Heavy Metal Contamination and Antimicrobial Resistance of Escherichia coli in the Akaki Wastewater Treatment Plant and Akaki River Catchment: A One Health Framework
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Date
2026
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Addis Abeba University
Abstract
Antimicrobial resistance (AMR) and heavy metal pollution in Wastewater treatment plants (WWTPs) and river catchments present significant global public health risks, potentially driving resistance via co-selection. This study assessed heavy metal contamination and AMR in Escherichia coli within the Akaki WWTP and river catchment, using a One Health framework, focusing on an extended spectrum beta-lactamase (ESBL) and carbapenemase production. A cross - sectional comparative study was conducted utilizing 232 samples from wastewater, river water, human stool, cattle feces, and milk. Six heavy metals (Cd,
Pb, Cr, Cu, Mn, and Zn) were quantified by ICP-OES. E. coli was isolated using standard biochemical methods and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF). Phenotypic resistance; ESBL and carbapenemase production were confirmed by disk diffusion, double-disk synergy tests (DDST) and modified carbapenem inactivation method (mCIM), respectively. Data were analyzed using logistic regression, chi-square, and one-way ANOVA (p < 0.05). Manganese (Mn) was the dominant contaminant, exceeding permissible across seasons. While, Zink (Zn) peaked during the rainy season. E. coli was isolated from 31 (13.4%) of samples, predominantly from water sources. High resistance was observed against Ampicillin (93.5%), Tetracycline (74.2%) , Sulphamethoxazole (64.5%), and Cefotaxime (58.0%). Multidrug resistance (MDR) rea ched 27 (87.1 %) and 14 (45.2%) were ESBL producers; no carbapenemase production was detected. Higher MDR and ESBL rates correlated with elevated Mn concentrations, indicating potential heavy metal–AMR co-selection. The Akaki WWTP and river catchment are critical reservoirs for MDR and ESBLproducing E. coli. Evidence of Mn driven co-selection underscores the urgent need for integrated One Health surveillance, improved wastewater efficiency and strict antimicrob ial stewardship
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Keywords
Antimicrobial resistance, Escherichia coli, Heavy metals, Manganese, Coselection, One Health