Prevalence of antimicrobial-resistant Escherichia coli in waste water at the Kiruddu compact waste water treatment plant.

Abstract

Antimicrobial resistance (AMR) is a critical global health threat, with projections estimating up to 10 million deaths annually by 2050 if left unaddressed. Wastewater treatment plants (WWTPs) are recognised hotspots for the propagation of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) into the environment. In Uganda, the Kiruddu Compact Wastewater Treatment Plant, which receives influents from a major healthcare facility and surrounding communities, presents potential risks for environmental AMR dissemination. This study aimed to assess the prevalence and antimicrobial resistance profiles of Escherichia coli in wastewater samples collected from different stages of treatment at the Kiruddu Compact Wastewater Treatment Plant in Kampala, Uganda. Across-sectional study was conducted from September 2024 to July 2025. A total of 55 wastewater samples were collected from influent (n=30) and effluent(n=25) points. Standard microbiological procedures (selective culture on mac Conkey and EMB agar, biochemical tests) were used for the isolation and identification of E. coli, followed by antimicrobial susceptibility testing using the Kirby-Bauer disk diffusion method. Data were analyzed using STATA version 15, with significance set at p-value < 0.05. Out of 55 samples, E. coli was isolated from 90.9% (n=50), with 100% (25/25) of effluent and 83.3% (25/30) of influent samples testing positive. Multidrug resistance (MDR) was detected in 64% (32/50) of E. coli isolates, with 80% (20/25) of MDR strains found in effluent samples. Resistance to ampicillin (98%), tetracycline (84%), ciprofloxacin (60%), and nalidixic acid (40%) was observed. Significant associations were found between MDR status and resistance to ciprofloxacin (p < 0.01) The high prevalence of multidrug-resistant E. coli in effluents from the Kiruddu WWTP highlights the plant's limited capacity to eliminate resistant bacteria, posing serious risks to environmental and public health. These findings underscore the urgent need for improved wastewater treatment technologies, routine AMR surveillance, and integrated One Health strategies to mitigate the spread of environmental AMR in Uganda