Prevalence of antibiotic-resistant Escherichia coli exceeds that of antibiotic-resistant coliforms in an urban river in Japan
DOI:
https://doi.org/10.51094/jxiv.1769Keywords:
Antimicrobial resistance, combined sewer overflow, E. coli, coliform, CHROMagar ECCAbstract
Coliforms and Escherichia coli are widely used as fecal indicator bacteria (FIB) in water-quality assessments. However, the potential of these bacteria to act as reservoirs of antimicrobial resistance (AMR) in urban rivers remains insufficiently characterized. This study investigated the dynamics of coliforms and E. coli in the Hirano River, an urban river in Osaka, Japan. Sampling was conducted over a 1-month period, including during a combined sewer overflow (CSO) event, and samples were analyzed using CHROMagar™ ECC medium for enumeration and to test resistance to ampicillin and tetracycline. Both coliforms and E. coli counts increased by more than two orders of magnitude following CSO discharge, indicating that untreated sewage substantially contributed to fecal contamination. Despite the higher abundance of coliforms, E. coli exhibited markedly greater resistance ratios, emphasizing its key role in the dissemination of environmental AMR. These findings highlight the importance of E. coli as both an FIB and a reservoir of antibiotic resistance in urban river systems.
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Submitted: 2025-10-19 12:37:01 UTC
Published: 2025-10-22 01:59:46 UTC
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Kazuaki Matsui
Rahman MD Mizanur
Tsuguri Inui
Mizuki Oda
Takeshi Miki
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