Antibiotic-resistance of Fecal Coliforms at the Bottom of the Tama River, Tokyo

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We investigated the midstream bottom of the Tama River, which flows through Tokyo, to evaluate the occurrence and degree of antibiotic-resistant fecal coliforms including multidrug-resistant fecal coliforms. The genera Klebsiella and Escherichia were the major isolates among the fecal coliforms. For the genus Klebsiella, the highest antibiotic resistance was observed for ampicillin (100%) , followed by kanamycin, tetracycline, cefotaxime, and cefoxitin. The highest resistance to E. coli was found for kanamycin (44.4%) , followed by ampicillin, tetracycline, chloramphenicol, amoxicillin-clavulanate, cefotaxime, ceftazidime, and aztreonam. Multidrug resistance （MDR） was observed in three E. coli isolates. A double disc synergy test confirmed the production of extended-spectrum β-lactamases by the six-antibiotic-resistant isolate E. coli hfa7, and the strain had CTX-M-1 group gene. Assessments of antibiotic-resistant fecal coliforms at the bottom of the Tama River are important toward the goals of preventing the spread of antibiotic-resistant fecal coliforms in humans, animals, and the environment.