title: Impacts of urbanization on the prevalence of antibiotic-resistant Escherichia coli in the Chaophraya River and its tributaries.
abstract: River water samples were taken from 32 locations around the basin of Chaophraya River and its four major tributaries in Thailand to investigate resistance ratios of Escherichia coli isolates to eight antibiotic agents of amoxicillin, sulfamethoxazole/trimethoprim, tetracycline, doxytetracycline, ciprofloxacin, levofloxacin, norfloxacin and ofloxacin. Principal component analysis was performed to characterize resistance patterns of the samples. Relevancy of the obtained principal components with urban land use and fecal contamination of the river were examined. The ratio of antibiotic-resistant bacteria is likely to increase when urban land use near the sampling site exceeds a certain ratio. The resistance ratio to fluoroquinolones tends to be high in a highly populated area. Meanwhile, no significant contribution of fecal contamination was found to increase the resistance ratio. These results suggest that an antibiotic-resistance ratio is dependent on conditions of local urbanization rather than the upstream conditions, and that the major sources of antibiotic-resistant bacteria in the Chaophraya River basin are possibly point sources located in the urban area which contains a high ratio of resistant bacteria.
authors.affiliation: Research Center for Sustainable Energy and Technology, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan E-mail: rhonda@se.kanazawa-u.ac.jp.
authors.forename: Ryo
authors.initials: R
authors.lastname: Honda
authors.affiliation: Department of Food, Life and Environmental Science, Faculty of Agriculture, Yamagata University, 1-23 Wakaba-machi, Tsuruoka, Yamagata 997-8555, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Environmental Research and Training Center, Department of Environmental Quality Promotion, Technopolis, Khlong 5, Khlong Luang, Pathumthani 12120, Thailand.
authors.forename: Variga
authors.initials: V
authors.lastname: Sawaittayotin
authors.affiliation: Institute for the Advanced Study of Sustainability, United Nations University, 5-53-70, Jingumae, Shibuya-ku, Tokyo 150-8925, Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Masago
authors.affiliation: Environmental Research and Training Center, Department of Environmental Quality Promotion, Technopolis, Khlong 5, Khlong Luang, Pathumthani 12120, Thailand.
authors.forename: Rungnapa
authors.initials: R
authors.lastname: Chulasak
authors.affiliation: Department of Environmental Engineering, Faculty of Engineering, Kasetsart University, 50 Phaholyothin Rd, Jatujak, Bangkok 10900, Thailand.
authors.forename: Kulchaya
authors.initials: K
authors.lastname: Tanong
authors.affiliation: Faculty of Engineering, University of Ruhuna, Galle, Sri Lanka.
authors.forename: G Tushara
authors.initials: GT
authors.lastname: Chaminda
authors.affiliation: Environmental Research and Training Center, Department of Environmental Quality Promotion, Technopolis, Khlong 5, Khlong Luang, Pathumthani 12120, Thailand.
authors.forename: Krison
authors.initials: K
authors.lastname: Wongsila
authors.affiliation: Environmental Research and Training Center, Department of Environmental Quality Promotion, Technopolis, Khlong 5, Khlong Luang, Pathumthani 12120, Thailand.
authors.forename: Chawala
authors.initials: C
authors.lastname: Sienglum
authors.affiliation: Environmental Research and Training Center, Department of Environmental Quality Promotion, Technopolis, Khlong 5, Khlong Luang, Pathumthani 12120, Thailand.
authors.forename: Varisara
authors.initials: V
authors.lastname: Sunthonwatthanaphong
authors.affiliation: Environmental Research and Training Center, Department of Environmental Quality Promotion, Technopolis, Khlong 5, Khlong Luang, Pathumthani 12120, Thailand.
authors.forename: Anupong
authors.initials: A
authors.lastname: Poonnotok
authors.affiliation: Department of Environmental Engineering/Center of Advanced Studies in Industrial Technology, Faculty of Engineering, Kasetsart University, 50 Phaholyothin Rd, Jatujak, Bangkok 10900, Thailand.
authors.forename: Wilai
authors.initials: W
authors.lastname: Chiemchaisri
authors.affiliation: Department of Environmental Engineering/Center of Advanced Studies in Industrial Technology, Faculty of Engineering, Kasetsart University, 50 Phaholyothin Rd, Jatujak, Bangkok 10900, Thailand.
authors.forename: Chart
authors.initials: C
authors.lastname: Chiemchaisri
authors.affiliation: Research Center for Water Environment Technology, School of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Furumai
authors.affiliation: Environmental Science Center, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D000658:Amoxicillin; D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D024881:Drug Resistance, Bacterial; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000302:isolation & purification / Q000502:physiology*; D024841:Fluoroquinolones; D008826:Microbial Sensitivity Tests; D009643:Norfloxacin; D015242:Ofloxacin; D045483:Rivers / Q000382:microbiology*; D013752:Tetracycline; D013785:Thailand; D014507:Urbanization; D014871:Water Microbiology
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D002939:Ciprofloxacin; D000658:Amoxicillin; D015242:Ofloxacin; D013752:Tetracycline; D009643:Norfloxacin