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Growth-inhibiting effects of 12 antibacterial agents and their mixtures on the freshwater microalga Pseudokirchneriella subcapitata

Authors

  • Li-Hua Yang,

    1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Tianhe, Guangzhou 510640, China
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  • Guang-Guo Ying,

    Corresponding author
    1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Tianhe, Guangzhou 510640, China
    • State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Tianhe, Guangzhou 510640, China
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  • Hao-Chang Su,

    1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Tianhe, Guangzhou 510640, China
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  • Jennifer L. Stauber,

    1. Commonwealth Scientific and Industrial Research Organisation Land and Water, PMB7, Bangor NSW 2234, Australia
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  • Merrin S. Adams,

    1. Commonwealth Scientific and Industrial Research Organisation Land and Water, PMB7, Bangor NSW 2234, Australia
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  • Monique T. Binet

    1. Commonwealth Scientific and Industrial Research Organisation Land and Water, PMB7, Bangor NSW 2234, Australia
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  • Published on the Web 1/10/2008.

Abstract

The growth-inhibiting and binary joint effects of 12 antibacterial agents on the freshwater green alga Pseudokirchneriella subcapitata (Korschikov) Hindák were investigated over 72-h exposures. The toxicity values (the median inhibitory concentration value, in micromoles) in decreasing order of sensitivity were triclosan (0.0018) > triclocarban (0.054) > roxithromycin (0.056) > clarithromycin (0.062) > tylosin (0.20) > tetracycline (2.25) > chlortetracycline (3.49) > norfloxacin (5.64) > sulfamethoxazole (7.50) > ciprofloxacin (20.22) > sulfamethazine (31.26) > trimethoprim (137.78). Several of these antibacterial compounds would be toxic at the micrograms per liter concentrations reported in surface waters and sewage effluents. Simple additive effects were observed in binary mixtures of sulfonamides, and most tylosin, triclosan, or triclocarban combinations. Potentially synergistic effects were observed in binary mixtures of the same class, such as macrolides, tetracyclines, and fluoroquinolones, as well as in some combined drugs, such as trimethoprim and sulfonamides or tylosin and tetracyclines. Potentially antagonistic effects were only observed between tylosin and triclocarban, triclosan and norfloxacin, and triclocarban and norfloxacin. Although present at low concentrations in the aquatic environment, mixtures of these antibacterial agents can potentially affect algal growth in freshwater systems due to their combined action.

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