title: Antibacterial activity of the soil-bound antimicrobials oxytetracycline and ofloxacin.
abstract: Soil contamination of antimicrobials has become an increasing concern because of the potential risks to the soil microbial ecosystem and human health. The present study investigated sorption and desorption behaviors of oxytetracycline (OTC) and ofloxacin (OFL) in 3 typical soils (A, B, and C), and evaluated the antibacterial activity of soil-adsorbed compounds to a pure sensitive strain Escherichia coli ATCC 25922. The results showed different sorption and desorption behaviors of OTC and OFL in the 3 soils, behaviors that were mainly influenced by soil organic matter content and cation exchange capacity (CEC) as well as pH value. In addition, complexation and cation-exchange reactions were shown to be the main sorption mechanisms. Strong adsorption was found in soil B (with a high organic matter content) and in soil C (with high CEC), whereas enhanced desorption was observed in soil A (with low organic matter content). The results also demonstrated that soil-bound antimicrobials retained antibacterial activity toward E. coli. Opposite patterns of antibacterial activity were found for the 2 antimicrobials in the 3 soils: A>B>C for OFL; and C>B>A for OTC. This finding suggests that soil-bound antimicrobials could still exert selective pressure on soil bacteria although less effectively in comparison with the dissolved forms.
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, People's Republic of China.
authors.forename: Feng-Jiao
authors.initials: FJ
authors.lastname: Peng
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Zhou
authors.forename: Guang-Guo
authors.initials: GG
authors.lastname: Ying
authors.forename: You-Sheng
authors.initials: YS
authors.lastname: Liu
authors.forename: Jian-Liang
authors.initials: JL
authors.lastname: Zhao
mesh_terms: D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000633:toxicity*; D004926:Escherichia coli / Q000187:drug effects*; D015242:Ofloxacin / Q000737:chemistry / Q000633:toxicity*; D010118:Oxytetracycline / Q000737:chemistry / Q000633:toxicity*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry / Q000633:toxicity*
chemical_list: D000900:Anti-Bacterial Agents; D012987:Soil; D012989:Soil Pollutants; D015242:Ofloxacin; D010118:Oxytetracycline
keywords: Adsorption; Antibacterial activity; Desorption; Hysteresis; Ofloxacin; Oxytetracycline