Department of Environmental Chemistry, IDAEA-CSIC, Jordi Girona 18-24, Barcelona 08034, Catalunya, Spain; Integrative Freshwater Ecology Group, Centre for Advanced Studies of Blanes, CEAB-CSIC, Accés Cala St. Francesc 14, E-17300 Blanes, Spain.
Department of Environmental Chemistry, IDAEA-CSIC, Jordi Girona 18-24, Barcelona 08034, Catalunya, Spain.
Water Res. 2017 May 15;115:309-317. doi: 10.1016/j.watres.2017.03.007. Epub 2017 Mar 6.
Two of the main mechanisms of bacterial resistance to sulfonamides in aquatic systems, spread of antibiotic resistance genes (ARG) among the microbial community and in-situ bacterial sulfonamide degradation, were studied in mesocosms experiments using water and cobble biofilms from upstream (pristine waters) and downstream (polluted waters) from the Llobregat river, NE Iberian Peninsula. Mesocosms were prepared at two different concentrations (5000 ng/L and 1000 ng/L) of sulfonamides antibiotics (sulfamethazine and sulfamethoxazole). Concentrations of ARG, nutrients, sulfonamides and their degradation products were measured during the time course of the experiments. Sulfonamides were efficiently degraded by the biofilms during the first four weeks of the experiment. The abundance of ARG in biofilms sharply decreased after addition of high concentrations of sulfonamides, but this was not observed in the mesocosms treated with low concentrations of sulfonamides. Sulfonamide degradation was faster in polluted waters and at high concentrations of sulfonamide (and lower ARG abundances), suggesting that both degradation and ARG are two complementary resistance strategies employed by the microbial community. This study shows that microbial degradation of antibiotics is an efficient resistance mechanism coupled with the presence of ARG, and suggests that in situ degradation prevails at high concentrations of antibiotics whereas physiological adaptation by ARG spread would be more important under relatively lower concentrations of antibiotics.
本研究采用中尺度实验，以来自西班牙东北部埃布罗河上游（原始水域）和下游（污染水域）的水和鹅卵石生物膜为研究对象，分别在磺胺类抗生素（磺胺甲噁唑和磺胺嘧啶）浓度为 5000ng/L 和 1000ng/L 的条件下，研究了水生系统中细菌对磺胺类药物产生耐药性的两个主要机制，即在微生物群落中传播抗生素抗性基因（ARG）和原位细菌磺胺类药物降解。在实验过程中，测量了 ARG、养分、磺胺类药物及其降解产物的浓度。磺胺类药物在实验的前四周被生物膜有效降解。然而，在添加高浓度磺胺类药物的中尺度实验中，生物膜中 ARG 的丰度急剧下降，但在添加低浓度磺胺类药物的中尺度实验中并未观察到这种情况。在污染水域和高浓度磺胺类药物（以及较低的 ARG 丰度）条件下，磺胺类药物的降解速度更快，这表明降解和 ARG 是微生物群落采用的两种互补耐药策略。本研究表明，抗生素的微生物降解是一种有效的耐药机制，同时伴随着 ARG 的存在，并且表明在抗生素浓度较高时，原位降解占主导地位，而在相对较低的抗生素浓度下，ARG 传播的生理适应可能更为重要。
