Antibiotics have become common pollutants in the environment. In most cases, the antibiotics in the environment exist as mixtures, posing joint effects on the organisms. Therefore, the mixture toxicity of the antibiotics can better reflect their environmental risks. In this paper, three types of commonly used antibiotics, i.e., sulfonamides (SAs), SA potentiators (SAPs) and tetracyclines (TCs) were investigated for their binary and tertiary mixture toxicity on three bacteria, Escherichia coli (E. coli), Vibrio fischeri (V. fischeri) and Bacillus subtilis (B.subtilis). It was found that SA-SAP mixtures and SA-SAP-TC mixtures presented synergetic effects on the three bacteria, while SA-TC and SAP-TC mixtures showed antagonistic effects. QSAR investigation suggested that the actual concentration ratio of the components in a mixture could vary a lot from the designed concentration ratio; moreover, the TCs in the ternary mixtures altered the toxic ratio of SAs and SAPs, which lead to the varying joint effects of the ternary mixtures on different bacteria. The present research proposes a novel idea for the mechanistic study of the mixture toxicity, both theoretically and methodologically; and the QSAR studies provide a reference for the prediction of the mixture toxicity, which could be helpful to the risk assessment on joint exposure to antibiotic mixtures.

抗生素已成为环境中的常见污染物。在大多数情况下，环境中的抗生素以混合物形式存在，对生物体产生联合作用。因此，抗生素的混合毒性可以更好地反映其环境风险。在本文中，研究了三种常用的抗生素，即磺酰胺（SAs），SA增强剂（SAPs）和四环素（TCs）对三种细菌（大肠杆菌（E. coli），弧菌）的二元和三级混合物毒性。鲵（五鲵）和枯草芽孢杆菌（枯草芽孢杆菌）。发现SA-SAP混合物和SA-SAP-TC混合物对三种细菌具有协同作用，而SA-TC和SAP-TC混合物表现出拮抗作用。QSAR研究表明，混合物中各组分的实际浓度比可能与设计浓度比有很大差异。此外，三元混合物中的TCs改变了SAs和SAPs的毒性比，导致三元混合物对不同细菌的不同联合作用。本研究为混合物毒性的机理研究从理论上和方法上提出了一个新的思路。QSAR研究为混合物毒性的预测提供了参考，可能有助于联合暴露于抗生素混合物的风险评估。