title: Mechanisms of Antibacterial Action of Quinoxaline 1,4-di-N-oxides againstClostridium perfringensandBrachyspira hyodysenteriae.
abstract: Quinoxaline 1,4-di-N-oxides (QdNOs) are a class of bioreductive compounds, however, their antibacterial mechanisms are still unclarified. The aim of this study was to assess the ability of two representative QdNO drugs, cyadox (CYA) and olaquindox (OLA), to produce reactive oxide species (ROS) in Gram-positive anaerobeClostridium perfringensCVCC1125 and Gram-negative anaerobeBrachyspira hyodysenteriaeB204. In addition, the effects of QdNOs on the integrity of bacterial cell walls and membranes as well as the morphological alterations and DNA oxidative damage inC. perfringensandB. hyodysenteriaewere analyzed. It was demonstrated that under anaerobic conditions, QdNOs were metabolized into the reduced products which did not show any antibacterial activity. A significant dose-related increase of intracellular ROS level and intracellular hydroxyl radicals were evident in bacteria exposed to QdNOs. The result of biochemical assay showed that the cell walls and membranes of the bacteria treated with QdNOs were damaged. After exposure to 1/2MIC to 4MIC of CYA and OLA,C. perfringensandB. hyodysenteriaebecame elongated and filamentous. Morphological observation with scanning and transmission electron microscopes revealed rupture, loss of cytoplasmic material and cell lysis in QdNO-treated bacteria, indicating serious damage of cells. There was an increase of 8-OHdG in the two strains treated by QdNOs, but it was lower inC. perfringensCVCC1125 than inB. hyodysenteriaeB204. Agarose gel electrophoresis showed the degradation of chromosomal DNA in both of the two anaerobes treated by QdNOs. The results suggest that QdNOs may killC. perfringensandB. hyodysenteriaevia the generation of ROS and hydroxyl radicals from the bacterial metabolism of QdNOs, which cause oxidative damage in bacteria under anaerobic conditions.
authors.affiliation: National Reference Laboratory of Veterinary Drug Residues (HZAU), Ministry of Agriculture Key Laboratory for the Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural University Wuhan, China.
authors.forename: Fanfan
authors.initials: F
authors.lastname: Xu
authors.affiliation: Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University Wuhan, China.
authors.forename: Guyue
authors.initials: G
authors.lastname: Cheng
authors.affiliation: Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University Wuhan, China.
authors.forename: Haihong
authors.initials: H
authors.lastname: Hao
authors.affiliation: National Reference Laboratory of Veterinary Drug Residues (HZAU), Ministry of Agriculture Key Laboratory for the Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural UniversityWuhan, China; Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China.
authors.forename: Yulian
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University Wuhan, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Wang
authors.affiliation: National Reference Laboratory of Veterinary Drug Residues (HZAU), Ministry of Agriculture Key Laboratory for the Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural UniversityWuhan, China; Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Chen
authors.affiliation: National Reference Laboratory of Veterinary Drug Residues (HZAU), Ministry of Agriculture Key Laboratory for the Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural UniversityWuhan, China; Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Peng
authors.affiliation: National Reference Laboratory of Veterinary Drug Residues (HZAU), Ministry of Agriculture Key Laboratory for the Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural UniversityWuhan, China; Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China.
authors.forename: Zhenli
authors.initials: Z
authors.lastname: Liu
authors.affiliation: National Reference Laboratory of Veterinary Drug Residues (HZAU), Ministry of Agriculture Key Laboratory for the Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural UniversityWuhan, China; Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China.
authors.forename: Zonghui
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: Ministry of Agriculture Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University Wuhan, China.
authors.forename: Menghong
authors.initials: M
authors.lastname: Dai
keywords: 4-di-N-oxides; Brachyspira hyodysenteriae; Clostridium perfringens; DNA damage; cell membrane; cell wall; quinoxaline 1