Mechanisms of Antibacterial Action of Quinoxaline 1,4-di-N-oxides against Clostridium perfringens and Brachyspira 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 anaerobe Clostridium perfringens CVCC1125 and Gram-negative anaerobe Brachyspira hyodysenteriae B204. 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 in C. perfringens and B. hyodysenteriae were 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. perfringens and B. hyodysenteriae became 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 in C. perfringens CVCC1125 than in B. hyodysenteriae B204. Agarose gel electrophoresis showed the degradation of chromosomal DNA in both of the two anaerobes treated by QdNOs. The results suggest that QdNOs may kill C. perfringens and B. hyodysenteriae via the generation of ROS and hydroxyl radicals from the bacterial metabolism of QdNOs, which cause oxidative damage in bacteria under anaerobic conditions.

Toxic metabolites, Sertoli cells and Y chromosome related genes are potentially linked to the reproductive toxicity induced by mequindox

“…As many studies suggested, QdNOs derivatives were used as growth promoters in husbandry because of their strong antimicrobial activity [ 1 , 2 , 4 , 5 , 12 ]. However, up to now, the antimicrobial activity of QdNOs has mainly focused on the parent drugs and subsequent reactive oxygen species (ROS) and hydroxyl radicals from the bacterial metabolism of QdNOs [ 63 ]. It still remains undiscovered whether their metabolites have antibacterial activity and further study should be conducted to focus on this issue.…”

Chemical composition, antioxidant activity and antibacterial mechanism of action from Marsilea minuta leaf hexane: methanol extract

“…The increase may be because of stress imposed on the bacteria by the extract, and in order to overcome the starvation, the bacteria produces more amount of ALP. Previous studies revealed that the ALP levels were increased in Clostridium perfringens and Brachyspira hyodysenteriae upon treatment with Quinoxaline 1,4-di- N -oxide derivatives compared to the non-treated groups [37]. Therefore, the observed significant increase in the ALP activities in the bacteria treated with M. minuta extract suggests an increase in the activities of the existing enzymes by the secondary metabolites.…”

Identification of N-Oxide-Containing Aromatic Heterocycles as Pharmacophores for Rumen Fermentation Modifiers

“…According to our studies on steer rumen aliquots, quinoxaline dioxide 3 decreased k d by 15% with respect to UIR and with a concomitant increase in the lag time of 38%. Quinoxaline dioxides, such as carbadox, olaquindox, and mequindox [41,42], have been used to prevent bacterial infections and to improve animal growth due to their actions against gram-positive and gram-negative bacteria. However, currently they are banned due to health concerns over their (and their metabolites’) toxic effect of oxidative stress [43].…”