Experimental evidence of the anti-bacterial activity pathway of copper ion treatment on Mycobacterium avium subsp. paratuberculosis

Copper causes significant damage to the integrity of many bacteria, mainly at the DNA level, through its redox states, as well as its reactive oxygen species (ROS) generating capacity at the cellular level. But whether these mechanisms also apply to Mycobacterium avium subsp. paratuberculosis (MAP) is unknown. In the present study, we have evaluated whether copper ions produce damage at the DNA level of MAP, either through their redox states or through ROS production. MAP-spiked PBS was first supplemented with different copper chelators (2) and ROS antioxidants (3), followed by treatment with copper ions at 942 ppm. MAP DNA integrity (qPCR, magnetic phage separation) was then evaluated. We found that bathocuproine (BCS), as a chelator, and D-mannitol, as an antioxidant of hydroxyl radicals, had a significant protective effect (P < 0.05) on DNA molecules, and that EDTA, as a chelator, and D-mannitol, as an antioxidant had a significant positive effect (P < 0.05) on the viability of this pathogen in contrast to the control and other chelators and anti-oxidants used. In light of the reported findings, it may be concluded that copper ions within MAP cells are directly related to MAP DNA damage.

Automated summary

Copper ions cause significant damage to the DNA integrity of Mycobacterium avium subsp. paratuberculosis (MAP) through their redox states and reactive oxygen species (ROS) generating capacity. This study evaluated the effects of copper ions on MAP DNA integrity and found that the chelator bathocuproine (BCS) and the antioxidant D-mannitol had a significant protective effect, while the chelator EDTA and the antioxidant D-mannitol had a significant positive effect on the viability of the pathogen.