Oxidative stress in Staphylococcus aureus associated to the cleavage of an isoxazolylnaphthoquinoneimine with antibacterial capacity

Staphylococcus aureus was inhibited by exposure to 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-4-imine (Q(1)). This compound was cleavaged in the presence of bacteria and an efflux of isoxazolamine was detected whereas in the S. aureus membrane and cytoplasm was observed an absorption band similar to that of the bencenoid ring. Non-viable bacteria showed intact Q(1) intracellularly and in the membrane. Antistaphylococcus effect was associated to Q(1) interaction with the respiratory chain, the oxydative metabolites were stimulated; there was cellular injury simultaneous to reduction of antibiotic molecule and efflux of isoxazol amine. The bacteria treated with Q(1) increased its oxygen consumption and superoxide anion generation. Superoxide dismutase (SOD) production was stimulated, but it was principally extracellular in S. aureus. Escherichia coli, a species resistant to the antibiotic, did not reduce Q(1) and showed lower superoxide anion generation; besides, there was an increase of intracellular SOD with extracellular decrease. (C) 1998 Academic Press.