Effect of combined oxidative and nitrosative stress on Neisseria meningitidis

Reactive oxygen and nitrogen species are produced by the human immune system in response to infection. Methods to detoxify these reactive species are vital to the survival of human pathogens, such as Neisseria meningitidis, which is the major aetiological agent of bacterial meningitis. Following activation, macrophages produce superoxide (O₂⁻), hydrogen peroxide (H₂O₂) and nitric oxide (NO). The toxicity of O₂⁻, generated using X/Xo (xanthine/xanthine oxidase), and H₂O₂ was investigated in the presence and absence of the NO donor DEA-NONOate [2-(N,N-diethylamino)-diazenolate-2-oxide diethylammonium salt]. Most of the toxicity from X/Xo was due to H₂O₂. In N. meningitidis, NO decreased the toxicity of the H₂O₂. In contrast, in the enteric bacterium Escherichia coli, NO increased the toxicity of the H₂O₂.