Relationship between oxidative and nitrosative stress induced by gentamicin and ciprofloxacin in bacteria

Abstract

Oxygen is essential to the life of the aerobic organisms, and most is used for the intracellular generation of energy, where several molecules are formed by partial reduction of oxygen. Because of its short half-life, low selectivity and high reactivity, biological targets of reactive oxygen species (ROS) include various components such as proteins, nucleic acids and lipids. The purpose of this work was to establish a relationship between ROS and reactive nitrogen intermediates (RNI) generation in bacteria exposed to antibiotics. ROS was determined by the reduction of nitro blue tetrazolium (NBT). In aqueous solutions, nitric oxide is converted to nitrite (NO2-), this was determined using a non-enzymatic colorimetric assay. NBT studies indicated stimulation of oxidative stress with an increase of ROS generated by the antibiotic in the bacteria. We observed an increase in the production of NO2- dose-dependent with CIP and GEN. The determination of ROS and RNI allowed establish differences in the alteration of oxidative metabolism in susceptible and resistant strains. Resistance to CIP and GEN may be related to the decreased production of ROS and RNI and consequently, a smaller macromolecules bacterial oxidation. These results contribute to a better understanding of the ROS and RNI regulation.