Figure 2. Combinations of NO and H₂O₂ augment their antimicrobial activity.

A) Approximately 5,000 CFU of B. bronchiseptica were exposed to a sub-antimicrobial concentration of H₂O₂ (2.5 µM) in combination with a concentration gradient of SPER/NO. B) B. bronchiseptica were exposed to a sub-antimicrobial concentration of SPER/NO (15 µM) in combination with a concentration gradient of H₂O₂. The addition of a sub-antimicrobial concentration of either NO or H₂O₂ augmented the antimicrobial activity of the other redox agent. C) B. bronchiseptica were subjected to incubation in reaction buffer containing both H₂O₂ and O₂^.−. SOD and catalase were included as experimental controls to verify the augmentative effect of H₂O₂ and O₂^.− in combination. In each case significant antimicrobial activity was measured at concentrations of redox species that were not effective individually. Bacterial survival was determined after a 5 h exposure period (± SEM) as compared to buffer controls and are representative of at least three independent experiments. “*” indicates statistical significance relative to control (P < 0.05). “#” indicates a statistically significant difference as compared to either 250 µM SPER/NO alone (Figure 2A) or to 10 µM H₂O₂ alone (Figure 2B) (P < 0.05).