Potentiate Antibacterial Activity via ROS

Potentiating antibacterial activity by enhancing microbial ROS production has been demonstrated previously (Brynildsen et al., 2013 (link)). To test the impact of ROS modulation (by sdhC or cyoA deletion) on bacterial viability in E. coli ATCC 25922, EC04 and EC59 strains, time-kill curves were assayed in MHB (Mueller-Hinton broth, Becton Dickinson, Le Pont-de-Claix, France) at ciprofloxacin and ofloxacin concentrations of 2xMIC (Table 1). Growth in drug-free broth was evaluated in parallel, as a control. Cultures were incubated at 37°C, and shaken at 180rpm. An initial inoculum of 10⁶ CFU/mL from a fresh overnight culture was used in all experiments. Bacterial concentrations were determined at 0, 1, 2, 3, 4, and 24 h by colony counting on drug-free agar.
In parallel, the time courses of E. coli ATCC 25922, EC04 and EC59 cells treated with Carboxin (500 μM), an inhibitor of succinate dehydrogenase (Brynildsen et al., 2013 (link)), and a fluoroquinolone (ciprofloxacin or ofloxacin at 2xMIC), were compared with treatment with fluoroquinolones alone. Carboxin (Sigma–Aldrich, Madrid, Spain) was dissolved in 100% ethanol (Brynildsen et al., 2013 (link)).