L-histidine augments the oxidative damage against Gram-negative bacteria by hydrogen peroxide

Abstract

Excessive damage to DNA and lipid membranes by reactive oxygen species reduces the viability of bacteria. In the present study, the proliferation of recA-deficient Escherichia coli strains was revealed to be inhibited by 1% L-histidine under aerobic conditions. This inhibition of proliferation was not observed under anaerobic conditions, indicating that L-histidine enhances oxidative DNA damage to E. coli cells. Reverse transcription-quantitative polymerase chain reaction analysis demonstrated that the expression of recA in E. coli MG1655 increased ~7-fold following treatment with 10 mM hydrogen peroxide (H2O2) plus 1% L-histidine, compared with that following exposure to H2O2 alone. L-histidine increased the genomic fragmentation of E. coli MG1655 following exposure to H2O2. In addition, L-histidine increased the generation of intracellular hydroxyl radicals in the presence of H2O2 in E. coli cells. Next, our group investigated the disinfection properties of the H2O2 and L-histidine combination. The combination of 100 mM H2O2 and 1.0% L-histidine significantly reduced the number of viable cells of extended-spectrum-β-lactamase-producing E. coli and multidrug-resistant Pseudomonas aeruginosa, and this treatment was more effective than 100 mM H2O2 alone, but this effect was not observed in methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus faecium. The combination of L-histidine and H2O2 may be a useful strategy to selectively increase the microbicidal activity of oxidative agents against Gram-negative bacteria.