Hydrogen Peroxide

Hydrogen peroxide has bactericidal (0.3%, 30 min) and yeasticidal (3%, 10 min) activity against most species, but an inconsistent fungicidal and mycobactericidal activity. Its antimicrobial activity is explained by oxidation of cellular components and damage to the cytoplasmatic membrane. Peroxidases and catalases, encoded by various genes, are important cellular defence mechanisms. Hydrogen peroxide can increase or decrease biofilm formation, depending on the species and the concentration of hydrogen peroxide. Biofilm removal is moderate in most studies (10%–89%). Its biofilm-fixing potential is unknown. High MIC values have been reported for meat-borne L. monocytogenes and clinical A. baumannii isolates, but their relevance is uncertain. Low-level exposure does not significantly alter the susceptibility of most species, but may increase catalase activity and cause cross-tolerance to aldehydes and hypochlorous acid. Only one Acinetobacter spp. spacecraft isolate with hydrogen peroxide resistance has been described (insufficient efficacy in suspension tests), but no resistant isolates have been found that failed the requirements of tests under practical conditions, or with a contamination of disinfectants. The overall probability of resistance to hydrogen peroxide of practical relevance is very low in the absence of biofilm.