BACTERICIDAL PROPERTIES OF HYDROGEN-PEROXIDE AND COPPER OR IRON-CONTAINING COMPLEX-IONS IN RELATION TO LEUKOCYTE FUNCTION

Various combinations of hydrogen peroxide, reductant (ascorbic acid an d superoxide ion), and copper or iron salts and their coordination com plexes were examined to determine their cytotoxicity toward several ba cteria with diverse metabolic capabilities and cell envelope structure s. Four sets of bactericidal conditions were identified, comprising: ( 1) high concentration levels (5-100 mM) of H2O2 in the absence of exog enous metal ions and reductant; (2) ferrous or ferric coordination com plexes plus enzymatically generated O-2(.-) and H2O2 at relatively low steady-state concentration levels; (3) cupric ion plus low concentrat ion levels of H2O2 (1 mu M-1 mM) and ascorbate (10 mu M-4 mM); (4) cup rous ion (or cupric ion plus ascorbate) in the absence of O-2 and H2O2 Rates of losses in viabilities increased proportionately with increas es in the concentration of H2O2 in metal-free environments and with ea ch of the components in the Cu2+/ascorbate/H2O2 bactericidal assay sys tem. Oxidant levels required for equivalent killing increased with inc reasing cell densities of the bacterial suspensions over the range inv estigated (2 x 10(7)-2 x 10(9) cfu/ml). Other experimental conditions or other combinations of reagents, most notably Fe3+/ascorbate/H2O2 sy stems, did not generate bactericidal environments. The patterns of res ponse of the three organisms tested, Streptococcus lactis, Escherichia coli, and Pseudomonas aeruginosa, were similar, suggesting common bac tericidal mechanisms. However, preliminary evidence suggests that the lethal lesions caused by the various bactericidal conditions are disti nct. As discussed, each of the four bactericidal conditions could conc eivably be attained within the phagosomes of leukocytes, although none has as yet been identified.