Interaction between Streptococcus pneumoniae and Staphylococcus aureus Generates · OH Radicals That Rapidly Kill Staphylococcus aureus Strains

Streptococcus pneumoniae strains produce hydrogen peroxide (H2 O2 ) to kill bacteria in the upper airways, including pathogenicStaphylococcus aureus strains. The targets ofS. pneumoniae -produced H2 O2 have not been discovered, in part because of a lack of knowledge about the underlying molecular mechanism. We demonstrated that an increased density ofS. pneumoniae killsS. aureus by means of H2 O2 produced by two enzymes, SpxB and LctO. We discovered that SpxB/LctO-produced H2 O2 is converted into a hydroxyl radical (· OH) that rapidly intoxicates and killsS. aureus . We successfully inhibited the toxicity of· OH with three different scavengers and detected· OH in the supernatant. The target(s) of the hydroxyl radicals represents a new alternative for the development of antimicrobials againstS. aureus infections.