Reactive oxygen species induce antibiotic tolerance during systemic Staphylococcus aureus infection

Staphylococcus aureus is a major human pathogen that causes an array of infections ranging from minor skin infections to more serious infections, including osteomyelitis, endocarditis, necrotizing pneumonia and sepsis 1 . These more serious infections usually arise from an initial bloodstream infection and are frequently recalcitrant to antibiotic treatment 1 . Phagocytosis by macrophages and neutrophils is the primary mechanism through which S. aureus infection is controlled by the immune system 2 . Macrophages have been shown to be a major reservoir of S. aureus in vivo 3 , but the role of macrophages in the induction of antibiotic tolerance has not been explored. Here, we show that macrophages not only fail to efficiently kill phagocytosed S. aureus , but also induce tolerance to multiple antibiotics. Reactive oxygen species generated by respiratory burst attack iron–sulfur cluster-containing proteins, including TCA-cycle enzymes, result in decreased respiration, lower ATP and increased antibiotic tolerance. We further show that respiratory burst induces antibiotic tolerance in the spleen during a murine systemic infection. These results suggest that a major component of the innate immune response is antagonistic to the bactericidal activities of antibiotics. Reactive oxygen species produced by macrophages following infection with Staphylococcus aureus attack bacterial iron–sulfur cluster-containing proteins, thereby leading to alterations in bacterial metabolism that increase their tolerance to antibiotics.