Investigating the survival advantage of Staphylococcus aureus persisters within a macrophage 2822

Abstract Description Staphylococcus aureus is an opportunistic pathogen that is a leading cause of nosocomial infections associated with foreign devices. Often, S. aureus is associated with relapsing infections thought to be mediated by persister cell formation, a dormant-like subpopulation tolerant to antibiotic treatment. Recently, persister cell formation was shown to depend on a reduction in tricarboxylic acid (TCA) cycle activity, as a knockout in the fumarase gene (fumC::NΣ) increased tolerance to antibiotics. Furthermore, persisters also conferred a survival advantage to antimicrobial peptides, LL-37, and human β-defensin 3, leading us to hypothesize a similar advantage exists within macrophages. To test this hypothesis, survival within a macrophage cell line was monitored between fumC::NΣ and wild type, with fumC::NΣ exhibiting a 1-log increase in bacterial burden. Next, a persister marker (Pcap5A::dsRed) was utilized in tandem with flow cytometry to monitor persister survival throughout the infection. Through 4-amino-5-methylamino-2’, 7’-difluoroflurescein and CM-H2DCFDA dyes, reactive oxygen and nitrogen species production were found to be similar in macrophages infected with fumC::NΣ and those infected with wild type S. aureus, indicating persisters confer a fitness advantage through other means. While the underlying mechanism needs further exploration, our results suggest that persisters provide a survival advantage within macrophages. Funding Sources Research reported in this abstract was supported by the National Institute of General Medical Science of the National Institutes of Health (NIH) under award number GM103427. Topic Categories Microbial, Parasitic, and Fungal Immunology (MPF)