Determining the effects of the type seven secretion system (T7SS) in staphylococcal innate immune interactions 3129

Abstract Description Staphylococcus aureus is an opportunistic pathogen that leads to upwards of twenty thousand deaths and five billion dollars in healthcare-related costs in the United States annually. While many virulence factors within S. aureus are well characterized, the type VII secretion system (T7SS), a protein secretion system found within many bacterial species, remains poorly understood. Studies within Streptococcus intermedius indicate the T7SS is responsible for secreting proteins that allow the pathogen to evade immune responses. To investigate whether the T7SS in S. aureus was important in survival to innate immunity, a Drosophila melanogaster sepsis model was utilized. A knockout in the essC gene encoding the T7SS ATPase was studied for differences in D. melanogaster survival. D. melanogaster infected with the essC knockout exhibited significantly increased survival compared to flies infected with wild-type S. aureus. Survival within a macrophage cell line was explored further to elucidate the mechanism behind the differential survival. RAW264.7 macrophages were infected with an essC knockout and wild-type S. aureus at a multiplicity of infection of 25. 24 hours post-infection, macrophages infected with the essC knockout exhibited a 1-log reduction in bacterial burden compared to macrophages infected with wild-type. The T7SS of S. aureus remains a poorly understood virulence factor that may play a pivotal role in bacterial survival to components of the innate immune system. Funding Sources 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)