Staphylococcus aureu s secreted lipases do not inhibit innate immune killing mechanisms.

causes an array of diseases in both humans and livestock. Pathogenesis is mediated by a plethora of proteins secreted by , many of which remain incompletely characterised. For example, abundantly secretes two isoforms of the enzyme lipase into the extracellular milieu, where they scavenge upon polymeric triglycerides. It has previously been suggested that lipases may interfere with the function of innate immune cells, such as macrophages and neutrophils, but the impact of lipases on phagocytic killing mechanisms remains unknown. We employed the epidemic clone USA300 strain LAC and its lipase deficient isogenic mutant, along with recombinant lipase proteins, in experimental infection assays. To determine if lipases can inhibit innate immune killing mechanisms, the bactericidal activity of whole blood, human neutrophils, and macrophages was analysed. In addition, gentamycin protection assays were carried out to examine the influence of lipases on innate immune cell escape. There were no differences in the survival of USA300 LAC wild type and its lipase-deficient isogenic mutant after incubation with human whole blood or neutrophils. Furthermore, there was no detectable lipase-dependent effect on phagocytosis, intracellular survival, or escape from both human primary and immortalised cell line macrophages, even upon supplementation with exogenous recombinant lipases. lipases do not inhibit bacterial killing mechanisms of human macrophages, neutrophils, or whole blood. These findings broaden our understanding of the interaction of with the innate immune system.