„Non-toxic“ S. aureus strains and CoNS S.
epidermidis induce IL1-ß after phagocytosis
Previously, killing within macrophages was linked to inflammasome
activation (Cohen et al., 2018; Muller et al., 2015; Shimada et al.,
2010; Sokolovska et al., 2013). We questioned whether „non-toxic“S. aureus was still able to provoke IL-1ß release as read-out for
inflammasome activation. Since there are also major differences betweenS. aureus strains (Pidwill et al. , 2021), we included anagr/sae mutant of strain Newman into the analysis. There was no
significant difference between bacterial survival or cytotoxicity of
„non-toxic“ USA300 versus „non-toxic“ strain Newman (Fig. 2A, 2B).
Interestingly, IL-1ß was detectable not only in cells infected with the
„non-toxic“ S. aureus strains but also in those infected withS. epidermidis (Fig. 2C). IL-1ß release indicates that
intracellular S. aureus as well as CoNS induce inflammasome
activation. However, since there is no significant difference between
species, inflammasome activation doesn’t account for the differences
observed in bacterial survival. We next tested bacterial survival,
cytotoxicity and IL-1ß release in human primary macrophages (hMDM).
Again CoNS S. epidermidis was more efficiently killed compared to
„non-toxic“ S. aureus (Fig. 2D). IL-ß release was not
significantly different between species (Fig. 2F).