Intracellular infection of S. aureus in relation to ClpX deficiency was investigated using 16HBE14o- bronchial epithelial cells (Fig. 7B and C; Fig. S21). In accordance with Kim et al. (30), we did not observe significant differences in internalization between the ClpX-proficient and -deficient strains (Fig. S20B). This evidence concerns the gene CLPX and infection.