FIG 4.

Regulation of S. aureus plc and srrA in response to in vitro and in vivo oxidative stress. The expression of plc (A) or srrA (B) was compared to that in PBS-treated controls by qRT-PCR in vitro, using various concentrations of either HOCl or H₂O₂ as sources of oxidative stress for 60 min. In addition, levels of plc (C) or srrA (D) expression were examined in PMNs 10 min after phagocytosis. PMNs treated with DPI or obtained from a patient who suffers from CGD were compared with normal PMNs. Controls included bacteria grown in broth, bacteria that had undergone 20 min of opsonization (Ops), and bacteria that had been resuspended in the PMN buffer for 10 min (Buf). For statistical analysis, all comparisons are against the broth-grown controls. The levels of plc and srrA expression were normalized to the level of expression of the DNA gyrase subunit B (gyrB). All results represent the means ± SEMs from three independent experiments. *, P < 0.05; **, P < 0.01.