(A and B) PGN was purified from MRSA and grown overnight with or without cefoxitin. HPLC profiles of muropeptides from PGN derived from untreated (A) or cefoxitin-treated (B) MRSA are shown. Fragments with reduced cross-links have a short elution time.

(C and D) PGN from untreated or cefoxitin-treated MRSA was used to stimulate murine BMDM (C), or human monocyte-derived macrophages (D) (80 μg/ml PGN) (data are representative of three experiments for C).

(E) PGN from MRSA treated with cefoxitin (Cef), ampicillin (Amp), or nafcillin (Naf) was used to stimulate murine BMDM (data are representative of four experiments).

(F) mecA mRNA from MRSA grown for 4 hr with or without cefoxitin was measured by qRT-PCR and standardized against expression of 16S rRNA (data are representative of two experiments).

(G) IL-1β release by murine BMDM incubated with live MRSA pretreated with cefoxitin for 4 hr (data are representative of three experiments).

(H) IL-1β stimulatory activity of clinical MRSA strains grown in the presence or absence of cefoxitin (data are representative of two experiments).