FIG 4.
Sensitization to β-lactams during DAP resistance is associated with decreased production of PBP 2a. (A) Western blot analysis of the PBP 2a protein in membrane and extracellular protein extracts from DAPr CB1634 cells grown without (control [C]) or with DAP, OXA, or the DAP-OXA combination. Carbonic anhydrase was used as a loading control. (B) RT-PCR analysis showing mecA gene expression in DAPr CB1634 cells grown without or with DAP, OXA, or the DAP-OXA combination. *, the fold change was significantly higher than that for the CB1634 control (no antibiotic) (P < 0.05); #, the fold change was significantly higher than that for cells exposed to DAP or OXA alone (P < 0.05). (C) Western blot analysis of the PBP 2a protein in membrane protein extracts from CB1643 ΔmprF (MAR17), CB1634 ΔmprF mprF (WT) (MAR18), and CB1634 ΔmprF mprFL826F (MAR19) cells grown without (control) or with DAP, OXA, or the DAP-OXA combination.