Figure 5. Quantification results for the expression of PBP2a (gene: mecA) and β-lactamase (gene: blaZ) at protein level by label-free quantitative proteomics method (a) and at transcription level by Q-RT-PCR method (b).

PBP2a and β-lactamase are the proteins involved in resistance mechanism of bacteria against β-lactam antibiotics. Label-free quantitative proteomics results show that the levels of PBP2a and β-lactamase are lower in the SIPI-8294/Oxa than Ery/Oxa and other treatment groups. The same trend was found at the mRNA level. These results suggest that the synergistic effect mechanism may be related to the interference with the oxacillin resistance mechanism. Asterisks (*) indicate differential expression at p < 0.05.