Proteomic Analysis of in Vitro Induced Fluoroquinolone Resistant Staphylococcus aureus

Widespread use of antimicrobial agents in bacterial infection treatment has led to the outbreak of large number of resistant strains. In this study, we exposed Staphylococcus aureus (S. aureus) ATCC 29213 to ciprofloxacin (CIP), ofloxacin (OFL) or levofloxacin (LEV) at sub-minimum inhibitory concentrations (sub-MIC) for 12 days to obtain resistant strains and cultured for 10 days without antibiotics to obtain revertant strains. The seven protein samples from the initial strain, the 3 resistant and 3 revertant strains were extracted via sonication and cleaned by using 2D clean-up kit (GE Healthcare, USA). Protein samples were then quantitated by using RCDC protein assay kit (Bio-Rad, USA). Two-dimensional polyacrylamide gel electrophoresis (2D- PAGE) was performed at pH range 3–10. Briefly, the extracted protein of FQ- exposed strains with resistant phenotypes could then be compared with initial S. aureus ATCC 29213 in order identify protein spots associated with antibiotic resistance phenotype. After performing of 2D-PAGE and analyzing the 2D gels by using DECOCON Delta 2D software (Delta Decodon GmbH, Germany), the change in the expression of proteins including both up- and down- regulated ones in different FQ- exposed strains could be observed. Those protein spots seemed well correlated to resistance phenotypes.