Global protein expression profile response of Escherichia coli ATCC 25922 exposed to enrofloxacin.

Although enrofloxacin (ENR) is widely used for therapy of bacterial infections in the veterinary clinical, bacterial resistance to ENR is becoming an increasing worldwide problem. The primary global response of Escherichia coli to ENR exposure before resistance is largely unknown on the proteomic level. The purpose of this study was to understand the physiological response of E. coli to a subinhibitory concentration of ENR using proteomic methods. Differentially expressed proteins of the whole-cell extracts were visualized by two-dimensional gel electrophoresis, and the selected proteins were purified and identified by MALDI-TOF/mass spectrometry analysis. The result showed that the number of proteins (mean±standard deviation) detected in the ENR-treated strains was significantly (p<0.05) reduced from 1115±25 to 732±19. In total, 42 differentially expressed proteins with more than twofold difference were identified, including 13 upregulated proteins (p<0.05) and 17 downregulated proteins (p<0.05), as well as the specific proteins expressed in the group with or without ENR-treated cells. The results show that the differentially expressed proteins identified in E. coli exposed to ENR included proteins involved with a classic resistance mechanism, such as bacterial cell membrane permeability mediated by OmpX and OmpW, and other adaptive changes that appear to represent the physiological basis and background of resistance to ENR.