Effect of fluoroquinolone exposure on the proteome of Salmonella enterica serovar Typhimurium

Abstract

Objectives: The physiological response of Salmonella enterica serovar Typhimurium to fluoroquinolone antibiotics was investigated using proteomic methods. Methods: Proteomes were prepared from strain SL1344 following treatment of broth cultures with ciprofloxacin (0.03 and 0.008 mg/L; 2× and 0.5× MIC) and enrofloxacin (0.03 mg/L) and from a multiple antibiotic resistant (MAR) mutant. Protein expression was determined by two-dimensional HPLC-MSn and also after exposure to ciprofloxacin by two-dimensional gel electrophoresis (2D-GE). Results: The number of proteins (mean ± SD) detected by 2D-GE derived from control cultures of the wild-type strain was significantly (P < 0.05) reduced from 296 ± 77 to 153 ± 36 following treatment with ciprofloxacin (0.03 mg/L). Raised expression (P < 0.05) of 17 proteins was also detected, and increases of up to 8-fold (P < 0.0001) were observed for subunits of F1F0 -ATP synthase, TolC and Imp. Analysis by two-dimensional HPLC-MSn provided higher proteome coverage with 787 ± 50 proteins detected, which was reduced (P < 0.005) to 560 ± 14 by ciprofloxacin (0.03 mg/L). Increased expression of 43 proteins was observed which included those detected by 2D-GE and additionally the efflux pump protein AcrB. The basal expression of the AcrAB/TolC efflux pump was elevated in the MAR mutant compared with the untreated wild-type and augmented following treatment with ciprofloxacin (0.03 mg/L). F1F0-ATP synthase and Imp were only elevated in the mutant when treated with ciprofloxacin. Conclusions: These studies suggest that increased expression of AcrAB/ TolC was associated with resistance while other increases, such as in F1F0-ATP synthase and Imp, were a response to fluoroquinolone. © 2006 Oxford University Press.