Subproteomic signature comparison of <i>in vitro</i> selected fluoroquinolone resistance and ciprofloxacin stress in <i>Salmonella</i> Typhimurium DT104B

<b>Background</b>: Fluoroquinolone resistance in nontyphoidal <i>Salmonella</i> is a situation of serious and international concern, particularly in <i>S.</i> Typhimurium DT104B multiresistant strains. Although known to be multifactorial, fluoroquinolone resistance is still far from a complete understanding. <b>Methods</b>: Subproteome changes between an experimentally selected fluoroquinolone-resistant strain (Se6-M) and its parent strain (Se6), and also in Se6-M under ciprofloxacin (CIP) stress, were evaluated in order to give new insights into the mechanisms involved. Proteomes were compared at the intracellular and membrane levels by a 2-DE~LC-MS/MS and a shotgun LC-MS/MS approach, respectively. <b>Results</b>: In total, 35 differentially abundant proteins were identified when comparing Se6 with Se6-M (25 more abundant in Se6 and 10 more abundant in Se6-M) and 82 were identified between Se6-M and Se6-M+CIP (51 more abundant in Se6-M and 31 more abundant under ciprofloxacin stress). <b>Conclusion</b>: Several proteins with known and possible roles in quinolone resistance were identified which provide important information about mechanism-related differential protein expression, supporting the current knowledge and also leading to new testable hypotheses on the mechanism of action of fluoroquinolone drugs.