Comparative subproteomic analysis of clinically acquired fluoroquinolone resistance and ciprofloxacin stress in Salmonella Typhimurium DT104B

Purpose: Antimicrobial resistance is a worldwide public health threat and Salmonella enterica subsp. enterica serotype Typhimurium phage type DT104B multiresistant strains with additional quinolone resistance have been responsible for global outbreaks and high mortality. Quinolone resistance is known to be multifactorial but is still far from a complete understanding. To give new insights about the resistance mechanisms involved, this work aimed to evaluate subproteome changes between an S. Typhimurium DT104B clinical strain that acquired fluoroquinolone resistance after treatment (Se20) and its pretreatment parental strain (Se6), and also subproteome variations in Se20 under ciprofloxacin (CIP) stress (Se20+CIP). Experimental design: The proteomes were compared at the intracellular and membrane levels by a 2-DE similar to LC-MS/MS and a shotgun LC-MS/MS approach, respectively. Results: In total, 14 differentially abundant proteins were identified when comparing Se6 with Se20 and 91 were identified between Se20 and Se20+CIP. Several proteins with known and possible roles in quinolone resistance (AAC(6')-Ib-cr4, OmpD, OmpX, GlmS, GlmU, H-NS, etc.) were identified and discussed. Conclusions and clinical relevance: The great number of proteins identified in this study provides important information about mechanism-related differential protein expression which supports the current knowledge and might lead to new testable hypotheses on the mechanism of action of fluoroquinolone drugs.