Expression profile of efflux pumps during the intracellular life of Shigella

In several bacterial pathogens, efflux pumps, besides exporting antimicrobial agents, play a role in bacterial pathogenicity. Shigella, the causative agent of bacillary dysentery, shares a high homology with its commensal ancestor Escherichia coli but, in contrast to E. coli, Shigella is submitted to intense gene decay and has lost many E. coli metabolic and housekeeping functions. By genome analysis we observed that 14, out of 20, operons encoding efflux pumps systems have been conserved in Shigella. To understand the potential role of efflux pumps in Shigella pathogenicity, we monitored their expression during invasion of macrophages and epithelial cells. The data obtained indicate that i) EmrKY efflux pump is notably and specifically induced within macrophages and its loss negatively affects Shigella’s fitness; ii) AcrAB, the main efflux pump in E. coli, is downregulated during intracellular life. Our observations reveal also that, during infection, Shigella modulates expression of specific efflux pumps. Experiments are in progress to investigate the role of these efflux pumps and the environmental stimuli that affect their expression.