Swarming bacteria move in multicellular groups and exhibit adaptive resistance to multiple 
antibiotics. Analysis of this phenomenon has revealed the protective power of high cell 
densities to withstand exposure to otherwise lethal antibiotic concentrations. We find that
high densities promote bacterial survival, even in a nonswarming state, but that the ability 
to move, as well as the speed of movement, confers an added advantage, making swarming an 
effective strategy for prevailing against antimicrobials. We find no evidence of induced 
resistance pathways or quorum sensing mechanisms controlling this group resistance, which 
occurs at a cost to cells directly exposed to the antibiotic. This work has relevance to 
the adaptive antibiotic resistance of bacterial biofilms.