Mid-log phase planktonic (green) and swarm (purple) cells of E. coli at increasing densities (OD600, x axis), either concentrated or diluted to achieve desired OD600, were treated with Kan20 (MIC99P) and Kan37.5 (~MIC99S), respectively, for 1 h at 37 °C with or without the addition of purified AcrA at indicated concentrations. CFU counts of survivors were used to calculate the survival fractions. Each of the three individual replicates are shown on a single bar. The data were analyzed using a mixed model ANOVA. Cell type, i.e., planktonic and swarm cells, were taken as the “between-subjects” factor and a Giesser–Greenhouse correction was applied to it; cell density and AcrA treatment were considered as “repeated measures”. The multiple comparisons were corrected using Dunnett testing, keeping a two-tailed significance level of 0.05. The obtained p value (0.000074) of interaction was significant. The maximum increase in survival observed was: (i) at 0.5 OD600, ~9% in planktonic cells compared to ~25% in swarm cells and (ii) at 2.0 OD600, ~17% in planktonic cells compared to ~50% in swarm cells. Source data are provided as a Source Data file.