Robustness of the dynamics describing resistance acquisition by HGT. The dynamics describing double resistance emergence by HGT were studied for 104 random sets of parameters (derived from distributions described in the main text). The moving average of the emergence of double resistance (see Methods) is plotted as a function of the entrance rates' ratio (). Note that the same data sets are used for a given value of under each of the three strategies, generating an association between the curves. The emergence rate under mixing is plotted in green, under cycling in blue, and under combining in red. When the emergence rates under mixing and cycling are very close, only the blue curve is visible. In (A) and (B), HGT is not affected by stress at all (θ = 1) so the delay of stress-induction mechanisms (ϕ) is irrelevant. In contrast, persistence of antibiotic resistance (σ) is influential in such cases, and we present two extreme values. (A) θ = 1,σ = 0.1. Cycling and mixing are the dominant strategies, where their relative efficiency decreases at asymmetric entrance rates. (B) θ = 1, σ = 1 . Combining is the preferred strategy for inhibiting double resistance emergence. In (C) and (D) HGT is stress induced with θ = 10, so while ϕ is now an influential parameter, the effect of σ is very minor (Additional file 1, section 1) and we present only the value σ = 0.5. (C) θ = 10, ϕ = 1, σ = 0.5 . Mixing is slightly more preferable than cycling, and cycling is most inefficient when entrance rates are asymmetric. (D) θ = 10, ϕ = 0, σ = 0.5 . Cycling is the preferred strategy for inhibiting double resistance emergence. HGT, horizontal gene transfer.