Data from: Costs of antibiotic resistance genes depend on host strain and environment and can influence community composition

Antibiotic resistance genes (ARGs) benefit host bacteria in environments
containing corresponding antibiotics, but it is less clear how they are
maintained in environments where antibiotic selection is weak or sporadic.
In particular, few studies have measured the effect of ARGs on host
fitness in the absence of direct selection or determined if any costs are
fixed or depend on the host strain, perhaps marking some ARG-host
combinations as reservoirs that can maintain ARGs in the absence of
antibiotic selection. We quantified the fitness effects of six ARGs in 11
diverse Escherichia spp. strains. Three ARGs (blaTEM-116, cat, and dfrA5,
encoding resistance to β-lactams, chloramphenicol, and trimethoprim,
respectively) imposed an overall cost but all ARGs had an effect in at
least one host strain, reflecting a significant strain interaction effect.
A simulation predicts these interactions cause the success of ARGs to
depend on available host strains, and, to a lesser extent, for successful
host strains to depend on the ARGs present in a community. These results
indicate the importance of considering ARG effects over different host
strains, especially the potential of reservoir strains that allow
resistance to persist in the absence of direct selection, in efforts to
understand resistance dynamics.