Idiosyncratic variation in the fitness costs of tetracycline‐resistance mutations in <i>Escherichia coli</i>

A bacterium's fitness relative to its competitors, both in the presence and absence of antibiotics, plays a key role ecological success clinical impact. In this study, we examine whether tetracycline‐resistant mutants are less fit drug than their sensitive parents, cost resistance is constant or variable across independently derived lines. Tetracycline‐resistant lines suffered, on average, reduction almost 8%. There was substantial among‐line variation cost. This not associated with level conferred by mutations, nor did it vary significantly several genetic backgrounds. The two resistant most extreme costs involved functionally unrelated mutations different However, there also significant for affecting same pathway even alleles gene. Our findings demonstrate that antibiotic do always correlate phenotypic underlying changes. Instead, these reflect idiosyncratic effects particular backgrounds which they occur.