Effects of Environment on Compensatory Mutations to Ameliorate Costs of Antibiotic Resistance

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Science  25 Feb 2000:
Vol. 287, Issue 5457, pp. 1479-1482
DOI: 10.1126/science.287.5457.1479

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Most types of antibiotic resistance impose a biological cost on bacterial fitness. These costs can be compensated, usually without loss of resistance, by second-site mutations during the evolution of the resistant bacteria in an experimental host or in a laboratory medium. Different fitness-compensating mutations were selected depending on whether the bacteria evolved through serial passage in mice or in a laboratory medium. This difference in mutation spectra was caused by either a growth condition–specific formation or selection of the compensated mutants. These results suggest that bacterial evolution to reduce the costs of antibiotic resistance can take different trajectories within and outside a host.

  • * These authors contributed equally to this work.

  • To whom correspondence should be addressed. E-mail: Dan.Andersson{at}

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