Twin antibiotic resistance screening Screening by insertional inactivation of a resistance gene Amp B X B pBR322 B Amp T Ampr or Ampicillin resistant? es ye yes Tetracycline resistant No yesAmpicillin resistant? yes yes Tetracycline resistant? No yes B X B B B X Ampr ori Ampr Tcr ori pBR322 Ampr Tcr ori -Screening by insertional inactivation of a resistance gene Twin antibiotic resistance screening