Variations in resistance to three antibiotics among some single-step mutants to Chloramphenicol resistance in a strain ofEscherichia coliK 12

Abstract

Chloramphenicol (CM), Aureomycin (AM) and Puromycin (PM) induce RNA synthesis inRC-stringent Escherichia colistarved of a required amino acid. This fact has been used to develop a method for comparing the levels of resistance of single-stepCM-rmutants to the three antibiotics. Three levels of resistance to each antibiotic were found among four mutants selected in a singleCM-sstrain. The mutant with the highest CM resistance has the lowest AM resistance, and vice versa, while the level of PM resistance was not correlated with that of either CM or AM. The four mutants all differed from each other in their patterns of resistance to the three antibiotics.