Elimination by Ethidium Bromide of Antibiotic Resistance in Enterobacteria and Staphylococci

SUMMARY: Ethidium bromide, a trypanocidal drug affecting nucleic acid synthesis, was found to be a powerful agent in eliminating some antibiotic resistance in bacteria. In staphylococci, penicillinase production was eliminated in mercury-resistant organisms, but not in mercury-sensitive ones. Among enterobacteria, two resistance factors showing the same resistance pattern were differently eliminated, and correlation between elimination and transfer of resistance factors was not always observed. F’-lac+ factor was also eliminated by ethidium bromide in Escherichia coli KI2. Elimination of antibiotic resistance was observed generally at high frequency, and could be better reproduced than with acridine dyes.