Attempted transfer of antibiotic resistance between Bacteroides and Escherichia coli.

Transfer of antibiotic resistance between Bacteroides organisms and E. coli in mixed culture under optimal anaerobic conditions was attempted. Donor strains used were E. coli with R factors of a number of compatibility groups and Bacteroides with unusually high antibiotic resistance. Recipient strains included E. coli strains with characteristics favouring conjugal transfer. Although control experiments verified that conjugal transfer of derepressed R factors could occur at a high frequency between E. coli in an anaerobic environment, transfer of antibiotic resistance between E. coli and Bacteroides was never demonstrated.