Mobilization of Non-conjugative Tetracycline, Streptomycin, Spectinomycin and Sulphonamide Resistance Determinants of Escherichia coli

Abstract

SUMMARY: Non-conjugative Tc, Sm, SmSu, SmSpc, SmSpcSu and TcSmSpcSu determinants (Tc, Sm, Spc and Su denote resistance to tetracycline, streptomycin, spectinomycin and sulphonamides, respectively) in wild-type Escherichia coli strains were mobilized with transfer factors F, I and A2 and implanted in E. coli K12. F and I were transmitted at very high rates in all matings in which these E. coli K12 strains were used as donors; the rate of A2 transmission was not measured. When the Tc determinants, derived from 32 of the wild-type E. coli strains, were serially transferred between strains of E. coli K12 they were transmitted either at a very low rate in both first and second matings, at a very low rate in the first mating and at a very high rate in the second mating, or at a very high rate in both matings. In the donors that transmitted at the low rate, the Tc determinants were probably chromosomally located, a recombination event between them and the transfer factors being responsible for the formation of the donors that transmitted at the high rate; once they became extrachromosomally located, the Tc determinants continued to be transmitted at the high rate. Of the resistance determinants studied, Tc was the only one suspected of being chromosomally located.