Inhibition of F'lac transfer by various antibacterial drugs in Escherichia coli.

Several antimicrobial agents including mitomycin C and molecules belonging to the 4-quinolone, aminoglycoside and beta-lactam groups inhibited plasmid transfer to a varying extent, in actively growing Escherichia coli. In contrast, the same antibiotics did not prevent effective conjugation in nongrowing bacteria with the exception of mitomycin C. These results indicate that the drugs inhibit plasmid transfer by interfering with bacterial host functions rather than by recognizing a specific plasmid-mediated target. Several drugs are therefore capable, in principle, of reducing the spread of plasmid-mediated antibiotic resistance.