In Vivo Conversion of Transferable Plasmid into R Plasmid in the Intestine of Gnotobiotic Mice

Abstract

A drug-susceptible strain of mouse Escherichia coli, E916, harboring a transferable plasmid, and a laboratory strain carrying a nonconjugative plasmid, pMKI::Tn2602 (ColEl::Tn5::Tn2602), were orally inoculated into germ-free mice. After administration of kanamycin (Km) in drinking water, Km-resistant (Km^r) E916 became dominant in the population of fecal flora. Plasmid DNA analysis revealed that Km^r E916 possessed a conjugative R plasmid consisting of a transferable plasmid and a Km-transposon (Tn5). The result indicates that the transferable plasmid was converted into an R plasmid while migrating between organisms in the intestine of gnotobiotic mice.