Transposition of a plasmid deoxyribonucleic acid sequence that mediates ampicillin resistance: identity of laboratory-constructed plasmids and clinical isolates

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Abstract
The structural gene for ampicillin resistance resides upon a 3.2 .times. 106-dalton sequence of DNA [ampicillin translocation unit], that can be transposed from replicon to replicon in laboratory experiments. TnA was transposed from a large conjugative plasmid to a small nonconjugative plasmid, RSF1010. Several RSF1010::TnA plasmids isolated in these laboratory experiments were identical to plasmids found in clinical isolates [Escherichia coli, Salmonella typhimurium and Proteus mirabilis]. These data provide direct support to the theory that transposition of drug resistance genes play a key role in the evolution of R plasmids.