Figure 51-7.

Schematic depicting the route by which antibiotic-resistant genes are acquired by bacteria in response to selection pressure of antibiotic use. The resistance gene pool represents all potential sources of DNA encoding antibiotic-resistant determinants in the environment; this includes hospitals, farms, or other microenvironments where antibiotics are used to control bacterial development. After uptake of single- or double-stranded DNA by the bacterial host, the incorporation of the resistance genes into stable replicons (DNA elements capable of autonomous replication) may occur by several different pathways that have not yet been identified. The involvement of integrins, as shown here, has been demonstrated for a large class of transposable elements in the Enterobacteriaceae. The resulting resistance plasmids could exist in linear or circular form in bacterial hosts. The final step in the cycle, dissemination, is brought about by one or more gene transfer mechanisms.

(From Davies J: Inactivation of antibiotics and the dissemination of resistance genes. Science 1994;264:375-382.)

© 2008