The human intestinal tract – a hotbed of resistance gene transfer? Part I1

Although bacteria can become resistant to antibiotics by mutation, a far quicker and easier way for them to achieve the same goal is to acquire pre-formed resistance genes from other bacteria. It is well established that such transfers across species and genus lines occur under laboratory conditions, but the important practical question is whether such transfers actually occur in situ and, if so, whether they occur rarely or frequently. Part I of this article will examine the evidence that horizontal transfer of DNA occurs rather commonly among bacteria in the human colon and may even occur between swallowed bacteria passing through the intestinal tract and resident bacteria. Most of these events seem to involve direct cell-to-cell transfer (conjugation), and they are often mediated by integrated elements, called conjugative transposons, as well as by plasmids.