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Overview of Dissemination Mechanisms of Genes Coding for Resistance to Antibiotics, Page 1 of 2
< Previous page Next page > /docserver/preview/fulltext/10.1128/9781555815615/9781555813031_Chap16-1.gif /docserver/preview/fulltext/10.1128/9781555815615/9781555813031_Chap16-2.gifAbstract:
This chapter provides an overview of dissemination mechanisms of genes coding for resistance to antibiotics. The emergence of antibiotic resistance determinants would not be as devastating if it were not for the inherent ability of bacteria to exchange genes at the cellular and molecular level. A plasmid genome database containing all sequenced plasmids was recently established. While plasmids participate in bacterial antibiotic resistance mainly by disseminating genes coding for drug resistance at the cellular level, other elements promote gene exchange at the molecular level. Integrative and conjugative elements (ICEs) encode diverse excision, recombination, and conjugation systems, in addition to specific functions, including resistance to antibiotics. The combination of dissemination at the cellular level through conjugation, natural transformation, transduction, with dissemination at the molecular level, and mutagenesis permits genes coding for antibiotic resistance to reach virtually all bacterial cells, resulting in a virtual elimination of barriers between types of bacteria. However, while the acquisition of resistance genes provides an advantage to the bacterial cells when in the presence of antibiotics, it has been shown that their presence comes with an associated fitness cost when the cells are growing in the absence of antibiotic selective pressure.