In the last decade, the alarming emergence of new drug resistant bacteria is threatening to return infectious diseases to be one of the leading causes of death. This rapid increase in the appearance of antibiotic-resistant bacteria is widely attributed to horizontal gene transfer (HGT). Although much work has been devoted to understanding the mechanisms that drive resistance gene transfer, little is known about the regulatory elements that confer this resistance. In this work, we systematically examine horizontally transferred regulatory regions of antibiotic resistance genes. To this end, we have used the Comprehensive Antibiotic Resistance Database (CARD) to collect sets of genes that convey various types of antibiotic resistance. For each set of genes we applied both HGT and horizontal regulatory transfer (HRT) detection methods. Our results suggest that coding regions of resistance genes are more horizontally transferred than regulatory areas. In addition, functional units which provide antibiotic resistance can be transferred between a plasmid and a chromosome. A better understanding of the regulatory machinery that confer antibiotic resistance will help us shed light on the molecular mechanisms that drive the emergence of new resistant bacteria.
