SuperbugsManaging antibiotics insufficient to reverse resistance

Researchers have discovered that reducing the use of antibiotics will not be enough to reverse the growing prevalence of antibiotic resistance for some types of bacteria.

Besides passing along the genes bestowing antibiotic resistance to their offspring, many bacteria can also swap genes amongst themselves through a process called conjugation. There has long been a debate, however, as to whether this process occurs fast enough to spread through a population that is not under attack by antibiotics.

In a new study, researchers from Duke University believe they have found a definitive answer to that question. Through a series of experiments with bacteria capable of conjugation, they show that all of the bacteria tested share genes fast enough to maintain resistance. They also show, however, that there are ways to disrupt the process and reverse antibiotic resistance.

The results were published in Nature Communications.

“The results came as a surprise to me when I first saw the data,” said Lingchong You, the Paul Ruffin Scarborough Associate Professor of Engineering at Duke University and corresponding author on the paper. “For all of the bacteria we tested, their conjugation rate is sufficiently fast that, even if you don’t use antibiotics, the resistance can be maintained —even if the genes carry a high cost.”

Most resistance to antibiotics arises and spreads through natural selection. If a few lucky bacteria have genes that help them survive a round of antibiotics, they quickly parent the next generation and pass on those genes.

Duke notes that many of these genes, however, come at a cost. For example, a mutation may allow a bacterium to build a thicker membrane to survive a particular antibiotic, but that mutation might also make it more difficult for the cell to reproduce. Without the selective pressure of antibiotics killing off the competition, bacteria with this mutation should disappear over time.