Small populations of pathogenic bacteria may be harder to kill off than larger populations because they respond differently to antibiotics, a new study by Emory University finds.
The journal eLife published the research, showing that a population of bacteria containing 100 cells or less responds to antibiotics randomly — not homogeneously like a larger population.
“We’ve shown that there may be nothing special about bacterial cells that aren’t killed by drug therapy — they survive by random chance,” says senior author Minsu Kim, an assistant professor in the Department of Physics and a member of Emory’s Antibiotic Resistance Center.
“This randomness is a double-edged sword,” Kim adds. “On the surface, it makes it more difficult to predict a treatment outcome. But we found a way to manipulate this inherent randomness in a way that clears a small population of bacteria with 100 percent probability. By tuning the growth and death rate of bacterial cells, you can clear small populations of even antibiotic-resistant bacteria using low antibiotic concentrations.”
Jessica Coates, as a graduate student at Emory, and Bo Ryoung Park, a research associate in the Kim lab, are co-first authors of the paper. Additional authors are graduate student Emrah Simsek and post-doctoral fellows Dai Le and Waqas Chaudry.
The researchers developed a treatment model using a cocktail of two different classes of antibiotic drugs. They first demonstrated the effectiveness of the model in laboratory experiments on a small population of E. coli bacteria without antibiotic-drug resistance. In later experiments, they found that the model also worked on a small population of clinically-isolated antibiotic-resistant E. coli.
“We hope that our model can help in the development of more sophisticated antibiotic drug protocols — making them more effective at lower doses for some infections,” Kim says. “It’s important because if you treat a bacterial infection and fail to kill it entirely, that can contribute to antibiotic resistance.”