E. Coli Strains Shed Light on Antibiotic Resistance

A new study from researchers in Japan has identified features that appear to be responsible for bacteria becoming resistant to antibiotics.

A new study from researchers in Japan has identified features that appear to be responsible for bacteria becoming resistant to antibiotics.

The investigators examined genetic and phenotypic changes in 44 antibiotic-resistant strains of Escherichia coli (E. coli). In their findings, which were published in Nature Communications, the researchers found that antibiotic resistance occurs through mutations that converge on similar physical changes in the bacteria.

The researchers examined strains of E. coli that were each resistant to 1 of 11 different antibiotics and observed how each of the 44 strains responded to 25 antibiotics.

Rather than each strain showing resistance to only 1 antibiotic, several strains developed resistance to several antibiotics. The study authors posited that similar gene expression might be the cause of such cross-resistance.

They also saw cross-susceptibility between 2 classes of antibiotics, meaning that bacteria showing resistance to 1 type of antibiotic became more vulnerable to another. Such cross-susceptible classes had dissimilar gene expressions and fixed mutations affecting a multidrug efflux pump that bacteria use to expel unwanted molecules. In this way, 1 strain of E. coli that could block aminoglycoside antibiotics could not at the same time effectively use its pump, which could explain why that strain is more susceptible to other antibiotics.

After gathering their data on changes in gene expression, resistance, cross-resistance, and cross-susceptibility, the researchers created a linear model that could predict antibiotic resistance and susceptibility patterns.

“We demonstrated using a simple linear model that changes in resistance and susceptibility can be predicted by the expression levels of a small number of genes,” the study authors wrote. “These same genes could, therefore, be used to describe the phenotypes responsible for the drug resistance and susceptibility.”

The researchers said their findings might help contribute to developing new ways to prevent antibiotic resistance.