Efflux-Pump Upregulation: From Tolerance to High-level Antibiotic Resistance?

A recent study shows that high expression of the efflux-pump AcrAB-TolC, which increases antibiotic tolerance, reduces DNA mismatch repair in Escherichia coli to promote spontaneous mutations. Because mutations in target genes can lead to high-level resistance, this highlights how transiently tolerant cells can develop resistance in response to antibiotic treatment.