Chromosomal System for Studying AmpC-Mediated β-Lactam Resistance Mutation in Escherichia coli

In some enterobacterial pathogens, but not in Escherichia coli, loss-of-function mutations in the ampD gene are a common route to β-lactam antibiotic resistance. We constructed an assay system for studying mechanism(s) of enterobacterial ampD mutation using the well-developed genetics of E. coli. We integrated the Enterobacter ampRC genes into the E. coli chromosome. These cells acquire spontaneous recombination- and SOS response-independent β-lactam resistance mutations in ampD. This chromosomal system is useful for studying mutation mechanisms that promote antibiotic resistance.