Experimental Prediction of the Evolution of Ceftazidime Resistance in the CTX-M-2 Extended-Spectrum Beta-Lactamase

We applied in vitro evolution to an Escherichia coli strain containing blaCTX-M-2 and obtained 10 independent mutant blaCTX-M-2 alleles that confer elevated resistance to ceftazidime (MIC ≥ 32 μg/ml) but lost the ability to confer resistance to cefepime. All alleles had a Pro-to-Ser substitution at position 167.