Purpose: Carbapenem-resistant Klebsiella pneumoniae  (CRKP) represents a serious problem worldwide. Herein, we describe the evolution of ceftazidime–avibactam (CZA) resistance by sequencing clinical isolates from a patient with CRKP infection undergoing CZA treatment.
Patients and Methods: In this study, six CRKP strains were isolated from sputum and blood samples of a patient with CRKP infection after intracerebral hemorrhage. Two strains were selected for whole-genome analysis.
Results: Drug susceptibility testing showed that the MIC of CZA for CRKP strains isolated after 6 days of CZA treatment was 64-fold higher than that for three CRKP strains isolated before CZA treatment (4 vs > 256 μg/mL), whereas the MIC of imipenem and meropenem was 128-fold (> 32 vs 0.25 μg/mL) and 16-fold (> 32 vs 2 μg/mL) lower relatively, respectively. Multilocus sequence typing showed that all six CRKP strains isolated from the patient were ST11 and pulsed-field gel electrophoresis confirmed that they were of the same clone. Two strains were selected for whole-genome analysis. The aspartic acid residue at position 179 in the Ω loop was replaced by a tyrosine residue in the resistant strain, and the plasmid carried a bla _KPC-2 to bla _KPC-33 mutation. The results of the modified carbapenem inactivation method and the carbapenemase inhibitor enhancement and colloidal gold enzyme immunochromatographic assays for bla _KPC-33 were negative.
Conclusion: This is the first report from Henan to show that treatment with CZA for 6 days can cause mutations and change the phenotype from CZA sensitive to resistant. Therefore, routine testing for drug susceptibility and carbapenemase phenotypes should be conducted during treatment with CZA, and genotype determination is essential.
Keywords: ceftazidime–avibactam, drug resistance, carbapenem-resistant Klebsiella pneumoniae , K. pneumoniae  carbapenemase-2, ST11