Emergence of blaKPC-71 variant and loss of aerobactin-encoding genes (iucABCD-iutA) in ST11-K64 carbapenem-resistant Klebsiella pneumoniae during ceftazidime-avibactam treatment.

OBJECTIVE: To investigate the within-host evolutionary dynamics of resistance and virulence in carbapenem-resistant Klebsiella pneumoniae during ceftazidime-avibactam treatment.

METHODS: Three K. pneumoniae strains were isolated from the sputum of the same patient. Broth microdilution method, whole-genome sequencing and genetic analysis were employed to clarify the dynamics and mechanisms of antibiotic resistance. Galleria mellonella infection models were used to investigate the changes in virulence.

RESULTS: The study described the changes of three strains of ST11-K64 carbapenem-resistant K. pneumoniae associated with pulmonary infection in vivo. The transition from a ceftazidime-avibactam-susceptible but imipenem-resistant isolate (JXZRKP1) to a ceftazidime-avibactam-resistant but imipenem-susceptible isolate (JXZRKP2) was attributed to the transformation of the blaKPC gene from blaKPC-2 to blaKPC-71 and upregulation of blaKPC gene expression. Notably, the blaKPC-71 enzyme exhibited a Ser182 duplication compared to the wild-type blaKPC-2 carbapenemase. The blaKPC gene of three strains was carried by the IS26-mediated tandem core structure ISKpn27-blaKPC-IS1182 on an IncFII-type plasmid. Furthermore, in comparison with JXZRKP2, the virulence plasmid of JXZRKP3 lost the aerobactin-encoding genes (iucABCD-iutA), resulting in diminished virulence in G. mellonella infection models, but there was no significant difference(P > .05).

CONCLUSIONS: We first discovered that the mutation from blaKPC-2 to blaKPC-71 leads to resistance to ceftazidime-avibactam, followed by the loss of the aerobactin-encoding gene (iucABCD-iutA) on the virulence plasmid in vivo. This study underscores the complexity of addressing carbapenem-resistant K. pneumoniae infections.