Emergence of KPC-8-producing K. pneumoniae infection without prior exposure to ceftazidime/avibactam: the threat of de novo infections by ceftazidime/avibactam-resistant KPC variants.

De novo infections caused by ceftazidime/avibactam-resistant KPC variants are rarely reported. We characterize the evolution of a KPC-8-producing Klebsiella pneumoniae strain involved in a primary infection without previous ceftazidime/avibactam treatment. During a 15-month follow-up, changes in carbapenem susceptibility due to porin alterations were observed, remaining susceptible to meropenem/vaborbactam, imipenem/relebactam, and cefiderocol. High- and low-permeability recombinant Escherichia coli isolates analysis revealed that, unlike the widespread ceftazidime/avibactam-resistant variant KPC-31, KPC-8 confers ceftazidime/avibactam resistance without decreasing carbapenemase activity.