Klebsiella pneumoniae Carbapenemase Variants Resistant to Ceftazidime-Avibactam: an Evolutionary Overview

Abstract

First variants of the Klebsiella pneumoniae carbapenemase (KPC), KPC-2 and KPC-3, have encountered a worldwide success, particularly in K. pneumoniae isolates. These beta-lactamases conferred resistance to most beta-lactams including carbapenems but remained susceptible to new beta-lactam/beta-lactamase inhibitors, such as ceftazidime-avibactam. After the marketing of ceftazidime-avibactam, numerous variants of KPC resistant to this association have been described among isolates recovered from clinical samples or derived from experimental studies. In KPC variants resistant to ceftazidime-avibactam, point mutations, insertions and/or deletions have been described in various hot spots. Deciphering the impact of these mutations is crucial, not only from a therapeutic point of view, but also to follow the evolution in time and space of KPC variants resistant to ceftazidime-avibactam. In this review, we describe the mutational landscape of the KPC beta-lactamase toward ceftazidime-avibactam resistance based on a multidisciplinary approach including epidemiology, microbiology, enzymology, and thermodynamics. We show that resistance is associated with three hot spots, with a high representation of insertions and deletions compared with other class A beta-lactamases. Moreover, extension of resistance to ceftazidime-avibactam is associated with a trade-off in the resistance to other beta-lactams and a decrease in enzyme stability. Nevertheless, the high natural stability of KPC could underlay the propensity of this enzyme to acquire in vivo mutations conferring resistance to ceftazidime-avibactam (CAZavi), particularly via insertions and deletions.

Keywords: KPC; KPC beta-lactamase; KPC-2; KPC-3; ceftazidime-avibactam; ceftazidime-avibactam resistance; deletions; epidemiology; insertions; omega loop; spectrum; stability; trade-off.

FIG 1

Geographical distribution of KPC-2 and KPC-3 and their most frequent circulating variants. The data used to generate this figure are listed in supplementary table 1.

FIG 2

Representative view of the overall KPC-2 fold (PDB 5UL8), showing positions of key active-site residues and loops. The S₇₀XXK₇₃ motif is colored in red, residues 104–106 and S₁₃₀D₁₃₁N₁₃₂ loop in magenta, the K₂₃₄T₂₃₅G₂₃₆ pattern in cyan, and the Ω-loop in blue.

FIG 3

Geographical distribution of CAZAVI-resistant KPC-2 and KPC-3 alleles. The data used to generate this figure are listed in supplementary table 2.

FIG 4

Representative view of the overall KPC-2 fold (PDB 5UL8), showing the 3 hot spots involved in ceftazidime-avibactam resistance: the omega loop is colored in blue, the 238–243 loop in orange and the 267–275 loop in green. For indication, S70 is colored in red.

FIG 5

Distribution of point mutations and indel in the different hot spots conferring resistance to CAZavi in KPC variants.

FIG 6

Antibiotic susceptibility of 16 antibiotics tested representing KPC-3, and the three different phenotypes resulting from mutations involved in ceftazidime-avibactam resistance illustrated with KPC-74, KPC-66 and KPC-29 expressed in E. coli TOP10. (AMX Amoxicillin, TIC Ticarcillin, FEP Cefepime, CEF Cefalotin, FOX Cefoxitin, CAZ Ceftazidime, AMC Co-amoxiclav, CTX Cefotaxime, PIP Piperacillin, ETP Ertapenem, ATM Aztreonam, PTZ Piperacillin-Tazobactam, FIX Cefixime, IMP imipenem, MERO Meropenem, and TEMO Temocillin).