Cross-resistance to cefiderocol and ceftazidime-avibactam in KPC β-lactamase mutants and the inoculum effect

Claire Amaris Hobson; Aurélie Cointe; Hervé Jacquier; Alaksh Choudhury; Mélanie Magnan; Céline Courroux; Olivier Tenaillon; Stéphane Bonacorsi; André Birgy

doi:10.1016/j.cmi.2021.04.016

Cross-resistance to cefiderocol and ceftazidime-avibactam in KPC β-lactamase mutants and the inoculum effect

Clin Microbiol Infect. 2021 Aug;27(8):1172.e7-1172.e10. doi: 10.1016/j.cmi.2021.04.016. Epub 2021 Apr 26.

Authors

Claire Amaris Hobson¹, Aurélie Cointe², Hervé Jacquier³, Alaksh Choudhury¹, Mélanie Magnan¹, Céline Courroux⁴, Olivier Tenaillon¹, Stéphane Bonacorsi², André Birgy⁵

Affiliations

¹ IAME, UMR 1137, INSERM, Université de Paris, AP-HP, France.
² IAME, UMR 1137, INSERM, Université de Paris, AP-HP, France; Laboratoire de Microbiologie, Hôpital Robert Debré, AP-HP, 75019 Paris, France.
³ IAME, UMR 1137, INSERM, Université de Paris, AP-HP, France; Laboratoire de Microbiologie, Département des Agents Infectieux, Hôpital Saint Louis-Lariboisière-Fernand Widal, AP-HP, Paris, France.
⁴ Laboratoire de Microbiologie, Hôpital Robert Debré, AP-HP, 75019 Paris, France.
⁵ IAME, UMR 1137, INSERM, Université de Paris, AP-HP, France; Laboratoire de Microbiologie, Hôpital Robert Debré, AP-HP, 75019 Paris, France. Electronic address: andre.birgy@aphp.fr.

PMID: 33915286
DOI: 10.1016/j.cmi.2021.04.016

Abstract

Objectives: Ceftazidime-avibactam (CZA) and cefiderocol are recently commercialized molecules active against highly drug-resistant bacteria, including carbapenem-resistant members of the Enterobacteriaceae. Mutants resistant to CZA have been described, notably in Klebsiella pneumoniae carbapenemase (KPC) producers. Considering the structural similarities between ceftazidime and cefiderocol, we hypothesized that resistance to CZA in KPC-producing members of the Enterobacterales may lead to cross-resistance to cefiderocol.

Methods: CZA-resistant mutants from three clinical isolates of the Enterobacterales carrying either bla_KPC-2 or bla_KPC-3 were selected in vitro. Mutants with increased MIC to CZA compared to the ancestral allele were cloned in a pBR322 plasmid and expressed in Escherichia coli TOP10. We evaluated the impact of these mutations on cefiderocol MICs and minimal bactericidal concentrations (MBCs), and we assessed the impact of bacterial inoculum size on cefiderocol MICs.

Results: We used 37 KPC mutants with increased CZA MICs. Of these, six have been described previously in clinical isolates. Compared to the wild-type alleles, increases in the cefiderocol MICs of 4- to 32-fold were observed for 75.6% of tested mutants (28/37), MICs reaching up to 4 mg/L in E. coli TOP10 for KPC-31 (D179Y-H274Y mutations). MBCs and MICs of cefiderocol were similar, confirming the bactericidal activity of this drug. Finally, when using higher inocula (10⁷ CFU/mL), a large increase in cefiderocol MIC was observed, and all isolates were categorized as resistant.

Conclusion: We observed that most of the CZA-resistant KPC variants have a possible impact on cefiderocol by increasing the cefiderocol MICs. In addition, cefiderocol is greatly impacted by the inoculum effect, suggesting that precautions should be taken when treating infections with a suspected high inoculum.

Keywords: Cefiderocol resistance; Ceftazidime–avibactam resistance; Cross-resistance; Inoculum effect; KPC β-lactamases; KPC-2; KPC-3; KPC-31.

MeSH terms

Anti-Bacterial Agents / pharmacology
Azabicyclo Compounds / pharmacology*
Bacterial Proteins / genetics
Cefiderocol
Ceftazidime / pharmacology*
Cephalosporins* / pharmacology
Drug Combinations
Drug Resistance, Multiple, Bacterial*
Escherichia coli / genetics
Klebsiella pneumoniae* / drug effects
Klebsiella pneumoniae* / genetics
Microbial Sensitivity Tests
beta-Lactamases / genetics

Substances

Anti-Bacterial Agents
Azabicyclo Compounds
Bacterial Proteins
Cephalosporins
Drug Combinations
avibactam, ceftazidime drug combination
Ceftazidime
beta-Lactamases
carbapenemase