In-vitro selection of ceftazidime-avibactam resistance in Enterobacteriaceae with KPC-3 carbapenemase

Livermore, David, Warner, Marina, Jamrozy, Dorota, Mushtaq, Shazad, Nichols, Wright W., Mustafa, Nazim and Woodford, Neil (2015) In-vitro selection of ceftazidime-avibactam resistance in Enterobacteriaceae with KPC-3 carbapenemase. Antimicrobial Agents and Chemotherapy, 59 (9). pp. 5324-5330. ISSN 0066-4804

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Abstract

Ceftazidime-avibactam is active against most Enterobacteriaceae isolates with KPC carbapenemases. We investigated whether this activity could be compromised by mutation. Single-step and multistep selections were attempted using ceftazidime-avibactam (avibactam fixed at 1 or 4 μg/ml) versus two strains each of Enterobacter cloacae and Klebsiella pneumoniae, all with the KPC-3 enzyme. Mutant blaKPC alleles were sequenced, and their parentage was confirmed by typing. Ceftazidime-avibactam selected mutants at up to 16× MIC, with frequencies of ca. 10−9. This contrasted with previous experience for ceftaroline-avibactam, where mutant frequencies under similar conditions were <10−9. The MICs of ceftazidime with 1 μg/ml avibactam for the ceftazidime-avibactam-selected mutants rose from 1 to 8 μg/ml to 16 to >256 μg/ml and those of ceftazidime with 4 μg/ml avibactam from 0.25 to 1 μg/ml to 4 to 128 μg/ml; ceftaroline-avibactam MICs rose less, typically from 0.5 to 1 μg/ml to 1 to 8 μg/ml. The MICs of carbapenems and cephalosporins except ceftazidime and piperacillin-tazobactam were reduced for many mutants. Sequencing of blaKPC revealed point and insertion changes in 12/13 mutants investigated, representing all four parents; one mutant lacked blaKPC changes and possibly had reduced permeability. Amino acid changes commonly involved Ω loop alterations or 1 to 6 amino acid insertions immediately C-terminal to this loop. The most frequent change, seen in four mutants from three strains, was Asp179Tyr, replacing a residue that ordinarily forms a salt bridge to stabilize the Ω loop. Since ceftaroline-avibactam was less affected than ceftazidime-avibactam, we postulate that these mutations increase ceftazidimase specificity rather than conferring avibactam resistance. The clinical relevance remains uncertain.

Item Type:	Article
Faculty \ School:	Faculty of Medicine and Health Sciences > Norwich Medical School
UEA Research Groups:	Faculty of Medicine and Health Sciences > Research Groups > Epidemiology and Public Health Faculty of Medicine and Health Sciences > Research Groups > Public Health and Health Services Research (former - to 2023)
Depositing User:	Pure Connector
Date Deposited:	24 Jul 2015 23:02
Last Modified:	04 Jul 2025 23:47
URI:	https://ueaeprints.uea.ac.uk/id/eprint/53795
DOI:	10.1128/AAC.00678-15

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