Frequencies and mechanisms of mutational resistance to ceftibuten/avibactam in Enterobacterales

Mushtaq, Shazad, Vickers, Anna, Doumith, Michel, Garello, Paolo, Woodford, Neil and Livermore, David M. ORCID: https://orcid.org/0000-0002-9856-3703 (2024) Frequencies and mechanisms of mutational resistance to ceftibuten/avibactam in Enterobacterales. Journal of Antimicrobial Chemotherapy. ISSN 0305-7453

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Abstract

Background: Antibiotic resistance complicates treatment of urinary infections, particularly when these ascend above the bladder, with few oral options remaining. New oral β-lactamase inhibitor combinations present a potential answer, with ceftibuten/avibactam—now undergoing clinical trials—widely active against strains with ESBLs and serine carbapenemases. To inform its development we undertook mutant selection studies. Methods: Single-step mutants were sought from Enterobacterales (n = 24) with AmpC, ESBL, OXA-48 and KPC β-lactamases. MICs were determined by CLSI agar dilution. Illumina WGS of selected mutants (n = 50) was performed. Results: Even at low MIC multiples, mutant frequencies were mostly only c. 10−8. β-Lactamase structural mutants were obtained only from KPC and AmpC enzymes. The KPC mutants had Trp105Arg or Ser130Thr substitutions, causing only small MIC shifts; the AmpC mutant had an Asn346Trp replacement, as previously selected with other avibactam combinations. No ESBL mutants were obtained. Rather, from Escherichia coli, we predominantly selected mutants with modifications to ftsI, encoding penicillin-binding protein (PBP) 3. From Klebsiella pneumoniae and Enterobacter cloacae we predominantly obtained variants with modification of uptake and efflux components or their regulators. ftsI mutants lacked cross-resistance to other avibactam combinations; uptake mutants had broader MIC rises. A few putative mutants had other lesion(s) of uncertain significance, or grew as small, stressed colonies lacking detectable lesions. Conclusions: There seems little risk of ESBLs mutating to confer ceftibuten/avibactam resistance, though some risk may apply for KPC and AmpC enzymes. The propensity to select E. coli ftsI/PBP3 mutants is notable and was not seen with other avibactam combinations.

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
Related URLs:	https://academic.oup.com/jac/advance-art...
Depositing User:	LivePure Connector
Date Deposited:	07 Jan 2025 02:17
Last Modified:	14 Jan 2025 00:58
URI:	https://ueaeprints.uea.ac.uk/id/eprint/98108
DOI:	10.1093/jac/dkae452

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