Functional and Structural Characterization of OXA-935, a Novel OXA-10-Family β-Lactamase from Pseudomonas aeruginosa

Nathan B. Pincus, Monica Rosas-Lemus, Samuel W.M. Gatesy, Hanna K. Bertucci, Joseph S Brunzelle, George Minasov, Ludmilla A. Shuvalova, Marine Lebrun-Corbin, Karla J.F. Satchell, Egon A. Ozer, Alan R Hauser, Kelly E.R. Bachta*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Resistance to antipseudomonal penicillins and cephalosporins is often driven by the overproduction of the intrinsic b-lactamase AmpC. However, OXA-10-family b-lactamases are a rich source of resistance in Pseudomonas aeruginosa. OXA b-lactamases have a propensity for mutation that leads to extended spectrum cephalosporinase and carbapenemase activity. In this study, we identified isolates from a subclade of the multidrug-resistant (MDR) high risk P. aeruginosa clonal complex CC446 with a resistance to ceftazidime. A genomic analysis revealed that these isolates harbored a plasmid containing a novel allele of blaOXA-10, named blaOXA-935, which was predicted to produce an OXA-10 variant with two amino acid substitutions: an aspartic acid instead of a glycine at position 157 and a serine instead of a phenylalanine at position 153. The G157D mutation, present in OXA-14, is associated with the resistance of P. aeruginosa to ceftazidime. Compared to OXA-14, OXA-935 showed increased catalytic efficiency for ceftazidime. The deletion of blaOXA-935 restored the sensitivity to ceftazidime, and susceptibility profiling of P. aeruginosa laboratory strains expressing blaOXA-935 revealed that OXA-935 conferred ceftazidime resistance. To better understand the impacts of the variant amino acids, we determined the crystal structures of OXA-14 and OXA-935. Compared to OXA-14, the F153S mutation in OXA-935 conferred increased flexibility in the omega (X) loop. Amino acid changes that confer extended spectrum cephalosporinase activity to OXA-10-family b-lactamases are concerning, given the rising reliance on novel b-lactam/b-lactamase inhibitor combinations, such as ceftolozane-tazobactam and ceftazidime-avibactam, to treat MDR P. aeruginosa infections.

Original languageEnglish (US)
JournalAntimicrobial agents and chemotherapy
Issue number10
StatePublished - Oct 2022


  • OXA-b-lactamase
  • Pseudomonas aeruginosa
  • antimicrobial resistance
  • ceftazidime
  • crystal structure

ASJC Scopus subject areas

  • Pharmacology (medical)
  • Infectious Diseases
  • Pharmacology


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