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Genetic and biochemical characterisation of OXA-232, a carbapenem-hydrolysing class D β-lactamase from

Anaïs Potron1, Emilie Rondinaud, Laurent Poirel

  • 1Service de Bactériologie-Virologie, INSERM U914 Emerging Resistance to Antibiotics, Hôpital de Bicêtre, Assistance Publique/Hôpitaux de Paris, Faculté de Médecine et Université Paris-Sud, K. Bicêtre, France.

International Journal of Antimicrobial Agents
|January 12, 2013
PubMed

Insights

Three enterobacterial isolates from India exhibited resistance to common antibiotics, producing a novel carbapenem-hydrolysing beta-lactamase, OXA-232. This enzyme shows reduced carbapenemase activity but increased penicillinase activity, found on a plasmid.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Infectious Diseases

Background:

  • Enterobacterial isolates from patients transferred from India to France in 2011 showed resistance to multiple beta-lactams and reduced susceptibility to carbapenems.
  • The emergence of carbapenem-resistant Enterobacteriaceae (CRE) poses a significant global health threat.

Purpose of the Study:

  • To characterize a novel carbapenem-hydrolysing beta-lactamase (CHBL) identified in clinical isolates of Klebsiella pneumoniae and Escherichia coli.
  • To investigate the genetic basis and hydrolytic properties of the newly discovered beta-lactamase.

Main Methods:

  • Bacterial isolates were identified using standard microbiological techniques.
  • Antimicrobial susceptibility testing was performed for various beta-lactam antibiotics, including carbapenems.
  • The novel beta-lactamase gene (blaOXA-232) was sequenced and compared to known beta-lactamase genes.
  • Enzyme activity assays were conducted to determine hydrolytic profiles against different beta-lactams.

Main Results:

  • Three enterobacterial isolates (two K. pneumoniae, one E. coli) expressed a novel CHBL, designated OXA-232.
  • OXA-232 differs from OXA-181 by one amino acid substitution and from OXA-48 by five substitutions.
  • OXA-232 demonstrated lower carbapenem-hydrolysing activity compared to OXA-181 but higher activity against penicillins.
  • The blaOXA-232 gene was located on a 6.1-kb ColE-type non-conjugative plasmid.

Conclusions:

  • A novel carbapenem-hydrolysing beta-lactamase, OXA-232, has been identified in clinical enterobacterial isolates.
  • The genetic location on a non-conjugative plasmid suggests potential for horizontal gene transfer and spread.
  • Understanding the characteristics of OXA-232 is crucial for monitoring and controlling the dissemination of carbapenem resistance.

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