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Novel genetic context of multiple bla OXA-58 genes in Acinetobacter genospecies 3

B A Evans1, A Hamouda, K J Towner

  • 1Faculty of Life Sciences, The University of Manchester, Manchester, UK.

The Journal of Antimicrobial Chemotherapy
|June 15, 2010
PubMed
Abstract

Insights

Acinetobacter genospecies 3 isolates show reduced carbapenem susceptibility due to OXA-58 beta-lactamase duplication. This gene duplication, mediated by the insertion sequence ISAba125, is a novel finding in Acinetobacter.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Acinetobacter genospecies 3 isolates are increasingly reported with OXA-type carbapenemases, leading to reduced susceptibility to carbapenem antibiotics.
  • Carbapenem resistance in Acinetobacter poses a significant threat to public health, necessitating research into resistance mechanisms.

Purpose of the Study:

  • To investigate the genetic environment surrounding the bla(OXA-58) gene in an Acinetobacter genospecies 3 isolate.
  • To characterize the mechanism of carbapenem resistance in the identified isolate.

Main Methods:

  • Species identification using 16S-23S rRNA restriction analysis.
  • Determination of minimum inhibitory concentrations (MICs) for imipenem, meropenem, and ertapenem.
  • Screening for carbapenemase genes (bla(OXA-23-like), bla(OXA-40-like), bla(OXA-51-like), bla(OXA-58-like)) using PCR.
  • Sequencing of the bla(OXA-58) genetic environment via inverse PCR and genome walking.
  • Investigation of genetic localization using Southern blotting.

Main Results:

  • Isolate A164 confirmed as Acinetobacter genospecies 3 with reduced carbapenem susceptibility.
  • The isolate harbored two copies of the bla(OXA-58) gene, potentially duplicated by the insertion sequence ISAba125.
  • Two copies of ISAba125 were inserted into ISAba3 elements, and the bla(OXA-58) genes were found to be plasmid-borne.

Conclusions:

  • This study reports the first instance of beta-lactamase gene duplication in Acinetobacter genospecies 3.
  • The findings highlight the role of the insertion sequence ISAba125 in mediating gene duplication events in Acinetobacter.

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