Poster Presentation Lorne Infection and Immunity 2020

IMP-4-producing Enterobacter cloacae complex genome analysis: understanding their phylogeny and virulence (#187)

Hanna E. Sidjabat 1 , Alaa M.A. Alsaggaf 1 , David L. Paterson 1 , Nicola Townell 2 , Adam D Irwin 1 , Graeme R Nimmo 2 , Jennifer Robson 3 , Karina Kennedy 4 , Gerhard Schenk 5
  1. The University of Queensland Centre for Clinical Research, Brisbane, QLD, Australia
  2. Pathology Queensland, Queensland Health, Brisbane, Queensland, Australia
  3. Microbiology, Sullivan Nicolaides Pathology, Brisbane
  4. Microbiology, ACT Pathology, Canberra, ACT, Australia
  5. School of Chemistry and Molecular Biosciences, The University of Queensland , Brisbane

Background: Infections by carbapenemase-producing Enterobacteriaceae (CPE) have become the biggest threat from antibiotic-resistant Gram-negative bacteria. IMP-4-producing Enterobacter cloacae has been the most commonly reported pathogen in CPE outbreaks in Australia. The majority of CPE studies have explored clonality and antibiotic resistance. Here, we describe the phylogeny and the potential virulence determinants of IMP-4-producing E. cloacae.

 

Materials and methods: The genomes of thirty-five clinical carbapenem-resistant E. cloacae isolates as determined by antibiotic susceptibility testing were sequenced. The variants of chromosomally-encoded AmpC beta-lactamase genes (blaACT), blaACT genetic surroundings and sequence types (STs) were determined. The clonal analysis of the study isolates was performed on both the genome and blaACT, including the genetic surroundings of the blaACT. Antimicrobial resistance mechanisms were identified to provide further insights in relation to their phylogeny. The iron acquisition mechanism and metabolism in association to the virulence of E. cloacae were also investigated.

Results: Thirty-two isolates were confirmed to possess blaIMP-4. The E. cloacae complex study isolates were E. hormaechei (n=14) and E. cloacae (n=21). There was no cluster specific for E. hormaechei and E. cloacae. A total of 18 STs were identified, with high diversity being observed. STs 45, 133 and 830 were the three most reported ones. Horizontal transmission of plasmids harbouring blaIMP-4 was the primary mechanism for the spread of carbapenemase-encoding genes. All isolates possessed the iron acquisition mechanisms characteristic of pathogens that cause serious infections independent of carbapenemase-encoding genes.

Conclusion: . Gene clusters linked to iron acquisition and metabolism (including siderophores and iron transport proteins) were consistent with the virulence of E. cloacae.