Poster Presentation BacPath 13: Molecular Analysis of Bacterial Pathogens Conference 2015

The epidemiology of blaCMY-2 in Escherichia coli: A change over time? (#137)

Kaitlin Tagg 1 , Andrew Ginn 2 , Sally Partridge 2 , Jon Iredell 2
  1. Centre for Infectious Diseases and Microbiology, Westmead Millennium Institute, Camperdown, NSW, Australia
  2. Centre for Infectious Diseases and Microbiology, Westmead Millennium Institute and University of Sydney, Westmead, NSW, Australia
Dissemination of plasmid-borne resistance genes is influenced by various factors including the genetic context of the gene itself, the transmission dynamics of the plasmid lineage/s carrying the gene and the relative success of the host bacterial strain. blaCMY-2 (and minor variants) is one of the most successful plasmid-borne β-lactamase genes worldwide, particularly in Escherichia coli, conferring resistance to both cephalosporins and β-lactamase inhibitors. Several plasmid lineages have been reported to carry blaCMY-2, including IncI1, IncA/C, IncF and IncK, but local epidemiological patterns vary. We investigated the epidemiology of blaCMY-2-like genes in E. coli strains from Sydney, Australia over two time periods (2005-09; 2013-14) to gain insight into the dynamics of their spread. Clinical E. coli strains (n=103) were characterised by multilocus sequence typing, PCR-based replicon typing, multiplex resistance gene PCR and Southern hybridisation and a subset were sequenced using Illumina MiSeq technology. Horizontal plasmid spread appeared to be an important mode of transmission in the earlier time period (2005-09) as blaCMY-2was predominantly carried by IncI1 plasmids in diverse E. coli strains, with few differences across the backbones of those plasmids that were sequenced. In contrast, blaCMY-2 was found inserted in the chromosome in half of the recent E. coli strains (2013-14) and very few of these contained IncI1 plasmids. Further analysis will reveal whether these strains are clonally related, potentially representing a local outbreak, or whether different clonal lineages have acquired a chromosomal blaCMY-2-like gene independently. These preliminary findings suggest that the epidemiology of blaCMY-2-like genes is complex, involving both plasmid spread and clonal expansion of host E. coli strains, and that the dynamics of transmission may be changing over time. The potential shift to chromosomally-located blaCMY-2 represents a major therapeutic concern.