Molecular Dissection of Drug Resistance Regions in Clinical <em>Escherichia coli</em> Isolates from a Sydney Hospital — The Association Specialists
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Molecular Dissection of Drug Resistance Regions in Clinical Escherichia coli Isolates from a Sydney Hospital (414)

Jessica McKinnon 1 , Jerran Santos 1 , Piklu Roy Chowdhury 1 , Steven Djordjevic 1
  1. ithree Institute, Science Faculty, University of Technology, Sydney

Introduction: Tracking resistance genes based on specific structural features of class 1 integrons is an integral part of clinical epidemiology. A class 1 integron is a gene capture and expression unit, most frequently found in Gram-negative bacteria. They are known to be the single biggest contributors to the spread of multi-drug resistance genes within clinical isolates.

Recent studies indicate that certain insertion elements target specific regions of class 1 integrons creating unique structures. Consequently, the resistance pool in such integrons goes unnoticed in standard molecular screening methodologies, although they are equally efficient in expressing and disseminating resistance genes. Examples of such class 1 integrons with atypical structures, now realised to have widely disseminated within E. coli specimens worldwide, were generated by the insertion of a specific genetic element known as IS26. This project aimed to capture the diversity of IS26 insertions within resistance regions of pathogenic E. coli samples in a specific Sydney hospital and to identify the resistance gene pool harboured by such atypical integrons.

Methods: Targeted PCR, Sanger and Next generation sequencing techniques were used to characterise clinical E. coli samples from Sydney Adventist Hospital isolated between 2010 and 2011.

Results: Nine class 1 integrons with IS26 inserted within the resistance regions were detected in a cohort of 99 class 1 integron positive samples, showing three signature structures. Each showed resistance to a number of antibiotics, some used strictly in veterinary medicine such as apramycin and streptomycin. Interestingly, the two most frequent structures detected were observed previously in animal isolates.

Conclusion: Our data suggests that antibiotic resistance is readily transferring between host populations via horizontal gene transfer of mobile elements in Sydney. The molecular signatures identified have the potential of being developed into a molecular kit that could be used in tracing lateral movement of resistance genes.