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|Title: ||Analysis of Australian multiply-antibiotic resistant Acinetobacter baumannii belonging to global clone 2|
|Authors: ||Nigro, Steven|
|Issue Date: ||20-Feb-2014|
|Publisher: ||University of Sydney|
School of Molecular Bioscience
|Abstract: ||A. baumannii resistant to multiple antibiotics provide a significant challenge in the treatment of infections. Multiply-antibiotic resistant (MAR) isolates mainly belong to two major global clones, GC1 and GC2, and the emergence of MAR strains worldwide is largely due to the spread of these clones. The objective of this study was to analyze the causes of antibiotic resistance in Australian GC2 isolates.
A. baumannii from hospitals in Sydney, Brisbane and Canberra were screened. A total of 83 isolates were placed in GC2. Most GC2s contained oxa23 in Tn2006 causing carbapenem resistance. The resistance genes, sul2, tetA(B), strA and strB were in a conserved resistance region in the majority of isolates. Eight subgroups were identified based on their aminoglycoside resistance patterns and genes.
Two types of antibiotic resistance island, AbGRI1 and AbGRI2, contained almost all the resistance genes. AbGRI1-2 was in comM in all the GC2 isolates except for one outbreak group with a minor variant. AbGRI1-2 had the common resistance region, Tn2006 and a novel IS, ISAba17. AbGRI2 was at a second position in the chromosome. The archetype was AbGRI2-1 and it had blaTEM, aphA1, aacC1, aadA1 and sul1. Six variants of AbGRI2 were identified. Four variants had lost parts of the island and the deletions were caused by IS26.
All of the GC2s had at least one plasmid. Most isolates had pA91, but a subgroup had a deletion derivative, pC2. Several groups had another plasmid. The aadB gene was in pRAY*-v1. The aphA6 gene was on three related plasmids, pD72, pC20 and pC13. pD72 carried aphA6 at a different site in the plasmid backbone relative to pC20/pC13.
A non-GC2 isolate, D46, shared a number of features with the GC2 collection. It had pieces of AbGRI1. D46 had another resistance region with macrolide resistance genes. The aadB gene was in pRAY* and there was a cryptic plasmid. A third plasmid, pD46-2, had aphA6 in the same position as pD72 but also Tn2006. This plasmid was conjugative.|
|Type of Work: ||PhD Doctorate|
|Type of Publication: ||Doctor of Philosophy Ph.D.|
|Appears in Collections:||Sydney Digital Theses (Open Access)|
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