asm2011 170611-for i3-final
TRANSCRIPT
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Thu Betteridge1, Sally R.Partridge2, Jon R.Iredell2,
and H.W.Stokes1
The I3 Institute, University of Technology, Sydney1.
Centre for Infectious Diseases & Microbiology, University of
Sydney, Westmead Hospital2
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• An increased incidence of hospital infection and global spread of drug-
resistant bacteria
• Lateral Genetic Transfer (LGT):
- is an inherent process among bacteria to generate genetic
diversity
- becomes the driving force for generation and dissemination of
resistance genes
2
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Genomic island
Transposons
Plasmids
ICEs
Integrons
IS elements
Mechanism of Genes Exchange:
• Conjugation
• Transformation
• Transduction
Mechanism of Genes Incorporation:
• Autonomous replication
• Transposition
• Site-specific recombination
• Homologous recombination
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Integrase +
attC
Cassette 2 A two-component system
intl
attI
Pc
Pint
attC2 attC1
etc…
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Chromosomal
integron?
IRt tniR tniQ tniB tniA IRi
IRi
qacEΔ1 sul1 orf5-(orf6)
5′-CS
attI1 3′-CS Δtni module
attI1 Cassette(s)
qacE (?)
Cassette(s)
IRt
Pre-clinical type
Clinical class 1 integrons
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Genomic island
Transposons
Plasmids
ICEs
Integrons
IS elements
Mechanism of Genes Exchange:
• Conjugation
• Transformation
• Transduction
Mechanism of Genes Incorporation:
• Autonomous replication
• Transposition
• Site-specific recombination
• Homologous recombination
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7
Chromosomal
integron?
IRt tniR tniQ tniB tniA IRi
IRi
qacEΔ1 sul1 orf5-(orf6)
5′-CS
attI1 3′-CS Δtni module
attI1 Cassette(s)
qacE (?)
Cassette(s)
IRt
Pre-clinical type
Clinical class 1 integrons
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• Is there a presence of pre-clinical type integrons
(contains a full tni module) in the human commensal bacterial population?
• If so, do they have the same tni modules as seen in Tn402 ? What type
of gene cassette(s) are they carrying?
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IRt IRi
5′-CS
attI1
3′-CS Δtni module Cassette(s)
3'-CS primers Tn402-tni module primers
Cassettes array primers
3'-CS tni module Cassettes
+ + +
+ - +
- - +
- + -
- - -
No. of
occurrences
9
9
3
4
9
Typical
Variant
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IRt
100% Tn402-like (3)
IRt
Tn6005-like (3)
IRt
pOZ172-like
(none)
tniR tniQ tniB tniA
res
89%
84%
100% to Tn5053
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dfrB3 gcuD qacE Tn402 in clinical strain (Klebsiella aerogenes)
IRi attI1
IRt
Full tni module Cassette(s)
Tn402
qacE 3 isolates (Klebsiella pneumonia)
(Escherichia coli) (Enterobacter sp.)
Our study
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JKB7 in commensal strain (Enterobacter cloacae)
IRt
JKB007 qacG
IRi attI1
Full tni module Cassette(s)
tniR tniQ tniB tniA
2 isolates (Escherichia coli)
Tn6005
1 isolates (Enterobacter sp.)
Our study JKB007 qacG
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blaIMP-4-qacG-aacA4-aphA15 pOZ172 in clinical strain (Citrobacter youngae)
aacA4-blaVIM-2 pPVV2-2 in clinical strain (Pseudomonas putida)
IRi attI1
IRt
Cassette(s)
pOZ172-like (with the hybrid Tn402/Tn5053 tni module)
tniR tniQ tniB tniA
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dfrB3 gcuD qacE clinical strain (Enterobacter aerogenes)
IRi attI1
IRt
Full tni module Cassette(s)
qacE commensal strain (Klebsiella pneumonia)*
Tn402-like transposons
blaVIM-2 aacA4 clinical strain (Pseudomonas putida)
orf1 orf1 aadA6 environmental strain (Comomonas testosteroni)
orf3 qacF environmental strain (Pseudomonas alcaligenes)
orfB orf132 environmental strain (Pseudomonas sp.)
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• Class 1 integrons with full tni module are more common than previously realised
• Site-specific recombination within the tni modules between members of the
Tn402/Tn5053 res hunter transposon family calls for more attention to these variant
integrons
• Class 1 integrons with full tni modules are dispersed to a wide range of bacterial species
and the varying gene cassette(s) content suggesting a dynamic gene flow from
environmental bacteria to human commensals and pathogens
• Detection and characterisation of gene cassette(s) from these variant Class 1 integrons
may help to predict the emergence of new resistant or virulent determinants before they
become prominent in bacterial populations
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Thu Betteridge1, Sally R.Partridge2, Jon R.Iredell2,
and H.W.Stokes1
The I3 Institute, University of Technology, Sydney1. Centre for
Infectious Diseases & Microbiology, University of Sydney,
Westmead Hospital2