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

• 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

3

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

4

Integrase +

attC

Cassette 2 A two-component system

intl

attI

Pc

Pint

attC2 attC1

etc…

5

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

6

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

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

8

• 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?

9

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

10

IRt

100% Tn402-like (3)

IRt

Tn6005-like (3)

IRt

pOZ172-like

(none)

tniR tniQ tniB tniA

res

89%

84%

100% to Tn5053

11

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

12

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

13

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

14

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.)

18

• 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

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