Tn 6060 , a Transposon from a Genomic Island in a Pseudomonas aeruginosa Clinical Isolate That Includes Two Class 1 Integrons

Abstract

A 25,441-bp transposon was recovered from a Pseudomonas aeruginosa clinical isolate. While the transposition module was >99% identical to sequence of Tn1403, the element had been subject to rearrangements, with two In70.2-like class 1 integrons inserted into it in an unusual "tail-to-tail" configuration. One cassette array was the same as that in In70.2; however, the second was different, generating a transposon that collectively includes six resistance cassettes.

The Integron: Adaptation On Demand

“…From a biological perspective, it could be argued that this reaction has little evolutionary meaning in CIs, where there is only one copy of the platform and the attI×attI reaction would most likely produce an undesirable dimer between replicating chromosomes. Interestingly, in the clinical environment, where integrons are plasmid-borne and have become prevalent to the point of redundancy (62,63), attI sites can be found in multiple copies within the cell. In this setting, the reaction between attI sites can have biological consequences through the rearrangement of cassette content between different integrons, and is a reaction of unknown relative importance.…”

Diverse Mobilized Class 1 Integrons Are Common in the Chromosomes of Pathogenic Pseudomonas aeruginosa Clinical Isolates

“…Recently, we identified a transposon containing two class 1 integrons, Tn6060 (Fig. 1), in a genomic island (here referred to as GI1) of the P. aeruginosa clinical isolate 37308 (21). The cassette arrays in Tn6060 have been commonly reported elsewhere, although the genetic context is, in most cases, not known (19,20,24).…”

“…P. aeruginosa isolates were recovered from three hospitals, two in Sydney, Australia (2010), and one in Montevideo, Uruguay (2008). Eleven intI1-positive isolates (nine from Sydney and two from Montevideo) known to carry class 1 integrons were screened for the presence of the transposition module of Tn6060 and for the insertion of it in GI1, as reported previously (21). Two isolates positive from this screen, C79 from Sydney and U09 from Montevideo, were selected to investigate the context of class 1 integrons via the construction of fosmid genomic libraries (21).…”

“…1). Also, Tn6162 transposons in both C79 and U09 were inserted into GI1 at the same location as Tn6060 in strain 37308 from Sydney (21). In both C79 and U09, PCR with appropriate primers (see Table S1 in the supplemental material) and sequencing confirmed that the GI in these strains is located in the same position in the chromosome as that reported in the cystic fibrosis strain PACS171b in which this GI (without an integron) was first found (7) and in the Tn6060-containing strain 37308.…”

“…Eleven intI1-positive isolates (nine from Sydney and two from Montevideo) known to carry class 1 integrons were screened for the presence of the transposition module of Tn6060 and for the insertion of it in GI1, as reported previously (21). Two isolates positive from this screen, C79 from Sydney and U09 from Montevideo, were selected to investigate the context of class 1 integrons via the construction of fosmid genomic libraries (21). These two isolates were epidemiologically unrelated and comprised two different genetic clones based on pulsed-field gel electrophoresis (PFGE) analysis (Table 1).…”