Complete sequence of pOZ176, a 500-kilobase IncP-2 plasmid encoding IMP-9-mediated carbapenem resistance, from outbreak isolate Pseudomonas aeruginosa 96 - PubMed (original) (raw)

Complete sequence of pOZ176, a 500-kilobase IncP-2 plasmid encoding IMP-9-mediated carbapenem resistance, from outbreak isolate Pseudomonas aeruginosa 96

Jianhui Xiong et al. Antimicrob Agents Chemother. 2013 Aug.

Abstract

Pseudomonas aeruginosa 96 (PA96) was isolated during a multicenter surveillance study in Guangzhou, China, in 2000. Whole-genome sequencing of this outbreak strain facilitated analysis of its IncP-2 carbapenem-resistant plasmid, pOZ176. The plasmid had a length of 500,839 bp and an average percent G+C content of 57%. Of the 618 predicted open reading frames, 65% encode hypothetical proteins. The pOZ176 backbone is not closely related to any plasmids thus far sequenced, but some similarity to pQBR103 of Pseudomonas fluorescens SBW25 was observed. Two multiresistant class 1 integrons and several insertion sequences were identified. The blaIMP-9-carrying integron contained aacA4 → bla(IMP-9) → aacA4, flanked upstream by Tn21 tnpMRA and downstream by a complete tni operon of Tn402 and a mer module, named Tn6016. The second integron carried aacA4 → catB8a → bla(OXA-10) and was flanked by Tn1403-like tnpRA and a sul1-type 3' conserved sequence (3'-CS), named Tn6217. Other features include three resistance genes similar to those of Tn5, a tellurite resistance operon, and two pil operons. The replication and maintenance systems exhibit similarity to a genomic island of Ralstonia solanacearum GM1000. Codon usage analysis suggests the recent acquisition of bla(IMP-9). The origins of the integrons on pOZ176 indicated separate horizontal gene transfer events driven by antibiotic selection. The novel mosaic structure of pOZ176 suggests that it is derived from environmental bacteria.

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Figures

Fig 1

Fig 1

The genome of pOZ176. The scale is indicated on the innermost circle. The second circle illustrates G+C skew in green (+) and purple (−), and circle 3 shows G+C content (deviation from the average) in light blue (+) and light green (−). The next two circles indicate positions of CDSs in minus (circle 4) and plus (circle 5) strands. The outermost circles indicate the positions of mobile elements, including the integron-containing Tn_6016_ and Tn_6217_, the IncP-2 tra-parBA-oriV-repA region, heavy metal resistance, two pil operons, and the two principal regions of weak similarity to pQBR103. CGview software was used to construct the genome map.

Fig 2

Fig 2

Two types of class 1 integrons identified in PA96, a Tn_402_-type integron in Tn_6016_ (A) and a sul1_-type integron in Tn_6217 (B). Arrow boxes show the genes and their orientations; each solid black oval indicates attI, and each open oval represents the attC of the preceding gene. tniA_Δ represents a truncation: 87 bp at the beginning of the gene were disrupted by a mer operon, which is ∼90% identical to that of Tn_5044. The small rectangular boxes represent the res site of the transposon, and the solid black boxes represent the 25-bp IRi and IRt sites. The IRt site of the integron in Tn_6016_ is missing; the small arrows represent the direction of promoters. HP, hypothetical protein; DrugR, drug resistance.

Fig 3

Fig 3

Evolutionary relationships of the pOZ176 replication initiator protein (RepA) and its 12 best hits in GenBank. The inclusion criteria for the 12 best hits were an E value of 0 and percent amino acid identity of 99% to 91%. The evolutionary history was inferred by using the maximum likelihood method with MEGA5 software. The consensus tree after 1,000 bootstrap iterations is shown. The evolutionary distances were computed by using the JTT matrix-based method.

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