Genome plasticity favours double chromosomal Tn4401b-blaKPC-2 transposon insertion in the Pseudomonas aeruginosa ST235 clone

Natasha Vanegas Gómez,Betsy Castro-Cardozo,Catalina Tovar,Carmen Elisa Llanos-Uribe,Ricaurte Alejandro Marquez-Ortiz,Javier Escobar-Pérez,Deisy Abril,José Ignacio Moncayo-Ortiz,Yina Marcela Guaca-González,Héctor Fabio Sánchez,Narda María Olarte Escobar,Jaime Castellanos,Zayda Lorena Corredor Rozo,Niradiz Reyes

doi:10.1186/s12866-019-1418-6

Abstract

BackgroundPseudomonas aeruginosa Sequence Type 235 is a clone that possesses an extraordinary ability to acquire mobile genetic elements and has been associated with the spread of resistance genes, including genes that encode for carbapenemases. Here, we aim to characterize the genetic platforms involved in resistance dissemination in blaKPC-2-positive P. aeruginosa ST235 in Colombia.ResultsIn a prospective surveillance study of infections in adult patients attended in five ICUs in five distant cities in Colombia, 58 isolates of P. aeruginosa were recovered, of which, 27 (46.6%) were resistant to carbapenems. The molecular analysis showed that 6 (22.2%) and 4 (14.8%) isolates harboured the blaVIM and blaKPC-2 genes, respectively. The four blaKPC-2-positive isolates showed a similar PFGE pulsotype and belonged to ST235. Complete genome sequencing of a representative ST235 isolate shows a unique chromosomal contig of 7097.241 bp with eight different resistance genes identified and five transposons: a Tn6162-like with ant(2″)-Ia, two Tn402-like with ant(3″)-Ia and blaOXA-2 and two Tn4401b with blaKPC-2. All transposons were inserted into the genomic islands. Interestingly, the two Tn4401b copies harbouring blaKPC-2 were adjacently inserted into a new genomic island (PAGI-17) with traces of a replicative transposition process. This double insertion was probably driven by several structural changes within the chromosomal region containing PAGI-17 in the ST235 background.ConclusionThis is the first report of a double Tn4401b chromosomal insertion in P. aeruginosa, just within a new genomic island (PAGI-17). This finding indicates once again the great genomic plasticity of this microorganism.

Highlights

Pseudomonas aeruginosa Sequence Type 235 is a clone that possesses an extraordinary ability to acquire mobile genetic elements and has been associated with the spread of resistance genes, including genes that encode for carbapenemases
After active clinical surveillance in the intensive care unit (ICU) at five distant cities, we found a broad population distribution of P. aeruginosa in Colombia; the ST235 clone was the only one harbouring blaKPC-2, and interestingly, those ST235 isolates harboured two copies of this gene that were located in two Tn4401b transposons in a new genomic island (GI) at the chromosome
With respect to the resistance behaviour, among all 58 isolates, 27 (46.6%) were resistant to at least one carbapenem antibiotic. Of these 27 carbapenem-resistant P. aeruginosa, six (22.2%) and four (14.8%) isolates contained the blaVIM and blaKPC-2 genes, respectively

Summary

Introduction

Pseudomonas aeruginosa Sequence Type 235 is a clone that possesses an extraordinary ability to acquire mobile genetic elements and has been associated with the spread of resistance genes, including genes that encode for carbapenemases. In P. aeruginosa, the blaKPC gene is rare (with variant 2 being the most frequent) and is mainly mobilized on both complete or truncated Tn4401b transposons, which have been reported in two different plasmid backbones (8 kb and 31.5 kb) belonging to the IncU and IncP-6 incompatibility groups, respectively [15, 16]. This blaKPC-2 variant has been identified in P. aeruginosa isolates belonging to sequence type (ST) 308, 1006, 1060 and 235 [15,16,17]

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