Hybrid Pathogenicity Island PAGI-5 Contributes to the Highly Virulent Phenotype of a Pseudomonas aeruginosa Isolate in Mammals

Abstract

Most known virulence determinants of Pseudomonas aeruginosa are remarkably conserved in this bacterium's core genome, yet individual strains differ significantly in virulence. One explanation for this discrepancy is that pathogenicity islands, regions of DNA found in some strains but not in others, contribute to the overall virulence of P. aeruginosa. Here we employed a strategy in which the virulence of a panel of P. aeruginosa isolates was tested in mouse and plant models of disease, and a highly virulent isolate, PSE9, was chosen for comparison by subtractive hybridization to a less virulent strain, PAO1. The resulting subtractive hybridization sequences were used as tags to identify genomic islands found in PSE9 but absent in PAO1. One 99-kb island, designated P. aeruginosa genomic island 5 (PAGI-5), was a hybrid of the known P. aeruginosa island PAPI-1 and novel sequences. Whereas the PAPI-1-like sequences were found in most tested isolates, the novel sequences were found only in the most virulent isolates. Deletional analysis confirmed that some of these novel sequences contributed to the highly virulent phenotype of PSE9. These results indicate that targeting highly virulent strains of P. aeruginosa may be a useful strategy for identifying pathogenicity islands and novel virulence determinants.

The Accessory Genome of Pseudomonas aeruginosa

“…Among a panel of 35 P. aeruginosa isolates cultured from patients with ventilator-associated pneumonia, these cargo regions were present in only the more virulent strains ( Fig. 3) (14). Additional studies confirmed that these regions of PAGI-5 contribute to pathogenicity, as deletion of either attenuated virulence in a mouse model of acute pneumonia (14).…”

“…2). Illustrating the capacity of ICEs to continually evolve through acquisition and loss of cargo ORFs, PAGI-5 carries two regions of cargo ORFs (NR-I and NR-II) that are absent in PAPI-1 (14). Among a panel of 35 P. aeruginosa isolates cultured from patients with ventilator-associated pneumonia, these cargo regions were present in only the more virulent strains ( Fig.…”

Fatores envolvidos com a mobilização de PAPI-1

“…Vários grupos de genes de PAPI-1 também estão presentes nos plasmídeos pKLC102 e pKLK106, e nas ilhas genômicas PAGI-2, PAGI-3 e PAGI-5 (Larbig, et al 2002;Battle, et al 2008). As regiões variantes em PAGI-2, -3 -5 parecem conferir capacidades diferentes de adaptação para estas linhagens, assim como as regiões variantes de PAPI-1 se mostraram relevantes em patogenicidade (Kiewitz, et al 2000;Klockgether, et al 2004;Battle, et al 2008).…”

“…As regiões variantes em PAGI-2, -3 -5 parecem conferir capacidades diferentes de adaptação para estas linhagens, assim como as regiões variantes de PAPI-1 se mostraram relevantes em patogenicidade (Kiewitz, et al 2000;Klockgether, et al 2004;Battle, et al 2008). Recentemente, ilhas semelhantes a PAGI-2 foram detectadas em 31 de um total de 71 linhagens de P. aeruginosa analisadas e também na -proteobactéria Cupriavidus (Ralstonia) metallidurans (Klockgether, et al 2007).…”

“…Entretanto, esta não foi a única ilha genômica encontrada nesta cepa altamente virulenta; juntamente com ela foram também descritas mais seis ilhas denominadas de PAGI-6 a -11. PAGI-5 foi a maior ilha genômica encontrada em PSE9 (Battle, et al 2008). Baseando-se em comparação de sequências, PAGI-5 é relacionada a uma grande família de ilhas genômicas que inclui PAPI-1 ) (objeto deste estudo e será descrita posteriormente), PAPI-2 e ilhas ExoU, bem como pKLC102 Kulasekara, et al 2006;Battle, et al 2008 …”