Abstract
Pseudomonas aeruginosa are noscomially acquired, opportunistic pathogens that pose a major threat to the health of burns patients and the immunocompromised. We sequenced the genomes of P. aeruginosa isolates RNS_PA1, RNS_PA46 and RNS_PAE05, which displayed resistance to almost all frontline antibiotics, including gentamicin, piperacillin, timentin, meropenem, ceftazidime and colistin. We provide evidence that the isolates are representatives of P. aeruginosa sequence type (ST) 235 and carry Tn6162 and Tn6163 in genomic islands 1 (GI1) and 2 (GI2), respectively. GI1 disrupts the endA gene at precisely the same chromosomal location as in P. aeruginosa strain VR-143/97, of unknown ST, creating an identical CA direct repeat. The class 1 integron associated with Tn6163 in GI2 carries a blaGES-5–aacA4–gcuE15–aphA15 cassette array conferring resistance to carbapenems and aminoglycosides. GI2 is flanked by a 12 nt direct repeat motif, abuts a tRNA-gly gene, and encodes proteins with putative roles in integration, conjugative transfer as well as integrative conjugative element-specific proteins. This suggests that GI2 may have evolved from a novel integrative conjugative element. Our data provide further support to the hypothesis that genomic islands play an important role in de novo evolution of multiple antibiotic resistance phenotypes in P. aeruginosa.
Highlights
Pseudomonas aeruginosa is an opportunistic pathogen and a significant threat to the health of immunocompromised patients hospitalized for periods longer than 7 days [1]
Isolates included in this study were tested for sensitivity to antibiotics used at Royal North Shore Hospital (RNSH) to treat P. aeruginosa infections, including gentamicin, piperacillin, ticarcillin and clavulanic acid, meropenem, ceftazidime and colistin
Defining features of the three isolates selected for genome sequence analysis were (i) that they were isolated from different patients/sources at the RNSH over a seventh month period, (ii) that they displayed minor differences in their resistance profile and intermediate resistance to colistin, a last line treatment option for P. aeruginosa infections, and (iii) a suspicion that they carried Tn6162 and Tn6163 using the PCR strategy described above
Summary
Pseudomonas aeruginosa is an opportunistic pathogen and a significant threat to the health of immunocompromised patients hospitalized for periods longer than 7 days [1]. It is a frequent cause of nosocomially derived infections [2,3] and can survive on hospital fomites for extended periods [4,5,6,7]. Multiple drug-resistant (MDR), extensively drug-resistant (XDR) and pan-resistant [8,9] P. aeruginosa linages cause life-threatening infections in nosocomial environments and severely restrict drug options to treat infection. The population structure of P. aeruginosa is described as non-clonal and epidemic [10].
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