Once-daily dosed gentamicin is more nephrotoxic than once-daily dosed tobramycin in clinically infected patients.

1 integron showed 100% nucleotide sequence identity to the corresponding segment of a plasmid from the human clinical P. aeruginosa strain B3 isolated in Guangzhou (accession no. EU588392). Moreover, the 3 ′ conserved region of the integron (qacED1 and sul1) and the upstream region of the bla IMP-45 gene including aacA4, the 5 ′ conserved segment (intI1) of the integron and a Tn1403-like transposon (tnpR and tnpA) exhibited 99.9% (2348/2349) and 100% (5728/5728) nucleotide sequence identity, respectively, to corresponding regions of plasmid pOZ176 from a clinical P. aeruginosa isolate also found in Guangzhou (Figure 1). In companion animals, carbapenemase-producing Escherichia coli carrying bla NDM-1 or bla OXA-48 and K. pneumoniae carrying bla OXA-48 have been isolated from clinical infections. 7,8 The future will show whether these observations represent 'the tip of the iceberg' or rare accidental findings. 8,9 In the present case, the frequency of identification of P. aeruginosa ST308 from human clinical samples as well as the high level of similarity of the genetic environment of bla IMP-45 from canine P. aeruginosa with integrons found in human P. aeruginosa strongly suggest a human-to-dog transfer of this IMP-45-producing isolate. Considering that (i) car-bapenems are not approved for use in animals and (ii) most of the carbapenemase genes found in animals have been shown to be part of multiresistance integrons or multiresistance gene regions, 3,10 – 12 co-selection and co-transfer of carbapenemase genes under the selective pressure imposed by other antimicrobial resistance genes seem to play a major role in the dissemination of carbapenemase genes. Moreover, the close contact between humans and their pet and companion animals facilitates the acquisition of carbapenem-resistant isolates of human origin by pet and companion animals. Nevertheless, surveillance of bacteria of animal origin for carbapenemase producers and prudent use of antimicrobial agents to decrease the options for co-selection of carbapenemase genes in animals are urgently warranted.