TABLE 1.
Phenotypic and genotypic characteristics of aminoglycoside susceptibility and resistance among Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii isolates included in this study
| Isolatea | Originb | Susceptibility testingc |
Aminoglycoside resistance gene(s)d | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Zone of inhibition (mm) |
MIC (μg/ml) |
|||||||||
| AMK | GEN | TOB | ARB | AMK | GEN | TOB | ARB | |||
| P. aeruginosa ATCC 27853 | 22 | 20 | 24 | 27 | 4 | 1 | 0.25 | 0.5 | ND | |
| Escherichia coli ATCC 25922 | 25 | 23 | 22 | 25 | 2 | 0.5 | 1 | 2 | ND | |
| A. baumannii 360/10 | São Paulo, Brazil | 11 | 6 | 6 | 8 | >128 | >128 | >128 | 256 | aacA4, aacA1, aphA7 |
| A. baumannii 874/13 | São Paulo, Brazil | 8 | 6 | 6 | 9 | >128e | >128 | >128 | 128 | aacA4, aac(3)-I, aphA7 |
| A. baumannii 143/14 | São Paulo, Brazil | 6 | 6 | 6 | 7 | >128 | >128 | >128 | 256 | aacA4, aacC1, aphA7, aadB, aadA1, aphA6 |
| P. aeruginosa HC402/07 | São Paulo, Brazil | 6 | 6 | 6 | 15 | >128 | >128 | >128 | 32 | aacA4, aph(3′)-IIb, aphA6, aadA6 |
| P. aeruginosa HC408/07 | São Paulo, Brazil | 6 | 6 | 6 | 22 | >128 | >128 | >128 | 4 | aacA4, aph(3′)-IIb, aphA6, aadB, aadA6 |
| P. aeruginosa HC305/07 | São Paulo, Brazil | 6 | 6 | 6 | 18 | >128 | >128 | >128 | 8 | aacA4, aph(3′)-IIb, aphA6, aadB, aadA6 |
| P. aeruginosa 463/12 | São Paulo, Brazil | 12 | 6 | 6 | 14 | >128 | >128 | >128 | 32 | aacA4, aph(3′)-IIb, aadB, aadA6, strA, strB |
| P. aeruginosa 1206/13 | São Paulo, Brazil | 6 | 6 | 6 | 17 | >128 | >128 | >128 | 8 | aacA4, aph(3′)-IIb, aphA6, aadA2 |
| P. aeruginosa 9me/14 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >128 | >128 | >128 | >256 | aacA4, aph(3′)-IIb, aadA7, rmtD1 |
| P. aeruginosa 862/07 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >128 | >128 | >128 | >256 | rmtD |
| P. aeruginosa HC367/07 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >128 | >128 | >128 | >256 | rmtD |
| P. aeruginosa HC103/07 | São Paulo, Brazil | 6 | 6 | 6 | 7 | >128 | >128 | >128 | >256 | rmtD |
| P. aeruginosa HC84/07 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >128 | >128 | >128 | 128 | rmtD |
| P. aeruginosa HC313/07 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >128 | >128 | >128 | >256 | rmtD |
| P. aeruginosa HC58/07 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >128 | >128 | >128 | >256 | rmtD |
| P. aeruginosa 883/07 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >128 | >128 | >128 | >256 | rmtD |
| P. aeruginosa 979/09 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >128 | >128 | >128 | >256 | rmtD |
| K. pneumoniae 931/08 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >256 | >256 | >256 | >256 | rmtGf |
| K. pneumoniae 1180/11 | São Paulo, Brazil | 6 | 6 | 6 | 6 | >256 | >256 | >256 | >256 | rmtGf |
| P. aeruginosa 102 | United States | 26 | 22 | 26 | 25 | 4 | 1 | 0.25 | 2 | aph(3′)-IIb |
| P. aeruginosa 104 | United States | 26 | 23 | 27 | 26 | 4 | 1 | 0.25 | 2 | aph(3′)-IIb |
| P. aeruginosa 105 | United States | 30 | 22 | 25 | 25 | 4 | 1 | 0.25 | 1 | aph(3′)-IIb |
| P. aeruginosa 106 | United States | 21 | 18 | 22 | 22 | 8 | 4 | 0.5 | 2 | aph(3′)-IIb |
| A. baumannii 162 | United States | 26 | 26 | 25 | 27 | 1 | 0.5 | 0.25 | 0.25 | — |
| A. baumannii 165 | United States | 26 | 27 | 26 | 28 | 1 | 1 | 0.25 | 0.25 | — |
| A. baumannii 172 | United States | 25 | 26 | 25 | 27 | 4 | 1 | 0.5 | 1 | — |
| A. baumannii 176 | United States | 25 | 23 | 24 | 25 | 2 | 1 | 0.5 | 2 | — |
E. coli ATCC 25922 and P. aeruginosa ATCC 27853 were used as negative controls for all experiments. A. baumannii 360/10, 874/13, and 143/14 and P. aeruginosa HC402/07, HC408/07, HC305/07, 463/12, 1206/13, and 9me/14 were subjected to WGS.
City and/or country of origin.
A value of 6 indicates the absence of a zone of inhibition. The concentrations of amikacin (AMK), gentamicin (GEN), tobramycin (TOB), and arbekacin (ARB) disks were 30, 10, 10, and 10 μg, respectively. Arbekacin disks were purchased from Eiken Chemical (Tokyo, Japan) and provided by Meiji Seika Kaisha Ltd.
Aminoglycoside resistance genes were identified by whole-genome sequencing; 16S-RMTase genes were also identified by PCR. Dashes indicate that no gene was detected. ND, not determined.
Isolate that showed a 4-fold MIC reduction with amikacin in combination with PAβN in an efflux assay.
These two isolates were not included for WGS, and the 16S-RMTases were detected by PCR.