TABLE 1.
Characteristics of the 62 amikacin-nonsusceptible pathogens
| Species (no. of isolates) | Beta-lactamase(s) produceda | No. of isolates with the following pattern of susceptibility or resistanceb to amikacin, gentamicin, and tobramycin: |
|||
|---|---|---|---|---|---|
| R/R/R | R/S/S | R/S/R | R/R/S | ||
| A. baumannii (21) | Any or none | 9 | 5 | 0 | 7 |
| OXA-23 and OXA-51 | 2 | 2 | 1 | ||
| OXA-24 and OXA-51 | 1 | 1 | |||
| OXA-51 | 1 | ||||
| OXA-51 and OXA-58 | 1 | ||||
| P. aeruginosa (21) | Any or none | 15 | 0 | 3 | 3 |
| GES-1 | 1 | ||||
| OXA-2, OXA-10, and VIM-2 | 1 | ||||
| OXA-14 | 1 | ||||
| VIM-2 | 2 | 1 | 1 | ||
| VIM-4 | 1 | ||||
| K. pneumoniae (20) | Any or none | 13 | 0 | 3 | 4 |
| KPC-2 | 3 | 1 | |||
| KPC-3 | 1 | 2 | |||
a
GES, Guiana extended-spectrum β-lactamase; KPC, Klebsiella pneumoniae carbapenemase; OXA, oxacillin-hydrolyzing extended-spectrum β-lactamase; VIM, Verona integron-encoded metallo-β-lactamase.
b
R, resistance; S, susceptibility. In each pattern, the first letter refers to amikacin, the second to gentamicin, and the third to tobramycin. The “R” designation for amikacin includes 13 isolates classified as intermediate (MIC, 32 μg/ml) and 49 isolates classified as resistant (MIC, ≥64 μg/ml) by CLSI standards (17). All 62 isolates were classified as resistant by EUCAST standards (MIC, >16 μg/ml) (18). These strains are referred to as “nonsusceptible” in the text.