TABLE 1.
Prevalence of isolates overexpressing mexAB-oprM and mexXY in relation to levels of resistance to TIC, CIP, or AMK
| Drug | Value (n)a at indicated MIC (μg/ml) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| TIC | 16b | 32 (39) | 64 (49) | 128 (34) | 256 (17) | 512 (4) | 1,024 (5) | 2,048 (5) | ≥2,048 (17) |
| % ABM | 31 (12) | 51 (25) | 59 (20) | 47 (8) | 25 (1) | 60 (3) | 20 (1) | 53 (9) | |
| Range of mexB expressionc | 2.1-5.7 | 2.0-52.8 | 2.0-20.0 | 2.8-7.8 | 2.6 | 2.0-4.3 | 3.1 | 2.2-4.6 | |
| CIP | <0.125 (5) | 0.125b (10) | 0.25 (22) | 0.5 (16) | 1 (14) | 2 (13) | 4 (8) | 8 (11) | 16 (18) | 32 (42) | 64 (9) | >64 (2) |
| % ABM | 0 (0) | 10 (1) | 45 (10) | 63 (10) | 850 (7) | 62 (8) | 63 (5) | 45 (5) | 44 (8) | 48 (20) | 56 (5) | 0 (0) |
| % XY | 20 (1) | 0 (0) | 27 (6) | 47 (7) | 36 (5) | 69 (9) | 50 (4) | 55 (6) | 83 (15) | 88 (37) | 100 (9) | 0 (0) |
| AMK | 1 (6) | 2 (19) | 4b (57) | 8 (34) | 16 (25) | 32 (10) | 64 (10) | 128 (7) | >128 (2) |
| % XY | 17 (1) | 32 (6) | 54 (31) | 56 (19) | 64 (16) | 100 (10) | 80 (8) | 86 (6) | 100 (2) |
| Range of mexY expressionc | 53.9 | 4.2-17.5 | 4.7-82.0 | 4.0-42.1 | 4.4-52.9 | 6.3-45.2 | 4.4-21.5 | 11.5-49.7 | 4.4-42.3 |
a
n, number of isolates.
b
MIC for the wild-type reference strain PAO1.
c
Mean values for two independent experiments.