Table 2.
Association of resistance mechanisms identified among the P. aeruginosa isolates (n = 59) and the modal MICs for tested antimicrobials observed in each association.
| Isolates and determinant of antimicrobial resistance (No. of isolates with OprD -) | Modal MIC a(μg/ml) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| MER | IPM | ATM | CAZ | FEP | AMK | GEN | CIP | ||
| PAO1 reference strain | - | 0.25 | 1 | 4 | 0.5 | 0.25 | 2 | 4 | 0.25- |
| No mechanisms of resistance identified | 7 (0) | 4 | 2 | 4-8b | 4 | 2 | 8 | 4 | 16 |
| XY+, MBL | 7 (6) | >32 | >32 | 8 | 256 | >32 | >256 | >256 | >32 |
| XY+ | 7 (5) | 16 | 8/16b | 32 | 8/256b | >32 | 256 | 2/>256b | 0.5/>32b |
| ABM+, XY+ | 5 (2) | 0.25/8b | 0.25/2b | 16 | 8 | 4 | 256 | 2- >256c | 32 |
| ABM+, XY+, MBL | 4 (3) | >32 | >32 | 8 | 256 | >32 | >256 | >256 | >32 |
| ABM+ | 3 (2) | 0.5-16b | 1 | 16 | 2-8c | 4 | 4-32c | 1-8c | 0.25-8c |
| XY+, GES-1 | 3 (2) | 8- >32c | 8- >32c | 8 | 128 | >32 | >256 | 256 | 16 |
| ABM+, XY+, AmpC+ | 2 (2) | 16/>32b | >32 | 8/32b | 32/64b | 16/32b | 4/64b | 1/8b | 2/4b |
| ABM+, GES-5 | 1 (1) | >32 | 32 | 8 | 32 | >32 | 128 | 128 | 32 |
| ABM+, CTX-M2 | 1 (1) | 4 | 1 | >32 | 2 | >32 | 128 | 256 | 16 |
| XY+, AmpC+, MBL | 2 (2) | 32/>32b | >32 | 16/>32b | 128/>256b | >32 | >256 | >256 | >32 |
| MBL | 2 (2) | >32 | >32 | 8 | 256 | >32 | >256 | >256 | 32 |
| AmpC+ | 3 (2) | 1-8 | 2-16c | 4-32c | 16-256c | 16 | 4 | 2 | 0.5-32c |
| OprD- | 12 (12) | ≤0.25 | 1-2 | 8 | 2 | 2 | 8 | 2 | 0.25 |
MER, meropenem; IPM, imipenem; ATM, aztreonam; CAZ, ceftazidime; FEP, cefepime; AMK, amikacin; GEN, gentamicin; CIP, ciprofloxacin.
The abbreviations XY+, ABM+, and AmpC+ designate MexXY, MexAB-OprM, and AmpC overexpression, respectively.
MBL, metallo-β-lactamase producer
OprD-, reduced expression of OprD porin.
a, Modal MIC is defined as the antimicrobial MICs that were more frequently observed at each association of resistance mechanisms.
b, two modal MICs observed;
c MIC range when no modal MIC was observed.