TABLE 1.
Susceptibilty profiles and characterization of the studied strains
| Strain | Description/relevant genotype | mexDa | MIC (μg/ml)b |
|||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TIC (R, >16) | ATM (R, >16) | PTZ (R, >16) | TAZ (R, >8) | FEP (R, >8) | IMP (R, >4) | MER (R, >8) | CTZ (R, >4) | CZA (R, >8) | IPR (R, >2) | CIP (R, >0.5) | AMI (R, >16) | TOB (R, >2) | COL (R, >2) | |||
| PAO1 | Wild-type reference strain | 1 | 16 | 4 | ≤4 | 2 | ≤1 | 2 | 1 | 0.5 | 1 | 0.25 | ≤0.12 | 4 | 0.5 | 2 |
| PAONB | nfxB knockout mutant of PAO1 | 744 ± 80 | ≤8 | ≤2 | ≤4 | ≤1 | 4 | ≤0.5 | ≤0.5 | 0.25 | ≤0.5 | ≤0.12 | 2 | ≤2 | ≤0.25 | 2 |
| HC-20-232 | Clinical isolate belonging to ST274 OprD (W277X), nfxB (nt213Δ7), mexD (Q178R, S133G) | 241 ± 12 | 32 | 8 | 8 | 64 | 64 | 32 | 16 | 16 | 32 | 1 | 1 | 8 | 2 | 2 |
| HC-20-232MxD | mexD knock out mutant of HC-20-232 | ND | 32 | 4 | 8 | 4 | 2 | 32 | 8 | 1 | 2 | 1 | ≤0.12 | 4 | 1 | 2 |
| HC-20-232 (pUCP nfxB) | HC-20-232 strain harboring plasmid pUCP24 with cloned wild-type nfxB | 4.9 ± 0.2 | 32 | 8 | 8 | 4 | 4 | 32 | 8 | 1 | 2 | 1 | ≤0.12 | 8 | 2 | 2 |
| PAMB148 | Clinical isolate belonging to ST274 ampD P41L (AmpC overexpression) | 1.3 ± 0.1 | 256 | 64 | >256 | 64 | 32 | 4 | 1 | 4 | 8 | 0.25 | ≤0.12 | 8 | 2 | 2 |
| PAMB148NB | nfxB knockout mutant of PAMB148 | 76 ± 17 | 128 | 32 | 256 | 64 | 32 | 2 | 1 | 2 | 4 | ≤0.12 | 2 | 4 | 1 | 2 |
a
Relative level of mexD mRNA with respect to that of wild-type PAO1 according to previously described protocols (22). ND, not done.
b
Broth microdilution MIC results obtained in triplicate experiments. EUCAST v 11.0 resistance breakpoints are indicated. TIC, ticarcillin; ATM, aztreonam; PTZ, piperacillin-tazobactam; TAZ, ceftazidime; FEP, cefepime; IMP, imipenem; MER, meropenem; CTZ, ceftolozane-tazobactam; CZA, ceftazidime-avibactam; IPR, imipenem/relebactam; CIP, ciprofloxacin; AMI, amikacin; TOB, tobramycin; COL, colistin.