TABLE 1 .
Strain | Plasmid | MexY mutation |
MIC (μg/ml)b |
||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
STR | PAR | NEO | AMI | ERY | SPC | CAM | NORc | CEFd | |||
K767 | None | WT | 32 | 256 | 32 | 2 | 512 | 512 | 64 | NDe | ND |
K3315 | None | None | 2 | 8 | 4 | 0.5 | 64 | 64 | 64 | ND | ND |
K3315 | pRK415 | None | 2 | 16 | 4 | 0.5 | 64 | 64 | 32 | 0.5 | 1 |
K3315 | pCL10 | WT | 8 | 64 | 8 | 1 | 512 | 512 | 32 | 2 | 4 |
K3315 | pCL14 | G216D | 2 | 16 | ND | ND | 64 | 64 | 32 | 0.5 | 1 |
K3315 | pCL13 | R184H | 4 | 32 | ND | ND | 256 | 256 | 32 | ND | ND |
K3315 | pCL11 | S16F | 4 | 32 | ND | ND | 256 | 256 | 32 | ND | ND |
K3315 | pCL17 | A960T | 4 | 16 | ND | ND | 256 | 256 | 32 | ND | ND |
K3315 | pCL15 | V339M | 4 | 16 | 8f | 1 | 512 | 256 | 32 | 2 | 1 |
K3315 | pCL12 | R166C | 4 | 32 | ND | ND | 256 | 512 | 32 | 2 | 4 |
K3315 | pCL16 | P562S | 8 | 32 | ND | ND | 256 | 512 | 32 | ND | ND |
K3315 | pCL19 | D133A | 4 | 16 | 4 | 0.5 | 256 | 1024 | 32 | ND | ND |
K3315 | pCL20 | D133S | 4 | 16 | 4 | 0.5 | 256 | 1024 | 32 | ND | ND |
K3315 | pCL18 | K79A | 8 | 128 | 8g | 1 | 512 | 1024 | 32 | ND | ND |
K3315 | pCL21 | Y613A | 4 | 16 | 4 | 0.5 | 512 | 256 | 32 | 2 | 2 |
The antimicrobial susceptibility of P. aeruginosa ΔmexY strain K3315 carrying the indicated plasmids expressing wild-type (WT) MexY or MexY derivatives with the indicated amino acid substitutions is reported. Results for WT strain K767 and plasmid-free K3315 are provided for comparison purposes.
MIC values lower than that measured for pCL10-carrying K3315 expressing WT MexY are bolded. MIC values higher than that measured for pCL10-carrying K3315 are italicized. STR, streptomycin; PAR, paromomycin; NEO, neomycin; AMI, amikacin; ERY, erythromycin; SPC, spectinomycin; CAM, chloramphenicol; NOR, norfloxacin; CEF, cefepime.
NOR MICs were determined in the presence of 8 µg/ml chloramphenicol. The NOR MIC for all strains in the absence of chloramphenicol was 0.5 µg/ml.
CEF MICs were determined in the presence of 8 µg/ml chloramphenicol. The CEF MIC determined in the absence of chloramphenicol was 1 (for pRK415 control and MexYG216D) or 2 (for MexYWT and its V339M, R166C, and Y613A variants) μg/ml.
ND, not determined.
At half the NEO MIC (4 µg/ml), MexYV339M-expressing K3315 grew reproducibly slower than K3315 expressing MexYWT (data not shown), indicating that the V339M mutation compromises neomycin resistance.
At half the NEO MIC (4 µg/ml), MexYK79A-expressing K3315 grew reproducibly faster than K3315 expressing MexYWT (data not shown), indicating that the K79A mutation enhances neomycin resistance.