TABLE 4.
Evaluation of the impact of various efflux mutations on potency of QPX7728 (PV50) to enhance antibiotic activity.
| Strain1 | Genotype/Description | Biapenem4 MIC (μg/ml) in the presence of varied concentrations of BLIs (μg/ml) |
MIC of the vector only strain (μg/ml) | QPX PV505 | VAB PV505 | ||
| alone | w/QPX | w/VAB | (μg/ml) | (μg/ml) | |||
| PAM4224 | Wild-type | 64 | 0.06 | 4 | 0.25 | 1 | 8 |
| PAM4365 | MexA::Tet | 64 | 0.125 | 0.25 | 0.25 | 1 | 0.5 |
| PAM4126 | mexR (MexAB-OprM)2 | 64 | 0.125 | 16 | 0.125 | 2 | 64 |
| PAM4129 | nfxB (MexCD-OprJ) | 8 | 0.03 | 0.25 | 0.03 | 0.5 | 4 |
| PAM4132 | mexT (MexEF-OprM)3 | 128 | 0.25 | 32 | 0.5 | 1 | >64 |
| PAM4150 | mexZ (MexXY-OprM) | 64 | 0.25 | 4 | 0.25 | 1 | 8 |
1KPC-2 was introduced into isogenic strains of P. aeruginosa containing various efflux mutations and used as a reporter for the QPX7728 BLI activity. 2Mutations in regulatory genes result in overproduction of specific efflux complexes that are shown in brackets. 3The production of a carbapenem porin OprD is reduced by the same mutation in mexT that leads to overproduction of the MexEF-OprN efflux pump. 4Biapenem was chosen as a reporter antibiotic because it’s activity against P. aeruginosa is not affected by efflux. The effect of increasing concentrations of QPX7728 on biapenem MIC against the strains producing KPC-2 in the background of various efflux mutations was determined in a standard checkerboard experiment. 5BLI potency was defined as PV50 (PV stands for potentiation value) which is a concentration of a BLI required to achieve 50% of antibiotic potentiation effect (conceptually equivalent to EC50). It is determined based on the concentration-response curve where antibiotic MICs are plotted vs. BLI concentrations. Data from Lomovskaya et al. (2020a).