Table 2.
Outer membrane diffusion pathways and the role of AcrAB-TolC pump in susceptibility to various antibiotics in E. coli.
| Antibiotic | Main diffusion pathway across OM | Permeability Coefficient (nm/s) | Increase in Resistance (fold) (ΔompF) | Sensitization (fold) (Bilayer perturbation by PMBN) | Sensitization (fold) (ΔacrAB) |
|---|---|---|---|---|---|
| Penicillin G | Porin | 20 | 4 | 1–3 | 2 |
| Ampicillin | Porin | 980 | 2 | 1 | 2 |
| Carbenicillin | Porin | 7.5 | 16 | 3 | 4b |
| Cloxacillin | Porin | ~20 | NDa | 5–30 | 128 |
| Cefazolin | Porin | 600 | 2 | ND | 1 |
| Tetracycline | Porin | 100 | 1.5 | 1 | 2–4 |
| Chloramphenicol | Porin | ND | 2.5 | ND | 2–8 |
| Novobiocin | Bilayer | ND | ND | 10–100 | 32,64b |
| Erythromycin | Bilayer | ND | ND | 8–30 | 16,64b |
a
Not determined.
b
These are values determined by using Salmonella enterica serovar Typhimurium (Nikaido et al., 1998).
PMBN, polymyxin B nonapeptide.
The E. coli data are from Pugsley & Schnaitman (1978), Harder et al. (1981), Nikaido et al. (1983), Nikaido & Normark (1987), Vaara (1992), Thanassi et al. (1995), and Mazzariol et al. (2000).