TABLE 3.
Efficacy of ceftazidime-avibactam against ESBL- and AmpC-producing strains of Enterobacteriaceae
| Isolate | Phenotype | β-Lactamase | MIC for ceftazidime (μg/ml) | ED50 (mg/kg [95% confidence limit]) fora: |
||||
|---|---|---|---|---|---|---|---|---|
| Ceftazidime |
Augmentinb | Tazocillinc | ||||||
| Alone | Plus avibactam |
|||||||
| 4:1 | 8:1 | |||||||
| E. coli 250GR12 | CAZ-S | 0.06 | <5 | <5 | <5 | 12 (5–25) | >50 | |
| E. coli 250GR43 | CAZ-S | 0.25 | 9 (3–17) | 5 (1–8) | 6 (4–11) | 22 (14–36) | >50 | |
| K. pneumoniae 283GR4 | CAZ-S | 0.25 | <1.5 | <1.5 | <1.5 | >50 | >50 | |
| K. pneumoniae 283IP53 | CAZ-S | ≤0.12 | 4 (0–5) | 4.5 (0–5) | 4.5 (0–5) | 27 (0–107) | >50 | |
| P. stuartti 321UC1 | CAZ-S | 1 | 6 (1–14) | 5 (1–10) | 4 (1–7) | >50 | >50 | |
| E. coli 250BE1 | CAZ-R | SHV-4 | ≥128 | >90 | 16 (10–27) | 16 (10–27) | 49 (28–533) | 39 (10–192) |
| K. pneumoniae 283IP10 | CAZ-R | AmpC; SHV-4 | 64 | >90 | 5 (1–8) | 9 (6–13) | 20 (12–34) | >90 |
| K. pneumoniae 283IP35 | CAZ-R | SHV-2 | >128 | >90 | 29 (19–50) | 18 (5–33) | >90 | >90 |
| K. pneumoniae 283IP84 | CAZ-R | TEM-3 | 64 | >90 | <5 | <5 | 43 (18–134) | >90 |
| E. cloacae 293GR8 | CAZ-R | AmpC | >128 | >90 | <10 | 11 (4–19) | >90 | >90 |
| E. cloacae 293GR38 | CAZ-R | AmpC | 64 | >90 | 58 (38–93) | 65 (41–126) | >90 | >90 |
| E. cloacae P99 | CAZ-R | AmpC | >128 | 85 (49–75) | 5 (3–9) | 10 (0–10) | >90 | 43 (7–75) |
| C. freundii 261GR3 | CAZ-R | AmpC | >128 | >90 | 13 (11–15) | 14 (11–26) | >90 | >90 |
| C. freundii 261GR6 | CAZ-R | AmpC | >128 | 84 (61–145) | 9 (0–10) | 9 (0–10) | >90 | >90 |
a
Mice were dosed twice at 1 and 4 h postinfection; the ED50 of the antibiotic component is reported here.
b
Commercially available amoxicillin-clavulanate (1/0.2 g) (Augmentin).
c
Commercially available piperacillin-tazobactam (4/0.5 g) (Tazocillin).