Table 3.
In vitro activities of ceftaroline, ceftobiprole, and ceftriaxone against combined blood and respiratory isolates of S. pneumoniae with various antibiotic resistance phenotypes
| S. pneumoniae groupa (n) and antimicrobial | MIC (μg/ml) |
% Susceptible isolatesc | % Intermediate isolatesc | % Resistant isolatesc | ||
|---|---|---|---|---|---|---|
| 50% | 90% | Range | ||||
| Penicillin-nonsusceptible isolates (25)b | ||||||
| Ceftaroline | ≤0.03 | 0.12 | ≤0.03–0.25 | 100 | NA | NA |
| Ceftobiprole | 0.06 | 0.25 | ≤0.03–0.5 | NA | NA | NA |
| Ceftriaxoned | ≤0.12 | 1 | ≤0.12–4 | 92.0 | 4.0 | 4.0 |
| Clarithromycin-nonsusceptible isolates (33) | ||||||
| Ceftaroline | ≤0.03 | 0.12 | ≤0.03–0.25 | 100 | NA | NA |
| Ceftobiprole | ≤0.03 | 0.25 | ≤0.03–0.5 | NA | NA | NA |
| Ceftriaxone | ≤0.12 | 1 | ≤0.12–4 | 94.0 | 3.0 | 3.0 |
| Multidrug-nonsusceptible isolates (17) | ||||||
| Ceftaroline | ≤0.03 | 0.12 | ≤0.03–0.25 | 100 | NA | NA |
| Ceftobiprole | 0.12 | 0.5 | ≤0.03–0.5 | NA | NA | NA |
| Ceftriaxone | ≤0.12 | 1 | ≤0.12–4 | 88.2 | 5.9 | 5.9 |
Penicillin-nonsusceptible isolates had MICs of ≥0.12 μg/ml (penicillin MICs were interpreted using oral penicillin V breakpoints from CLSI document M100-S20 [10]). Clarithromycin-nonsusceptible isolates had MICs of ≥0.5 μg/ml. Multidrug-nonsusceptible isolates were penicillin nonsusceptible and clarithromycin nonsusceptible.
For the 25 penicillin-nonsusceptible isolates, the penicillin MIC for 11 isolates was 0.12 μg/ml, that for 3 isolates was 0.25 μg/ml, that for 3 isolates was 0.5 μg/ml, that for 3 isolates was 1 μg/ml, and that for 5 isolates was 2 μg/ml.
NA, not available.
Using ceftriaxone breakpoints (susceptible, ≤1 μg/ml; intermediate, 2 μg/ml; and resistant, ≥4 μg/ml), the percentages of isolates that were susceptible, intermediate, and resistant were 99.0, 0.5, and 0.5% for all isolates, 100, 0, and 0% for blood isolates, and 98.0, 1.0, and 1.0% for respiratory isolates.