TABLE 2.
Proportion of pneumococcal isolates resistant to various antimicrobial agents according to their susceptibility to penicillin, 1995 to 2001
| Agent | MIC threshold (μg/ml) | % of isolates by degree of penicillin susceptibilitya (no. of isolates tested)
|
|||
|---|---|---|---|---|---|
| Susceptible | Intermediate susceptibility | Resistant | Very-high-level resistance | ||
| Amoxicillin | ≥8b | 0 (16,855) | 0.1 (2,148) | 21.9 (2,946) | 90.8 (218) |
| Cefotaxime | ≥2b | 0.01 (18,102) | 2.8 (2,486) | 34.6 (3,182) | 97.8 (225) |
| ≥8 | 0 (18,102) | 1.1 (2,486) | 2.9 (3,182) | 67.6 (225) | |
| Cefuroxime | ≥2b | 0.1 (11,638) | 42.2 (1,660) | 99.5 (2,324) | 100 (144) |
| ≥8 | 0.01 (11,638) | 3.0 (1,660) | 65.2 (2,324) | 100 (145) | |
| Meropenem | ≥1b | 0.01 (18,102) | 0.6 (2,486) | 48.5 (3,182) | 97.8 (225) |
| Erythromycin | ≥1b | 3.9 (18,102) | 38.4 (2,486) | 66.4 (3,182) | 54.7 (225) |
| ≥8 | 2.6 (18,102) | 25.5 (2,486) | 55.3 (3,182) | 48.0 (225) | |
| Trimethoprim-sulfamethoxazole | ≥4/≥76b | 6.2 (18,102) | 50.6 (2,486) | 92.4 (3,182) | 96.4 (225) |
| Tetracycline | ≥8b | 1.6 (18,102) | 3.9 (2,486) | 27 (3,182) | 13.8 (225) |
| Levofloxacin | ≥8b | 0.2 (10,916) | 0.3 (1,465) | 0.9 (2,187) | 1.4 (143) |
| Clindamycin | ≥1b | 0.6 (18,102) | 9.5 (2,486) | 14.9 (3,182) | 9.8 (225) |
| ≥8 | 0.03 (18,102) | 6.4 (2,486) | 10.2 (3,182) | 7.1 (225) | |
a
Penicillin susceptibility was defined according to NCCLS breakpoints for 2003 (23) as follows: susceptible, MIC < 0.06 μg/ml; intermediate susceptibility, MIC of 0.12 to 1.0 μg/ml; resistance, MIC of 2 to 4 μg/ml; very-high-level resistance, MIC ≥ 8 μg/ml. Susceptibility test panels varied from year to year, and so not all isolates were tested against the same panel of antimicrobial agents.
b
Threshold for resistance according to NCCLS breakpoints for 2003 (23); the meningitis breakpoint for cefotaxime is shown.